FR2652691A1 - Asynchronous time-based optical communications system - Google Patents

Abstract

Asynchronous time-based optical communications system having a central unit (SN), terminal transmission circuits (UE), terminal reception circuits (UR), and broadcast servers (BS), connected via optical links (UEL; URL; BL) to the central unit. The central unit consists of an optical device for spectral-spatial-temperal commutation (SSTSN), a control means (CPU) and a synchronisation signal generator (CKU). The commutation device (SSTSN) is connected optically to the terminal transmission circuits, to the terminal reception circuits, to the broadcast servers and to configuration transmission circuits (CE), signalling transmission circuits (SE), configuration reception circuits (CR) and signalling reception circuits (SR) of the control means. The synchronisation signal generator is connected via a first link (H1) to the commutation device and via a second link (H2) to the control means (CPU) which is itself connected via a control link (CB) to the commutation device (SSTSN). The system jointly uses a first set of optical transmission frequencies (Fa) and a second set of optical control frequencies (Fb) for commutation.

Description

 The invention relates to a multiservice wide optical time band communication system, operating in asynchronous time mode, making it possible to create integrated optical communication networks in which the communications signals are transmitted and switched optically without intermediate transformations of the transmitted signals.

ATM (Asynchronous) information transfer techniques
Transfer Mode) and STM (Synchronous Transfer Mode) are well known and current BISDN communication networks operate according to one or the other of these techniques.

 In STM technique, communicating source and receiver are connected for the duration of their communication by a circuit constituted by one or more time channels of a succession of cyclic time multiplexes generally framed; time switching centers provide the necessary time and space switches between the various multiplexes used by the circuit according to a cyclic mechanism using stored control data, for the duration of the communication, in the switch control devices of each center.

The information to be transmitted is formatted at the source in samples of fixed format, successively transmitted on the time channel or channels assigned to the communication.

 Many synchronous time switching devices have been described, in particular time switches with controlled propagation using delay lines to effect the time shift of the signals. French patent 2,119,152 dated 12/22/70 describes such switches, specifying that the delay lines can be produced inter alia by means of optical fibers. An experimental optical propagation time switch was produced in the ATT Bell-Labs laboratories and described in the article by RA Thomson and PP Giordano, "Experimental Photonic Time-Slot Interchanger Using Optical Fibers as Re-Entrant Delay Line Memories ", OFCC, 02/86. This switch implements electrically controlled optical fibers and directional couplers.

 The ATM technique combines, by adapting them, the mechanisms of time transmission and packet transmission: communicating sources and receivers are connected for the duration of the communication by a virtual circuit to which is assigned a physical route consisting of a succession of time multiplex links and switching centers. The time resources are used in statistical mode between the various sources to which no specific time channel is assigned on the links. A source or receiver can be involved in a multiplicity of different simultaneous communications with different destinations.

 The information to be transmitted is formatted at source in fixed format cells, each comprising identification and routing information; the cells are transmitted acyclically on untimed time-division multiplex links depending on the availability of unmarked transmission channels.

 Switching cells is therefore akin to time switching, involving spatial switching and time shift.

However, since the multiplexing mode is statistical, the time shift resources are themselves used statistically and therefore managed as queues. Switching a cell requires prior analysis of the identification and routing information it contains.

 ATM switching systems have been described, in particular by French patent 2,538,976 of 12/29/82: "system for switching synchronous packets of fixed length".

 These known systems use optical transmission means to connect the subscribers and interconnect the exchanges and electronic means to switch the signals. Opto-electric and electro-optical conversions of the signals are therefore carried out at the borders of the transmission means and of the switching means, as well as a demodulation of the signals in the switching means in order to consult the routing information. These conversion and analysis means increase the structure of the systems, reduce their reliability and increase their cost.

 New communication techniques based on optical spectral multiplexing are also known: optical sources and receivers are connected to a passive propagation medium realizing the equal distribution between the receivers of the energy produced by each transmitter. The transmitters and receivers are tunable on a multiplicity of optical frequencies which each constitute a transmission channel allowing a direction of a communication to flow. Three main functional modes are possible: each source is permanently calibrated on an allocated frequency, the communication is established by agreement of the communicating receiver on said frequency, each receiver is permanently tuned to an allocated frequency, communication is established by agreement of the communicating transmitter on said frequency, the frequency is assigned to a communication at the time of its establishment, communicating transmitter and receiver are tuned on said frequency.

 Such frequency switching systems have been described, in particular by patents - EP 77,292 published on 04/20/83: "Communication network using single-mode fibers as transmission means for the optical channels multiplexed in the frequency range carrier optical waves ", - FR 2 586 874 of 29/8/85:" Telecommunication device by optical fibers ", - FR 2 593 654 of 28/01/86:" Coherent photonic telecommunication device ".

 These systems do not operate in spectro-temporal mode. The optical frequencies used as a communication medium are, in the best of cases, used for the duration of the communication.

 A multiservice operation, which can establish from a single terminal several communications having different destinations, is only possible if the terminals are each equipped with a multiplicity of transmission and reception devices. Each established communication mobilizes one or two optical frequencies.

 In view of what is known about ATM systems, optical systems using only frequency multiplexing appear to be ill-suited to multiservice operation.

Finally, the use of an optoelectronic wavelength switching device, replacing an electronic spatial switch, for switching between input buffer memories (FIFO) and output buffer memories (Elastic Buffer ) a fast packet switch with N optical input lines and N optical output lines, was described in the article by MSGoodman and Al, Bell Communications Research, "Demonstration of Fast Wawelength Tuning For a High Performance
Packet Switch ", Conferences on Optical Communication, 11-15 / 09/88
Brighton UK, pages 255 to 258, IEE.

 In this fast packet switch, the N input buffer memories and the N output buffer memories are electronic memories, the first are each electrically connected by an input device to the receiver of an optical input line and by a wavelength tunable laser output device,. the seconds are each electrically connected by an input device to an optoelectronic receiver tuned to a particular optical wavelength, and by an output device to the transmitter of an optical output line,. the N tunable lasers, each connected to an input buffer memory, and the N optoelectronic receivers tuned in wavelength, each connected to an output buffer memory, are optically connected to a passive star optical coupler NxN,. the transfer of a packet between an input buffer memory and an output buffer memory is carried out by tuning the emission laser connected to the output of the input buffer memory on the tuning wavelength of the optoelectronic receiver connected to the input of the destination output buffer for the duration of the packet transmission.

 In this fast packet switch, - the signals to be transmitted undergo several transformations during switching operations, such as opto-electric and electro-optical conversions, (demodulation and remodulation of optical signals), deserialization and serialization of electric signals, - packet routing requires the use of routing information included in the packets themselves and therefore of demodulating the carrier signal, - the optical switching device, comprising the transmitters, broadcaster and receivers, is confined in a restricted space, - the capacity of the switching means is limited by the number of discriminable wavelengths, each wavelength being assigned to a receiver.

 The object of the invention is to provide a broadband multiservice optical communication system, in which the transmission and switching of signals is carried out end to end by the only means of optical techniques without requiring a multiple succession of optoelectronic conversions and electro-optics, demodulations and modulations of said signals.

 Another object of the invention is to provide a multiservice optical communication system in which a terminal can, by means of the same optical transmitter and / or the same optical receiver, establish a multiplicity of simultaneous communications having destinations or different origins.

 Another object of the invention is to provide a multiservice optical communication system in which the use of wavelengths or optical frequencies is optimized so as to increase the connection capacity in terminals of the system.

 Another object of the invention is an asynchronous time optical communication system which operates without requiring an analysis of the transferred information other than that directly permitted by the sole means of optics and electronic optics without prior demodulation or conversion. optical communication signals.

 Another object of the invention is to provide the spatial and temporal switches of the optical signals carrying the information by optical and optoelectronic means, themselves controlled by optical signals.

 The subject of the invention is an ATM asynchronous time optical communication system, having a communication central, q terminal reception circuits connected by at most q optical terminal reception links to the communication central, p terminal transmission circuits. each linked by an optical terminal transmission link to the central office, said terminal transmission and terminal reception circuits being distributed in x remote communication terminals each having a transmission circuit and a reception circuit, y terminals d transmission each having a transmission circuit, z reception terminals each having a reception circuit, characterized in that each terminal reception circuit comprises. at least one configuration optical receiver tuned to an optical frequency of a first group of optical frequencies of a first set of optical frequencies, a transmission optical receiver tunable to any optical frequency of a second group of optical frequencies of said first set of optical frequencies,. an optical frequency tuning means of said optical transmission receiver,. and a means for time synchronization of the information received, that each terminal transmission circuit comprises an optical transmission transmitter tunable to any optical frequency of said second group of optical frequencies, an optical frequency tuning means of said optical transmitter and means for time synchronization and time framing of the information to be transmitted, that the communication center comprises an optical spectro-space-time switching device, a control means, and a synchronization signal generator, than the switching device is optically connected to the optical transmission links and to the optical reception links, which the control means comprises .. at least one configuration transmission circuit having a configuration optical transmitter tuned to an optical frequency of said first group of optical frequencies , .. at least one signaling transmission circuit having one transmits optical transmission tuner tunable to any optical frequency of said second group of optical frequencies, .. at least one configuration reception circuit and at least one signal reception circuit, each having at least one optical configuration receiver tuned to one optical frequency of said first group of optical frequencies, .. and an optical transmission receiver tunable to any optical frequency of said second group of optical frequencies,. that said exchange is connected to the switching device by .. a control link, .. at least one configuration configuration optical link each being optically connected to the configuration optical transmitter of a configuration transmission circuit, .. at least one optical configuration reception link, each being optically connected to the optical configuration and transmission receivers of a configuration reception circuit, .. at least one optical signaling transmission link each being optically connected to the optical transmitter of a signaling circuit, and .. at least one optical signaling reception link each being optically connected to the optical configuration and transmission receivers of a signaling receiving circuit, and that the signal generator synchronization is connected by a first synchronization link to the switching device and by a second connection d e synchronization by means of control.

According to another characteristic, the switching device
Spectro-spatio-temporal includes. an optical exploration circuit optically connected to the optical transmission terminals and to the optical signaling transmission links, said optical transmission links each carrying a spectro-time transmission multiplex consisting of channels each carrying a sample information optics,. an optical distributor of control orders,. a control circuit linked on the one hand optically to the optical scanning circuit by a first optical link carrying a destination spectro-temporal multiplex comprising as many channels as there are transmission links, to the optical distributor by a second optical link carrying a spectro-temporal multiplex of control orders having a number of channels equal to that of said destination multiplex, each channel of the control order multiplex being in time phase with a channel of the same rank in said destination multiplex and routing a control order, and to the synchronization generator by the first synchronization link, and on the other hand by control means by the control link,. n optical time switches, with controlled propagation, each being optically connected to an output of the optical scanning circuit and to an output of the optical distributor of control orders, an optical diffuser optically connected at the output of the time switches and to the optical transmission of configuration, and having outputs optically connected each at the input of an optical filter,. s optical filters each optically connected at the output to one of the terminal reception optical connections, signaling reception, configuration reception, a filter configuration circuit connected at the input to the control link and at the output to a control input for each filter optical.

 According to another characteristic, the destination multiplex is constituted by sampling the channels occurring at the same instant at the input of the exploration circuit on each of the transmission links, each channel of the control order multiplex having the same rank as a transmission link conveys a control order consisting of an optical signal at an optical frequency of a second set of optical frequencies, each optical frequency of which is characteristic of a propagation delay in real time which must undergo, in a time switch , the message conveyed by the channel of said transmission link, said optical frequency being determined by the control circuit, and the optical distributor delivers to each time switch corresponding to the rank of a channel of the multiplex of control orders control order conveyed by said channel of the control order multiplex.

The communication system of the invention uses several multiplexes, - a time-division multiplex framed CEM transmission called configuration multiplex, including. the optical carrier frequency of the Fal group serves as a reference for the optical frequency encoding systems of the terminals,. the frame code is used as a time reference for the time synchronization of the terminals,. and the other channels are used for the transmission of configuration messages from the terminals, - a time-division multiplex reception without raster CRM carrying optical samples carried by a frequency of the group Fa2, which is used to support response messages from the terminals in the operations of configuration, - a pair of so-called signaling multiplexes, having a SEM spectro time transmission multiplex and a reception multiplex
SRM, used for signaling exchanges between the terminals and the central control means, - a multiplicity of spectro-time transmission multiplex UEM and a multiplicity of time reception multiplex URM, which multiplex UEM and URM are the communication multiplexes, which multiplex SEM, SRM, UEM and URM carry optical samples each carried by an optical frequency of group Fa2, and for control, - an OLM multiplex, called destination multiplex, - a CLM multiplex, called control order multiplex, which multiplex OLM and CLM are framed time multiplexes having a period equal to the duration of one channel of the communication multiplexes and a number of channels per frame equal to at least the total number of UEL and SEL lines connected to the spectro-space-based switching device. time SSTSN.

 The optical samples conveyed by the various multiplexes have a duration T and are temporally formed of a central part, containing the transmitted information, framed on either side of non-information carrying parts constituting switching windows.

 The relative durations of the three parts are such that it is not necessary to achieve, before switching, perfect time alignment of the samples with respect to the local clocks of the switching device in order to avoid degrading the information transmitted.

 The information transmitted is either a digital signal or an analog signal: in the first case, the signal is formatted in cells each containing a multiplicity of bytes, in the second case the signal is temporally divided into samples.

 Each cell or signal sample is transmitted by an optical sample encoded at the optical frequency characteristic of the destination of the signal which constitutes for the switching means of the exchange the switching reference and for the reception means of the terminals the selection reference. .

 The control circuit CC comprises a multiplicity of elementary generators of order of control of the time switches TSU, each responsible for the management of the channels of one of the reception reception multiplexes CRM, SRM and URM and for the elaboration of the orders for control of the TSU switches for all the optical samples to be routed on these reception transmission multiplexes whatever the origin.

 The number of generators equipped is at least equal to the number of CRM, SRM and URM multiplexes implemented in the system, equal to the number of frequencies f2 of the second group Fa2 of the optical frequencies and at most equal to the number of discriminable optical frequencies in the optical spectrum.

 The invention will be clarified by the description which follows of a preferred embodiment of the invention, given by way of nonlimiting example, with reference to the appended drawings in which: FIG. 1A schematically represents the system of spectro-spatio-temporal communication of the invention, - Figure 1B schematically shows a spectro-spatio-temporal switching device equipping the spectro-spatio-temporal communication system of the invention, - Figures 2 to 5 show the diagrams in principle of an embodiment of the various circuits constituting the spectro-spatio-temporal switching device, ie, FIG. 2A - a circuit "explorer of the input lines", FIG. 2B - a circuit "distributor of control orders to the propagation time switches ", FIG. 3A - a circuit combining the explorer of the input lines and the distributor of control commands with the optical propagation time switches ,. FIG. 3B - a variant of the circuit combining the explorer of the input lines and the distributor of control orders to optical time switches with propagation, FIG. 4A - a circuit for developing control of the circuits "explorer of the input lines" and "distributor of control orders to time propagating switches", respectively described by FIGS. 2A and 2B,. FIG. 4B - a circuit for developing the circuit combining the explorer and the distributor, described by FIGS. 3A or 3B,. FIG. 4C - a generator of the multiplex for controlling optical propagation time switches, FIG. 4D - an exemplary embodiment of a spectral demultiplexer,. FIG. 4E - a circuit of an elementary generator of command order for the optical time switches with propagation,. FIG. 5A - an optical time switch with propagation,. FIG. 5B - a connection point of the optical propagation time switch,. FIG. 5C - an alternative embodiment of the optical propagation time switch using a kxl coupler,. FIG. 5D - another alternative embodiment of the optical propagation time switch using k 2xl couplers, - FIG. 6 schematically represents a communication terminal.

 FIG. 1A describes in principle the organization of the spectro-spatio-temporal communication system according to the invention.

The system implements at least one communication center
SN to which are connected, on the one hand. p terminal transmission circuits UE (UE1 to UEp), each having an optical transmission transmitter connected to said optical terminal transmission link, an optical frequency tuning means of said optical transmitter, information source means to transmit and time synchronization and time framing means of said information, each circuit being connected by an optical transmission link UEL (UEL1 to UELp),. q UR terminal reception circuits (UR1 to URq), each having an optical transmission receiver and at least one configuration optical receiver connected to said optical terminal reception link, an optical frequency tuning means of said optical transmission receiver , a time synchronization means and means for exploiting the information received, each circuit being connected by an optical link for receiving URL (URL1 to URLq), and on the other hand, possibly, one or more broadcasting servers BS , such as for example broadcasting audiovisual programs, each by an optical broadcasting link BL.

Said terminal transmission circuits UE and terminal reception circuits UR are distributed in. X communication terminals each having a transmission circuit
UE and a reception circuit UR, each connected by an optical transmission link UEL and an optical reception link URL, .. y transmission terminals each having a transmission circuit UE, each connected by an optical connection UEL transmission, .. z reception terminals each having a reception circuit
UR, each connected by an optical link for receiving URLs.

The numbers p and q of transmission circuits and reception circuits are such that
p = x + yq = x + z
Several broadcasting servers BS and / or several transmission terminals can be grouped together in server centers.

 Receiving terminals are generally installed at subscribers or data collection centers.

 The communication terminals are installed with subscribers, in the exchanges interconnected with the SN exchange as well as in the server centers, of which they allow interactive access by the exchange for the management of operation and, possibly by the users, for the management of services. .

 In addition to said transmission and reception circuits, each communication terminal has various other functional means including. a synchronizable generator of clock signals,. an optical frequency reference means. and a control means supervising the various other functional means.

 The transmission and / or reception terminals grouped together in the same server center and the reception terminals located with subscribers are managed by said other functional means of the communication terminal installed in the server center or at the subscriber.

 The optical transmission UEL and URL reception links connecting the same communication terminal are each supported by an optical fiber or use the same optical fiber equipped at its ends with optical duplexers separating the two directions of transmission, associated with means of optical isolation.

 A single optical fiber only supports a single optical transmission link UEL.

 The same optical fiber can support several URL optical links, which fiber is then equipped, at its end remote from the exchange, with an optical diffuser constituted for example by a star optical coupler.

 The optical links BL connecting the servers BS of the same server center are each supported by an optical fiber or grouped by means of an optical coupler in the server center on the same optical fiber connecting to the server center.

 The central SN comprises the following means: - a spectro-spatio-temporal switching device SSTSN having: two groups of inputs of respective capacity n and m. A first group of n inputs I1 to In, of which p are each optically connected to one of the optical links UEL, and of which at least one of the remaining np, such as In, is connected to an optical transmission signaling signal SEL, .. a second group of m inputs, of which ml inputs, such as the input Ib, are each connected to an optical fiber supporting one or more BL links each connecting a broadcasting server BS, and at least one of the m2 = (m-ml) remaining inputs, such as the Ic input, is connected to an optical configuration transmission link CEL,. a group of identical optical outputs of which .. q outputs (01 to Oq) are, in the general case, each connected to an optical link URL, .. at least one, such as the On output, is connected to an optical reception link signaling SRL and .. at least one, such as the Oc output, is connected to a CRL configuration optical reception link. a synchronization access connected to a synchronization link H1,. a control access connected to a control link CB, - a control means CPU having. at least one transmission circuit of configuration CE comprising an optical configuration transmitter connected to an optical transmission link of configuration CEL,. at least one CR configuration reception circuit comprising an optical transmission receiver and at least one optical configuration receiver, connected to an optical CRL configuration reception link,. at least one signaling transmission circuit SE comprising an optical signaling transmitter connected to an optical signaling transmission link SEL,. at least one signaling reception circuit SR comprising a signaling receiver and at least one configuration receiver, connected to an optical signaling signaling reception link SRL, - a synchronization signal generator CKU connected. to the spectro-spatio-temporal switching device SSTSN by the synchronization link H1,. by means of CPU control by a synchronization link H2.

The control means CPU is connected. to the spectro-spatio-temporal switching device SSTSN by said optical configuration and signaling transmission and reception links (CEL, CRL; SEL, SRL) and by a control link CB, to the synchronization signal generator CKLJ by the link H2 synchronization,
In the case where several optical links URL are supported by the same optical fiber, this is connected to only one of the outputs Oi of the spectro-space-time switching device
SSTSN.

 Each optical configuration transmitter is tuned to an optical frequency of a first group Fal of optical frequencies, having f1 optical frequencies and belonging to a first set of frequencies Fa which is the set of optical transmission frequencies of the device of the invention , and each optical configuration receiver is tuned, as a function of its rank, to an optical frequency of said first group of optical frequencies.

 Said optical transmission transmitters and optical transmission receivers can be tuned to any optical frequency of a second group Fa2 of optical frequencies of the set Fa, having f2 frequencies, different from the frequencies of the first group Fal of optical frequencies.

 Each broadcasting optical link BL of a broadcasting server BS is connected in the server BS to at least one optical transmitter called the optical broadcasting transmitter, the reception circuits UR optionally comprise one or more optical broadcasting receivers.

 Said optical broadcast transmitters and optical broadcast receivers can be tuned to any optical frequency of a third group Fa3 of optical frequencies of the set Fa, having f3 frequencies, different from the frequencies of the first and second groups Fal and Fa2 of frequencies optical.

According to another embodiment of the invention, each UR reception circuit comprises at least one optical receiver, tunable to any optical frequency from the three groups
Fal, Fa2, Fa3 of optical frequencies constituting the first set Fa of optical frequencies.

Said first set of optical frequencies Fa, set of optical transmission frequencies of the device of the invention, therefore includes the three groups of optical frequencies
Fal, Fa2 and Fa3 having respectively fl, f2 and f3 distinct frequencies.

The number fa of the optical frequencies of the first set of optical frequencies Fa is equal to the sum of the numbers of frequencies of each group:
fa = fl + f2 + f3
The term "frequency" is used in the present description for the convenience of the presentation: in fact, it is a narrow spectral band, centered on an optical frequency, discriminable either by means of a filtering device optical, or by means of an optoelectric filtering device known under the name of heterodyne photoreceptor.

 The maximum number famax of the optical frequencies of said first set Fa of the optical frequencies is equal to the maximum number fmax of the optical frequencies technically discriminable in an optical spectrum by the technical means mentioned above.

fa C famax = fmax
Each optical transmitter transmits on the link which is connected to it a time multiplex, each optical receiver receives by the link to which it is connected at least one time multiplex, which time multiplexes, except for multiplexes
EMCs described below, are temporally structured in a series of undifferentiated time channels of duration T, and are not framed. In the following descriptions, for the sake of convenience, it is assumed that each time channel of a series of undifferentiated channels is identifiable by a time reference
Ti, relating to the clock of the communication system.

 CEM multiplexes are framed multiplexes with a c-channel frame and a c.T period.

 The first channel of each frame carries an identification code for the start of the frame, as is known in the temporal techniques. The other channels are undifferentiated and therefore identical to the channels of the other multiplexes.

 In each time channel Ti is transmitted an optical sample of duration T, carrying information to be transmitted. The optical carrier frequency of each sample is characteristic of its destination, either functional or physical: the optical frequency encoding of the samples is carried out by the transmission circuit according to their physical or functional destination.

 The information to be transmitted can be either a digital signal or an analog signal: in the first case, the signal is formatted in cells each containing a multiplicity of bytes, for example 36 or 53 bytes, in the second case the signal is temporally cut into samples.

 Each cell or signal sample is transmitted by optical sample encoded at an optical frequency characteristic of the destination of the signal.

 The optical frequency carrying a sample constitutes for the referral means of the central office the referral reference and for the reception means of the terminals the selection reference.

 In the preferred embodiment of the invention, each optical sample of duration T is temporally formed of a central part, containing the information transmitted, framed on either side of parts, not carrying information, constituting switching windows. The relative durations of the three parts are such that it is not necessary to achieve, before switching, perfect time alignment of the samples with respect to the local clocks of the switching device in order to avoid degrading the information transmitted.

 When all the optical samples of a multiplex are carried by the same optical frequency, the multiplex is designated below as time multiplex.

 When the successive optical samples of a multiplex can be carried by different optical frequencies, the multiplex is designated hereinafter as spectro-temporal multiplex.

 Each transmission circuit CE transmits on its CEL link a time multiplex CEM, called configuration transmission multiplex.

The CEM time multiplexes are, whatever the operating mode of the communication system, framed multiplexes.

They are systematically all broadcast by the switching device SSTSN on each of the CRL, SRL and URL links and received by said optical receivers for configuring the reception circuits connected to said links. Each time multiplex
CEM is carried by one of the optical frequencies of the frequency group Fal, which optical frequency is characteristic of the rank of the multiplex in the set of CEM multiplexes.

 The optical frequencies of the Fal groups are functionally characteristic of the configuration functionality.

Each transmission circuit SE transmits on its link SEL a spectro-temporal multiplex SEM, known as signaling transmission multiplex, each transmission circuit UE transmits on its link UEL a spectro-temporal multiplex UEM, known as communication transmission multiplex, which multiplex spectro-temporal SEM and UEM carry a succession of supported optical samples, each according to its destination, by one of the f2 frequencies of the group
Fa2 of the optical frequencies.

 The optical frequencies of the Fa2 groups are functionally characteristic of the communication functionality, including the signaling functionality.

 Each CRL link carries a time multiplex CRM, known as configuration reception multiplex, each SRL link carries a time multiplex SRM, known as signaling reception multiplex, each active URL link carries a time multiplex URM, said communication reception multiplex.

 The time multiplexes CRM, SRM and URM are each carried by one of the f2 optical frequencies of the group Fa2 of the optical frequencies, which optical frequency is characteristic, for the switching means, of the rank of the multiplex in the set of multiplexes CRM, SRM and URM, and therefore of a spatial destination in the communication system, which is not necessarily invariant in time as explained in the description of the functioning of the communication system.

 The time multiplexes CRM, SRM and URM are sent optically by the SSTSN device on the CRL, SRL and URL links and received optically by said transmission receivers of the reception circuits connected to said links.

 Each BL link carries at least one multiplex designated below as BCM multiplex; each of the BCM multiplexes is carried by one of the f3 optical frequencies of the Fa3 group, which optical frequency is characteristic of the rank of the BCM multiplex in all of the BCM multiplexes and therefore constitutes, for the central office switching means and the reception circuits terminals; the BCM multiplex selection parameter.

 The optical frequencies of the Fa3 groups are functionally characteristic of the broadcasting functionality. The BCM multiplexes are broadcast, optionally selectively, on the URL links by the switching device SSTSN, and received by the said optical distribution receivers of the reception circuits connected to these links.

In the most common application of the invention, an active URL link carries an URM multiplex, all of the CEM multiplexes and possibly BCM multiplexes, each link
CRL carries a CRM multiplex and CEM multiplexes, and each SRL link carries an SRM multiplex and CEM multiplexes.

In the central unit of the invention, the spectro-spatio-temporal switching device SSTSN - distributes, as a function of their carrier optical frequency Fa2i, each sample of the spectro-temporal multiplexes transmitting SEM and
UEM, at the CRM, SRM or URM reception time multiplex carried by the Fa2i frequencies, - broadcasts on each of the CRL and SRL links the CEM multiplexes and on each of the URL links, in addition to the URM multiplexes concerned, the CEM multiplexes and possibly selectively BCM multiplexes.

If fmax is the maximum number of technically discriminable optical frequencies in an optical spectrum, assuming that the exchange SN only serves communication terminals and implements only one link of each of the CRL, CEL, SEL and SRL, hypothesis expressed by the relations y = z = O; p = q = x
fl = 1; f3 = O; f2 = fmax-l the maximum number xmax of communication terminals which can be connected to the exchange is
xmax = fmax-3 the maximum number Emax of the spectro-time transmission multiplexes (SEM, UEM) implemented is
Emax = fmax-2 the maximum number Rmax of the reception multiplexes (CRM, SRM, URM) to be managed by the spectro-space-time switching device SSTSN is
Rmax = fmax-l
FIG. 1B represents the organization of the switching device SSTSN equipping the spectrospatio-temporal communication system of the invention, a figure in which: - I1 to In, Ib and Ic are the optical inputs,. 01 to Oq, On and Oc are the optical outputs, .H1 and CB are respectively the synchronization and control links of the spectro-space-time switching device
SSTSN, - LS is an optical circuit exploring the input lines carrying the spectro-time transmission multiplexes UEM and SEM.

 LS is optically connected. by its inputs 210.1 to 210.n at the inputs I1 to In, by each of its outputs 211.1 to 211.n at the input 501 of an optical time switch TSU,. and by its control input and output 201 and 202 and its output 203 respectively at output 402 and at inputs 403 and 410 of a control circuit CC.

LS samples the contemporary optical samples of the UEM and SEM multiplexes coming from the inputs I1 to In of SSTSN and present on its inputs 210.1 to 210.n, groups the optical signals obtained in a cyclic spectro-temporal multiplex, called multiplex
OLM which is issued on output 203, and transfers to its outputs 211.1 to 211.n the optical samples received on its inputs.

 The OLM multiplex, with a useful capacity of n channels each associated with one of the inputs 210.1 to 210.n and therefore with one of the inputs I1 to In of SSTSN, has a cycle time equal to the duration T of a channel of the multiplex of the connections connected to the inputs I1 to In. The optical signals which it carries are, by their spectral characteristics, similar to the optical samples present on the inputs I1 to In from which they originate, and therefore representative of the destinations of said optical samples. They are therefore each supported by an optical frequency of the second group of optical frequencies Fa2.

- CC is the control circuit of the spectro spatio-temporal switching device. It is connected. on the one hand optically .. by its accesses 402, 403 and 410 to the line explorer LS as described above, .. by its outputs 404 and 411 and its input 405 respectively at the control inputs 301 and 303 and at the output control 302 of a CD distributor, .. by its access 401 to the synchronization link H1, on the other hand .. by its access 406 to the control link CB.

 CC optically analyzes the signals of the OLM multiplex received on the input 410, generates the control orders of the time switches TSU according to the availability of the destination links of the samples present on the inputs I1 to In of the switching device, designated by the characteristics spectral of the signals of the OLM multiplex, and transmits these control orders to the CD distributor by a cyclic spectro-temporal multiplex, called the CLM multiplex, transmitted on the output 411, having the same number n of useful channels and the same cyclic period as the multiplex OLM.

 Each channel of the CLM multiplex. is in time phase, to the nearest computation time, with the same rank channel of the OLM multiplex,. routes the successive control commands of the time switch TSU of the same rank.

 The control orders are developed and transmitted in the form of optical signals each carried by one of the fb optical frequencies of a second set Fb of optical frequencies called the control frequencies of the time switches TSU.

 The second set Fb of optical frequencies is independent of the first set Fa of optical frequencies and can belong to the same spectral domain.

 Each of the fb optical frequencies of the second set Fb of optical frequencies is characteristic of a particular value of the time offset which must undergo, in the SSTSN device, any incident sample of a spectro-time transmission multiplex to be inserted in a free channel. , or an affected channel, of the destination receiving time multiplex, that is to say of a time crossing value by the sample of a time switch TSU.

 In the embodiment of the TSU switches described in FIGS. 5A, 5C or 5D, in which the time shift of the samples is obtained by means of a delay line with multiple outputs each connected to a connection point, each of the fb optical frequencies constitutes both the address of an optical connection point in all of the optical connection points equipping the same time switch TSU and the order of command of said optical connection point.

- CD is an optical circuit distributing control orders to the time switches TSU1 to TSUn, which control orders consist of the optical signals carried by the multiplex
CLM received on entry 303.

 CD is optically connected by its control input and output 301 and 302 and the input 303 respectively to the ports 404, 405 and 411 of the CC control circuit and by its outputs 311.1 to 311.n to the control inputs 502 of the time switches TSU .

CD points to each of the outputs 311.1 to 311.n the control orders conveyed by the CLM multiplex according to their rank in the frame of the multiplex, the succession of the same rank orders of the successive frames of the CLM multiplex constituting the multiplex of the orders of TSU switch command of the same rank.

- TSU1 to TSUn are n optical time switches with controlled propagation, each connected by input 501 to the output of the same rank in the group of outputs 211.1 to 211.n of the explorer LS, by the control input 502 to the output of the same rank in the group of outputs 311.1 to 311.n from the CD distributor,. by each of the outputs 51.1 to 51.k if the switches are of the type described in FIG. 5A, or by the output 51 if the switches are of the type described in one of FIGS. 5C and 5D, at an input of the optical diffuser OD .

 Each switch TSU receives on its input 501 a transmission time multiplex UEM or SEM, and on its control input 502 a control multiplex, each order of which relates to the contemporary optical sample of the transmission multiplex, and, as a function of the control orders received, realizes the temporal rearrangement of the successive optical samples of the input time multiplex.

- OD is an optical diffuser having. (m + (nk)) inputs connected to the m inputs of the second group of inputs of SSTSN and to the k outputs of each of the n time switches TSU when these are of the type of FIG. 5A, or (m + n) inputs when the switches TSU are of the type of FIGS. 5C or 5D, and s outputs each connected to the input of an optical amplifier filter of a set of s filters WF, set constituted by the filters WF1 to WFq, WFn and WFc of the Figure 1B.

 OD performs a spectral multiplexing of all the optical samples presented on its inputs and delivers on each of its outputs a spectral multiplex of all the incident samples.

 One embodiment of such an optical diffuser is described in the French patent application published under the reference 2 625 815: "Optical diffuser of type N by N".

- The WF optical amplifier filters each have an input optically connected to an output of the diffuser OD, an output optically connected to an output Oi of the spectro-spatio-temporal switching device SSTSN and a control input connected to the output of a FCC filter configuration circuit, which FCC circuit is connected at the input to the control link CB by which it receives the filter configuration commands from the central control unit CPU.

The WF filters are transparent for the frequencies of the first group of optical frequencies Fal and can each be tuned to one of the f2 frequencies of the second group of optical frequencies
Fa2, which frequency is then characteristic of the destination constituted by optical reception link, URL, CRL or SRL, connected at the output of the filter.

 The WF filters are also tunable on one or more frequencies of the third group Fa3 of the optical frequencies.

 According to another embodiment of the invention, the filters WF are each tuned so as to be transparent for one or more subgroups of optical frequencies of the groups of optical frequencies Fal and Fa2, and possibly of the group of optical frequencies Fa3, each subgroup of optical frequencies comprising at least one frequency,. and to block the propagation of any foreign optical frequency to the tuning subgroups.

 According to another embodiment of the invention, the amplifier filters WF are identically transparent for the three groups of optical frequencies Fal, Fa2 and Fa3, their filtering function being limited to blocking the propagation of any optical frequency foreign to the three groups.

 The set of WF optical amplifier filters constitutes a spatial distribution device directing on each of the reception links the only multiplexes which concern it. Spatially limiting the distribution of multiplexes, it protects communications.

 An embodiment of the various circuits is described below by way of example and constitutes the simplest embodiment of the invention; the optical samples produced by the sources are modulated between two levels of optical energy, the lowest level of which is such that it enables the circuits of FIG. 4C to operate, identifying the carrier optical frequency.

 FIG. 2A describes the principle of an embodiment of the exploration circuit of the input lines LS of FIG. 1A, exploration circuit consisting of: - a control device, called "first control device", connected by its input 201 and its output 202 to the control circuit CC, - an optical selector whose inputs 210.1 to 210.n are each connected to one of the inputs I1 to In of the switching device SSTSN,. outputs 211.1 to 211.n are each connected to the input of a switch TSU, output 203 is connected to the control circuit CC.

 Said first control device is formed by an assembly in series of n optical couplers 221.1 to 221.n each having an input and a first and a second output, and of nl identical optical delay lines such as 222.1 each having an input and an output, the assembly being such that the first output of each coupler, with the exception of the last, is connected to the input of a delay line whose output is itself connected to the input of the following coupler , the input of the first coupler 221.1 and the first output of the last coupler 221.n being respectively connected to the input 201 and to the output 202 of said first control device, the second outputs of each of the couplers 221.1 to 221.n being connected, possibly via an optical amplifier such as 223.1, to an input for controlling the optical selector.

 Said optical selector is formed by an assembly of n optical switches 224.1 to 224.n each having a first and a second input, an output and a control input, and of n optical couplers 226.1 to 226.n each having an input , a first and a second output, and of identical delay lines 227.1 to 227.n, each having an input and an output, assembly in which the optical switches such as 224.1 are put in series by connection of the output of one at the first input of the next, the output of the switch 224.1 being connected to the output 203 of the optical selector,. the second input of each optical switch such as 224.1 is connected to the second output of the coupler of the same rank, such as 226.1, possibly via an optical amplifier, such as 225.1, the control inputs of the optical switches constitute the control inputs of the optical selector and are each connected to the second output of the optical coupler of the same rank as 221.1 of said first control device, the input of each optical coupler as 226.1 is connected to the input of the same rank of the n inputs 210.1 to 210 .n of the explorer, the first output of each coupler such as 226.1 is connected to the input of the delay line such as 227.1, the output of which is connected to the output of the same rank as 211.1 of the explorer.

FIG. 2B describes the principle of an embodiment of the distributor CD of control orders to the time switches
TSU. Said CD distributor consists of: - a control device, known as a "second control device", the input 301 and the output 302 of which are connected to the control circuit CC, - a distribution line, the input 303 is connected to the control circuit CC and whose outputs 311.1 to 311.n are each connected to the control input of a switch TSU.

 Said second control device is formed by an assembly of n couplers with one input and two outputs, 321.1 to 321.n, and by nl identical delay lines such as 322.1, assembly identical to that, previously described, of said first control device of the LS explorer of the input lines.

 Said distribution line is formed of an assembly comprising nn optical switches 324.1 to 324.n each having an input, a first and a second output and a control input, nn hysteresis optical amplifiers 325.1 to 325.n, nn lines delay 326.1 to 326.n each having a different length characteristic of the rank of the delay line, assembly in which the n optical switches are arranged in series by connection of the first output of one to the input of the next, l the input of switch 324.1 being connected to input 303 of the distribution line, the second outputs of each of the n optical switches are each connected via one of the n optical hysteresis amplifiers to the input of a of the n delay lines, the outputs of the n delay lines are each connected to one of the outputs 311.1 to 311.n of the distribution line, the control inputs of the optical switches. ues, such as 324.1, are each connected to the second output of the coupler of the same rank, such as 321.1, of said second control device, possibly via an amplifier such as 323.1.

 Hysteresis optical amplifiers, such as 325.1, are, for example, made up of an optoelectronic amplifier device functioning as a monostable.

 FIGS. 3A and 3B each describe an embodiment of the line explorer LS and of the order distributor CD in which the said first and second control devices described in FIGS. 2A and 2B are grouped together in a single device command says "third command device".

 In the first embodiment shown in FIG. 3A, the so-called "third control device" is constituted by assembling in series the n couplers 221.1 to 221.n and the n couplers 321.1 to 321.n already described and n first lines to delay 231.1 to 231.n and nl second delay lines such as delay line 331.1 according to the following principle:. the first output of the coupler 221.i is connected to the input of the delay line 231.i, the output of which is connected to the input of the coupler 321.i, the first output of which is itself connected to the input of the delay line 331.i, the output of the latter being connected to the input of the coupler 221.i + 1,. the input of the first coupler 221.1 and the first output of the last coupler 321.n being connected respectively to the input 201 and to the output 202 of said third control device.

 The delay created by a couple of delay lines such as 231.1 and 331.1 is equal to the delay created by the delay lines 222.1 or 322.1 of the assemblies of FIGS. 2A or 2B.

In the case of using the assembly of FIG. 3A in the preferred embodiment of the invention, the nl delay lines such as 331.1 of said "third control device" would have a zero delay value. In this use, these nl delay lines are not equipped but replaced by a direct connection from the first output of the coupler 321.i to the input of the coupler 221.i + l, the delay of the delay lines such 231.1 then being equal to the delay created by the delay lines 222.1 or 322.1 of the circuits of Figures 2A or 2B. This variant embodiment of the line explorer LS and the order distributor
CD is shown in Figure 3B.

 The assemblies of the other means used in the assembly for producing the selector and the distribution line are, in the two FIGS. 3A and 3B identical to those described in FIGS. 2A and 2B.

 Unless otherwise indicated, in the description which follows, FIGS. 3A and 3B, representing the same functional object, are designated by the reference in FIG. 3.

 The combination of FIGS. 4A and 4C on the one hand, and the combination of FIGS. 4B and 4C on the other hand, describe the construction of the control circuit CC respectively. in the case where the line explorer LS and the order distributor CD are produced according to the assemblies described in FIGS. 2A and 2B, and in the case where they are produced according to the assembly described in FIG. 3 (3A or 3B ), which CC control circuit comprises in both cases a command generation circuit (FIG. 4A or 4B) and a generator of control orders (FIG. 4C).

FIGS. 4A and 4B describe the circuit for developing control of the control devices, respectively for the first and the second case defined above, the connection of said control circuit to the external means being as follows:. the optical input 401 is optically connected to the synchronization link H1 of the switching device SSTSN, itself optically connected to the synchronization signal generator
CKU,. electrical input 406 is connected to the control link
CB, itself connected by central control unit CPU,. the optical output 402 and the optical input 403 (fig. 4A or fig. 4B) are respectively connected to the optical input 201 and the optical output 202 of the control device (fig. 2A or fig. 3).

. the output 404 and the optical input 405 (FIG. 4A) are optically connected respectively to the input 301 and to the output 302 of the control device (FIG. 2B).

 In FIG. 4A, an optical generator 421 of optical pulse of calibrated duration is connected by its input to the input 401 of the circuit and by its output to the input of an optical coupler 422 distributing the optical energy equally. to two outputs, the first of which is directly connected to the first input of an optical switch 423.1 and the second of which is connected to the input of a delay line 424, the output of which is itself connected to the first input of a optical switch 423.2, switches 423.1 and 423.2 each having two inputs and two outputs and being electrically controllable by the control link CB connected to input 406.

 The second output of the optical switch 423.1 is connected to the input of a delay line 425.1, the output of which is connected to the output 402 of the circuit, and the second input of the optical switch 423.1 is connected, possibly via an optical calibrating amplifier 427.1, at the output of the delay line 426.1, the input of which is itself connected to the input 403 of the circuit.

 Likewise, the second output of the optical switch 423.2 is connected to the input of a delay line 425.2, the output of which is connected to the output 404 of the circuit, and the second input of the optical switch 423.2 is connected, optionally by the by means of an optical calibrating amplifier 427.2, at the output of the delay line 426.2, the input of which is itself connected to the input 405 of the circuit.

 The delay lines 425.1, 425.2, 426.1 and 426.2 are adjustable optical delay lines and the optical calibrating amplifiers 427.1 and 427.2 are, for example, made up of an optoelectronic device functioning as a monostable with delayed triggering.

 The circuit described in FIG. 4B uses the same optical generator 421 as above, the output of which is directly connected to the first input of an optical switch 423, electrically controllable by the access link 406.

 The second output of the optical switch 423 is connected to the input of a delay line 425, the output of which is connected to the output 402 of the circuit, and the second input of the optical switch 423 is connected, possibly via an optical calibrating amplifier 427, at the output of the delay line 426, the input of which is connected to the input 403 of the circuit.

 The optical delay lines 425 and 426 are adjustable delay lines and the optical calibrator amplifier 427 is, for example, made up of an optoelectronic device functioning as a monostable with delayed triggering.

 FIG. 4C describes the generator of the multiplex CLM of the control commands of the time switches TSU.

 The connection of said generator to external means is as follows:. the optical accesses, input 410 and output 41l, are respectively connected to output 203 of the line explorer (fig. 2A or fig. 3) and to input 303 of the control signal distributor (fig. 2B or fig . 3), the electrical accesses 490 are connected to the CB link accessing the central control unit CPU control.

 The optical input 410, which receives the OLM multiplex, is connected, possibly via an optical amplifier 43, to the input 440 of a spectral demultiplexer 44, having f outputs, 441.1 to 441.f, connected each optically to an elementary generator, such as 45.f, optical control orders of a time switch TSU.

 Each of the f elementary generators 45.1 to 45.f is connected. optically by its input, such as 450.f, at one of the outputs, such as 441.f, of the spectral demultiplexer 44, and by its output, such as output 451.f, at an input, such as 460.f, of an optical coupler 46 having f inputs, 460.1 to 460.f, and an output 461, electrically by a multiple access, such as 453.f, to an access such as 49f of a group of f accesses 49.1 to 49.f of a supervisor 49, electrically by an access such as 452.f to one of the f outputs such as 481.f of a control frequency synchronization circuit 48.

 Said circuit 48 is itself optically connected by its optical input 480 to the second output of an optical coupler 47 having one input and two outputs, which coupler 47 is also optically connected by its input to the output 461 of the optical coupler 46 and by its first output at the input of an adjustable optical delay line 42, the output of which is connected to the output 411 of the generator of the CLM multiplex control commands for the time propagating switches.

 Said spectral demultiplexer 44 is of a type using an optical diffraction grating, well known to those skilled in the art, or of a type with tunable filters, one embodiment of which is described below.

 FIG. 4D describes an embodiment of a spectral demultiplexer, such as the circuit 44 of FIG. 4C.

 The optical input 440 of the demultiplexer is connected to a passive distributor 442 which spatially divides the optical wave reaching it into f output channels 443.1 to 443.f, which are each optically connected to a tunable filter such as 444.1, whose optical output is connected, possibly via an optical amplifier such as 446.1, to the optical output of the demultiplexer corresponding to the channel such as output 441.1.

 The tunable filters 444.1 to 444.f each consist of a semiconductor optical amplifier device, electrically controlled by the associated tuning circuit, such as 445.1 for the tunable filter 444.1, which allows to center the very narrow gain curve of l amplifier on the nominal filtering optical frequency.

 By tuning each of the filters 444.1 to 444.f on one of the f optical frequencies of a group F of optical frequencies, the whole of the passive distributor 442 and the tunable filters 444.1 to 444.f therefore behaves like a spectral demultiplexer for all spectral or time spectro multiplex, using the f frequencies, present on the input of the passive distributor 442.

 In the circuit of the invention, the group F of the optical tuning frequencies of the filters comprises at least the f2 frequencies of the group of the optical frequencies Fa2 previously defined.

 The number f of the outputs of the passive distributor 442 and of the filters 444 of FIG. 4D and of the generators 45.1 to 45.f of FIG. 4C is therefore at least equal to f2 and at most equal to fmax, maximum number of technically discriminable optical frequencies. in an optical spectrum.

 FIG. 4E describes in detail the circuit of an elementary generator for ordering control of the optical time switches with propagation TSU, such as the circuit 45.f of FIG. 4C.

 The optical input 450 is connected, optionally by means of an optical amplifier 1, to the input of an optical coupler 2 of the one input and two output type. The coupler 2 is connected by its first output to the first input of an optical switch 3, produced by an optical switch, of a type with two inputs and two electrically controllable outputs, or by an optically controllable optical connection point such as that of FIG. 5B, the control input of which is electrically connected to an access 4534, and by its second output to an optical delay line 5, the output of which is connected to the optical input of a detector 7.

 The output of the optical switch 3 is optically connected to the optical excitation input 4a of a tunable optical source 4 whose output 4b is optically connected to the output 451 of the elementary generator and the input 4c for controlling tuning is electrically connected to the output of a circuit 6 generating an electrical tuning signal from the optical source 4.

 The circuit 6 is connected by a first control input to the output of a counter 8 and by a second control input to the input 452 of the elementary generator.

 The counter 8 is electrically connected by a first input to the output of the detector 7, moreover connected to an access 4531, by a second input to an access 4532 and by a third input to an access 4533, the said accesses and the access 4534 connected to the control input of the switch 3 forming the multiple access such as 453.f of FIG. 4C connected to the supervisor 49.

 The optical source 4 can be tuned to any frequency Fbj of the fb optical frequencies of the second set Fb of optical frequencies defined during the description of FIG. 1B, fb being at most equal to the maximum number fmax of the technically discriminable optical frequencies in an optical spectrum , for example by the filtering means OF in FIG. 5B.

 FIG. 5A describes an embodiment of an optical time switch with propagation TSU, in which. 501 and 502 are respectively the input of the switch and the control input of the switch respectively optically connected to one of the outputs of the line explorer LS and to the same rank output of the order distributor CD as already described,. 51.1 to 51.k are the k outputs of the switch, each one being optically connected to an input of the optical diffuser OD, which is of a type with (m + (n.k)) inputs and s outputs.

 The time switch consists of - a first optical multiple-delay delay line, formed by the serial assembly of kl identical optical delay lines 54.1 to 54. (k-1) and k identical optical couplers 53.1 to 53 .k, each having an input and a first and a second output and directing on the second output a fraction of the optical energy arriving on the input and on the first output the rest of the optical energy, assembly such as input 501 of the switch is optically connected to the input of coupler 53.1, the first outputs of couplers 53.1 to 53. (k-1) are each connected to the input of one of the delay lines 54.1 to 54. (k- 1), the output of which is itself connected to the input of the coupler 53.i of next rank, the output of the last delay line 54. (k-1) being connected to the input of the last coupler 53. k whose first output is not used in the assembly, - a second line to reta rd with multiple sockets all optical, formed by the assembly in series of k identical optical couplers 56.1 to 56.k, of the same model as the coupler 53.1, and of kl delay lines 57.1 to 57. (k-1) identical and with the same characteristics as the delay line 54.1, assembly identical to that of the couplers and delay lines 53.i and 54.i described above, and in which the control input 502 is optically connected to the input coupler 56.1, - k optically controlled optical connection points (55.1 to 55.k), of a model described in FIG. 5B, each tuned to one of the optical frequencies of said second set Fb of optical frequencies, already defined in the description of FIG. 4E, in increasing or decreasing order of frequencies, each optically connected by the input to the second output of the coupler of the same rank of the first multiple tap delay line, by the output to the same rank exit from gr oupe of outputs 51.1 to 51.k, and by the control input to the second output of the coupler of the same rank of the second delay line with multiple taps.

FIG. 5B describes an embodiment of a connection point such as 55.1, implemented in the optical time switch with propagation TSU described above, consisting of - an optical amplifier OA, of semiconductor type, whose input and the optical output are optically connected respectively to the optical input SI and the optical output SO of the connection point, - of an optoelectronic detector D whose output is electrically connected to the control input of the optical amplifier OA and l optical input at the optical output of an OF optical filter, - of an OF optical filter, tunable on any frequency
Fbj of the Fb group of optical frequencies, the optical input of which is connected to the optical control input SC of the connection point.

 Any optical signal of frequency Fbj present on the input SC of the connection point crosses the filter OF and causes the operation of the detector D which delivers on its output an electrical signal of excitation of the optical amplifier OA, which consequently emits on its output SO, by amplifying it, the optical signal present on its input SI, and this as long as the optical signal of frequency Fbj lasts.

 FIGS. 5C and 5D each describe an embodiment of a time switch TSU having a single output 51.

 In addition to the elements constituting the assembly of FIG. 5A - the assembly of FIG. 5C implements an optical coupler 58 having k inputs, each connected to the output of one of the k connection points 55.1 to 55.k and a connected output at the output 51 of the switch TSU, - the assembly of FIG. 5D implements k optical couplers 58.1 to 58.k, each having a first, a second inputs and an output, which couplers are associated in series by connection of the output of the coupler of rank i to the first input of the coupler of rank i + 1, the first input of the coupler 58.1 not being connected and the output of the coupler 58.k being connected to the output 51 of the switch TSU, and are each connected by the second entry at the exit of the connection point 55.1 to 55.K of the same rank.

In case the spectro-temporal switching device
SSTSN implements time switches TSU such as those described in FIGS. 5C or 5D, the optical diffuser OD used in the device SSTSN is of a type having n + m inputs and s outputs.

 FIG. 6 schematically represents a communication terminal comprising - a reception circuit 61, of UR type, connected by its optical input 6100 to an optical fiber 601 for connection to the central SN, supporting the URL link on which an transmit multiplex is transmitted optically CEM configuration and URM communication reception multiplex, - a transmission circuit 62, of UE type, connected by its optical output 6200 to an optical fiber 602 for connection to the exchange supporting the UEL link on which the spectro-multiplex is transmitted time transmission of UEM communication, - an optical frequency reference means 63 having an input connected to an output 6104 of the reception circuit 61, a first output connected to an input 6103 of the reception circuit 61 and to an input 6203 of the communication circuit transmission 62, and a second output, - control means 64 having an input connected to an output 6105 of the reception circuit ion 61, a first output connected to an input 6102 of the reception circuit 61 and to an input 6202 of the transmission circuit 62, and a second output, - a synchronizable generator of clock signals 65 having an input connected to the output 6105 of the reception circuit 61, a first output connected to one between 6101 of the reception circuit 61 and to an input 6201 of the transmission circuit 62, and a second output.

 Said second outputs of said frequency reference means, control means and synchronizable generator of clock signals are optionally connected respectively to inputs 6103, 6102, 6101 of other reception circuits identical to circuit 61 constituting reception terminals, and / or to other inputs 6203, 6202, 6201 of other transmission circuits identical to the circuit 61 constituting transmission terminals.

 The reception circuit 61 comprises an optical receiver of configuration 611 tuned to one of the frequencies of the first group of optical frequencies Fal, receiving said multiplex CEM, an optical receiver of transmission 612, tunable to any of the optical frequencies of the second group of frequencies Fa2 , receiving said URM multiplex,. a frequency tuning means 613 of the optical transmission receiver 612,. a time synchronization means 614 of the information cells received,. a means of processing 615 of the information received.

 The optical configuration receiver 611 is connected by its optical input to the optical input 6100 of the reception circuit, by a first output, delivering an optical frequency reference signal to output 6104 and by a second output delivering the information received from the EMC multiplex at output 6105 of the receiving circuit.

The optical transmission receiver 612 is connected by an optical input to the optical input 6100 of the reception circuit, by a control input to an output of the frequency tuning means 613, and by an output delivering the information received from the multiplex.
URM at an input of the time synchronization means 614.

 The time synchronization means 614 is connected by an output to an input of the operating means 615.

 The frequency tuning means 613, time synchronization 614 and operating 615 are each connected by a control input to the input 6102 of the reception circuit 61, the time synchronization 614 and operating 615 means being also each connected by a synchronization input to the input 6101 of the reception circuit and the frequency tuning means 613 being itself connected by a frequency reference input to the input 6103 of the reception circuit.

 The transmission circuit 62 comprises an optical transmission transmitter 621, tunable to any of the optical frequencies of the second group of frequencies Fa2, a frequency tuning means 622 of the optical transmission transmitter, a time synchronization means 624 of the information cells to be sent,. a source means 625 of the information cells to be transmitted,. a time framing means 623.

 The optical transmission transmitter 621 is connected by an optical output to the optical output 6200 of the transmission circuit, by a control input to an output of the frequency tuning means 622, and by a signal input to an output of the time synchronization means 624 transmitting the information cells to be transmitted optically in the UEM multiplex.

 The time synchronization means 624 is connected by an input to an output of the source means 625 and by a synchronization input to a first output of the time alignment means 623, a second output of which is connected to a synchronization input of the tuning means frequency 622.

 The frequency tuning means 622, of time framing 623 and source 625 are each connected by a control input to the input 6202 of the transmission circuit 62, the time framing means 623 and source 625 are also each connected by a synchronization input at the input 6201 of the transmission circuit and the frequency tuning means 622 being itself connected by a frequency reference input to the input 6203 of the transmission circuit.

 The invention will be better understood from the descriptions below, given by way of example with reference to the various figures previously described,. first of all, the general operation of the spectro-space-time communication system of the invention in asynchronous time mode, which is the preferred functional mode of the invention,. secondly of the elementary operation of the spectro-spatio-temporal switching device SSTSN of the invention, in the case of the preferred embodiment.

* GENERAL OPERATION IN ATM MODE
To simplify the description of the general operation, - the arrangements and procedures commonly implemented in communication systems and therefore well known, used in the context of the invention, are not described in detail, - it is also assumed that the communication system of the invention is configured as follows. the CPU management means (Fig.l) is connected to the SSTSN device by a single link of each of the CEL, SEL, CRL, SRL types each carrying a CEM or SEM or CRM or SRM multiplex,. the terminals connected to the central SN are communication terminals, each comprising a transmission circuit UE transmitting on its transmission link UEL a spectro-time transmission multiplex transmission UEM by means of a tunable transmission optical transmitter, .. a reception circuit UR receiving by the reception link
URL CEM configuration multiplex and reception multiplex
URM, the UR reception circuit having an optical configuration receiver and an optical transmission receiver, and various other functional means including optical frequency tuning means of said optical transmitters and receivers, a synchronizable generator of clock signals, a time synchronization means and a time framing means of the transmission circuit, a time synchronization means of the reception circuit, and a control means supervising the various other functional means.

With reference to the preceding descriptions, it is recalled that - the CEM multiplex is a framed multiplex. each channel has a duration T, the frame groups together c channels, the period of the frame is equal to cT,. the first channel of each frame carries an identification code for the start of the frame, as is known in the temporal techniques,. the other channels are undifferentiated; they are used by the CPU to transmit the configuration messages to the terminals, - the CRM, SEM, SRM, UEM and URM multiplexes are organized into a series of undifferentiated time channels of duration T, - the undifferentiated time channels convey the information to transmit in the form of optical samples of duration T having temporally three parts of which only the second part carries the transmitted information, the first and third parts constituting switching windows avoiding having to perfectly frame the samples to be switched in the time system local of the SSTSN switching device, - the information to be transmitted, when it is digital, is formatted in cells which are each conveyed by an optical sample, - the optical samples are encoded on transmission at an optical frequency characteristic of their destination , with the exception of samples of broadcast multiplexes, such as the CEM multiplex, which are all optically encoded at a frequency characteristic of the configuration function, - the spectro-spatio-temporal switching device SSTSN. broadcasts on each of the reception links CRL, SRL and URL the CEM multiplex, switches the optical samples of the spectro-time transmission multiplexes SEM and UEM as a function of their carrier optical frequency which is characteristic of their destination, first temporally as a function of the availability of the channels of the destination multiplexes, then spatially by spectral multiplexing, broadcasting and selection by spectral filtering of the samples having the same carrier frequency,. sends the switched samples to the CRL reception links,
SRL or URL, in the channels of the CRM or SRM or URM reception time multiplexes - the CEM multiplex is broadcast on each reception link and received by the optical receiver for configuration of the reception circuits
CR, SR, UR, and the CRM, SRM or URM multiplexes transmitted on the links
CRL or SRL or URL are respectively received optically by the optical transmission receiver of the CR reception circuits or
SR or UR.

* Initial positioning
When the system is started, - the optical transmitter of the transmission circuit CE, the optical receiver for configuring the reception circuits CR, SR and UR are tuned to the optical frequency Fal.l and all the filters WF are adjusted for be transparent at this optical frequency, - the optical receiver for transmitting the CR reception circuits and
SR, and the WF filters connected to the CRL and SRL links are tuned on the frequencies Fa2.1 and Fa2.2 respectively.

 As soon as this situation is established, by the mechanisms described below, the clock signal generators of the terminals synchronize with the central office synchronization signal generator CKU,. the terminals have a frequency reference allowing the operation of the optical frequency tuning means of their optical transmission transmitters and receivers; the terminals can then be initialized by the control means CPU of the connection center.

* Synchronization, initialization of terminals.

The mechanisms of time synchronization, frequency tuning, and initialization in the system of the invention are as follows:
In the central SN, the synchronization signal generator CKU permanently transmits on the link H2 a period clock signal
T, delimiting the time channels, and a clock signal of period cT, delimiting the frames, which signals are used by the control means CPU to temporally format the multiplex
EMC. The CEM multiplex is emitted by the optical transmitter of the transmission circuit CE at the optical frequency Fal.1 on the CEL link and broadcast by the optical diffuser OD of the space-time spectro switching device SSTSN, the filters WF being transparent to the frequency Fal.l, on all the reception links, in particular the URL links, connected to the SSTSN device.

 The configuration receiver of each reception circuit, tuned to the optical frequency Fal.l, permanently receives the CEM multiplex.

 The start of frame identification code, routed by the first channel of the CEM multiplex, is used by clock signal generators of the terminals to synchronize with the pilot clock of the synchronization generator CKU of the central SN according to known methods in time systems.

Each local clock signal generator transmits, inter alia, to the means for synchronizing the transmission and reception circuits of the terminal a channel synchronization signal
The optical frequency Fal.l of the CEM multiplex is used by the frequency tuning means of the terminals as a reference frequency for tuning the optical transmitters and optical receivers for transmission of the transmission and reception circuits on the frequencies of the group Fa2 of the frequencies optical
When the system is put into service and each time a terminal is put into service, an initialization procedure for each terminal to be put into service is launched by the CPU control means :: - the CPU control means. assigns a frequency Fa2.i to the reception circuit UR of the terminal to be initialized,. positions, in SSTSN and via the FCC circuit for configuring the filters, the WF filter connected to the URL link of the terminal to be initialized on said frequency Fa2.i, transmits to the terminal in initialization, by the CEM multiplex, a message of initialization containing: the identity of the terminal, .. a code designating the initialization function, .. the references Fa2.1 and Fa2.2 of the optical frequencies carrying the CRM and SRM multiplexes, .. the reference of the optical frequency Fa2 .i temporarily assigned to the UR reception circuit of the terminal.

 On receipt of the initialization message, the control means of the terminal on initialization, grants the optical receiver for transmission of the reception circuit to the optical frequency Fa2.i and proceeds to the adjustment of the time framing means of the synchronization circuit of the circuit d 'program.

 The time alignment means phase the channel clock received from the local clock signal generators so that the time channels of the UEM multiplex, temporally positioned by the phase shift channel clock, appear at the input of the switching device SSTSN of the central office in phase with the channel clock of said SSTSN device, the temporal alignment of the channels however not having to be perfect due to the temporal organization of the optical samples as indicated previously. Before correction, the phase shift of the channels at the input of SSTSN is at least equal to the sum of the propagation times of the optical samples of the CEM multiplex on the URL link and of the UEM multiplex on the UEL link.

 The procedure for adjusting the framing means implements the following sequence of operations:. recording of a phase shift value in the time framing means of the synchronization circuit of the transmission circuit, omission of a framing code in the form of an optical sample encoded by the optical transmitter at the optical frequency Fa2. i, in a channel of the multiplex UEM synchronized with the phase-shifted clock originating from the framing means,. switching of the sample by the SSTSN device, and transmission in the first time-accessible channel of the URM multiplex of frequency Fa2.i, reception of the code switched by the reception circuit of the terminal, and control of the code received.

This sequence is repeated by increasing with each new sequence the registered value of the phase shift, until the code received, degraded by switching as long as the phase of the sample is bad at the input of the switching device.
SSTSN, be correct.

 The value of the phase shift which enabled the first correct transmission is recorded by the control means of the terminal and the procedure is continued by increasing the value of the phase shift until an incorrect transmission is obtained.

 This new phase shift value is recorded and the time alignment means is then adjusted by the terminal control means to the average value of the two recorded phase shift values.

 The terminal is therefore operational.

Once the adjustment has been made, the terminal sends a message via its UEM multiplex signaling that the framing has been carried out, carried by optical samples encoded at the frequency Fa2.1 designated as that of the CRM multiplex, which samples are, after switching in SSTSN transmitted on the CRM multiplex and received by
CPU.

On receipt of the "framing performed" code, the CPU sends a control message to the terminal, encoded at the frequency Fa2.i, transmitted in the SEM multiplex on the SEL link and then routed by
SSTSN in the URM multiplex of the terminal. The terminal responds to CPU by transmitting in its UEM multiplex a message, containing the control code received, optically encoded at the frequency Fa2.2, designated as that of the SRM multiplex, which message, switched by
SSTSN in the SRM multiplex on the SRL link, is received by CPU.

On receipt of this last message, and after checking the code received in return, CPU. sets at rest, via the FCC circuit for configuring the filters, the WF filter connected to the URL link serving the terminal, previously tuned to the frequency
Fa2.i,. commands, by a message encoded at the frequency Fal.1 and transmitted in the CEM multiplex, the standby of the terminal which, upon reception, positions the optical receiver for transmission of its reception circuit at rest, acknowledges reception to CPU by a message sent in the UEM multiplex at the designated frequency Fa2.1 of the CRM multiplex and goes into standby position, which consists of permanent listening to the CEM multiplex by means of the optical receiver for configuring its reception circuit, tuned to the frequency Fal.l,. and, upon receipt of the message from the terminal, releases the optical frequency
Fa2.i.

 * Activation and end of activity of a terminal.

A terminal in standby state, having to establish a communication with another terminal, transmits on its UEM multiplex, at the frequency Fa2.1 designated as the access frequency of the multiplex
CRM, a message to CPU, containing its identity and a request for allocation of reception frequency. On receipt of this message, the CPU assigns a frequency Fa2.j to the terminal, grants the WF filter giving access to the reception link URL of the terminal on the said allocated frequency and transmits to the terminal by message sent by the CEM multiplex the reference of the frequency Fa2.j allocated. This frequency Fa2.j is kept by the terminal throughout its period of activity.

At the end of the activity period, the terminal sends on its UEM multiplex at the frequency Fa2.1 designated as the access frequency of the CRM multiplex, an end of activity message to
CPU, containing its designation and the reference Fa2.j of the frequency to be released, and goes into standby. When the message is received, the CPU positions the WF filter connected to the terminal's URL link at rest and releases the frequency Fa2.j.

* Establishment of a communication.

 Any terminal positioned in activity having to establish a communication transmits to CPU, by the multiplex SRM, a call message containing its identity and that of the requested terminal.

If the requested terminal is not active, the CPU assigns this terminal a free receiving frequency Fa2.k, grants the WF filter connected to the URL link of this terminal on the frequency
Fa2.k, and transmits to the terminal requested by the CEM multiplex an activation message, containing the identity of the terminal requested, the order of activation and the reference of the frequency Fa2.k allocated. The requested terminal, having detected the message and having positioned itself, acknowledges receipt to the CPU by an optically encoded message at the frequency Fa2.1 which is routed by SSTSN in the CRM multiplex on the CRL link from which it is received by the CPU.

 CPU then transmits to the requesting terminal the reference of the frequency Fa2.k allocated to the called party, by a message encoded at the frequency Fa2.j of the requester, transmitted in the multiplex SEM on the link SEL and routed by SSTSN in the multiplex URM on the URL link of the applicant accessible by frequency Fa2.j.

If the requested terminal is active at the time of the call,
CPU transmits, as soon as received the request, by the SEM multiplex the reference of the frequency Fa2.k already allocated to the requested terminal.

 Upon receipt of the requested Fa2.k frequency reference, the requesting terminal can send to it a call message encoded at the frequency Fa2.k containing the designation of its own reception frequency Fa2.j.

 If the requested terminal does not respond, the requesting terminal renews the procedure.

 * Multiple communications.

 The same terminal can, at a given time, be in communication with a multiplicity of different terminals.

 Consider for example a terminal j, to which the access frequency Fa2.j has been allocated, in communication with a terminal v, whose access frequency is Fa2.v, and another terminal w, whose access frequency is Fa2.w.

The information cells, relating to communications (j / v) and (j / w), are statistically multiplexed at the input of the transmission circuit of terminal j and transmitted in the multiplex UEM.j on the link UEL.j by the optical transmitter of the transmission circuit in the form of optical samples respectively encoded at the frequency
Fa2.v or Fa2.w, characteristic of their destination.

In the switching device SSTSN, the optical samples encoded at the frequency Fa2.v and the optical samples encoded at the frequency Fa2.w, originating from the multiplex UEM.j, are first shifted in time by the same switch TSU. j to be placed each in the first free channel of their destination multiplex, the URM.v multiplex for the first and the multiplex
URM.w for the latter; the shifting of the first is carried out under the control of the elementary command order generator 45.v, the shifting of the second under the control of the elementary command order generator 45.w from the group of elementary command generators 45.1 to 45. f of Figure 4C.

At their exit from the switch TSUj, after diffusion by the diffuser OD, these samples are spectrally selected by the filters WF.v and WF.w and emitted, the first in the multiplex
URM.v on the link URL.v which transmits them to terminal v, the second in the multiplex URM.w on the link URL.w which transmits them to terminal w. In these terminals, the samples are received by the optical transmission receiver of the terminal reception circuit tuned to their optical carrier frequency.

 The information cells relating to the communication (v / d), statistically multiplexed with other different destination cells, are transmitted by the transmission circuit of the terminal v in its multiplex UEM.v on its link UEL.v under the form of optical samples, encoded at the frequency Fa2.j of access to the terminal j.

 Similarly, at the same time, the information cells relating to the communication (w / d), statistically multiplexed with other cells of different destination, are transmitted by the transmission circuit of the terminal w in its multiplex UEM. w on its UEL.w link in the form of optical samples, encoded at the frequency Fa2.j of access to the terminal j.

In the switching device SSTSN, the optical samples encoded at the frequency Fa2.j, coming from the multiplexes
UEM.v and UEM.w,. are successively shifted in time by the switches
TSU.v and TSU.w, under the control of the same elementary command command generator 45. j of the group of elementary command generators 45.1 to 45.f of FIG. 4C, to be placed each, in the destination multiplex URM .j, in the first channel deemed free at the time of the elaboration of the control order for their time switching, then at their output from the TSU switches, after broadcasting by the broadcaster OD, are spectrally selected by the filter WF.j and transmitted in the URM.j multiplex on the URL.j link which transmits them
at terminal j.

 In this terminal, they are successively received by the optical transmission receiver of the reception circuit tuned to the frequency Fa2.j.

 It goes without saying that the cells transmitted by the various terminals each include a code identifying the communication concerned to allow their exploitation at the output of the reception circuit, which is well known in the technique of asynchronous transfer.

* Taxation
The charging of communications is in charge of the central unit's CPU control means.

 To perform this function, the CPU has the references of the communicating terminals, obtained during the establishment of the communications, and the data of a measurement of the flow of optical samples carried out by the circuit 49 of FIG. 4C, by means of counters of flow activated by a counting signal defined in the description below of the detailed operation of the switching device SSTSN, which data include the source reference and the destination reference, which are respectively deducted by circuit 49 from the time reference of the counting signal from the OLM multiplex, and from the reference of the generator 45.i having delivered the counting signal,. the output status of a flow meter assigned to monitoring communication defined by the two previous references.

DETAILED OPERATION OF THE SSTSN SWITCHING DEVICE.

 The detailed operation of the SSTSN switching device is described below.

A time framing of the channels being carried out on transmission by the framing means, the adjustment of which has been described, the contemporary channels of the various spectro-time transmission multiplexes (UEM, SEM) are present on the inputs I1 to In of SSTSN temporally. in phase with each other and with respect to a local clock of the central office CKU synchronization signal generator
SN (fig. 1A).

 They each carry an optical sample carried by a frequency Fa2.i characteristic of its destination.

 They are therefore in phase with the inputs 210.1 to 210.n of the explorer of the input lines (FIG. 3), directly connected to the inputs such as In.

 Ti and T being respectively the time reference and the duration of a channel of the transmission multiplexes, n being the number of inputs of the line explorer, at the start of each channel instant Ti, the calibrated optical pulse generator 421 of the control circuit of FIG. 4B, excited by an optical clock pulse received from the generator CKU by the link H1 on the input 401, formats an optical pulse called the exploration pulse of duration t = T / n + 2, which is sent on the output 402 temporally offset by a time t by the delay line 425.

This exploration pulse, received on the input 201 of the circuit of FIG. 3B propagates in said third control device, temporally offset by a duration t by each of the delay lines 231.1 to 231.n, by successively commanding the optical switches 224.1 to 224.n of said optical selector, which each successively transmit on output 203, by formatting it at time t, an optical signal called "address signal".

This address signal is split by each switch such as 224.1 in the signal present on its input, which present signal consists of the part of energy taken by the associated coupler, such 226.1, from the optical sample of the transmit multiplex present on the optical selector input, such as 210.1, for the moment
Ti, part of energy which is possibly amplified and calibrated in level by the amplifier such as 225.1.

 The n successive address signals transmitted on the output 203 during the instant Ti constitute the useful part of a frame of the OLM multiplex described in the description of FIG. 1B, which frame comprises n + 2 channels, the first and last of which are used for framing time of the multiplex.

 The rank r of an address signal in the n address signals of the same frame is characteristic of the source of the optical sample of the transmission multiplex from which the address signal is derived.

 The optical carrier frequency Fa2i of each of these n address signals is characteristic of the destination of the optical sample of the transmission multiplex from which the address signal is derived.

The n address signals of each frame of the OLM multiplex, passing through the input 410 and the amplifier 43 of the circuit of FIG. 4C, are successively analyzed by the spectral demultiplexer 44 which switches them as a function of their carrier optical frequency Fa2i to a elementary generators of control orders such as 45.f, which are each responsible for managing the channels of one of the reception and reception multiplexes CRM, SRM and
URM, and the development of switch control orders
TSU for all the optical samples to be routed on these reception transmission multiplexes whatever the origin.

 In the elementary generator of control orders, such as 45.f, the embodiment of which is shown in FIG. 4E, the optical address signal from the spectral demultiplexer is applied to the input 450,. amplified by the optical amplifier 1, temporally calibrated by the optical switch 3 excited by a clock signal of period t, delivered by the supervisor 49 of FIG. 4C on the link 4534, clock signal whose form factor is such that it makes it possible to inhibit the transient states between the successive optical address signals, and, part of its energy having been taken up by the coupler 2 and emitted in the delay line 5, is present on the input 4a of the optical source 4.

 The optical source 4, tunable to any frequency of the fb optical frequencies of the second set Fb of optical frequencies, is positioned by means of the tuner signal generator 6 to transmit on the frequency Fbj designated by the information present at the output of the counter 8.

 The designated frequency Fbj is characteristic on the one hand of the real time delay to be introduced into the propagation of the optical sample to be switched, from which the optical address signal coming from the input 4a is derived, to allow its insertion in the first channel free from the destination receiving multiplex, and on the other hand from the connection point to be excited in the TSU switch (Fig. 5A, 5B or 5C) processing the optical sample.

 Receiving the optical signal address on its input 4a, the optical source 4 of FIG. 4E transmits on its output 4b, for the whole duration of this address signal, that is to say for a duration at most equal to t, an optical signal for controlling the switch. TSU concerned at the optical frequency Fbj.

 At the end of this emission, the detector 7, excited by the part of energy having passed through the delay line 5, emits an optical pulse which causes an increment of value +1 of the information at the output of the counter 8. The new output from the counter 8 positions, via the tuning generator 6, the source 4 on the new frequency Fbj + l to be transmitted so that the next optical sample to be switched is temporally delayed so as to be routed by the new first available channel of the destination multiplex.

 The output pulse of the detector 7 is moreover emitted by the link 4531 to the circuit 49 of FIG. 4C which exploits it on the one hand as part of a process of permanent monitoring of the bit rates of the different terminals, known as the procedure "sentinel" and on the other hand as a counting signal for the incrementation of debit counters whose states are periodically transmitted to the CPU control means which uses them for the charging of communications.

 In the event of saturation of the recipient reception transmission links, or if the connection possibilities of the TSU switches, characterized by the overflow of the counter 8, are exceeded, a signal is transmitted by the link 4533 to the circuit 49 which temporarily blocks the operation of the elementary generator. by positioning the optical switch 3 in the non-conducting position via the link 4534, this to avoid overwriting optical samples already being switched in the TSU switches,. the possible increments of value +1 of the counter 8 by an inhibition order issued on the link 4533.

At the start of the instant Ti + 1 corresponding to a new frame of the OLM multiplex, a pulse emitted by the circuit 49 of FIG. 4C on the input 4532 of the counter 8 of each of the elementary generators of control orders such as 45.f decrements these counters 8 by a value -1 so as to reset them to the value of the real delay to be achieved for the next connections ordered in the TSU switches, except in the case where the counter is positioned at its minimum value, in which case it remains positioned on this value:. if at the end of an instant Ti, a counter 8 displays a value
Fbj + l different from the minimum value FbO, at the start of the instant
Ti + 1, the counter is positioned at the value Fbj,. if it displays the minimum value FbO, it remains positioned on this value FbO.

 During the initialization operations of the switching device SSTSN, the circuit 49 positions the counters 8 in the initial state (such as FbO), by the link 4533 whose other functions have been described above.

 The new output information from the counter 8 positions, via the tuning generator 6, the source 4 on the new frequency Fbj + 1 to be transmitted so that the next optical sample to be switched is temporally delayed so as to be routed by the new first available channel of the destination multiplex.

 At each Ti, the successive control orders issued by the various elementary generators such as 45.f in FIG. 4C, are routed by the coupler 46 and the adjustable delay line 42, on the output 411 where they follow one another and constitute the part active of a frame of the CLM control order multiplex, which comprises, like that of the OLM multiplex from which it comes n + 2 channels, the first and last of which are used for time framing of the multiplex, and the n others carry the possible orders of ordered.

 The adjustable delay line 42 is adjusted so that the channels of the CLM multiplex are offset with respect to the channels of the same rank of the OLM multiplex with a duration t = T / n + 2.

 If d is the duration of the operations described above for developing a control order, measured between the appearance of the exploration pulse on the second output of the coupler 221.1 of said "third control device" in FIG. 3B and the appearance at the input of the delay line 42 of the control order, coming from the address signal created by the switch 224.1 controlled by the output of this coupler 221.1, the delay line will be adjusted to the delay value td.

 In the case where the assembly of FIG. 3A is used in place of the assembly of FIG. 3B, the delay line 42 is adjusted to the delay value 0, the delay lines such as 231.1 and 331.1 of FIG. 3A respectively value delay d and td.

 In the event that the duration d defined above is greater than the duration t, the arrangement described in FIGS. 3A or 3B is not implemented. It is replaced by an assembly associating the circuits described in FIGS. 2A and 2B, which are controlled by the control circuit described in FIG. 4A, in place of the circuit 4B mentioned above. In this case, the delay line 424 of Figure 4A has a delay value equal to d and the delay line 42 of Figure 4C has a zero delay value.

 The multiplex CLM is transmitted from the output 411 of the generator of the control orders of FIG. 4C on the input 303 of the distribution line of FIG. 3B in which it propagates.

 Successively controlled by the signal appearing at the output of the couplers 321.1 to 321.n on passage of the exploration pulse propagating in the said third control device as already described above, the switches 324.1 to 324.n switch to the 'hysteresis amplifier, such as 325.1, connected to their second output, the control order carried by the contemporary CLM multiplex channel of their control pulse.

The hysteresis amplifier, such as 325.1, receiving a command order of duration close to t and carried by the optical frequency
Fbj, displays on its output an optical signal of the same frequency Fbj and with a duration equal to T, which signal is then delayed by the delay line such as 326.1 with a duration equal to (n + lr) t, r being the rank of the delay line concerned in the group of n delay lines 326.1 to 326.n.

 By this mechanism, the control orders carried out during the channel instant Ti of the transmission multiplexes exit in phase at Ti + 1, each on one of the outputs 311.1 to 311.n of the distribution line.

 The optical samples coming from the various spectro-temporal emission multiplexes (UEM, SEM), arriving in phase at Ti on the inputs 210.1 to 210.n from the explorer of the input lines and delayed by a time T in their path in the delay lines such as 227.1, therefore exit in phase at Ti + 1, each on one of the outputs 211.1 to 211.n from the explorer of the input lines, and therefore simultaneously with the control orders which are to cause their switching in TSU switches.

 Each optical sample and the associated control order are therefore in phase, respectively on the input 501 and the control input 502 of the time switch TSUr connected to the outputs 211.r of the circuit LS and 311.r of the circuit CD.

 In this switch TSUr, like the switch TSU represented in FIG. 5, they propagate in phase, respectively in the first and second multiple-tap delay lines of the time switch TSU, delayed by a time T by each of the elementary delay lines crossings, such as 54.1 and 57.1.

 In the first delay line, each coupler such as 53.1 takes a share of the energy of the optical sample which passes through it and therefore presents a similar signal at the level of the connection point such as 55.1 which is connected to it. energy close to the incident optical sample and in particular of the same optical frequency Fa2i.

 In the second delay line, each coupler such 56.1 takes a part of the energy of the control order which passes through it and therefore presents on the control input of the connection point such 55.1 which is connected to it a signal which has the same optical frequency Fbj and the same duration as the incident command order.

 When at Tj, the control signal passes through the coupler 56.j, the signal picked up causes the connection point 55.j to operate on the control frequency Fbj according to the mechanism already described above (fig. 5A). The signal from the optical sample present at this time at the input of the connection point is therefore amplified and transferred to the output of the connection point where it reproduces the incident optical sample and constitutes the switched optical sample.

 The switched optical sample is presented by output 51.j (fig.5A) or output 51, via coupler 58 (fig.5C) or from the series of couplers 58.j to 58.k (fig .5D), at the entrance to the OD optical diffuser (fig. 1B).

 At a given instant Tj, a multiplicity of samples, carried by different optical frequencies, propagating in the same switch TSU, can be switched simultaneously and can therefore occur simultaneously on or at the output of the switch.

 But at a given instant Tj, by virtue of the mechanism for developing control orders for the switches TSU described above, only one sample and only one carried by a frequency can be switched, in the set of switches TSU Fa2i optics given. All the optical samples arriving at an instant Tj at the inputs of the diffuser are therefore spectrally different and therefore spectrally multiplexable without risk of disturbing the information transmitted by their medium.

 At each instant Tj, the optical diffuser OD spectrally multiplexes all the switched optical samples coming from the outputs of the switches TSU, each carried by an optical frequency different from the group Fa2 of the optical frequencies, and the optical signals coming from the ports Ic and Ib, respectively carried each by one of the optical frequencies either of the group Fal of the optical frequencies or of the group Fa3 according to the type of access, and diffuses on each of its outputs a spectral multiplex formed of all the samples and optical signals presented on its inputs, the energy of each incident signal or sample being distributed equally among all of the outputs.

The optical amplifier filters WF, such as WF1, each connected to an output of the diffuser, transparent for the optical frequencies of the groups Fal, possibly tuned to one or more of the frequencies Fa3, and each tuned to a particular frequency of the group of the frequencies Fa2, or a frequency band of the frequency group Fa2 as already explained in the description of FIG. 1B and the description of the general operation, select from the incident spectral multiplex and amplify the only samples and optical signals carried by the same frequencies as their frequencies agreement, and transmit on their output and therefore on the output of the SSTSN device to which their output is optically connected, such as 01 for the WF1 filter, a spectral multiplex containing the only spectrally selected signals and samples, whose sequence in time forms the CEM, BCM and URM or CRM or SRM time multiplexes, each carried by one of the optical frequencies of the group Fal, the group Fa3 and the group Fa2 respectively of the optical frequencies of the set
Fa optical transmission frequencies.

 The system of the invention, by virtue of the fact that it transmits and switches the communication signals only by optical means, avoids the use of electro-optical and opto-electric conversion devices between the optical transmission means and the switching means existing in currently known asynchronous time systems.

 It thus allows an economy of means, a simplification of the structure of the communication networks and consequently a simplification of the operation and an improvement of the overall reliability.

 The optical communication system of the invention, due to the fact that it operates in ATM asynchronous time mode, makes it possible to reduce the means of transmission and reception of multiservice terminals to a single transmitter and a single communication receiver without affecting the capacity. of the terminal to carry a multiplicity of contemporary communications, different as to their destinations, which is not the case with currently known optical frequency systems.

 The optical communication system of the invention, because it dynamically manages the frequencies by assigning them to the only terminals in operation, makes it possible to connect a number of terminals greater than the number of the discriminable frequencies in the spectrum, the number of terminals connectable being a function of traffic characteristics and not a function of only the number of discriminable frequencies.

 The optical communication system of the invention, because it transports the information in the form of optical samples coded in optical frequency according to the destination, which optical frequencies of the samples are sufficient to develop, by optical means, the orders of switching without any other operation on the optical samples than taking an optical energy, - saves resources in the control devices, in which it is not necessary to use the demodulation, analysis and for modulating the transmitted information existing in currently known ATM systems, - simplifies, compared with what is known of these systems, the functioning of the switching means, - and improves the security of transmission of the signals since no operation is made on the information transmitted.

 The optical communication system of the invention, because it transports information in the form of optical samples which, in passing through the transmission and switching means, undergo no other treatment than optical amplifications, propagation in delay lines, spectral multiplexing and spectral filtering, which treatments are known as not altering the signals, - is therefore insensitive to the nature of the information transmitted, which can be either digital information or an analog signal, - can therefore process the two types of information simultaneously and without particular discrimination, - and therefore widen the field of potential applications of multiservice systems.

 The optical communication system of the invention, by the single use of optical technology for the production of switching means, and by the simplicity of the means and mechanisms used, the entire switching device, including its operating control under the sole control of a clock signal and optical signals directly from the samples to be switched, offers an original and economical solution to the complex problems of ATM switching.

 The system of the invention thus marks real progress with respect to the prior art for equipping broadband multiservice communication networks by the facilities which it allows in the organization of said networks, by the economy of means it allows and the security it provides in the transmission of information signals.

 Of course, the invention is in no way limited to the embodiments described and shown which have been given only as examples; in particular, without departing from the scope of the invention, it is possible to modify certain provisions or replace certain means by equivalent means.

Claims (24)

1 - Asynchronous temporal optical communication system having a communication center (SN), q terminal reception circuits (UR1 to URq) connected by at most q optical terminal reception links (URL1 to URLq) to the communication center, p terminal transmission circuits (UE1 to UEp) each connected by an optical terminal transmission link (UEL1 to UELp) to the central office, said terminal transmission and terminal reception circuits being distributed in x remote communication terminals each having a transmission circuit and a reception circuit, y transmission terminals each having a transmission circuit, z reception terminals each having a reception circuit, characterized in that each terminal reception circuit comprises at at least one configuration optical receiver tuned to an optical frequency (Fali) of a first group of optical frequencies (Fal) of a first set of optical frequencies (Fa), a recept eur transmission optics tunable to any optical frequency of a second group of optical frequencies (Fa2) of said first set of optical frequencies (Fa), an optical frequency tuning means of said optical transmission receiver,. and a means for time synchronization of the information received, that each terminal transmission circuit comprises an optical transmission transmitter tunable to any optical frequency of said second group of optical frequencies (Fa2), an optical frequency tuning means of said optical transmitter and means for time synchronization and time framing of the information to be transmitted, which the communication center (SN) comprises. an optical spectro-spatio-temporal switching device (SSTSN),. a control means (CPU), and a synchronization signal generator (CKU), that the switching device (SSTSN) is optically connected to the optical transmission links and to the optical reception links,  that the control means (CPU) comprises .. at least one configuration transmission circuit (CE) having an optical configuration transmitter tuned to an optical frequency (Fali) of said first group of optical frequencies (Fal), .. to at least one signaling transmission circuit (SE) having a transmission optical transmitter tunable to any optical frequency of said second group of optical frequencies (Fa2), .. at least one configuration reception circuit (CR) and at least one signaling reception circuit (SR), each having at least one configuration optical receiver tuned to an optical frequency (Fali) of said first group of optical frequencies (Fal), and a transmission optical receiver tunable to any optical frequency of said second group of optical frequencies (Fa2), that said control means (CPU) is connected to the switching device (SSTSN) by .. a control link (CB), .. at least one link configuration configuration optical ison (CEL), each one being optically connected to the configuration configuration optical transmitter of a configuration transmission circuit (CE), .. at least one configuration reception optical link (CRL), each being optically connected to the optical configuration and transmission receivers of a configuration reception circuit (CR), .. at least one optical signaling transmission link (SEL), each being optically connected to the optical transmitter d a signaling circuit (SE), and at least one optical signaling reception link (SRL), each one being optically connected to the optical configuration and transmission receivers of a signaling reception circuit (SR), and that the synchronization signal generator (CKU) is connected by a first synchronization link (H1) to the switching device (SSTSN) and by a second synchronization link (H2) to the control means (CPU). 2 - Optical communication system according to claim l, characterized in that each configuration transmission circuit (CE) transmits on its configuration transmission link (CEL) a configuration transmission time multiplex (CEM) broadcast by the switching device (SSTSN) on each of the optical configuration reception (CRL), signaling reception (SRL) and terminal reception (URL) links, which each configuration sending time multiplex is carried by an optical frequency of the first optical frequency group (Fal) of the first set of optical frequencies (Fa), that an optical frequency of the second group of optical frequencies (Fa2) of said first set of optical frequencies (Fa) is dynamically assigned by said control means (CPU) to each active transmission receiver of the configuration reception (CR), signaling reception (SR) and reception reception circuits rminal (UR), each terminal transmission circuit (UE) and signaling transmission circuit (SE) communicating with any transmission receiver in activity by transmitting a message in the form of a series of optical samples encoded at the optical frequency allocated to said active transmission receiver, said optical samples being transmitted by each terminal transmission circuit (UE) in a spectro-time communication transmission multiplex (UEM) on its terminal transmission link (UEL) ), and by each signaling transmission circuit (SE) in a spectro-time signaling transmission multiplex (SEM) on its signaling transmission link (SEL), than each spectro-time transmission multiplex (UEM; SEM) comprises an untwisted succession of time channels of the same duration (T) each carrying an optical sample of optical frequency characteristic of the destination transmission receiver, that each optical sample is, by the switching device (SSTSN) and according to its carrier optical frequency, optically switched in time and then optically switched to one of said optical reception links in which it is routed by a first free channel of a reception time multiplex of said reception link, and that each reception time multiplex (CRM ; SRM; URM) comprises a succession of undifferentiated time channels of the same duration (T) each carrying an optical sample, the optical samples of the same reception time multiplex all having the same optical frequency. 3 - optical communication system according to claim 1, characterized in that it also comprises at least one broadcasting server (BS), each server being optically connected to the switching device (SSTSN) by an optical broadcasting link (BL ) connected in the server to at least one optical broadcast transmitter, that the terminal reception circuits (UR) have at least one optical broadcast receiver, said optical broadcast receivers of a terminal reception circuit being optically connected to the terminal reception link (URL) connecting said terminal to the switching device (SSTSN), that said optical broadcast transmitters and optical broadcast receivers are tunable to any optical frequency of a third group of optical frequencies (Fa3) of said first set of optical frequencies (Fa),  and that at least one optical frequency of said third group of optical frequencies (Fa3) is allocated to each broadcast transmitter, each broadcast transmitter transmitting on said allocated frequency a message broadcast by the switching device (SSTSN) on each of the transmission links. reception of terminal (URL), each broadcast receiver receiving said message by agreeing on said frequency allocated to the broadcast transmitter having sent it. 4 - Optical communication system according to claim 1, characterized in that the spectro-temporal switching device (SSTSN) comprises an optical scanning circuit (LS) optically connected to the optical terminal transmission links (UEL1 to UELp ), and to the optical signaling transmission links (SEL), said optical transmission links (UEL, SEL) each carrying a spectro-time transmission multiplex consisting of channels each carrying an optical information sample,. an optical distributor (CD) of control orders,. a control circuit (CC) connected on the one hand optically to the optical scanning circuit (LS) by a first optical link carrying a destination spectro-time multiplex (OLM) comprising as many channels as there are links d transmission to the optical distributor (CD) by a second optical link carrying a spectro-temporal multiplex (CLM) of control orders having a number of channels equal to that of said destination multiplex, each channel of the control order multiplex being in time phase with a channel of the same rank of said destination multiplex and routing a control order, and to the synchronization generator (CKU) by the first synchronization link (H1), and on the other hand to the control means (CPU ) via the control link (CB),. n optical time switches (TSU1 to TSUn), with controlled propagation, each being optically connected to an output of the optical scanning circuit (LS) and to an output of the optical distributor (CD) of control orders,. an optical diffuser (OD) optically connected at the output of the time switches (TSU) and to the optical configuration transmission links (CEL), and having outputs each optically connected at the input of an optical filter (WF1 to WFs),. s optical filters (WF1 to WFs) each optically connected as an output to one of the terminal reception optical links (URL1 to URLq), signaling reception (SRL), configuration reception (CRL), a filter configuration circuit (FCC) connected at the input to the control link (CB) and at the output to a control input for each optical filter (WF1 to WFs). 5 - optical communication system according to claim 4, characterized in that the destination multiplex (OLM) is formed by sampling the channels occurring at the same instant at the input of the exploration circuit (LS) on each of the links d transmission (UEL and SEL), which each channel of the control order multiplex (CLM) having the same rank as a transmission link carries a control order consisting of an optical signal at an optical frequency (Fbi) of a second set of optical frequencies (Fb) each optical frequency of which is characteristic of a propagation delay in real time which must undergo, in a time switch (TSU), the message conveyed by the channel of said transmission link, said optical frequency (Fbi) being determined by the control circuit (CC), and that the optical distributor (CD) delivers to each time switch (TSU) corresponding to the rank of a channel of the multiplex of control orders (CL M) the control order conveyed by said channel of the control order multiplex. 6 - Optical communication system according to claim 4, characterized in that the optical diffuser (OD) is also optically connected at the input to broadcast servers (BS) by optical broadcast links (BL). 7 - optical communication system according to claim 4, characterized in that the optical exploration circuit (LS) comprises an optical selector and a first control device,  that the optical selector is constituted by. n optical switches (224.1 to 224.n) in series, each having first and second inputs, one output and one control input,. n optical couplers (226.1 to 226.n) each having an input, a first and a second output, and n identical optical delay lines (227.1 to 227.n), that the optical switches are connected in series by connection of the output from one to the first input of the next, the output of a last optical switch being optically connected to the control circuit (CC) by said first optical link, that the second input of each optical switch (224.i) is connected at the second output of the optical coupler of the same rank (226.i), that each optical coupler (226.i) has its input connected to an input of the optical scanning circuit (LS), its first output connected to the input of an optical delay line (227.i), itself optically connected at output to a time switch (TSU.i) with controlled propagation, that the first control device is constituted by n optical control couplers (221.1 to 221. n) each having an entry, a p first and a second outputs, and nl optical delay control lines (222.1 to 222.n-1), that the first output of each optical control coupler (221.i), with the exception of the last, is connected in input of an optical control delay line (222.i), itself connected as an output to the input of the next optical control coupler, as the input of a first optical control coupler and the first output of a last optical control coupler are optically connected to the control circuit (CC), and that the second output of each optical control coupler (221.i) is optically connected to the control input of an optical switch of the same rank (224.i) of the optical selector. 8 - optical communication system according to claim 7, characterized in that the second input of each optical switch (224.i) is connected by an optical amplifier (225.i) to the second output of the optical coupler of the same rank ( 226.i), and that the second output of each optical control coupler (221.i) is optically connected by an optical amplifier (223.i) to the control input of an optical switch of the same rank (224. i) the optical selector. 9 - optical communication system according to claim 4, characterized in that the optical distributor (CD) of control orders comprises a second control device and a distribution line, that the second control device is constituted by n couplers control optics (321.1 to 321.n) and nl control optical delay lines (322.1 to 322.n-1), each control optical coupler having an input, a first and a second output, as the first output of each optical control coupler (321.i), with the exception of the last, is connected at the input of an optical control delay line (322.i) itself connected at the output to the input of the following optical coupler, that the input of a first optical control coupler and the first output of a last optical control coupler are connected to the control circuit (CC), that the distribution line is constituted by n optical switches (324.1 to 324.n ) each having a e input, first and second outputs and a control input, n optical hysteresis amplifiers (325.1 to 325.n) and n optical delay lines (326.1 to 326.n) each having a different length characteristic of rank i of the delay line, that the optical switches are connected in series by connecting the first output of one to the input of the next, the input of a first optical switch being optically connected to the control circuit (CC) by said second optical link, that the second output of each optical switch (324.i) is connected via an optical hysteresis amplifier (325.i) at the input of an optical delay line (326.i) itself optically connected as an output to a time propagation propagation switch (TSU.i), and that the second output of each optical control coupler (321.i) of the second control device is connected to the control input of the switch optical of the same rank (324.i) of the distribution line. 10 - Optical communication system according to claim 9, characterized in that the second output of each optical control coupler (321.i) of the second control device is connected by an optical amplifier (323.i) to the input control switch of the same rank optical switch (324.i) of the distribution line. 11 - Optical communication system according to claim 4, characterized in that the optical scanning circuit (LS) and the optical distributor (CD) of control orders have a third common control device, than the optical circuit d exploration consists of an optical selector having. n optical selection switches (224.1 to 224.n) in series, each having first and second inputs, one output and one control input,. n optical selection couplers (226.1 to 226.n) each having  an entry, a first and a second exit,. and n identical optical selection delay lines (227.1 to 227.n), that the optical selection switches are put in series by connecting the output of one to the first input of the next, the output of a last switch selection optic being optically connected to the control circuit (CC) by said first optical link, that the second input of each optical selection switch (224.i) is connected to the second output of the optical selection coupler of the same rank (226 .i), that each optical selection coupler (226.i) has its input connected to an input of the optical scanning circuit (LS), its first output connected to the input of an optical selection delay line (227. i) itself connected at the output to an optical time switch (TSU.i) with controlled propagation, which the distribution line is made up of. n optical distribution switches (324.1 to 324.n) each having an input, a first and a second output and a control input,. n optical hysteresis amplifiers (325.1 to 325.n) and n optical distribution delay lines (326.1 to 326.n) each having a different length characteristic of the rank i of the distribution delay line, than optical distribution switches are connected in series by connecting the first output of one to the input of the next, the input of a first optical distribution switch being optically connected to the control circuit (CC) by said second optical link, that the second output of each optical distribution switch (324.i) is connected via an optical hysteresis amplifier (325.i) at the input of an optical distribution delay line (326.i) itself connected optically as an output to a time propagation propagation switch (TSU.i), which the third control device consists of. n optical selection control couplers (221.1 to 221.n),. n optical distribution control couplers (321.1 to 321.n),. n first optical delay lines (231.1 to 231.n). and nl second optical delay lines (331.1 to 331.n-1), each optical selection control coupler and each optical distribution control coupler having an input, a first and a second output, as the first output of a optical selection control coupler (221.i) is connected to one of the first optical delay lines (231.i) itself connected to the input of an optical distribution control coupler (321.i), the first output is connected by one of the second optical delay lines (331.i) to the input of a next optical selection control coupler, with the exception of the last optical distribution control coupler whose first output is connected optically to the control circuit (CC), the input of a first optical selection control coupler being connected optically to the control circuit, that the second output of each optical selection control coupler (221.i) is connected to the control input of an optical selection switch of the same rank (224.i), and that the second output of each optical distribution control coupler (321.i) is connected to the control input of an optical switch of distribution (324.i) of the same rank. 12 - optical communication system according to claim 4, characterized in that the optical scanning circuit (LS) and the optical distributor (CD) of control orders have a fourth common control device, than the optical circuit d exploration consists of an optical selector having nn optical selection switches (224.1 to 224.n) in series, each having a first and a second input, an output and a control input,. n optical selection couplers (226.1 to 226.n) each having an input, a first and a second output,. and n identical optical selection delay lines (227.1 to 227.n), that the optical selection switches are put in series by connecting the output of one to the first input of the next, the output of a last switch selection optic being optically connected to the control circuit (CC) by said first optical link, that the second input of each optical selection switch (224.i) is connected to the second output of the optical selection coupler of the same rank (226 .i), that each optical selection coupler (226.i) has its input optically connected to an input of the optical scanning circuit (LS), its first output connected to the input of an optical selection delay line (227 .i), itself optically connected as an output to an optical time switch (TSU.i) with controlled propagation, which the distribution line consists of. n optical distribution switches (324.1 to 324.n) each having an input, a first and a second output and a control input,. n optical hysteresis amplifiers (325.1 to 325.n) and n optical distribution delay lines (326.1 to 326.n) each having a different length characteristic of rank i of the optical distribution delay line, than the optical switches of distribution are connected in series by connecting the first output of one to the input of the next, the input of a first optical distribution switch being optically connected to the control circuit (CC) by said second optical link, that the second output of each optical distribution switch (324.i) is connected via an optical hysteresis amplifier (325.i) at the input of an optical distribution delay line (326.i) itself optically connected at the output to a time switch with controlled propagation (TSU.i), which the fourth control device consists of. n optical selection control couplers (221.1 to 221.n),. n optical distribution control couplers (321.1 to 321.n),. n optical control delay lines (231.1 to 231.n), each optical selection control coupler and each optical distribution control coupler having an input, a first and a second output, than the first output of an optical coupler selection control line (221.i) is connected by an optical control delay line (231.i) to the input of an optical distribution control coupler (321.i), the first output of which is connected to the input of a following optical selection control coupler, with the exception of the last optical distribution control coupler, the first output of which is optically connected to the control circuit (CC), the input of a first optical coupler of the selection control being optically connected to the control circuit, that the second output of each optical selection control coupler (221.i) is connected to the control input of an optical selection switch of the same rank (224. i), and that e the second output of each optical distribution control coupler (321.i) is connected to the control input of an optical distribution switch (324.i) of the same rank. 13- Optical communication system according to one of claims 11 and 12, characterized in that the second input of each optical selection switch (224.i) is connected to the second output of the optical selection coupler of the same rank ( 226.i) by an optical amplifier (225.i), that the second output of each optical selection control coupler (221.i) is connected by an optical amplifier (223.i) to the control input an optical selection switch of the same rank (224.i), and that the second output of each optical distribution control coupler (321.i) is connected by an optical amplifier (323.i) to the control input d '' an optical distribution switch (324.i) of the same rank. 14 - optical communication system according to claim 5, characterized in that the control circuit (CC) comprises a control processing circuit connected on the one hand optically to the exploration circuit (LS), to the distributor (CD ) and to the synchronization generator (CKU) by the first synchronization link (H1) and on the other hand to the control means (CPU) by the control link (CB), and a generator of control orders connected by a optically goes to the exploration circuit (LS) by the first link and to the distributor (CD) by the second link and on the other hand to the control means (CPU) by the control link (CB). 15 - optical communication system according to claim 14, characterized in that the control processing circuit comprises an optical generator (421) of calibrated pulse, optically connected at the input to the first synchronization link (H1) and at output to an input of an optical coupler (422) having a first output connected to a first input of a first optical switch (423.1) and a second output connected by a first optical delay line (424) to a first input d a second optical switch (423.2), that the first and second optical switches each have a control input connected to said control link (CB), that the first optical switch (423.1) has a second input connected optically by a second line delay (426.1) to the scanning circuit (LS), and an output optically connected by a third optical delay line (425.1) to the scanning circuit (LS), and the second optical switch (423.2) has a second input connected by a fourth optical delay line (426.2) to the distributor (CD) and an output connected by a fifth optical delay line (425.2) to the distributor (CD). 16 - Optical communication system according to claim 14, characterized in that the control processing circuit comprises an optical generator (421) of calibrated pulse, optically connected at the input to the first synchronization link (H1) and at output to a first input of an optical switch (423) having a second input connected by an optical delay line (426) to the scanning circuit (LS), an output optically connected by another optical delay line (425) to the exploration circuit (LS) and a control input connected to said control link (CB). 17 - optical communication system according to claim 14, characterized in that the generator of control orders comprises  a spectral demultiplexer (44) having an input optically connected to the exploration circuit (LS) by the first link and f outputs,. f elementary generators of control orders (45.1 to 45.f),. a supervisor (49) having f outputs and an input connected to the control link (CB),. a synchronization circuit (48) having an input and f outputs,. and an optical coupler (46) having f inputs and an output connected to an input of an optical output coupler (47) having a first output optically connected by a delay line (42) to the second link and a second output connected optically at the input of the synchronization circuit (48), and that each elementary generator (45.i) has a first input optically connected to an output of the spectral demultiplexer (44), a second input connected to an output of the supervisor (49 ), a third input connected to an output of the synchronization circuit (48) and an output connected to an input of the optical coupler (46), each elementary generator (45.i) issuing optical control orders of the time switches with controlled propagation (TSU), each control order being transmitted on the second link at a frequency (FBi) of said second set of optical frequencies (Fb), said frequency being characteristic of a time propagation in the time switch (TSU) receiving the order. 18 - optical communication system according to claim 17, characterized in that each elementary generator (45.i) comprises an optical coupler (2) having an input connected to the first input (450) of the elementary generator, a first and a second outputs, an optical switch (3) having an input connected to the first output of the coupler, an optical source (4) having an excitation input (4a) connected to the output of the optical switch and an output (4b) which constitutes the output (451.i) of the elementary generator, an optical detector (7) having an input connected by an optical delay line (5) to the second output of the optical coupler (2), a counter (8) having an output connected to a first input of a tuning signal generator circuit (6) itself connected as an output to a control input constituting the third input (452) of the elementary generator, said counter (8) having a first input connected on the one hand at the output of the optical detector (7) and on the other hand at a first access (4531), a second input connected to a second access (4532) and a third input connected to a third access (4533), said optical switch (3) having a control input connected to a fourth access (4534), said first, second, third and fourth access constituting the second input of the elementary generator, connected to the supervisor (49). 19 - Optical communication system according to claim 17, characterized in that the spectral demultiplexer (44) comprises a passive distributor (42), f tunable optical filters (444.i) each associated with a tuning circuit (445. i), and that the passive distributor has an input optically connected to the exploration circuit (LS) and f outputs each optically connected to a tunable optical filter itself optically connected at output to an elementary generator (45.i). 20 - Optical communication system according to claim 4, characterized in that each optical propagation time switch (TSU) with controlled propagation consists of first and second optical delay lines with multiple taps, identical, and k optically controlled optical connection points (55.1 to 55.k), each having first and second inputs and one output, that each multiple tap optical delay line is made up of k optical couplers (53.1 to 53.k; 56.1 to 56.k) identical, in series with kl optical delay lines (54.1 to 54. (k-1); 57.1 to 57. (k-1)) identical, each optical coupler having a first output connected by a line to optical delay at an input of a next optical coupler, except for a last optical coupler whose first output is unused, that a first optical coupler (53.1) of the first multiple tap delay line has its input optically connected to a output of the scanning circuit (LS) from which it receives the channels of a transmission link optically connected to the input of said scanning circuit, which a first optical coupler (56.1) of the second multiple tap delay line has its input optically connected to an output of the distributor (CD) from which it receives, for each channel of a transmission link, a control order consisting of an optical signal at an optical frequency (Fbi) from a second set of frequencies optical (Fb), said optical frequency being characteristic of a propagation time in said first delay line, that each optical coupler of the first multiple tap delay line has a second output connected to the first input of a point of optical connection, that each optical coupler of the second multiple tap delay line has a second output connected to the second input of an optical connection point, said second input being an optical connection point control input, each optical connection point being controlled by a control command carried by an optical signal at an optical frequency corresponding to an operating frequency of said connection point, and that the output of each optical connection constitutes an optical output of the time switch (TSU). 21 - Optical communication system according to claim 20, characterized in that each output of an optical connection point is optically connected to an input of said optical diffuser (OD). 22 - Optical communication system according to claim 20, characterized in that the outputs of the k optical connection points are connected at the input of an optical coupler (58) with k inputs and one output, and that said output is optically connected at an input of said optical diffuser (OD). 23 - optical communication system according to claim 20, characterized in that each time switch (TSU) also comprises k optical output couplers (58.1 to 58.k) each having a first and a second input and an output, as said optical output couplers are connected in series by connecting the output of one to the second input of the next, except for a last optical output coupler whose output is optically connected to an input of said optical diffuser (OD) and a first optical output coupler whose second input is unused, and that each optical output coupler has its first input connected to the output of an optical connection point. 24 - Optical communication system according to claim 20, characterized in that each optical connection point (55.i) consists of an optical amplifier (OA) having an input, an output and a control input,. an optoelectronic detector (D) having an output connected to said control input, and an input,. and a tunable optical filter (OF) having an optical input which constitutes the second input of the optical connection point, and an output connected to the input of said optoelectronic detector (D),  and that the input and output of the optical amplifier (OA) constitute the first optical input and output of the optical connection point.