WO2014195431A1

WO2014195431A1 - Systems for continuous bidirectional communication by atmospheric link

Info

Publication number: WO2014195431A1
Application number: PCT/EP2014/061757
Authority: WO
Inventors: Pascal Joffre
Original assignee: Reseau Ferre De France; Micro Module
Priority date: 2013-06-05
Filing date: 2014-06-05
Publication date: 2014-12-11
Also published as: FR3006835B1; FR3006835A1; EP3005586A1

Abstract

The present invention relates to a system for continuous bidirectional communication by atmospheric link between an infrastructure, and at least one mobile entity in motion with respect to the infrastructure, the optical transponders (3, 4) being each equipped with an auto-pointing system making it possible to ensure communication between the fixed transponders and the onboard transponders, the system being characterized in that each fixed optical transponder is coupled to at least one optical fibre disposed along the infrastructure by way of an optical insertion/extraction device, a central control unit being adapted for commanding the optical insertion/extraction devices and/or the laser emission/reception devices as a function of the position of the mobile entity, in such a way that one of the onboard transponders (4) communicates with a fixed transponder (3) while the other onboard transponder (4) performs an operation of pointing with another fixed transponder (3).

Description

BIDIRECTIONAL COMMUNICATION SYSTEMS CONTINUE

BY ATMOSPHERIC LINK

FIELD OF THE INVENTION

The present invention relates to two-way continuous communication systems by optical link at several wavelengths between an infrastructure and a mobile moving relative to this infrastructure. The invention relates in particular to the communication systems between a train and a railway infrastructure. It can also concern the case of a motor vehicle driving on a road infrastructure or a boat moving on a waterway.

STATE OF THE ART

Atmospheric optical link communication systems are known between a mobile network associated with a mobile in motion and a fixed network associated with an infrastructure on which the mobile is traveling, in which fixed transponders are arranged along the infrastructure, while mobiles are equipped with embedded transponders. Each optical transponder is equipped with a self-pointing device on the optical transponders opposite which makes it possible to establish a communication between a fixed transponder and an onboard transponder.

When moving the mobile relative to the infrastructure, the communication must be transferred from one fixed station to another (this mechanism is called "handover"). State-of-the-art systems include handover mechanisms at the OSI 2 (link layer), OSI 3 (network layer) and higher layers. In such systems, an access router associated with the fixed network transfers the data stream from one fixed station to another depending on the position of the mobile. Such a system involves physically breaking the communication between the mobile device and the infrastructure during each transfer from a fixed transponder to a other. The duration of the "handover" is all the higher as the on-board transponder needs a significant amount of time to detect the active fixed transponder and perform the pointing operation with it. The breaking of the communication during each transfer from one fixed transponder to another considerably degrades the quality of the communication, especially as the signaling messages necessary for the establishment of the communication between a fixed transponder and an onboard transponder are often lost.

Some state-of-the-art systems use buffers to accumulate packets to be transmitted during the establishment phase of the connection and transmit them when a connection is established. Such systems have many disadvantages. They are particularly vulnerable to packet loss due to a buffer overflow, which occurs when the physical link is not restored while the buffer has reached its capacity. maximum storage. In addition, a buffer overflow often causes process blockage and communication failure. An increase in the capacity of the buffer is still possible but increases the response time (latency) of the network, which is detrimental to the quality of communication especially applications of "real-time" type (telephony, videoconferencing, remote office...).

There is also a significant risk of packet loss when packets follow a route that has not yet been updated by the access router, and do not arrive at the new access point but at the old access point. In such cases, the packets must be returned by the sender resulting in a limitation of the rate.

SUMMARY OF THE INVENTION The invention proposes a communication system in which the handover mechanism is managed at the OSI 1 (physical layer), OSI 2 (link layer) and higher layers. Since the handover is managed at the level of the lower layers and therefore upstream of the routing of the packets, the update of the routing of the packets according to the changes of access point to the network is done with anticipation and not a posteriori without anticipation. The invention significantly reduces the risk of packet loss in the handover mechanism located in the lowest hardware layer of the network, very upstream in the routing of packets. Thus, in the nominal operating mode, there is no data loss by buffer overflow, the network latency time is minimum and the maximum rate.

The invention overcomes at least one of the aforementioned drawbacks by proposing a continuous bidirectional communication system by atmospheric connection between an infrastructure equipped with fixed optical transponders connected to laser transmission / reception devices, and at least one moving mobile by compared to the infrastructure and equipped with at least two onboard optical transponders connected to laser transmission / reception devices, the optical transponders are each equipped with a self-pointing system adapted to perform a pointing operation on a optical transponders facing each other, to ensure communication between the fixed transponders and the onboard transponders, the system being characterized in that each fixed optical transponder is coupled to at least one optical fiber arranged along the infrastructure by the intermediate of an optical insertion / extraction device, a comma unit central station being adapted to control the optical insertion / extraction devices and / or the laser transmission / reception devices according to the position of the mobile, so that one of the on-board transponders communicates with a fixed transponder while the other onboard transponder performs a pointing operation with another fixed transponder. The invention is advantageously completed by the following characteristics, taken individually or in any of their technically possible combinations:

the optical insertion / extraction devices are optical switches, and in that two consecutive optical transponders are coupled to different optical fibers, the central control unit being adapted to switch the optical switches one after the other in the direction of movement of the mobile, so that one of the onboard transponders communicates with a fixed transponder while the other transponder board performs the pointing operation with another fixed transponder; the optical insertion / extraction devices are selective at a wavelength band of their own and fixed, the laser transmission / reception devices being wavelength-adaptable, a central control unit being adapted to vary the transmission / reception wavelength of the laser transmission / reception devices as a function of the position of the mobile, so that the transmission / reception wavelengths of the laser transmission / reception devices belong to the wavelength band of the optical insertion / extraction multiplexer of at least one of the fixed optical transponders on which the onboard optical transponders are pointed;

the wavelength band injected / extracted by the optical insertion / extraction devices is reconfigurable, the central control unit being adapted to vary the wavelength band injected / extracted from each insertion / extraction multiplexer according to the position of the mobile, so that the wavelengths of the laser transmission / reception devices belong to the wavelength band injected / extracted from the optical insertion / extraction multiplexer of at least a fixed optical transponders on which the onboard optical transponders are pointed; each optical fiber is connected to a wavelength selective optical router whose outputs are connected to a fixed network switch, the wavelength selective optical router and / or the fixed network switch being controlled by the control unit central so that the data flow from the onboard laser transmit / receive devices results in at least one set of two network ports of the network switch, the two network ports operating in aggregation within the network switch; the communication system comprises a plurality of fixed network switches distributed along the infrastructure, one of the network ports of each fixed network switch being connected to a network port of the two adjacent fixed network switches so as to ensure continuity of communication between the switches fixed network; one or more wavelengths of the laser transmission / reception devices is dedicated to the transmission of the control signals between the central control unit and the transmission / reception device, and / or the optical insertion / extraction devices ; the optical transponders are equipped with a micropositioning system of the end of the optical fiber to establish a fiber-to-fiber optical link self-pointing in free space between the transponders; the optical transponders are equipped with an optical-microwave converter and a sectoral antenna to establish a free-air microwave link between the optical transponders; the optical insertion / extraction devices consist of a main optical fiber and a secondary optical fiber contiguous to the main optical fiber on a junction zone, one or more Bragg gratings being inscribed in the junction zone of the fibers. primary and secondary optics such that certain wavelengths are extracted from the main optical fiber to the secondary optical fiber or inserted from the secondary optical fiber to the main optical fiber; the main and secondary optical fibers are integral with a piezoelectric bimetallic strip so that the application of an electrical voltage across the piezoelectric bimetallic strip results in a deformation of the Bragg grating or networks inscribed in the zone of junction of primary and secondary optical fibers;

the wavelength-adaptive laser transmission / reception devices comprise a tunable wavelength laser emission / reception device and an electro-optical external modulator. The invention also proposes a method of continuous bidirectional communication by atmospheric link between an infrastructure equipped with fixed optical transponders connected to laser transmission / reception devices, and at least one moving mobile with respect to the infrastructure and equipped with at least two onboard optical transponders connected to laser transmission / reception devices, the optical transponders are each equipped with a self-pointing system adapted to perform a pointing operation on one of the optical transponders opposite, so as to providing communication between the fixed transponders and the onboard transponders, each fixed optical transponder being coupled to at least one optical fiber arranged along the infrastructure via an optical insertion / extraction device, the method being characterized in what optical insertion / extraction devices and / or devices fs emission / reception laser are controlled according to the position of the mobile, so that one of the onboard transponders communicates with a fixed transponder while the other transponder board performs a pointing operation with another fixed transponder.

DESCRIPTION OF THE FIGURES

Other objectives, characteristics and advantages will come out of the detailed description which follows with reference to the drawings given by way of non-limiting illustration, among which:

- Figure 1 shows a communication system according to the invention;

- Figure 1a shows an onboard concentrator;

- Figure 2 shows a rolling stock equipped with this communication system in a railway infrastructure;

FIG. 3 represents a hybrid optical / electrical cable;

FIG. 3bis shows a connection means between the optical / electrical hybrid cable and an optical transponder 3.

FIG. 4 diagrammatically represents the principle of operation of the optical transponders;

FIG. 4bis represents the micro-positioner of the optical transponder;

FIG. 4ter is a view in the plane A identified in FIG. 4a;

FIG. 5 represents an optical transponder with radio link;

FIG. 6 represents a hybrid optical / herztian hybrid transponder;

FIG. 7 represents an example of an optical transponder adapted to the railway application;

- Figure 7a is a view along the axis "A" identified in Figure 7;

FIG. 8 represents another example of an optical transponder;

- Figure 8bis is a view along the axis A identified in Figure 8;

- Figures 9, 10 and 1 1 show three system variants according to the invention;

FIGS. 9a, 10a and 11a show three variants of devices optical insertion / extraction;

FIG. 12 represents an optical amplifier according to the invention;

FIG. 13 represents an exemplary network architecture according to the invention;

FIG. 14 represents an example of power supply of the communication system;

FIG. 15 represents a wavelength tunable transmission / reception device according to an embodiment of the invention;

FIG. 16 represents an electrically reconfigurable wavelength optoelectronic router according to one embodiment of the invention;

FIG. 17 represents a Bragg grating optical insertion / extraction device on non-reconfigurable optical fiber according to one embodiment of the invention;

FIG. 17a illustrates optical injection / extraction by Bragg grating;

FIG. 18 represents a Bragg grating optical insertion / extraction device on a reconfigurable optical fiber according to one embodiment of the invention;

FIG. 18 bis illustrates the optical insertion / extraction with a reconfigurable Bragg grating.

DETAILED DESCRIPTION OF THE INVENTION

In the rest of the text, transponder is an automatic device that receives, amplifies and retransmits signals on different frequencies (or wavelengths). An optical transponder is a transponder whose output and / or input is connected to an optical fiber. An optical terminal designates a fixed optical transponder and its connection means to the infrastructure.

FIG. 1 shows a continuous bidirectional communication system 1 by atmospheric electromagnetic link between an infrastructure B and at least one mobile A moving relative to the infrastructure B. One or more optical fibers 5 are arranged along the infrastructure B on which the mobile A circulates. The optical fibers 5 are connected to a concentrator fixed 30 itself connected to a fixed wide-area network 300. The concentrator 30 consists of wavelength selective optical routers 7 (of the reconfigurable type "WSS" for "Wavelength Selective Switch" or non-reconfigurable "WDM" for "Wavelength Device Multiplexer "), connected to a controllable optoelectronic switch 9. This optoelectronic switch 9 has network ports 91 equipped with laser transmit / receive devices 95. A central control unit 8 is electrically connected to the optoelectronic switch 9 and to the optical routers 7. Fixed optical transponders 3 arranged along the infrastructure B are connected to the optical fibers 5 via an optical insertion / extraction device 6.

Each mobile A is equipped with at least two embedded optical transponders 4, connected to an on-board concentrator 40, itself connected to a network 400 internal to the mobile A. With reference to FIG. 1a, the on-board concentrator 40 is similar to the fixed concentrator 30; it consists of wavelength selective optical routers 7 connected to a controllable optoelectronic switch 9 through ports 91 equipped with laser emission / reception devices 95. An on-board control unit 48 is electrically connected to the optoelectronic switch 9 and optical routers 7 to enable dynamic control. The on-board control units 48 of the different mobiles are slaved to the central control unit 8.

With reference to FIG. 2, the infrastructure B is for example a rail infrastructure and the mobile A has rolling stock running on this infrastructure B. The optical transponders 3 are fixed for example on catenary poles at a height of about 4 m. The fixed optical transponders 3 are arranged for example every 100 to 400m along the railway infrastructure A. The embedded optical transponders 4 are fixed in the upper structures of the rolling stock A preferably at the front and at the rear by example at a height of about 4m. For this purpose and with reference to FIG. 4, the optical insertion / extraction device 6 comprises a first electrical connection connected to a control unit of the transponder 310 and a second connection connected to an optical fiber 314 whose free end extends inside the transponders 3 or 4 to form a free-space optical beam 305 via a micro-positioner 304, an optical coupler 312 and a mirror 302. The optical fiber 314 typically has a core diameter of 9μηη and a sheath diameter of 125μηη.

Optical transponders 3 and 4 communicate by atmospheric optical link.

The optical transponders 3 and 4 are advantageously each equipped with a self-pointing system for ensuring communication between the fixed transponders 3 and the onboard transponders 4 on each mobile. Each optical transponder 3 and 4 is advantageously equipped with a self-pointing system 31 making it possible to establish continuous communication with a transponder opposite by slaving the orientation of the optical transponder in the direction of one of the optical transponders facing each other. , ie, each onboard optical transponder 4 is equipped with a self-pointing system 31 controlling the orientation thereof in the direction of one of the fixed optical transponders 3 and each fixed optical transponder 3 is equipped with a self-pointing system 31 controlling the orientation of the latter in the direction of one of the onboard transponders 4.

The self-pointing system 31 is a system adapted to automatically detect the presence of optical transponders opposite the optical transponder that it equips and automatically align it with one of the optical transponders opposite, preferably the optical transponder opposite. the closest. For this purpose, the self-pointing system 31 aligns the end of the optical fiber 314 with the spot of the incident beam coming from the optical transponders opposite and adjusts the direction of the optical beam coming from the fiber in order to direct the same. here on the optical transponder opposite. The self-pointing system 31 fitted to each of the transponders 3 and 4 is adapted to align the optical beam 305 issuing from the optical fiber 314 of one transponder on the end of the optical fiber 314 of the other transponder and vice versa. in such a way as to ensure a bidirectional and continuous atmospheric optical connection between the two systems A and B. The self-pointing system 31 comprises a wide emission angular sector optical source 318, a wide reception angular sector optical photodetector 319, a plane mirror 302 rotating about a vertical axis 303 actuated by a piezo-rotary motor 301. This motor makes it possible to adjust the angle of sight of the beam 305 in the horizontal plane over a wide range (5 ° to 360 °) . Another piezo-rotary motor 31 1 makes it possible to adjust the angle of sight of this same beam in the vertical plane over a smaller range.

The wide angle sector optical source 318 is a set of several source modules with large angular aperture (several degrees each) whose axes are oriented perpendicularly to the vertical axis 303 and forming a regular radial distribution. These source modules comprise, for example, a light-emitting diode or a semiconductor laser emitting in the Infrared 1 to 2μηη band, preferably with a wavelength greater than 1, 4μηη to ensure the eye safety of people moving in the vicinity.

The optical photodetector wide angular sector 319 is a set of several photodetector modules with large angular aperture (several degrees each) whose axes are oriented perpendicularly to the vertical axis 303 and forming a regular radial distribution. These photo-detector modules consist for example of 4-quadrant photodiodes of large area or of a matrix of pixels of the semiconductor type III-V, for example GalnAs.

The optical beam from the source 318 and received by the photodetector 319 of the optical transponder opposite allows optical transponders 3 and 4 to locate each other over a wide angular field (from 5 ° to 360 ° as required). Thus, even if the mirrors 302 of the optical transponders 3 and 4 do not exactly point to one another, it is possible to know the angular difference "large field" to return to the self-pointing situation "small field "using the motors 301 and 31 1 within each optical transponder 3 and 4.

With reference to FIG. 4a, in order to more finely adjust the score between the transponders 3 and 4, the auto-pointing system 31 also comprises, around the free end of the optical fiber 314, at least three satellite optical fibers. 315 and a micro-positioning device 304. The satellite optical fibers 315 form a bead of optical fibers whose end is positioned with high precision, typically to a tenth of a micron using the micropositioning device 304.

The optical fibers 315 are of multimode type with 100μηη core and 125μηη sheath to collect the maximum luminous flux, for example gathered by means of a mixer 317 and each connected to a photo-detector 308. The set of photos detector 308 gives information on the small field angular deviation which allows the transponder control unit 310 to control the micro-positioner 304 so as to finely adjust the pointing of the beam 305 in each transponder 3 and 4. The transponder Fixed optics 3 can further control local peripherals such as cameras, sensors or actuators placed in its immediate vicinity and connected to a network 200.

With reference to FIG. 4ter, the end of the optical fiber bead 314 and 315 is finely positioned in the X direction or in the Y direction by means of the micro-positioning device 304 which can be piezoelectric, electrostatic or electromagnetic, according to the state of the art.

With reference to FIGS. 7 and 7a and 8 and 8a, the piezoelectric micro-positioning device 304 is, for example, a bimetallic piezoelectric actuator consisting of two piezoelectric blades welded to one another. Fibers optics 314 and 315 are then secured to this piezoelectric actuator bimetallic. When a voltage is applied by the transponder control unit 310 to the bimetallic piezoelectric actuator 304 in an X or Y direction, the latter deforms causing the optical fiber 314 to tilt in one direction or in the other according to the polarity of the electric voltage. A control unit 310 controls the voltage applied to the bimetallic piezoelectric actuator 304 so as to control the inclination of the optical fiber 314 and thus adjust the position of the end of the optical fiber with respect to the axis of the optical fiber. mirror 302b. The control unit 310 controls the electrical voltage applied to the bimetallic piezoelectric actuator 304 so as, on the one hand, to align the end of the optical fiber 314 with the spot of the incident beam resulting from the optical transponders 3 or 4 opposite and, secondly adjust the direction of the optical beam from the fiber after reflection on the rotating mirror 302b in the vertical plane to direct it to one of the optical transponders 3 or 4 opposite.

FIG. 7a shows several spots 313a and 313b of an optical beam coming from the optical fiber 314 of a transponder 4 on the train A on the photodetector of a fixed transponder 3 positioned along the railway infrastructure B. When the two transponders 3 and 4 in communication are not pointing, the two spots 313b are not centered on the end of the optical fiber 314. When the two transponders 3 and 4 are in a situation of pointing and in communication, the spot 313a is centered on the end of the optical fiber 314. The measurement of the signal of the optical fibers 315 thus enables the piezoelectric actuator 304 and the control unit 310 to enslave in real time the position of the end of the optical fiber 314 on the spot 313a. FIG. 8bis shows several spots 313a and 313b of an optical beam coming from the optical fiber 314 of a fixed optical transponder 3 positioned along the railway infrastructure on the photodetector of an optical transponder 4 embarked on the train A. According to an alternative embodiment and with reference to FIG. 5, the optical transponders 3 and 4 communicate with each other by radio link. atmospheric. For this purpose, they are equipped with an optical-microwave converter 323 connected to the optical injection / extraction device 6 and a sectoral antenna 322 electrically connected to the optical-microwave converter 323. The optical transponders 3 and 4 then comprise a radome 321 for communication using a radio-relay system formed by the sectoral antenna 322. The optical-microwave converter 323 is controlled by the control unit of the transponder 310. The antenna 322 is not actuated around the axis 303 because it is assumed that its angular aperture is sufficiently wide or is of electronic scanning type to communicate with the antenna 322 facing. In an alternative embodiment, the antenna 322 is oriented with a motor in a manner similar to the movement of the optical mirror 302. In this case, the detection of the angular difference can be made by the antenna 322 itself or by the optical transceiver assembly 318 and 319. The optical-microwave converters 323 use high frequencies, for example, greater than 10GHz to limit the size of the antennas 322, form radio-relay systems 324 rather directional and allow high-speed communications. The different channels conveyed by the optical fiber 5 in the form of a wavelength to the optical transponder 3 are advantageously transposed into a microwave channel in the radio link to be restored through the transponder 4 in the mobile A.

The optical-microwave converter 323 can advantageously integrate at least one wavelength tunable laser emission / reception device 95 (FIG. 15 below) controlled by the control unit 310 of the optical transponder 3 in order to be compatible with the reconfigurable optical injection / extraction devices 6.

According to another variant embodiment and with reference to FIG. 6, the transponders 3 and 4 are optical / wireless hybrid and can communicate with each other by means of both an atmospheric radio link and an optical link. atmospheric. For this purpose, the optical / microwave hybrid transponders comprise in the lower part the elements of the atmospheric optical link optical transponders described above and in the upper part the elements of the transponders with atmospheric hertzian link described above. The optical injection / extraction device 6 as well as the optical fiber 5 can then be split to form two independent communication chains.

With reference to FIGS. 7 and 8, each mirror 302 and its coupler 312 is replaced by one and the same parabolic mirror out of 90 ° axis 302b placed on a support of revolution rotating around the vertical axis 303 and actuated by a piezo-rotary motor 301. This parabolic mirror 302b is adapted to focus an optical beam 305 through the cylindrical window 306 on the input face of the optical fiber 314 and conversely direct an optical beam from this optical fiber 314 to one of the transponders optics 3 or 4 opposite. A control unit 310 controls the piezo-rotary motor 301 which drives the parabolic mirror 302b so as, on the one hand, to align the latter with the incident beam coming from the optical transponders 3 or 4 opposite, and secondly to adjust the direction of the beam coming from the optical fiber after reflection on the mirror 302b in the horizontal plane in order to direct it on one of the optical transponders 3 or 4 opposite.

With reference to FIG. 8, the optical transponders 4 embarked on the train A are identical to the fixed transponders 3 with the difference that their height is reduced. Indeed, optical transponders 4 are integrated into the roof of rolling stock A at the front and rear (height of about 4m relative to the rail). The power consumption constraints are lower since the rolling stock A generally has a significant source of electrical energy on board.

With reference to FIG. 1, the wavelength selective optical injection / extraction devices 6 operate in such a way that the data flow coming from the on-board concentrator 40 leads to at least one set of two network ports 91 of the switch network 9, the two network ports 91 operating in aggregation within the fixed concentrator 30, so as to provide a continuous bidirectional data flow between the network 300 of the infrastructure B and the network 400 of the mobile A. One or more wavelengths flowing in the optical fiber 5 is advantageously dedicated to the transmission of control signals between the central control unit 8 which plays the role of master and the onboard control unit (s) 48 which acts as the slave. This is the case for example for the dynamic allocation of the wavelengths allocated to each mobile.

Thus, each mobile A has a subset of wavelengths included in the bandwidth of the transmitting / receiving devices 95 according to its bandwidth requirements (aggregation of channels to increase the bit rate) or in safety (redundancy links and physical isolation of different subnets).

The central control unit 8 is adapted to control the optical insertion / extraction devices 6a, 6c and / or the laser transmission / reception devices 95, so that one of the onboard transponders 4 communicates with a transponder fixed 3 while the other onboard transponder 4 performs the pointing operation with another fixed transponder 3.

According to a first embodiment, and with reference to FIGS. 9 and 9bis, the optical insertion / extraction devices 6 are optical switches 6a "1 to 2" according to the state of the art, adapted to switch between two positions. on the one hand a first position in which all the wavelengths flowing in the optical fiber 5 are fed back into the optical fiber 5 and a second position in which all the wavelengths flowing in the optical fiber 5 are fed to the optical transponder 3 via the optical fiber 314. The switch 6a is switched via an electrical link with the control unit 310 of the associated optical transponder 3. In this embodiment, the system 1 comprises at least two optical fibers 5. Two consecutive optical transponders 3 are coupled to different optical fibers 5.

The central control unit 8 is adapted to switch via the control unit 310 associated with the optical switches 6a one after the other in the direction of movement of the mobile A, so that one of the transponders 4 embedded on the mobile A communicates with one of the fixed transponders 3 coupled to the first fiber 5 while the other transponder 4 on board the mobile A restores the pointing and communication with another fixed transponders 3 coupled to the second fiber So that at least one of the two links is always active.

In this first embodiment, there can be only one mobile A per infrastructure section corresponding to the same group of optical fibers 5 against all channels of wavelength are available for communication between the infrastructure B and mobile A. For example, there are 72 (144) C-band DWDM optical channels at 100 GHz (50 GHz) spacing or 36 (72) "computer" sub-networks using a wavelength pair . In the case of the "railway" application, this configuration is adapted to the signaling in fixed cantons (1 to 3km) which imposes the presence of a single train by canton.

According to a second embodiment, and with reference to FIGS. 10 and 10a, the optical insertion / extraction devices 6b are each selective to a wavelength band of their own and not reconfigurable. The laser emission / reception devices 95 are adaptable in wavelength. The central control unit 8 is adapted to vary the emission / reception wavelength of the laser transmission / reception devices 95 as a function of the position of the mobile A, so that the wavelengths of transmission / reception of the laser transmission / reception devices 95 belong to the wavelength band of the optical insertion / extraction multiplexer 6b of at least one of the optical transponders 3 of the infrastructure B on which the transponders optics 4 of the mobile A are pointed. In this second embodiment, the optical routers 7 are reconfigurable and adapted according to the optical insertion / extraction devices 6b used to connect the network 400 of the mobile A to the same group of network ports 91 aggregated in the optoelectronic switch 9 of FIG. so that at least one of the two links is active.

In this second embodiment, and with reference to FIG. 10a, the optical insertion / extraction devices 6 are non-reconfigurable "OADMs" multiplexers 6b ("Optical Add-Drop Multiplexer") which add or remove one or more lengths of wave circulating in the optical fiber 5 to the optical fiber 314 of the transponder 3, without going through an optical-electrical conversion of course. In principle, each optical insertion / extraction multiplexer 6b comprises three multiplexers / demultiplexers 62 and fixed mirrors 61 which are, for example, Bragg gratings or multi-dielectric thin layers. The multiplexed signal coming from the optical fiber 314 of the transponder 3 enters a first multiplexer / demultiplexer 62 where the different wavelengths are separated spatially and then inserted or extracted using the fixed mirrors 61 and the two other multiplexers / demultiplexers 62 in the optical fiber 5. With reference to FIG. 17, a non-reconfigurable optical insertion / extraction device 6b consists, for example, of an elongate rigid support 60 on which a main optical fiber 62 is glued with a secondary optical fiber 63 parallel and joined. A Bragg grating 61 is photo-inscribed in the junction area of the optical fibers 62 and 63 so as to inject / extract for example two pairs of consecutive wavelengths of the main optical fiber 62 in the secondary optical fiber 63. main optical fiber 62 is connected to an optical fiber 5a on the one hand and to an optical fiber 5b on the other hand by means of solder 64. The secondary optical fiber 63 is connected to the optical fiber 314 by a solder 64. This device is very compact and can be easily integrated into a type 153 cowling cassette described above. With reference to FIG. 17bis, the pitch of the Bragg grating 61 (denoted by Λ) is determined to select this or that wavelength injected / extracted in the device 6b. For this, the angle of incidence of the optical signal with the normal to the Bragg grating slightly inclined with respect to the axis of the optical fiber is such that the light is no longer guided in the core of the optical fiber of the optical fiber. 'index' n 'and passes from one optical fiber 62 to the other 63. Only light of wavelength λ which verifies the Bragg relation Λ = λ / 2n.sina is thus selected. Since the refractive index is of the order of 1.5 in a silica optical fiber and the angle of incidence is very close to 90 °, it can be considered that the pitch of the grating Λ is of the order of λ. / 3 is 0.5μηη in C band (1520nm to 1577nm). The number of strata of the Bragg grating, that is to say its length makes the coupling more or less selective, an array of 5 mm in length for example will have a bandwidth of 0.1 nm largely sufficient to isolate the different DWDM lines spaced at about 1 nm (or 100GHz). In order to select several wavelengths, it suffices to place the different corresponding step gratings afterwards or to make a certain modulation of the pitch of the grating 61 placed in the common zone of the optical fibers 62 and 63.

In this second embodiment, and with reference to FIG. 15, the laser transmission / reception devices 95 interposed between the network ports 91 of the optoelectronic switches 9 and the optical routers 7 within a concentrator 30 or 40 are tunable in wavelength. The laser emission / reception devices 95 comprise a wavelength tunable laser emission device 956 delivering a continuous optical signal to an external optoelectronic modulator 954, for example of the Mach-Zender type connected to the electrical signal TX of the network port 91. on the one hand and with the aid of an optical fiber to the optical router 7 on the other hand. The optical router 7 receives the optical signal TX modulated at a wavelength electrically reconfigurable by the control unit 8. The optical signal RX supplied by the optical router 7 comes from the on-board laser emission / reception devices 95 integrated in the embedded converter 40 in the mobile A which is associated with the network port 91 of the fixed switch 9, each mobile A circulating on the infrastructure B being associated with a group of network ports 91. In this case, the optical router 7 is controlled by the control unit 8 to adjust the correct route of the optical signal. The optical signal RX is converted by a photodetector 959 which is for example a fast GalnAs photodiode for supplying the electrical signal RX to the network ports 91 of the switch 9.

With reference to FIG. 16, an optical router 7 comprises in principle a diffractive optical component 75 spatially separating all the wavelengths flowing in the optical fiber 5. A set of electrically reconfigurable mirrors 73 controlled by the control unit 8 is associated with each network port 91 for routing the necessary pair of wavelengths. The same network port 91 can thus circulate any pair of wavelengths among those available. These optoelectronic components are also called "wavelength selective switch" (or "Wavelength Selectable Switch" in English), they use either micro-mirror matrices controlled by electrical voltages or crystal space modulators liquid that directly diffract the incident optical signal to the different optical paths. Such an optical router 7 makes it possible to assign to each of the network ports 91 the right pair of wavelengths in coherence with the operation of the transmitting / receiving devices 95 according to the instructions given by the control unit 8.

In this second embodiment, there may be several mobiles A per block, up to half the number of fixed optical transponders 3. The mobiles A can cross without interrupting the communication. The number of channels "m" available on board mobiles A depends on each optical insertion / extraction device 6 for communication between infrastructure B and mobile A. In practice, the number of channels "m" available on board mobiles A is relatively limited, and typically equal to two or three (72 DWDM wavelengths spaced 100GHz C-band for 10-15 optical terminals per section of optical fiber 5). In the case of the "rail" application, this configuration is adapted to the signaling in mobile deformable blocks. According to a third embodiment, and with reference to FIGS. 11 and 11a, the band of wavelengths injected / extracted by the optical insertion / extraction multiplexers 6c is reconfigurable. The central control unit 8 is then adapted to vary the wavelength band injected / extracted from each optical insertion / extraction multiplexer 6c as a function of the position of the mobile A, so that the lengths of The wave of the laser transmission / reception devices 95 belong to the wavelength band injected / extracted from the optical insertion / extraction multiplexer 6c of at least one of the fixed optical transponders 3 on which the onboard optical transponders 4 are pointed.

In this third embodiment, and with reference to FIG. 11a, the optical insertion / extraction devices 6c are wavelength-adaptable. These are "ROADM" multiplexers ("Reconfigurable Optical Add-Drop Multiplexer" in English) that add or remove one or more wavelengths flowing in the optical fiber 5 to the optical fiber 314 of the transponder 3 dynamically. In principle, each optical insertion / extraction multiplexer 6c comprises three multiplexers / demultiplexers 62 and a set of switches 61 which are for example adaptive pitch Bragg gratings, liquid crystal components or electrically controlled micromirrors. The multiplexed signal coming from the optical fiber 314 of the transponder 3 enters a first multiplexer / demultiplexer 62 where the different wavelengths are separated spatially and then inserted or extracted using the set of switches 61 and the two other multiplexers. / demultiplexers 62 in the optical fiber 5.

With reference to FIGS. 18 and 18bis, a wavelength-adaptive optical insertion / extraction device 6c is for example similar to the non-reconfigurable optical insertion / extraction device 6b described above with the exception that the support 60 is a bimetallic bimetallic one which makes it possible to deform the Bragg gratings which are connected by the application of a voltage V. For a positive / negative voltage, the step Λ of the Bragg grating is increased / reduced because the bimetal extends / contracts the optical fibers 62 and 63 increasing / reducing the injected / extracted wavelength (s). The electrical voltage V is controlled by the control unit 310 integrated in each optical terminal 3. It is necessary to provide at least one Bragg grating with a wavelength dedicated to the "monitoring" of the control device of the bimetallic bimetallic strip. to overcome temperature variations or other environmental parameters.

In this third embodiment, one or more wavelengths flowing in the optical fiber 5 is advantageously dedicated to the transmission of the control signals between the central control unit 8 and the optical insertion / extraction devices 6c.

In this third embodiment, several mobile A can coexist per section of optical fiber 5, up to half the number of optical terminals 13. The mobile A can intersect without interruption of communication. The number of "m" channels available on board mobile A depends only on the number of network ports 91 implemented in the switches 9, that is to say that it can be quite large, and typically greater than three channels. . In this configuration, the number of mobile A that can coexist in continuous bidirectional communication with the infrastructure B is maximum and above all the number of network ports 91 to implement is minimal. In the case of the "rail" application, this configuration is adapted to the signaling in mobile deformable blocks.

With reference to FIG. 12, the optical fibers 5 pass through an amplification module 55 to amplify the optical signal of the optical fiber 5 in the two directions of propagation. An optical amplification module 55 comprises two wavelength multiplexers 52 for separating the optical channels TX (emitted by a laser transmission / reception device 95) on the one hand and the optical channels RX (received by a laser transmission / reception device 95) on the other hand. The TX and RX optical channels each pass through an optical amplifier 51 of the "EDFA"("Erbium Doped Fiber Amplifier") type. Such an amplification module 55 can advantageously be integrated in a fixed optical insertion / extraction device 6 and can be controlled respectively by the central control unit 8. It can also advantageously be integrated into a cutoff of the optical fiber 5 at the level of a switch 7 in a concentrator 30 or cut-off of the optical fiber 314 at the switch 7 in a device 40 of the mobile A.

With reference to FIG. 13, the network architecture implements at least one core network 20 operating at a very high bit rate (100 to 400 Gb / s) making it possible to interconnect different sections of infrastructure B using devices secondary optical injection / extraction 12, all the concentrators 30 being connected to the same high-speed optical backbone 1 1. Each secondary optical injection / extraction device 12 includes a passive multiplexing and amplification means necessary for a long optical backbone 1 1 which can double-connect all the concentrators 30 to each of the network cores 20 placed at each end of infrastructure B.

With reference to FIG. 14, a power supply line 10 supplies all the elements of the infrastructure and in particular the fixed transponders 3 from a generating station 50. This supply line 10 is parallel to the optical fibers 5 and integrated into the cable optical / electrical hybrid 15 to which each transponder 3 is connected. The generating stations 50 are supplied with medium voltage (380 V three-phase or 230 V single-phase) by a main supply line 13 from a main generating station 56 connected to the electrical network. global 500 which also feeds the network core 20. This configuration makes it possible to integrate the low-voltage power lines in the same sheath and facilitate maintenance operations in the presence of electrical voltages without danger to the personnel. In return, it is necessary to limit the distance between the secondary stations 50 especially since the power consumption of optical terminals 3 is important. Advantageously integrates in the power supply module 320 optical transponders 3 an electric accumulator for smoothing consumption and avoiding current peaks on the line 10.

With reference to FIG. 3, the optical fibers 5 and the supply lines 10 are advantageously grouped together in a sheath 154 and together form an optical / electrical hybrid cable 15. The supply lines 10 are, for example, copper, then having a line resistance of about 34 ohms per kilometer and per mm ² section. A maximum consumption per optical terminal of 10W gives for example a bidirectional current of 0, 1A in the line 10 and 3.4v of voltage drop or 7% loss joule for a single line of 1 km in length with a section of 1 mm ² . In this example, a cable 15 with about six optical fibers sheath diameter 0.9mm and 10 pairs of conductors 10 sheath diameter 1, 5mm would serve a section of infrastructure of a length of 2km. Such a cable 15 would have an outer diameter of 10 to 15 mm depending on whether it is intended to be included in a sleeve or to be buried in the ground. Because all its internal strands are of uniform diameter of 1 to 1.5mm, its flexibility remains satisfactory and complies with the standards of Telecom low current cables.

With reference to FIG. 3bis, the optical fibers 5 and the power supply lines 10 connected to an optical terminal 3 are extracted from the optical / electrical hybrid cable 15 at the level of a coiling cassette 153 integrated in the optical terminal 13. For example, the coiling cassette 153 is integrated in the optical / electrical hybrid cable 15 by removing the sheath 154 of the optical / electrical hybrid cable 15 over a length of at least 500 mm without interrupting the optical fibers 5 or the power supply lines 10 for to make at least one loop 151 with all the optical fibers 5 respecting a minimum radius of curvature of 50 mm acceptable for a monomode optical fiber silica standard 9 / 125μηη and a loop 152 with the supply lines 10. Only the loop of the optical fiber 5 intended to be connected with the fixed transponder 3 is interrupted to be connected to the insertion / extraction device 6 integrated in the optical transponder 3 at these two points of entry / exit with usual optical connectors. For more redundancy and operational safety, the two power supply lines 10 are advantageously used for each optical terminal 3. For an optical transponder 4, this technique can also be used with a single cable 15 which is stored in the coaxial cassette 153. The optical amplification module 51 is advantageously integrated in the cassette 153.

The coil cassette 153 may also be used to interconnect two infrastructures B between each other or an infrastructure B with another type 300 wide area network using a secondary cable whose optical fibers 5 and / or Power supply 10 are connected to those of infrastructure B using loops 151 and 152 incorporating optical and / or electrical welds. Seals 155 are associated with the cables 15 to ensure the tightness of the sheaths 154 with the cassette 153. The coiling cassette 153 thus constitutes a kind of "tight optical / electrical seal" which can be stored in a draft chamber buried in the traditional way or preferentially integrated into the base of each fixed optical terminal 3 placed in height thus releasing the sealing constraints (injection of neutral gas ...).

Claims

Continuous bidirectional communication system (1) by atmospheric connection between an infrastructure (B) equipped with fixed optical transponders (3) connected to laser transmission / reception devices (95), and at least one mobile (A) moving by compared to the infrastructure (B) and equipped with at least two embedded optical transponders (4), opposite the fixed optical transponders (3), and connected to laser transmission / reception devices (95), the optical transponders (3, 4) each being equipped with a self-pointing system (31) adapted to perform a pointing operation with one of the optical transponders (3, 4) opposite, so as to ensure communication between the fixed transponders (3) and on-board transponders (4), the system (1) being characterized in that each fixed optical transponder (3) is coupled to at least one optical fiber (5) arranged along the infrastructure (B) by via an insertive device optical erection / extraction (6, 6a, 6b, 6c), a central control unit (8) being adapted to drive the optical insertion / extraction devices (6a, 6c) and / or the laser transmission / reception devices ( 95) according to the position of the mobile, so that one of the onboard transponders (4) communicates with a fixed transponder (3) while the other onboard transponder (4) performs a pointing operation with another fixed transponder (3).

Communication system (1) according to claim 1, characterized in that the optical insertion / extraction devices (6, 6a, 6b, 6c) are optical switches (6a), and in that two consecutive optical transponders (3) are coupled to different optical fibers (5), the central control unit (8) being adapted to switch the optical switches (6, 6a) one after the other in the direction of movement of the mobile (A), so that one of the on-board transponders (4) communicates with a fixed transponder (3) while the other onboard transponder (4) performs the pointing operation with another fixed transponder (3).

Communication system (1) according to claim 1, characterized in that the optical insertion / extraction devices (6b) are selective to a wavelength band of their own and fixed, the laser emission / reception devices (95) being wavelength-adaptable, a central control unit (8) being adapted to vary the transmit / receive wavelength of the laser transmit / receive devices (95) according to the position of the mobile (A), so that the transmission / reception wavelengths of the laser transmission / reception devices (95) belong to the wavelength band of the optical insertion / extraction multiplexer (6). , 6a, 6b, 6c) of at least one of the fixed optical transponders (3) on which the onboard optical transponders (4) are pointed.

Communication system (1) according to claim 1, characterized in that the wavelength band injected / extracted by the optical insertion / extraction devices (6c) is reconfigurable, the central control unit (8) being adapted for varying the injected / extracted wavelength band of each optical insertion / extraction multiplexer (6c) according to the position of the moving body, so that the wavelengths of the laser transmit / receive devices (95) belong to the wavelength band injected / extracted from the optical insertion / extraction multiplexer (6c) of at least one of the fixed optical transponders (3) on which the onboard optical transponders (4) are pointed.

Communication system (1) according to one of the preceding claims, characterized in that each optical fiber (5) is connected to a wavelength selective optical router (7) whose outputs are connected to a fixed network switch (9). ), the wavelength selective optical router (7) and / or the fixed network switch (9) being controlled by the central control unit (8) so that the data flow from the on-board laser transmission / reception devices (95) results in at least one set two network ports (91) of the network switch (9), the two network ports (91) aggregating within the network switch

(9).

Communication system (1) according to claim 5, characterized in that it comprises a plurality of fixed network switches (9) distributed along the infrastructure (B), one of the network ports (91) of each fixed network switch (9). ) being connected to a network port (91) of the two adjacent fixed network switches (9) so as to ensure continuity of communication between the fixed network switches (9). Communication system (1) according to one of the preceding claims, characterized in that one or more wavelengths of the laser transmission / reception devices (95) is dedicated to the transmission of the control signals between the central control unit (8) and the transmission / reception device (40), and / or the optical insertion / extraction devices (6, 6a, 6c).

Communication system (1) according to one of the preceding claims, wherein the self-pointing system (31) comprises a micropositioning system (304) of the end of an optical fiber (314) for establishing a connection optical "fiber to fiber" self-pointing in free space between the transponders (3, 4).

9. Communication system (1) according to one of the preceding claims, wherein the optical transponders (3, 4) are equipped with an optical-microwave converter (323) and a sectoral antenna (322) to establish a free air link between the optical transponders (3) and (4).

The communication system (1) according to one of claims 3 or 4, wherein the optical insertion / extraction devices (6b, 6c) consist of a main optical fiber (62) and a secondary optical fiber. (63) contiguous to the main optical fiber (62) over a junction area, one or more Bragg gratings (61) being inscribed in the junction area of the main and secondary optical fibers (62, 63) so that certain wavelengths are extracted from the main optical fiber (62) to the secondary optical fiber (63) or inserted from the secondary optical fiber (62) to the main optical fiber (63).

1 1. Communication system (1) according to claims 10 and 4 taken in combination, wherein the main optical fibers (62) and secondary

(63) are integral with a piezoelectric bimetallic strip (60) so that the application of an electrical voltage across the piezoelectric bimetallic strip (60) causes deformation of the Bragg grating (s) (61) registered in the junction area of the main and secondary optical fibers (62, 63).

The communication system (1) according to one of the preceding claims, wherein the wavelength-adaptive laser transmission / reception devices (95) comprise a laser transmission / reception device (956) having a length of tunable wave and an electro-optical external modulator (954).

13. A method of continuous bidirectional communication by atmospheric connection between an infrastructure (B) equipped with fixed optical transponders (3) connected to laser transmission / reception devices (95), and at least one mobile (A) moving relative to at the infrastructure (B) and equipped with at least two onboard optical transponders (4) connected to laser transmission / reception devices (95), the optical transponders (3, 4) are equipped with each of a self-pointing system adapted to perform a pointing operation with one of the transponders (3, 4) opposite, so as to ensure communication between the fixed transponders (3) and the onboard transponders (4), each fixed optical transponder (3) being coupled to at least one optical fiber (5) arranged along the infrastructure (B) via an optical insertion / extraction device (6, 6a, 6b, 6c) , the method being characterized in that the optical insertion / extraction devices (6a, 6c) and / or laser transmission / reception devices (95) are controlled according to the position of the mobile, so that the one of the on-board transponders (4) communicates with a fixed transponder (3) while the other onboard transponder (4) performs a pointing operation with another fixed transponder (3).