FR2822312A1 - Optical communication for subscriber stations includes two optical links operating at different frequencies along single optical channel - Google Patents

Abstract

The system comprises a first optical communication link and second optical communication link for each subscriber station. These provide multiplexing and demultiplexing of electrical signals and conversion into optical signals of two predefined wavelengths.( lambda 1). Each station includes a multiplexing and demultiplexing device enabling the first and second optical communication links to connect to an optical channel by means of a single bi-directional optical connection. The system for increasing the volume of data passing through a subscriber station comprises a first optical communication link. This provides multiplexing and demultiplexing of electrical signals and conversion into optical signals of predefined wavelength ( lambda 1). This first optical link is connected to an optical telecommunication loop comprising at least one bi-directional optical channel. A second optical communication link is also provided, operating at a different predefined wavelength ( lambda 2). Each station includes a multiplexing and demultiplexing device connecting the first and second optical communication links to the optical channel of the loop by means of a single bi-directional optical connection.

Description

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 The present invention relates to a device for increasing the volume of data passing through a subscriber station and over an optical loop of a telecommunications network to which the station is connected.

 The subscribers, customers and operators, are connected to an optical telecommunications network by means of an optical loop made up of pairs of optical fibers, each pair constituting a bidirectional optical path.

 A fraction of the total bandwidth of the optical loop is allocated to each subscriber.

 Subscribers communicate on the optical loop using optical communication devices or Optical Distribution Systems, commonly called "SOD".

 These SODs perform the multiplexing and demultiplexing of the various electrical signals and ensure the conversion between the electrical signals and the optical signals. They only accept a fixed number of input signals.

 For example, according to the PDH standard for optical telecommunications, a SOD manages from 1 to 16 Digital Primary Blocks, which are blocks of digital signals at a nominal bit rate of 2 Mbit / s commonly called "BPN".

According to the SDH standard for optical telecommunications, a SOD manages from 1 to 63 BPN.

 The speeds required by subscribers, customers and operators, as well as the number of customers are constantly increasing. This inevitably leads to problems of saturation of the SODs at first, then of the optical loops.

 One technique for increasing volume is to replace existing SODs with SODs of higher capacity. This operation requires the interruption of links to existing equipment as well as the mobilization of a specialized team during time slots to minimize disruption, especially at night.

 For example, switching over 450 connections to a new SOD represents two months of work and a cost of FF 2000 per link of 2 Mbits / s.

 In addition, this technique does not solve the problems of saturation of the optical loops.

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 One solution to avoid saturation is to develop new optical loops, but this entails very high costs.

 Indeed, the deregulation of telecommunications has led certain players to form local fiber optic loops in areas belonging to them (local authority, ZAC, etc.). These actors can then set up reserved areas making it impossible for other entities to use their existing passages or pipes and greatly reducing the possibility of increasing an already existing network.

 To this must be added the increase in the price of optical fibers due to a quantitative shortage of materials.

 In fact, when it is not prohibited, the creation of a new entry point on an optical loop is very expensive and the cost of a fraction of bandwidth increases appreciably with the problems of saturation. This prevents the subscription of new customers or the connection of a new SOD for a subscriber whose SODs are saturated, as well as the purchase of a larger fraction of bandwidth.

 The present invention aims to remedy these problems by making it possible to increase the volume of data passing through a subscriber station and to double the transfer capacity of the fraction of bandwidth allocated to this subscriber.

 The subject of the invention is a device for increasing the volume of data passing through a subscriber station comprising a first optical communication device making it possible to multiplex and demultiplex data in the form of electrical signals and to ensure the conversion between said data. electrical signals and optical signals of predefined wavelength, said first optical communication device being connected to a telecommunication optical loop comprising at least one bidirectional optical path, characterized in that it comprises at least one second optical communication device operating at a predefined wavelength other than the first optical communication device and associated with it by at least one optical multiplexing and demultiplexing device connecting the first and said at least one second optical communication device to said at least one optical path of said optical loop by a single con bidirectional optical connection.

 According to other characteristics of the invention:

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nomètres et la seconde longueur d'onde utilisée est une longueur d'onde com- prise entre 1530 nanomètres et 1560 nanomètres et de préférence de 1550 nanomètres, le premier et le second dispositifs de communication optique ainsi que ledit au moins un dispositif de multiplexage et de démultiplexage étant adaptés pour fonctionner à ces deux longueurs d'ondes ; - ladite boucle optique comporte deux chemins optiques bidirectionnels différents, lesdits premiers et lesdits seconds dispositifs de communication optique étant reliés à chacun desdits deux chemins optiques par un dispositif de multiplexage et de démultiplexage optiques ; et - ladite boucle optique est une boucle optique fonctionnant selon la norme SDH, lesdits dispositifs de communication optique et lesdits dispositifs de multiplexage et de démultiplexage optiques étant adaptés pour fonctionner selon la norme SDH. - said optical multiplexing and demultiplexing devices are spatial multiplexing devices of different wavelengths thus making it possible to increase the volume of data passing, in the form of a multiplexed signal, over a given fraction of the band bandwidth of said optical loop; the first wavelength used is a wavelength between 1270 nanometers and 1365 nanometers and preferably 1310 nanometers

nometres and the second wavelength used is a wavelength between 1530 nanometers and 1560 nanometers and preferably 1550 nanometers, the first and the second optical communication devices as well as said at least one multiplexing device and demultiplexing being adapted to operate at these two wavelengths; - Said optical loop comprises two different bidirectional optical paths, said first and said second optical communication devices being connected to each of said two optical paths by an optical multiplexing and demultiplexing device; and - said optical loop is an optical loop operating according to the SDH standard, said optical communication devices and said optical multiplexing and demultiplexing devices being adapted to operate according to the SDH standard.

 The invention also relates to a method for upgrading a subscriber station comprising a first optical communication device operating at a first wavelength, consisting in adding to said subscriber station, a device according to the invention in order to result in a subscriber station having two optical communication devices operating one at the first wavelength and the other at a second wavelength and connected to said at least one optical path by at least one optical multiplexing and demultiplexing device.

 According to other characteristics of the invention, said optical multiplexing devices, used in this method, are installed in existing optical equipment.

 The invention will be better understood on reading the description which follows, and made with reference to the appended drawings, in which:

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 - Figure 1 shows a telecommunications network on an optical loop comprising subscribers stations of conventional type and subscriber stations according to the invention; - Figure 2 shows the detail of the connection according to the invention of two subscribers to an optical loop according to the SDH standard of optical telecommunications; and - Figures 3 and 4 show two configurations of implantation of the optical multiplexing and demultiplexing device according to the invention.

 In Figure 1, there is shown schematically a telecommunications network on an optical loop.

 This network comprises an optical loop 1, composed of two optical fibers, not shown, constituting a bidirectional optical path 2 transmission-reception. For example, the optical fibers are single-mode optical fibers whose core and sheath have respective diameters of 62.5! lm and 125! um.

 On this optical path 2, optical signals pass at different wavelengths. In the example described, we limit ourselves to two different wavelengths, 1 and 2.

 Several subscriber stations 3,4, 5,6, 7 and 8 are connected to this optical loop 1.

 The basic element of the subscriber stations 3,4, 5,6, 7 and 8 is an optical communication device or Optical Distribution System commonly called SOD. These SODs 11,12,13,14,15,16,17,18 and 19 only accept Digital Primary Blocks, commonly called BPN, designated by the general reference 20, whose nominal bit rate is, for example, 2 Mbps.

 In each of the SODs 11, 12, 13, 14, 15, 16, 17, 18 and 19, the BPNs 20 are multiplexed then converted into optical signals and, conversely, the optical signals are converted into electrical signals then demultiplexed.

 Conventionally, an SOD accepts a fixed number of BPNs, the maximum of which is, for example, 16 or 63 as indicated above.

 The subscriber stations 4,5, and 8 are of the conventional type. They each have an SOD 13,14 and 19 respectively operating either at the wavelength λ. i is at wavelength S2, each being connected by a bidirectional optical link to the two fibers of the optical loop 1.

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The subscriber stations 3, 6 and 7 are subscriber stations according to the invention. They each consist of two SODs 11, 12; 15, 16 and 17, 18, the two SODs of the same pair operating one at the wavelength λ, i and the other at the wavelength A2.

 Each pair of SODs of the same subscriber station 3.5 and 6 according to the invention is connected to the optical path 2 by means of a device 22, 23 and 24 for optical multiplexing and demultiplexing. These devices 22, 23 and 24 provide the multiplexing as well as the demultiplexing and the separation of the two wavelengths A1 and 2. They can receive signals multiplexed at the wavelength A1 +? fi2 as well as signals at a single wavelength A1 or 2. In fact, the two SODs 11,12; 15, 16 and 17, 18 of the same pair are connected to the optical path 2 by means of a single entry point.

 The subscriber stations equipped according to the invention can therefore significantly increase their data transfer capacity without having to resort to a new entry point on the optical loop 1. This thus overcomes the saturation of the SODs without the significant additional cost of the subscription of a new entry point.

d'onde A1 et S2 Les deux signaux sont superposés l'un à l'autre. De fait, on double la quantité d'informations passant sur une fraction donnée de bande passante de la boucle optique 1. In addition, the multiplexing and demultiplexing devices 22, 23 and 24 carry out, in conventional manner, a spatial multiplexing of the lengths

wave A1 and S2 The two signals are superimposed on each other. In fact, the amount of information passing over a given fraction of bandwidth of the optical loop 1 is doubled.

 The transfer capacity on the optical loop 1 is therefore significantly increased, without the installation having undergone the slightest modification or without the subscribers 3, 6 and 7, equipped according to the invention, using band fractions. wider bandwidth.

 Each of the optical multiplexing and demultiplexing devices 22, 23 and 24 can, for example, be formed of a waveguide on a silica substrate by deposition with flame hydrolysis or by chemical vapor deposition, at which we added on each branch connected to a SOD, a filter, not shown, in order to cut the wavelength which is not intended for the corresponding SOD.

 The SODs connected to such a device therefore do not risk being disturbed in their operation, for example by glare due to the power

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optique de la longueur d'onde non utilisée. Ces dispositifs ne nécessitant pas d'outils de supervision, on peut les installer chez les abonnés à faible coût.

optical wavelength not used. These devices do not require supervision tools, they can be installed at low cost subscribers.

In a mixed architecture such as that shown, including conventional type subscriber stations and subscriber stations according to the invention, all the elements operating at the same wavelength can communicate with each other. So the SODs 11, 13, 15, 17 and 19 operating at wavelength k can communicate with each other as can the SODs 12, 14, 16 and 18 operating at wavelength? w2.

 Indeed, SODs are adapted to receive only one wavelength. In fact, the SODs 13 and 19 of the stations 4 and 8 of the conventional type, can receive a multiplexed signal ^ 1 + ^ 2 coming from one of the stations 3,6 or 7 according to the invention and only process the length signal of wave ki which it contains, despite the drawbacks due to the risk of dazzling of the receiver by the length k2 of untreated wave.

 Similarly, the SOD 14 of station 5 of the conventional type can receive an Il + multiplexed signal? ; 2 and process only the wavelength signal S2 it contains.

 Of course, the same subscriber can have several stations according to the invention or several stations of conventional type or a combination of stations of conventional type and stations according to the invention.

 In Figure 2, there is shown the detail of the connection of two subscriber stations according to the invention to an optical loop meeting the SDH standard.

 One of the current standards in the field of optical telecommunications is the SDH standard or "Synchronous Digital Hierarchy". Among other known technical characteristics, an optical loop meeting the SDH standard such as the optical loop 30, has a maximum transfer rate of 10 gigabits / s and has two optical paths, a normal optical path 31 and a backup optical path 32 The latter is used to convey the optical signals only in the event of failure of the normal optical path 31.

 Each of the two optical paths 31 and 32 consists, as previously, of two optical fibers, not shown.

 In the context of the SDH standard for optical telecommunications, wavelengths are used; = 1310 nm and 2 = 1550 nm to convey the optical signals on the optical loop 30. These wavelengths correspond to

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 two wavelengths among those for which there is the weakest weakening.

 Two subscriber stations according to the invention, a client station C and an operator station 0, are connected to the optical loop 30.

 They each include two SODs 35, 36 and 37.38. SODs 35.37 and 36.38 operate at wavelengths II and A2 respectively.

 The SODs 35, 36, 37 and 38 of the subscriber stations C and 0 connected to the optical loop 30, integrate functions not shown making it possible to test the integrity of an optical path and to switch communications between the normal optical path 31 and the optical backup path 32.

 The SODs 35 and 36 of the station C are connected to the normal optical path 31 by means of a device 40 for optical multiplexing and demultiplexing, identical to the equivalent devices described above with reference to FIG. 1.

 They are also connected to the emergency optical path 32 by means of another device 41 for optical multiplexing and demultiplexing.

 Thus, thanks to the two optical multiplexing and demultiplexing devices 40 and 41, the two SODs 35 and 36 of the station C are connected to each of the two optical paths 31 and 32 via a single bidirectional optical connection.

 Likewise, the SODs 37 and 38 of the subscriber station 0 are connected to the normal optical path 31 by means of an optical multiplexing and demultiplexing device 42 and to the backup optical path 32 by means of a device 43.

 Advantageously, the devices 40, 41, 42 and 43 for multiplexing and optical demultiplexing can be installed directly in existing equipment. This makes it possible to transform a conventional type post into a post according to the invention.

Conventionally, the SODs 35 and 36 of the client station C are arranged in a bay 46. This bay 46 is connected to the optical loop 30 by means of secure optical connection boxes 48 and 50, commonly called "CROS". CROS 48 allows connection to normal optical path 31, and CROS 50 allows connection to emergency optical path 32.-
In order not to increase the size of the client station C, and because of the small number of optical connections, the devices are installed

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 40 and 41 for optical multiplexing and demultiplexing directly in bay 46. The detail of this connection is described below with reference to FIG. 3.

 The operator station 0 comprises an optical bay or "farm" 52 of the conventional type, making it possible to arrange, in a modular manner, a large number of optical devices.

 This optical farm 52 can, for example, be an optical farm produced by the company Alcatel known in the field of optical telecommunications.

 In order to carry out the invention, the optical farm 52 is installed with devices 42 and 43 for optical multiplexing and demultiplexing between optical equipment 54 and 55 for connection to the optical loop 30 and optical equipment 56 and 57 of connection to SOD 37 and 38. The detail of this connection is described below with reference to FIG. 4.

 The operation of the system described with reference to Figure 2 is as follows.

 Electrical signals 20 sent by the client are routed to the SODs 35 and 36. These multiplex the various signals and convert the electrical signal obtained into an optical signal. The SOD 35 transmits an optical signal of wavelength II. SOD 36 emits an optical signal of wavelength # 2.

 These two optical signals each arrive on an affluent branch of the multiplexing device 40. The multiplexed optical signal 1 + X2 thus obtained is conveyed, via the CROS 48, on one of the two fibers constituting the normal optical path 31 of the optical loop 30.

The two signals # 1 and # 2 pass simultaneously on the optical loop 30, superimposed on each other in the form of a spatial multiplex signal? 2
This multiplexed optical signal λ1 + fv2 is recovered from the side of operator 0 by the connection equipment 54. It is then demultiplexed by the demultiplexing device 42 into two optical signals of respective wavelengths À1 and À2. These signals are transmitted respectively, via the connection equipment 56, to the SOD 37 and 38. The SOD 37 receives only the wavelength signals S1 and the SOD 38 receives only the wavelength signals # 2.

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 The SODs 37 and 38 in turn convert these optical signals into a series of electrical signals which will be routed to, for example, a cross-connect 60 for the data and an auto-switch 62 for the voice.

 Signal processing is identical in the operator 0 to client C direction.

 In the event of a malfunction of the normal optical path 31, the SODs 35, 36, 37 and 38 switch to the backup optical path 32 and perform the same operations as above thanks to the connection equipment 50, 55 and 57 and the multiplexing devices and optical demultiplexing 41 and 43.

 In Figure 3, there is shown the implementation of an optical multiplexing and demultiplexing device according to the invention, in existing equipment.

 Only the detail of the connection to the normal optical path 31 has been shown in this figure.

 Conventionally, there are in the bay 46 trays or drawers, coiling and splicing.

These trays make it possible to keep a length of fiber in reserve in order to be able to modify the physical arrangement of the material, and to make splices making it possible to connect the various optical devices.

These plates can be, for example, those produced under the reference ORMJ 1.0 by the company Pirelli, known in the field of optical telecommunications.

In the context of the invention, in order to be able to connect the two SODs 35 and 36 to the normal optical path 31, the optical multiplexing and demultiplexing device 40 is directly implanted in a drawer 64 for coiling and splicing.

 This device 40 consists of an optical multiplexer 40Ex and an optical demultiplexer 40Rx.

 The optical multiplexer 40Ex of the device 40 makes it possible to multiplex the emission signals Ein and Exz coming from the SODs 35 and 36 respectively.

 # outputs an optical multiplex signal Exi + Ex2 intended for the transmission optical fiber of the normal optical path 31.

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The optical demultiplexer 40Rx of the device 40 makes it possible to demultiplex and separate the multiplexed signal RXA1 + RXA2 received and to extract from it the signals Rx # 1 and Rx # 2 respectively for the SODs 35 and 36.

 The elements 40Rx and 40Ex are inserted directly on the optical fibers by means of optical welds 65 of known type.

 The elements 40Rx and 40Ex can be, for example, those produced under the reference WDM by the aforementioned company Pirelli.

 The two SODs 35 and 36 are thus connected, by means of the device 40, to the optical fibers for transmitting and receiving the normal optical path 31 of the optical loop 30.

 The same modification is made in another coiling and splicing drawer (not shown) in order to connect the SODs 35 and 36 to the emergency optical path 32 (FIG. 2).

 In Figure 4, there is shown another implementation of an optical multiplexing and demultiplexing device according to the invention, in existing equipment.

 Only the detail of the connection to the normal optical path has been shown in this figure.

 The optical farm 52 has a large number of cassettes intended to receive optical equipment.

 These cassettes can be, for example, those produced under the reference SSF12 by the aforementioned company Pirelli.

 In the context of the invention, in order to be able to connect the two SODs 37 and 38 to the normal optical path 31, two cassettes 66 and 67 are available.

They constitute the multiplexing and demultiplexing device 42.

plexer les signaux d'émission Exi et Exs provenant respectivement des SOD 37 et 38. t émet en sortie un signal optique multiplex Exi+ EX à destination de la fibre optique d'émission du chemin optique normal 31. The cassette 66 receives the optical multiplexer 42Ex which allows multiple

plexing the emission signals Exi and Exs coming respectively from the SODs 37 and 38. t emits as an output a multiplex optical signal Exi + EX intended for the emission optical fiber of the normal optical path 31.

The cassette 67 receives the optical demultiplexer 42Rx which makes it possible to demultiplex and separate the multiplexed signal Rx # 1 + Rx # 2 received and to extract the signals Rxi and Rx therefrom. 2 respectively for SOD 37 and 38.

 The elements 42Rx and 42Ex are connected by means of optical welds 70 of known type.

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The elements 42Rx and 42Ex can be, for example, those produced under the reference WDM by the aforementioned company Pirelli.

The two SODs 37 and 38 are thus connected by means of the device 42, to the optical fibers for transmission and reception of the normal optical path 31.

 The same modifications are made on two other cassettes (not shown) in order to connect the SODs 37 and 38 to the emergency optical path 32 (FIG. 2).

SOD et un dispositif optique de multiplexage. Thanks to the arrangements described, the positions according to the invention are either modified conventional type positions or positions incorporating original two

SOD and an optical multiplexing device.

In the case of a transformation of a conventional post, the invention is all the more suitable for an optical loop according to the SDH standard that the use of the backup optical path makes it possible to perform the migration without interruption of the use.

 The practical implementation of the transformation of a conventional type post into a post according to the invention is described below with reference to FIG. 2.

We consider a subscriber station of the conventional type, comprising a first SOD 35 operating at a wavelength 1, connected to the optical loop 30 operating according to the SDH standard,
To modify this station, it is sufficient to interrupt the link between the SOD 35 and the normal optical path 31. This has the consequence of switching communications on the emergency optical path 32 without interrupting the service.

An optical multiplexing and demultiplexing device 40 according to the invention is inserted on the connection to the normal optical path 31.

Is this device 40 then connected to the existing SOD 35 and to a second SOD 36 operating at wavelength? t2.

 Similarly, in order to connect the two SODs 35,36 to the optical backup path 32, a second optical multiplexing and demultiplexing device 4 is inserted on the connection to the optical backup path 32.

 This allows the connection of a second SOD 36 on an access point to the existing optical loop 30. The presence of a backup optical path 32 makes it possible to carry out this migration without interrupting use.

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 Although two embodiments have been described, they are not considered to limit the scope of the present invention.

 In particular, it is easy to imagine an application of the invention for defining subscriber stations having three SODs each operating at a different wavelength and connected to an optical loop by a single bidirectional connection by means of a multiplexing device and optical demultiplexing operating with these three wavelengths.

 Similarly, one can easily imagine the application of the invention to other wavelengths than those defined in the text.

Claims (7)

 CLAIMS 1. Device for increasing the volume of data passing through a subscriber station (3,6, 7; C, 0) comprising a first optical communication device (11, 15,17; 35,37) for multiplexing and demultiplexing data in the form of electrical signals (20) and ensuring conversion between said electrical signals (20) and optical signals of predefined wavelength (1), said first optical communication device (11,15 , 17; 35,37) being connected to a telecommunication optical loop (1; 30) comprising at least one bidirectional optical path (2; 31,32), characterized in that it comprises at least one second optical communication device (12, 16,18; 36, 38) operating at a different predefined wavelength (in2) than the first optical communication device (11, 15,17; 35, 37) and associated with it by at least an optical multiplexing and demultiplexing device (22,23, 24; 40, 41,42, 43) connected ant the first (11,15,17; 35,37) and said at least one second (12,16,18; 36,38) optical communication devices to said at least one optical path (2; 31,32) of said optical loop (1; 30) by a single bidirectional optical connection.  2. Device according to claim 1, characterized in that said optical multiplexing and demultiplexing devices (22, 23,24; 40,41, 42, 43), are spatial multiplexing devices of different wavelengths (1 , 2) thus making it possible to increase the volume of data passing through, in the form of a multiplexed signal (1 + 2), over a given fraction of bandwidth of said optical loop (1; 30).  3. Device according to one of claims 1 to 2, characterized in that the first wavelength used (? T1) is a wavelength between 1270 nanometers and 1365 nanometers and preferably 1310 nanometers and the second wavelength used (2) is a wavelength between 1530 nanometers and 1560 nanometers and preferably 1550 nanometers, the first (11.15, 17; 35, 37) and the second (12.16, 18 ; 36,38) optical communication devices as well as said at least one multiplexing device and

 demultiplexing- (22, 23, 24; 40, 41, 42, 43) being adapted to operate at these two wavelengths.  4. Device according to any one of claims 1 to 3 characterized in that said optical loop (30) comprises two bidirectional optical paths <Desc / Clms Page number 14>  different tional (31, 32), said first (35, 37) and said second (36, 38) optical communication devices being connected to each of said two optical paths (31, 32) by an optical multiplexing and demultiplexing device ( 40.41, 42.43).  5. Device according to claim 4 characterized in that said optical loop (30) is an optical loop operating according to the SDH standard, said optical communication devices (35,36, 37,38) and said optical multiplexing and demultiplexing devices ( 40, 41, 42, 43) being adapted to operate according to the SDH standard.  6. Method for upgrading a subscriber station (C, O) comprising a first optical communication device (35,37) operating at a first wavelength (1), characterized in that it consists of adding to said subscriber station (C, O), a device according to any one of claims 1 to 5 in order to end up at a subscriber station having two optical communication devices operating one ( 35.37) at the first wavelength (1) and the other (36.38) at a second wavelength (. 2) and connected to said at least one optical path (31.32) by at least an optical multiplexing and demultiplexing device (40,41, 42,43).  7. Method according to claim 6, characterized in that said optical multiplexing devices (40,41, 42,43) are installed in an existing optical equipment (46, 52).