FR2545948A1 - Wavelength multiplexing-demultiplexing device using optical fibres - Google Patents

Abstract

The present invention relates to a wavelength multiplexing-demultiplexing device using optical fibres. For a bidirectional connection having three channels, two outgoing channels and one return channel, the device comprises an optical connection fibre 30 which has bevelled rooftop-like faces 11a, 11b and is coupled to two intermediate optical fibres 13, 14, one of which is bidirectional, and means 42, 44 for selecting the wavelengths. Application to telecommunication systems based on optical fibre.

Description

MULTIPLEXING AND DEMULTIPLEXING DEVICE
PAK FIBER OPTICAL WAVELENGTHS
The present invention relates to a device for multiplexing and demultiplexing unidirectional or bidirectional wavelengths using optical fibers.

 In optical transmission systems, it is necessary to multiplex into a single main optical fiber, called the link or transmission fiber, signals of different wavelengths each modulated by the information to be transmitted, and vice versa. Such optical systems are said to be unidirectional or unidirectional when the different wavelengths propagate in a single direction of the connecting fiber, and are said to be bidirectional when the connecting fiber transmits in a direction different wavelengths called go and in the other direction one or more other wavelengths known as of return. At the present time, the systems of bidirectional optical connections are used in many fields such as for example telematics, the telephone transmissions or the networks cable systems in which a central station communicates with peripheral stations constituted by subscriber transceiver devices.

 Various types of multiplexer / demultiplexer are known for channels or channels for transmitting wavelengths on a single unidirectional or bidirectional connecting fiber. One of them consists in multiplexing and demultiplexing the different wavelengths using, in combination with the connecting fiber, as many intermediate optical fibers as there are wavelengths to be multiplexed and demultiplexing, as described for example in the article published in the journal "OPTICS LETTES", July 1980, volume 5, no 7, pages 321 and 322, entitled: "Compact wavelength multiplexer using optical-fiber pieces". article, the multiplexer and demultiplexer is of the unidirectional type with two channels, and is in the form of a T by using on the one hand a connecting fiber of which one of the ends is bevelled and carries an interference filter with dielectric multilayers, and on the other hand two intermediate optical fibers each transmitting a wavelength and carrying on one of their respective ends with a cross section two other inter ferential filters, one of which is attached to an edge of the beveled end e of the bonding fiber and whose filter filter, orthogonal to the previous one, is attached to the periphery of the bonding fiber at its interference filter. The optical signals at the two wavelengths used, namely o, 32um and 1 , 2te, are therefore multiplexed and demultiplexed during their passage through the three interference filters which ensure, for multiplexing, a distribution in wavelength in the connecting fiber, and for demultiplexing, a selection of wavelength in each intermediate fiber.

 However, such a multiplexing-anemultiplexing device with intermediate optical fibers has drawbacks. First of all, this device requires three interference filters to ensure the only multiplexing and demultiplexing of two wavelengths, which significantly increases its manufacturing cost. In addition, it proves difficult to deposit an interference multilayer filter on the bevelled face of an optical fiber, so that the implementation of the device is very complex. In addition, like the flat face of the 'one of the intermediate fibers is attached to the circular periphery of the connecting fiber, a geometrical mismatch is created between these two fibers (flat surface against curved surface), therefore causing imperfect coupling between the fibers; this therefore results in diffractions of the light signals, and therefore the introduction of losses. Consequently, the multiplexer / demultiplexer exhibits unsatisfactory performance, and in particular a significant insertion loss and high crosstalk.

 The aim of the present invention is to remedy these drawbacks by proposing a multiplexing-demultiplexing device using intermediate optical fibers, which is entirely satisfactory, of a simple structure and easy to implement, of low manufacturing cost, has excellent performance (minimal insertion loss and low risk of crosstalk), and is suitable for both one-way and two-way links.

 Thus, for a unidirectional link, the invention relates to a wavelength multiplexing device comprising an optical fiber for binding intended to transmit the multiplexed wavelengths and having an input face and an output face, characterized in that the entry face of the connecting fiber consists at least partially of two bevelled parts each forming a projecting angle given with the axis of the connecting fiber, and in that the device comprises at least two fibers wavelength transmission intermediate optics, coupled respectively to the two bevelled parts, so that the wavelength optical signals transmitted by the intermediate fibers penetrate into the connecting fiber through the two bevelled parts of its input face , which produces a wavelength multiplexing in the link fiber.

 The demultiplexing device, according to the invention, associated with this unidirectional link is similar to the multiplexer described above with in addition wavelength selection means coupled between each intermediate fiber and each respective bevelled part, so that the optical signals at the multiplexed wavelengths transmitted by the connecting fiber are received selectively by the intermediate fibers, the selection means thus producing a demultiplexing of the wavelengths.

 In a similar way, for a bidirectional link, that is to say for a single connecting fiber transmitting in one direction the wavelengths said to go and in the other direction at least one wavelength called back, the multiplexing demultiplexing device according to the invention also comprises at least two intermediate fibers respectively coupled to the two bevelled parts of one of the faces of the> -fibering fiber, and length selection means. wave coupled between each intermediate fiber and each respective bevelled part, at least one of the intermediate fibers being bidirectional.

Other characteristics and advantages of the invention will appear more clearly in the detailed description which follows and refers to the appended drawings given solely by way of example and in which:
- Figure 1 shows a general diagram of an optical multiplexing demultiplexing for a bidirectional link by optical fiber;
- Figures 2a and 2b respectively show sectional views of the multiplexer and the associated demultiplexer according to the invention, for a unidirectional link with three channels; and
- Figures 3a and 3b respectively show sectional views of the multiplexer and the associated demultiplexer according to the invention, for a bidirectional link with three channels, two of which go and one return.

 In these different figures, the same references relate to the same elements.

 In FIG. 1, there is shown at 10 a multiplexer of n different wavelengths X 2 2 1i n and at 20 the associated demultiplexer, for example for a cable distribution system on a single main optical fiber 30 called the link or transmission.

 The optical link is said to be unidirectional or monodirectional when the optical fiber 30 transmits in one direction, from the multiplexer 10 to the demultiplexer 20, the light signals at n wavelengths) 2 ...) n emitted by photo-emitting diodes , such as for example laser diodes or light-emitting diodes (not shown) and received by photodetector diodes, such as for example avalanche photodiodes or PIN type photodiodes (not shown).

On the other hand, the link is said to be bidirectional when the optical fiber 30 transmits in one direction, as before, the light signals to the n wavelengths said to go # 1 # 2 ... # n and in the other sense one or more wavelengths called return of which only one has been represented at # 0 in FIG. 1, the latter being emitted by a light emitting diode (not shown) coupled to the demultiplexer 20 and received by a photodetector diode (not represented) coupled to the multiplexer 10. Thus, for example for a cable distribution system, the optical multiplexing-demultiplexing device as shown in FIG. 1 is bidirectional with (n + 1) channels or transmission channels, that is to say å n forward channels for the transmission of video signals at wavelengths # 1 # 2 ... #n and to a return channel for the transmission of an additional signal, such as for example a remote control signal, at the length wave
FIGS. 2a and 2b respectively represent the multiplexer 10 and the associated demultiplexer 20 for a unidirectional optical link - at three different wavelengths 1, and A 3, equal respectively for example to 0.78 m, 0.86 m and 1 , 3 m.

 For the unidirectional multiplexer 10 shown in FIG. 2a, the optical link fiber 30 is a multimode fiber with index hopping or with an index gradient, the core 30a of which has a given diameter, for example equal to 100 mt, and whose the optical sheath 30b also has a given diameter, for example equal to 140 μm. The optical fiber 30 is therefore a 100 / 140rm fiber for which the digital aperture is of the order of 0.25 to 0.29.

 As it appears in FIG. 2a, the entry face of the connecting fiber 30 is bevelled in two parts 11a and abb each forming a salient angle given with the axis of the connecting fiber, so that the end fiber 30 has a roof shape or inverted V centered on its axis XX '. Thus, each bevelled part 11a and lob forms with the axis XX ′ of the fiber an angle a given, for example equal to 600. This angle a is chosen so as to increase the value of the angle of acceptance of the multimode fiber 30.

 Of course, the entry face of the connecting fiber 30 can be bevelled in a form other than that of a roof centered on its axis, such as for example a frustoconical shape, that is to say with two bevelled sides. joined by a straight flank orthogonal to the axis of the optical fiber, without departing from the scope of the invention.

 In the case of a unidirectional multiplexing of two wavelengths A1 and A2, the multiplexer 10 comprises two intermediate optical fibers 13 and 14, multimode with index jump or with index gradient, each having a given diameter smaller than that of the connecting fiber 30. Thus, the intermediate or junction fiber 13 intended for transmitting the first wavelength comprises an assembly 13a optical core-sheath, for example of 50 μm in diameter and a coating 13 b, for example of 125 μm in diameter. Likewise, the intermediate or junction fiber 14 intended to transmit the second wavelength) 2 comprises an assembly 14a optical core-sheath, for example of 50 μm in diameter and a coating 14b, for example of 125 μl in diameter.

 The two intermediate fibers 13 and 14 are respectively coupled to the two bevelled parts Il a and llb of the entry face of the connecting fiber 30, so that the maximum light energy at each wavelength X 1 and) is injected into the core 30a of the connecting fiber. Thus, to obtain this maximum coupling, each intermediate fiber is positioned, relative to the corresponding bevelled part, at a point in space defined experimentally by the angle e (or e) formed by the longitudinal axis of the intermediate fiber with the normal NN 'of the bevelled face, by the distance x (or x') between the intermediate fiber and the bevelled face, and by the distance y (or y ') between the intermediate fiber and the point O end of the bevelled face. The angle e (or i ') and the dimension x (or x') can of course be zero. In FIG. 2a, as in the other figures, the positioning of the intermediate fibers has been deliberately exaggerated with respect to the bevelled faces of the connecting fiber, for the sake of clarity.

 To optimize the coupling of the light energy between the intermediate fibers 13 and 14 and the connecting fiber 30, it is possible on the one hand to draw each intermediate fiber over a certain length at its emission end, and on the other hand apart from having optical means for focusing the optical signal at the wavelength transmitted by each intermediate fiber. These focusing means comprise for example a coupling micro-lens 16 attached to the output face called the wavelength emission face of each intermediate fiber 13 and 14.

 Once the intermediate fibers 13 and 14 are correctly coupled to the two bevelled parts 11a and 11b of the connection fiber 30, the optical signals at the two wavelengths X1 and transmitted by the two intermediate fibers 13 and 14 penetrate into the connection fiber 30 by the two bevelled parts of its input face, which produces the multiplexing of the two wavelengths A 1 and X 2 in the fiber 30, by wavelength distribution.

Consequently, the fiber 30 transmits in one direction the two multiplexed wavelengths (X 1 + A2) 2>.

 This unidirectional multiplexing of the two wavelengths X 1 and X 2 corresponds to a demultiplexing of these same wavelengths, carried out by means of the device 20 which will now be described with reference to FIG. 2b.

 In this figure, the connecting fiber 30 has a bevelled roof exit face in a manner similar to that described with reference to Figure 2a (bevelled parts I la and llb).

 It will be noted that the angle a 'given formed by the axis XX' of the fiber and each bevelled part may be equal to or different from the angle a defined on the multiplexing side.

 As before, the demultiplexer 20 comprises two intermediate optical fibers 23 and 24, stripped over a certain length, of respective diameter smaller than that of the connecting fiber 30, and positioned relative to the bevelled parts in a manner quite similar to that described with reference to FIG. 2a, and according to the same coupling parameters e, x and y (or ew, x and y ') as defined above.

As it appears in FIG. 2b, the demultiplexer 20 comprises wavelength selection means, constituted for example by two dielectric multilayer interference filters, coupled between each intermediate fiber and each bevelled part of the connecting fiber. Thus, by choosing the first wavelength B1 for the intermediate fiber 23 and the second wavelength A2 for the intermediate fiber 24, for example, the wavelength X1 is deposited on the input face called reception of the intermediate fiber 23 a first interference filter 26 designed so as to operate in transmission at the wavelength X 1 and in reflection at the wavelength A 2. Similarly, for example, it is deposited on the input face said to receive the wavelength X 2 of the intermediate fiber 24 a second interference filter 27 operating in transmission at the wavelength xi A2 and in reflection at the wavelength
Of course, the two interference filters 26 and 27 could also each be deposited on one of the bevelled parts of the outlet face of the connecting fiber 30, without departing from the scope of the invention.

Thus, the optical signals at the two multiplexed wavelengths (1 + A2) and transmitted by the connecting fiber 30 are received selectively by the two intermediate fibers 23 and 24, so that the first interference filter 26 transmits only the length X 1 in fiber 23 and reflects the optical signal at wavelength A2 in the connecting fiber 30, and vice versa for the second interference filter 27. Consequently, the two interference filters 26 and 27 produce the demultiplexing of the two wavelengths 1 and
In the case of a unidirectional multiplexing of three wavelengths) 2 and A. 3, it suffices to add a third multimode intermediate fiber 18 (FIG. 2a) intended to transmit the third wavelength; 3 and positioned at a determined distance, possibly zero, from the point O top of the roof of the bevelled end of the fiber 30, and so that its optical axis is coincident with the axis XX 'of the connecting fiber 30. The intermediate fiber 18 comprises an assembly 18a optical core-sheath for example 50) im in diameter and a coating 18b, for example 125tm in diameter, and stripped at its emission end.

 It will be noted that the intermediate fiber 18 centered on the axis XX ′ of the connecting fiber 30 can be dispensed with a coupling microlens in the case where the fiber 18 is a monomode or multimode fiber for which the maximum light energy is confined around of its axis, as is known per se.

 Thus, the optical signals at the three wavelengths l '2 and # 3 transmitted by the three intermediate fibers 13, 14 and 18 penetrate into the connecting fiber 30, which produces the multiplexing of the three wavelengths () ç1 + # 2 + i) in fiber 30, by wavelength distribution.

To now demultiplex these three wavelengths A1, A2 and a3, it suffices to position a third intermediate optical fiber 28 (FIG. 2b) in a manner completely similar to that described for the intermediate fiber 18 on the Figure 2a, that is to say centered on the axis XX 'of the fiber 30 and at a determined distance, e, which may be zero, from the point O' top of the roof of the bevelled exit face of the fiber connection 30. In addition, an interference filter 29 operating in transmission at wavelength xi 3 is deposited, for example on the input face known as receiving the wavelength A 3 of the third intermediate fiber 28 and in reflection at the other two wavelengths A1 and
Thus, the optical signals at the three multi-plexed wavelengths (1.1 + A 2 + A3) and transmitted by the connecting fiber 30 are received, after selection by the three interference filters 26, 27 and 29, by the three intermediate fibers 23, 24 and 28, thus producing the demultiplexing of the three wavelengths X 2 and À
FIGS. 3a and 3b respectively represent the multiplexer 10 and the associated demultiplexer 20 for a bidirectional link with three channels or channels, two of which go and one return.

 By way of illustration, the two outgoing channels transmit the two different wavelengths B 1, for example equal to 0.86> im and i, for example equal to 1.3 m, while the return channel transmits the wavelength X 0 different from the other two, and equal for example to 0.78 m.

 In FIG. 3a, the bidirectional multiplexer 10 comprises the two intermediate optical fibers 13 and 14 positioned with respect to the two bevelled parts 11a and 1b of the input-output face of the connecting fiber 30 in a completely similar fact to that described with reference to Figure 2a.

As indicated in FIG. 3a, the intermediate fiber 13 is bidirectional, that is to say that it transmits in one direction one of the forward wavelengths, for example the wavelength X 1 and transmits the return wavelength B0 in the other direction, while the intermediate fiber 14 is unidirectional, that is to say that it transmits in one direction only the other forward wavelength
In addition, the bidirectional multiplexer 10 includes wavelength selection means coupled between each intermediate fiber and each respective bevelled part of the connecting fiber. Thus, these selection means comprise for example two dielectric multilayer interference filters 42 and 44 deposited on the output face known as the wavelength emission output of the intermediate fibers 13 and 14. More specifically, the interference filter 42 is designed to operate in transmission at both the first go wavelength N and the return wavelength A0, and in reflection only for the second go wavelength B27 while the interference filter 44 is designed to operate in transmission only for the second wavelength X2 and in reflection for the return wavelength X2
Thus, the interference filters have the function on the one hand of selectively separating the wavelengths, and on the other hand of reflecting the non-selected wavelengths.

 Of course, as before, the two interference filters 42 and 44 could also be deposited on the two bevelled parts 11a and 11b of the input-output face of the connecting fiber 30, without departing from the scope of the invention.

 The optical signals at the two wavelengths of going A and X transmitted by the two intermediate fibers 13 and 14 therefore penetrate, after passing through the two interference filters 42 and 44 operating in transmission, into the connecting fiber 30 by the two bevelled parts of its input-output face, which produces the multiplexing of the two wavelengths (1 + X2) in the link fiber 30, while the return wavelength Ao is received, after selection by the interference filter 42, by the bidirectional intermediate fiber 13.

 Similarly, the bidirectional demultiplexer 20 shown in FIG. 3b comprises the two intermediate optical fibers 23 and 24 positioned with respect to the two bi-wired portions 11a and lob of the exit-entry face of the connecting fiber 30 in an identical manner to that described with reference to Figure 2b.

In addition, one of the two intermediate fibers 23 and 24 is also bidirectional, such as for example the fiber 23 shown in FIG. 3b. This intermediate fiber 23 therefore transmits in one direction the first forward wavelength N and in the other direction the return wavelength AoS while the intermediate fiber 24 is unidirectional, transmitting only in one direction the second length wave
The two intermediate fibers 23 and 24 comprise, on their input face called reception of the two forward wavelengths, two dielectric multilayer interference filters 46 and 47 designed so that the filter 46 operates in transmission for the two wavelengths 7 O and 1 and in reflection for the wavelength A2, while the filter 47 operates in transmission for the wavelength X 2 and in reflection for the wavelength to go NOT
Thus, the optical signals at the two forward multiplex wavelengths t -A 1 + A2) and transmitted by the connecting fiber 30 are received, after selection by the two interference filters 46 and 47, by the two intermediate fibers 23 and 24, thus producing the demultiplexing of the two wavelengths X 1 and X 2.

 As for the return wavelength X 0 transmitted by the bidirectional intermediate fiber 23, it penetrates, after passing through the interference filter 46 operating in transmission, into the connecting fiber 30 by the bevelled part 11a of its outlet face- entry, and then propagates in the connecting fiber 30.

 It will be noted that the three-channel bidirectional multiplexing-demultiplexing device described with reference to FIGS. 3a and 3b could also be used, with the appropriate modifications, for a bidirectional four-channel link, that is to say either two forward channels and two return channels, that is to say three outward channels and one return channel, without going beyond the ambit of the invention.

 Of course, the invention is in no way limited to the embodiment described and shown and includes all the technical equivalents of the means described as well as their combinations if these are carried out according to the spirit of the invention and implemented in the The scope of the following claims.

Claims (17)

 1. Wavelength multiplexing device for unidirectional link, comprising an optical link fiber (30) intended for transmitting the multiplexed wavelengths and having an input face and an output face, characterized in that the entry face of the connecting fiber consists at least partially of two bevelled parts (villa, llb) each forming a given salient angle (a) with the axis of the connecting fiber, and in that the device comprises at at least two intermediate optical fibers (13, 14) for wavelength transmission, respectively coupled to the two bevelled parts (lla, Ilb), so that the optical signals at wavelengths transmitted by the intermediate fibers (13, 14 ) penetrate the connecting fiber (30) through the two bevelled parts of its entry face, which produces a wavelength multiplexing in the connecting fiber.  2. Device according to claim 1, characterized in that it comprises, between the output face known as the emission of wavelength of each intermediate fiber and the input face of the connecting fiber, optical means ( 16) focusing the optical signal at the wavelength transmitted by each intermediate fiber.  3. Device according to claim 2, characterized in that the focusing means comprise a microlensing lens (16) fixed on the outlet face of each intermediate fiber.  4. Device according to one of claims 1 to 3, characterized in that the spatial positioning of the intermediate fibers (13, 14) relative to the respective bevelled parts (Ia, Ilb) is such that the maximum light energy in output of the intermediate fibers is coupled to the connecting fiber (30).  5. Device according to one of the preceding claims, characterized in that the two bevelled parts (1a, llb) of the entry face of the connecting fiber (30) form a roof centered on the axis of the fiber link.  6. Device according to one of the preceding claims, characterized in that it comprises an intermediate dental optical supplement fiber (18) coupled to the entry face of the connecting fiber (30) so that its optical axis is confused with that of the connecting fiber.  7. Device for demultiplexing wavelengths for unidirectional link, comprising an optical link fiber (30) transmitting at least two multiplexed wavelengths and having an input face and an output face, characterized in that the exit face of the connecting fiber consists at least partially of two bevelled parts (1a, llb) each forming a given salient angle (a ') with the axis of the connecting fiber, and in that the device comprises ~ at least two intermediate optical fibers (23, 24) for wavelength transmission, respectively coupled to the two bevelled parts (11a, 11b), and means (26, 27) for wavelength selection coupled between each intermediate fiber and each respective bevelled part, so that the optical signals at the wavelengths multiplexed and transmitted by the connecting fiber (30) are selectively received by the intermediate fibers (23, 24), the selection means thus producing awavelength demultiplexing.  8. Device according to claim 7, characterized in that the selection means comprise interference filters (26, 27) each deposited on the input face called wavelength reception of each intermediate fiber (23, 24) , so that the optical signals at multiplexed wavelengths and transmitted by the connecting fiber leave it by the two bevelled parts and are selectively transmitted in the intermediate fibers by means of interference filters.  9. Device according to one of claims 7 or 8, characterized in that the spatial positioning of the intermediate fibers (23, 24) relative to the respective bevelled parts (11a, 11b) is such that the maximum light energy output bond fiber (30) is received, after selection, by each intermediate fiber.  10. Device according to one of claims 7 to 9, characterized in that the two bevelled parts (11a, 11b) of the exit face of the connecting fiber (30) form a roof centered on the axis of the fiber link.  11. Device according to one of claims 7 to 10, characterized in that, for an additional wavelength transmitted by the connecting fiber and in multiplexing with those intended to be received selectively by the intermediate fibers, the device comprises a additional intermediate optical fiber (28) coupled via the selection means (29) to the exit face of the connecting fiber so that its optical axis coincides with that of the connecting fiber, the additional intermediate fiber (28) receiving, after selection, the additional wavelength.  12. Multiplexing device for wavelengths for bidirectional link, comprising an optical fiber link (30) intended to transmit in one direction the multiplexed wavelengths said to go and transmitting in the other direction at least one length so-called return wave differs from the outgoing wave, the connecting fiber having a face serving both as an input face for the forward wavelengths and as an output face for the wavelength of return, characterized in that the entry-exit face of the connecting fiber consists at least partially of two bevelled parts (11a, 11b) each forming a given salient angle (a) with the axis of the connecting fiber , and in that the device comprises at least two intermediate optical fibers (13, 14) for transmitting wavelengths, coupled respectively to the two bevelled parts (11a, llb), and of which at least one (13) of which is bidirectional, and means (42, 44) of length selection wavelengths coupled between each intermediate fiber and each respective bevelled part, so that the optical signals at the forward wavelengths transmitted by the intermediate fibers (13, 14) penetrate into the connecting fiber (30) by the two bevelled parts of its input-output face, producing the multiplexing of the forward wavelengths, while the optical signal at the return wavelength is received, after selection; by the bidirectional intermediate fiber (13).  13. Device according to claim 12, characterized in that the selection means comprise interference filters (42, 44) each deposited on the output face known as the emission wavelength of go of each intermediate fiber (13 , 14).  14. Device according to one of claims 12 or 13, characterized in that the two bevelled parts (Ia, llb) of the input-output face of the connecting fiber (30) form a roof centered on the axis of the connecting fiber.  15. Device for demultiplexing wavelengths for bidirectional link, comprising a link optical fiber (30) transmitting in one direction at least two multiplexed wavelengths said to go and intended to transmit in the other direction at least a so-called return wavelength different from that of go, the bonding fiber having a face serving at the same time as exit face for the go wavelengths and of entry face for the length of return wave, characterized in that the exit-entry face of the connecting fiber consists at least partially of two bevelled parts (1a, llb) each forming a given salient angle (a ') with the axis of the connecting fiber, and in that the device comprises at least two intermediate optical fibers (23, 24) for transmitting wavelengths, coupled respectively to the two bevelled parts (bila, Lob), and of which at least one ( 23) of them is bidirectional, and means (46, 47) for selecting wavelength ion coupled between each intermediate fiber and each respective beveled part, so that the optical signals at the wavelengths of going multiplexed and transmitted by the connecting fiber (30) are received selectively by the intermediate fibers ( 23, 24), the selection means thus producing the demultiplexing of the forward wavelengths, while the optical signal at the return wavelength transmitted by the bidirectional intermediate fiber (23) penetrates, after passing through the selection means, in the connecting fiber (30) by one of the bevelled parts of its input exit face.  16. Device according to Claim 15, characterized in that the selection means comprise interference filters (46, 47) each deposited on the input face known as the wavelength reception input of each intermediate fiber (23 , 243.  17. Device according to one of claims 15 or 16, charac terized in that the two bevelled parts (lla, llb) of the exit-entry face of the connecting fiber (30) form a roof centered on the axis of the binding fiber.