Coupler-extractor for optical signals.

The present invention relates to an extractor-coupler device of a signal transmitted by optical fibers. It is more particularly intended to be interposed on a transmission optical fiber so as to allow, while maintaining the continuity of transmission of the initial signal through the upstream device to downstream, extract a part of the signal to a detector, and at the same time to reintroduce a new signal in the downstream direction; the new signal will also both be the same extract after regeneration signal, or another carrier signal new information superimposed on the initial information.

The presently known devices used for this purpose generally comprise, between the upstream transmission fiber and the fiber downstream transmission, an optical system for rendering parallel the light rays coming from the upstream fiber, and an optical system focusing the parallel beam again on entry of the downstream fiber. In the part where the rays are parallel, the device comprises a semi-reflective system that derives a controlled fraction of the light to a detector or other receptor system.

Such a device has the disadvantage, when it is intended to reintroduce a new signal, the semi-reflective surface passes a part of the re-introduced light, which then passes directly to the detector and distorts the information that is collected.

The French patent application 81-08636 published under No. 2505056 of the same applicant provides a first solution to this problem by a device comprising a main concave spherical mirror whose central part forms another small deviation concave spherical mirror, same vertex and the same radius as the main mirror, but whose center-C₂ is slightly offset from the center C₁ the main mirror. The primary mirror then ensures the continuity of transmission of the greater part of the optical signal between an upstream fiber and a downstream fiber. arranged symmetrically with respect to C₁, While the smaller central deflection mirror makes it possible to remove a portion of the signal to an extraction fiber disposed symmetrically to the upstream fiber in relation to C₂And to introduce a new signal by a fiber reinjection disposed symmetrically to the downstream fiber in relation to C₂.

But the realization of such a complex mirror with a small central part of the axis is deviated from the main axis, poses technical and economic problems and lend itself to industrial manufacture in large quantities.

The invention provides a new solution and is applied to an optical signal extractor coupler between a fiber feed upstream transmission and downstream transmission fiber for reference, intended both to ensure the continuity of the transmission between the fibers, extracting a portion of the signal to a detector, and / or coupling to the downstream fiber a new signal from a transmitter, coupler of the type having a vertex of a concave spherical mirror S and center C₁And wherein the end of the upstream transmission fiber is disposed in the plane P perpendicular to the axis Cl SC₁In slightly offset position with respect to Ci so that its image by the mirror symmetrical form relative to C on the end of a receiving fiber.

According to the invention it comprises a second concave spherical mirror part interposed between the first mirror and the plane P, this second mirror partially reflecting by symmetrically distributed areas compared to its top, having its center C₂ in the plane P, but slightly offset from the center C₁ mirror; Furthermore the ends of the binder fiber to the detector and the binder fiber to the emitter are arranged in the plane P, respectively, symmetrically to the end of the upstream fiber and the downstream fiber in relation to C₂.

According to a preferred embodiment of the invention the assembly is monobloc and Ci centers and C₂ are offset by a distance equal to the diameter of the fibers while the ends of the fibers are contiguous and aligned in the direction C₁- C₂.

The invention is best understood with reference to a particular embodiment given by way of example and illustrated by the accompanying drawings.<ul><li>Figures 1 and 2 are block diagrams illustrating the capabilities of the device. Figure 1 relates to the case of a partial extraction of the signal and an injection of another independent signal. Figure 2 relates to the case where the extracted signal portion is fed back after regeneration, while the main part of the signal is transmitted by giving it a slight delay.</li><li>Figure 3 is a simplified representation of a unitary extractor-coupler realized according to the invention.</li><li>Figure 4 is a section on IV-IV of Figure 3.</li><li>Figures 5 and 6 show the relative positions of the fibers leading to the extractor-coupler, respectively in the case of the block diagrams of Figures 1 and 2.</li></ul>

By first referring to Figure 1 we see that the extractor-coupler shown here in phantom upstream receives the optical fiber 1 carries a signal of which must be transmitted to the downstream fiber 2 as the direct path symbolically represented by a solid line. The device also has the function to extract a portion of the signal to drift into the fiber 3 connected to a detector D; it must also provide the injection into the downstream fiber 2 of the additional signal originating from the transmitter E and transmitted by the fiber 4. The bypass and injection paths are shown symbolically in broken lines.

According to the scheme of Figure 2 the extracted signal and derivative to the fiber 3 is regenerated in 8 to then be fed back by the fiber 4 to the downstream fiber 2. The regeneration circuits 8 that can cause a delay of the signal reinjected by 4 relative the original signal directly transmitted, a rephasing of the two signals is carried out by forcing the light transmitted from 1 to 2 to travel a further path in an intermediate retardant fiber 7. This fiber retardant is connected to the device by its ends 5 and 6.

Referring now to Figures 3 and 4 which correspond to the diagram of Figure 1 it will be seen that the four fibers 1, 2, 3 and 4 are embedded in a block 10 so that their ends are flush with the planar face 11 of the block . The four fibers are aligned in relative positions which will be specified later. The surface 11 forms the contact interface with another transparent block 12 whose other end forms a spherical surface 13 whose center C₂ is in the plane 11. The surface 13 is treated to be partially reflective, the reflective areas are arranged symmetrically relative to the apex defined by the major diameter perpendicular to the plane 11. Figure 4 shows an example of the distribution of reflecting zones, here in two opposite sectors. The block 12 is extended by a third slide block 14 with the same index as the block 12 and having a spherical surface coupled to the surface 13 and a flat surface 15 parallel to the plane 11. The latter block 14, always with the same index, is in contact on the plane face 15, and its other face 17 forms a spherical mirror whose the center is also on the plane 11.

Sliding on the surface 15 of the position block 16 is regu- Glee relative to the block 12 so that the two centers Ci and C₂ are slightly offset in the plane 11. The assembly is also set so that, as best seen in Figure 5 the fibers 1 and 2 are arranged symmetrically with respect to C, while in the same alignment, the fibers 3 and 4 are respectively symmetrical position of the fibers 1 and 2 with respect to C₂. After setting the blocks are glued to each other to form a monobloc assembly.

The light from the fiber 1 meets the first surface 13 which, for its reflective areas, a game refers to the symmetrical point of the fiber 1 with respect to C₂, I.e. to the fiber 3, and this part is thus diverted to the detector D.

The greater part of the light passes through the transparent portion of the surface 13 and is reflected by the mirror 17 toward the symmetric point of the fiber 1 with respect to C₁, Ie towards the fiber 2.

Similarly, the light from the fiber 4 is partially reflected on the reflective areas 13 to the symmetrical point of the fiber 4 with respect to C₂, Ie the fiber 2 which thus receives and both of the light 1 and 4.

The other part of the light from the fiber 4 and which has passed through the transparent areas of the surface 13 is reflected by the mirror 17 to a point 4 'symmetrical to the fiber 4 with respect to C (Figure 5); that light exits the device.

Note that if a portion of the reflected light towards the fiber 2, and in particular high intensity from the transmitter by the fiber 4, instead of penetrating completely into the fiber 2 is partially reflected by the end the fiber to form a flare, it will then follow the opposite route and, thanks to the symmetrical shape of the reflective areas 13, it will meet again that the reflective areas and returned to 4 without disturbing exit 3 toward the detector .

The device of Figure 3 also allows the realization of the diagram of Figure 2, using six fibers whose ends are aligned with the plane 11, with the relative positions shown in Figure 6.

Here again the light from 1, by partial reflection on the partial mirror 13 and reflection on the mirror rest 17 is sent to the symmetrical points of 1, respectively, compared to C₂ and -C_l, Ie on the fiber 3 branch and the end 5 of the fiber datrice retar 7. Likewise the regenerated signal inputted by 4, and the main lumen from 7 by 6 gather on the same fiber downstream 2, 4 symmetrical with respect to C₂ symmetrical and 6 with respect to C₁.

Naturally, the invention is not strictly limited to the embodiment which has been described as an example, but it also covers the achievements that would differ only in details, by manufacturing variation or by use of equivalent means.

Thus, the assembly may function optically in the same way if the spherical mirrors 17 and 13 were separate mirrors held by suitable means in the relative positions shown relative to the plane 11 containing the fiber ends and the centers of the mirrors. However the described monobloc construction has indisputable advantages for both the instrument setting for reliability and directed component.

Similarly, the symmetry conditions of the relative positions of the fibers relative to the centers Cl and C₂ do not require that all the fibers are aligned provided that their ends are in the plane 11 and in the vicinity of the centers Ci and C₂. But the device described, with the fibers aligned and joined, is easier to perform repeatedly. The fact that the fibers are aligned and jointives.impose so that the distance between Ci and C centers₂ is equal to the diameter of a fiber.