FR2523735A1 - High capacity fibre optic channel switching device - has orientation controllable deflectors for emitter-receiver fibre pair selection - Google Patents

Abstract

The switching device has one or more fibre optic bundles, each fibre being either on emitter (21) or receiver (22) of information with one end occupying a right section of the bundle. Associated with each fibre is an optical emitter (23) or receiver (24) such as a lens on a perpendicular panel (11). Each emitter emits towards the interior of the switching device the light flux received by an emitter fibre within its angle of acceptance, while each receiver receives a flux emitted by one such emitter and sends it into another fibre thus ensuring liaison between two fibres. Light from one emitter fibre (21) is projected as a parallel beam of rays (27) from an emitter (23) and is deflected by a deflector (25) on a panel (12) of deflectors such as mirrors towards a plane mirror (13). The reflected beam is again deflected by another deflector (26) on the deflector panel towards a receiver (24) on the emitter/receiver panel which introduces it into a receiver fibre (22). The device has a means for choosing the deflectors concerned and controlling their orientation so as to select which fibres are put into liason.

Description

SYSEME OF OPTICAL COILILUTATION
The present invention relates to a compression device between media transmission paths consisting of optical fibers.

 According to the prior art there are devices that direct the light flux from a path consisting of a fiber to any one of two or more fibers, thus allowing the exchange of information between several separate channels. Such devices of the kind, for example, those described in the review "Electric Wave" Vol. 59, Roll, November 1979, use various principles: electromechanical, electro-optical or magneto-optical.

The number of switched channels is always of the order of a few units.

The prior art does not disclose, to our knowledge, a true optical fiber switching center with a number N of inputs and N outputs with N> 100 which would make it possible to establish N links simultaneously. To allow the switching of a large number of channels, it is conceivable to transpose in a switching device between media channels consisting of optical fibers, the principle "cross-bar" applied in the switching devices between channels 2 media bleeding .We know that for N channels the number of switches is N
Also, in the optical case, the application of such a principle would have several disadvantages: on the one hand, an extremely low transmission factor due to the crossing often, for the establishment of a route, a large number of optical switches, on the other hand, a very large size of the device (several square meters of section) and, more importantly, a variable transmission factor from one channel to another.

 One of the aims of the invention is to propose a device for switching between media channels consisting of optical fibers whose switching capacity is of the order of at least 100 channels.

 Another goal is still that this device uses only a small number of switches, equal to the number N of channels to be switched.

 Another goal is still that the channels have substantially the same transmission factor. For this purpose, the invention proposes a device for switching between media channels consisting of optical fibers, the so-called transmitters at one of their ends of information, the other receivers at one of their ends with information, remarkable in that it comprises means for groupemellt and fixation of the optical fibers in one or two beams, the said ends of these fibers being located in a plane of cross section of these beams, optical devices emitters or receivers of flux optical fiber emitted or received by each fiber arranged in one or more panels perpendicular to the fibers and facing their ends and such that the flux emitted or received by each fiber propagates inside the device in substantially cylindrical beams and axes parallel output of the transmitting or receiving panels, optical deviating devices in number equal to the number of channels to switch orie ntables and arranged in panels deviating, each, the beam from one of the fibers to any one of the other fibers and means of detecting the message from one of the transmitting fibers and control diverters in view to choose the pair of fibers to be connected.

 According to a first embodiment, the transmitting and receiving fibers are grouped into a single beam and the deviating devices each comprise an orientable optical element operating in reflection, these elements being arranged in a single panel, and a common element fixed in form. a plane mirror whose reflecting face is facing the orientable elements and reflects the beam from the element relative to one of the fibers to the deflector element of the other fiber to be connected.

 According to a second embodiment, the transmitting and receiving fibers are grouped into a single beam and the deviating devices each comprise an orientable element operating in transmission, all of these elements being arranged in a single panel, and a common element. fixed in the form of a plane mirror whose reflecting face is facing the orientable elements and reflects the beam from the element relative to one of the fibers to the deflector element of the other fiber to be connected.

 According to a third embodiment, the transmitting and receiving fibers are grouped according to two end bundles placed face to face, the axes of the fibers being parallel, the transmitting or receiving optical devices are grouped in two panels each assigned to one of the In the bundles, the dielectric devices consist of steerable elements operating in transmission and grouped in two parallel panels facing each other, each being assigned to one of the bundles of fibers.

 Preferably, the link between two fibers is controlled from a message from the transmitting fiber which, when not participating in a link, is in optical connection with a detector which captures messages and provides a signal to control the orientation of the deviators concerned by the link.

 The flux receivers or emitters are advantageously each constituted of a lens placed in front of each fiber end and of the same axis as the latter. According to one variant, the position of the lens with respect to said end and its focal length are such as to give the end of the fiber an image on the lens assigned to the fiber to be bonded and of the same diameter as the latter lens. . According to another variant, the fiber end is placed in the focal plane of the lens. The deviating elements when they operate in reflection are each a mirror that can be oriented in two directions or a diasporameter comprising two prisms that can move about a common axis of rotation, the rear face of the second prism (in the direction of propagation of the light) being reflective. It can still be a network engraved on a plane mirror prisms variable index and reflective rear face. When these diverters must operate in transmission, we use diasporameters without reflective face, acousto-optical or other elements generating variable pitch networks and variable orientation or variable index prisms without reflective face.

The invention will become more apparent with the aid of the following description of some embodiments given by way of non-limiting example, said description being accompanied by drawings which represent
Figure 1 is a schematic perspective view of the optical switching device according to a first embodiment of the invention, said device operating in reflection.

 2: a cross-sectional view, perpendicular to the recesses, respectively transceivers and deviators of the device shown in FIG.

 Figure 3: the same view as before with a particular element of the device.

4: a sectional view of an optical link made between two fibers according to a first variant,
Figure 5 is a sectional view of an optical link made between two fibers, according to a second variant.

 Figure 6 is a perspective view of an optical switching device according to a second embodiment of the invention, said device operating in reflection with transmission-biasing deflectors.

 Figure 7 is a perspective view of an optical device according to a third embodiment of the invention, operating in transmission.

 In FIG. 1, schematically representing in perspective a first embodiment of the invention operating in reflection, one distinguishes successively under the reference numeral 11 the so-called transmitter and receiver panel (devices which are defined below), under the reference numeral 12 panel deviators and under the reference 13 a plane mirror. The fibers to be connected optically form the beam 14, their ends occupying a cross section of this beam. This beam is only partially represented so as not to overload the drawing. The emitters and receivers are optical devices each assigned to one of the fibers of the beam 14. Each emitter transmits towards the interior of the device the light flux received from a so-called transmitting fiber at its acceptance angle, while each receiver receives a stream emitted by such an emitter and sends it to another fiber thus ensuring the connection between two fibers. Such emitters or receivers are for example the devices represented in circles 15 and 16. The panels 11, 12 and the mirror 13 are perpendicular to the same plane. The light emitted from the emitters of the panel 11 is received and diverted towards the mirror 13 by the panel 12, then reflected by the mirror 13 in the direction of the panel 12, then deflected again to the panel 11 on the receivers thereof. The panels and mirror preferably have a rectangular shape or niêwe square and optically the device has an optical axis 17 perpendicular to the panel llet which passes through the center C thereof and that of the panel 12, optical axis which corresponds the axis 18 reflected normal to the panel 13.

 FIG. 2, which represents a section of the device by the plane defined by the axes 17 and 18, shows how the connection between two fibers is effected, for example the fibers 21 and 22 respectively provided with the transmitting device 23 and the receiving device 24 .

To these emitter 23 and receiver 24 and in the direction of their respective optical axes perpendicular to the panel 11, correspond in the panel deviators 12, respectively deviators 25 and 26.

The orientations of 25 and 26 are such that the parallel ray beam 27 issuing from 23 and gathering the radiation flux coming from the fiber 21, after successive reflections on 25, on the mirror 13 and on 26 falls on the receiver 24, the flow being introduced into the fiber 22. The device comprises means of choice of the deviators concerned and control of the orientation of these deviators. In particular, during the connection to be made between the fibers 21 and 22, it is necessary to choose the deflectors 25 and 26 and to control their orientation.

 According to a preferred embodiment, said detection and control are carried out in the manner indicated with reference to FIG. 3, partly taking again FIG. 2. The device comprises a detector 28 placed for example in the panel of the deviators. In the absence of a connection to be made between fibers, the orientations of the deviators are such that the beams coming from all the emitters such as 27 converge, after reflection on the mirror 13, on the detector 28. In FIG. the simplification of the drawing, only some of these beams are represented reduced to their main radius. When a link is to be made between two fibers, the fibers 21, 22 for example, a message from the transmitting fiber 21 is received by 28 and translated into a signal of choice of the deviators 25, 26 to implement and their orientation.

 The following considerations indicate the possibilities in the number of channels that can be set using the device. The panel 11 of the transceivers is preferably square.

In what follows, y denotes the side of this square, D the distance between the center of the transceiver panel 11 and the center of the panel 12 of the deviators. To ensure that the panel 1 does not constitute an obstacle to all the beams reflected by the panel 12, the angle i of the panels should satisfy the relation (1) tgi> y
2D
The shortest links to be established are those which connect two adjacent fibers on the transceiver panel 11, the length of these links being of the order of 4D. The longest link is that which connects two fibers located at ends of a diagonal of the panel 11, the length X of this connection is

In the case where tgi = 0.5, (i = 26.50) and the mirror 13 touches the panel 11, y = D and the relation (2) becomes
(3) X = 4.45 D
The ratio between the shortest link and the longest is of the order of 0.9, so close to unity. It follows that the device makes it possible to obtain an almost identical adaptation of the geometrical extents for all the links, that is to say to undergo only a small loss of flux for certain links.

FIG. 4 makes it possible to calculate the number of possible connections as a function of the dimensions of the panels, given the fiber characteristics in the case where the links use bundles with a cylindrical structure. The connection is assumed to be established between the respective end fibers 31, 32. For the sake of simplicity of drawings, the existence of deviators has been omitted and assumed that these fibers have the same axis 33, which obviously does not remove nothing to the con clusions that will follow. The emitters and receivers belonging to the panel 11 are respectively the lenses 3h, 35 of identical radii R and axis 33, spaced from each other by the distance X equal to the length of the link. For the beam between transmitter and receiver to be cylindrical, the image of 31 through 34 must be confused with 35, and the image of 32 through 35 must be confused with 34. In this figure, the angle U represents the opening of the fiber, at the angle with the axis 33 of the main beam resting on an extreme edge of the fiber and the center of the lens 35, x the distance between fiber and transmitting lens or between fiber and receiving lens. Calling the radius of the heart of the fiber, we have from this figure
r R
r = R and x sin u = R
x X of bù in the end
(4) X r sin U = R2
If the transmitting lenses are arranged in rows and columns on the panel, the total number of lenses N of these lenses is given by the relationship that follows relations 1 to 4, namely
(5) N 4 (Y) 2
2R
A typical embodiment relates to a device for which y = 100 mm r = 0.1 mm sin u = 0.5 tgi = 0.5.

Relations 1 to 5 then lead to
D = 100 mm X = 445 mm R = 4.7 mm N 4 112
The diameter of the section of the cylindrical bundles is then about 10 mm, that is to say reasonably of the order of magnitude of the mechanical devices to operate the deviators.

FIG. 5 relates to another type of optical fiber connection embodiment in the case where r sin u is small. The same elements as in FIG. 3 are found with the same numbers, but the ends 31 and 32 of fibers are placed in the focal plane of the lenses 34 and 35, respectively. The divergence of the beam can indeed remain very small even if its diameter (2R) is chosen of the order of 10 mm, dimension compatible with those of the actuators of the deviators
For example, for r = 0.003 mm and sin u = 0.2, the focal length of the lenses should be f = 25 mm, which leads to an angle of beam angle Δ = 4 radian, which is negligible, the beam being therefore practically cylindrical.

In Figure 6 is shown a second embodiment operating in reflection but whose deviators operate in transmission. The fibers to be connected constitute the beam 50. The transceivers are united according to the panel 51 occupying a cross-section of the beam 50. The deflection elements are arranged along the panel 52 parallel to the panel 51. The device also comprises the mirror 53. parallel to 51. The light coming from a fiber emitted from an emitter of the panel 51 in the form of a substantially parallel beam is deflected a first time by passing through a first deflector of the panel 52 and then reflected by the mirror 53 and deflected a second time through a second deflector of the panel 52 before being received by a receiver of the panel 51 in correspondence with another fiber.According to a variant, the panels 51 and 52 are substantially merged, which gives the device a minimal footprint. The distance between the panels 52 and 53 then being D and y being the side of these supposed square panels, the maximum deviation 6 that a deviator can produce is such that

The shortest path of a link is 2D and the longest way

R, r, y and U having the same meanings as in the first embodiment are still linked by the previous relations (4) and (5).

An example relating to an embodiment according to this second embodiment relates to a device for which 6 = 150, y = 100 mm, r = 0.1 mm, sin U = 0.5, which leads to
D = 263 mm, X = 546 mm, R = 5.22, N 4
Fig. 7 shows a third embodiment operating completely in transmission. The fibers to be connected are made up of two bundles of the same axis 60, namely the beam 61 of so-called transmitting fibers and the bundle 62 of the so-called receptor fibers. The device is designed to connect a fiber of the beam 61 with a fiber of the beam 62. At the output of the beam 61 is the panel 63 of the transmitters and at the entrance of the beam 62 the panel 64 of the receivers, each of the transmitters or receivers being in correspondence respectively with an emitting fiber or a receiving fiber.Between the transmitting and receiving panels are a first and a second panel of deviating elements respectively 65 and 66 parallel to the panels 63 and 64. A beam of parallel rays of light, for example the beam 67 from the transmitter 68 corresponding to the fiber 69 and belonging to the panel 63, beam which propagates parallel to the axis 60 is deflected by the deflector 70 of the panel 65 and then by the deflector 71 of the panel 66, which returns the beam 67 again parallel to the axis 60, which beam is received by the receiver 72 of the panel 64, then directed into the fiber 73, the fibers 69 t 73 being thereby connected. According to one variant, the panels on the one hand 63 and 65 and on the other hand 64 and 66 are placed very close to one another so as to minimize the bulk of the device. separating the two groups of panels 63, 65 and 64, 66, relations 1 to 7 are still valid for this variant of the third embodiment, which leads to say that for a 2D space device = 526 mm, the number possible paths is such that N 4 91. It goes without saying that the devices of the invention according to the second and third embodiments include, as in the first embodiment, for connecting the different pairs of transmitting fibers and receiving means for selecting the deviators concerned by the links and the orientation of these deviators, said means being modeled, for example, on those indicated with respect to the first embodiment.

With regard to the transmitting and receiving elements as well as the deflection elements, the invention makes use of the devices of the known art. The emitting and receiving elements consist of lenses with very small aberrations so as to limit the losses of light flux. Given the appreciable openings of the fibers (sin u = 0.2 corresponds to an aperture f / 2.5), the lenses are preferably aplanetic. For long focal lengths (f> 10 mm), said elements consist for example of a lens comprising an aspherical diopter or two lenses of different glasses, corrected for spherical aberration and coma. For short focal lengths (f <10 mm), either ordinary convex flat lenses, spherical lenses or index gradient lenses are used. Whether focal lengths are long or short, these elements can be consist of holoraphic lenses. The deflecting elements consist, each, in the case where they must work in reflection, either in a small plane mirror whose normal is orientable according to two independent parameters (mounting cardan or kneecap), or in a diasporameter whose rear face is reflective and each of the two constituent prisms can rotate from the angle imposed on it, either with a grating engraved on a plane mirror, or with a variable-index prism and reflective rear face. In the case where these deflection elements must work in transmission, they advantageously consist of diasporameters without reflecting face, acousto-optical or other elements generating variable pitch networks and variable orientation, or variable index prisms.

Claims (14)

CLAIMS: 1. Device for switching between media channels consisting of optical fibers, at one end of an information, the other receivers at one of their ends, characterized in that it comprises means for grouping and fixing the optical fibers in one or two beams, the aforesaid ends of these fibers being located in a cross-sectional plane of these beams, optical devices emitting or receiving optical flux emitted or received by each fiber, arranged in one or more panels perpendicular to the fibers and facing their ends and such that the flux emitted or received by each fiber propagates inside the switching device in substantially cylindrical beams and parallel axes at the output of the panels transmitters or receivers and optical deflection devices, in number equal to the number of channels to be switched, orientable di sposed according to panels each deviating the beam from one of the fibers to any of the other fibers and means for detecting the message from one of the fibers and control deviators to choose the torque of fibers to be connected. 2. Switching device according to claim 1, characterized in that the transmitting and receiving fibers are grouped into a single beam and in that the deviator devices each comprise a steerable optical element operating in reflection, all of these elements being arranged according to the same panel and a fixed common element in the form of a plane mirror whose reflecting face is facing the orientable elements and reflects the beam from the element relative to one of the fibers to the deflecting element of the other fiber to connect. 3. Switching device according to claim 2, characterized in that the transmitting and receiving fibers are grouped into a single beam and in that the deflection devices each comprise an orientable element operating in transmission, all of these elements being arranged according to the same panel and a fixed common element in the form of a plane mirror whose reflecting face is facing the orientable elements and reflects the beam from the element relative to one of the fibers to the deflector element of the other fiber to connect. 4. Comanulation device according to claim 1, characterized in that the fibers are grouped according to two end bundles placed face to face, the axes of the starboard fibers, the emitting or receiving optical devices are grouped into two panels each assigned at one of the beams, the driver devices consist of orientable elements operating in transmission and grouped according to two parallel panels facing each other, each being assigned to one of the bundles of fibers. 5; Switching device according to one of Claims 1 to 4, characterized in that the optical devices emitting or receiving flux emitted or received by each fiber each consist of a lens placed in front of each fiber end and of the same axis as that here, the position of the lens relative to said end and its focal length being such that it gives the end of the fiber an image on the lens assigned to the fiber to be bonded and of the same diameter as the latter lens. 6. Device according to one of claims 1 to 4, characterized in that the optical devices emitter or flux receivers emitted or received by each fiber each consist of a lens placed in front of each fiber end and of the same axis as that here, the fiber end being placed in the focal plane of the lens. 7. Switching device according to one of claims 2, 5, 6, characterized in that the orientable elements deviators consist of planar mirrors and control means of the orientation of the normal to these mirrors following two independent settings. 8. Switching device according to one of claims 2, 5, 6, characterized in that the adjustable elements of the deviators consist of diasporameters having two prisms movable about a common axis of rotation, the rear face of the second prism in the direction of light propagation being reflective and means for controlling the rotation of the prisms relative to each other. 9. Device according to one of claims 2, 5, 6, characterized in that the deflecting elements each consist of a network etched on a plane mirror. 10. Device according to one of claims 2, 5, 6, characterized in that the deflecting elements are each constituted by a variable index prism with reflective rear face, 11. Device according to one of claims 3, 4, 5, 6, characterized in that the adjustable elements of the deviators consist of diasporameters comprising two prisms without reflecting side rotating about a common axis of rotation and control means of the rotation of the prisms relative to each other. 12. Device according to one of claims 3, 4, 5, 6, characterized in that the orientable elements deviators consist of acousto-optical elements generating variable pitch networks and variable orientation. 13. Device according to one of claims 3, 5, 6, characterized in that the adjustable elements of the deviators consist of prisms variable index. 14. Device according to one of claims 1 to 13, characterized in that the message detection means from one of the fibers and deviator control for selecting the pair of fibers to be connected make up a detector placed in a deflector plane on which are directed in the absence of message flows from all the fibers and control means deviators by the signal received by the detector to guide the deviators relating to the two fibers to be connected .