Optical fibre transmitter and receiver module

Abstract

The invention relates to an optical transmitter and receiver module (100), which includes: - an optical fibre (10), - a substrate (50) for positioning the optical fibre, - a light source (20), - a photodetector (30), and - an optical element (40). A first side face (55) of the substrate (50) and a first end face (14) of the optical fibre together form a common face. The optical element (40) includes an input face (41) on which a dichroic filter (45) is deposited, the input face being arranged to face the common face. The common face has two successive planar portions: - a first planar portion (91) defining a plane having an angle β relative to a plane (P) perpendicular to an optical axis of the optical fibre, and - a second planar portion (92) defining a plane having an angle α with respect to the optical axis.

Description

[0001] Fiber optic transmission and reception module

[0002] Technical field of the invention

[0003] The present invention relates to an optical fiber(s) transmission and reception module.

[0004] The invention can be used in particular for optical communications or for providing lighting.

[0005] The invention finds an advantageous application in the aeronautical field, particularly for equipping an aircraft.

[0006] Previous technique

[0007] Optical transmit and receive modules are commonly referred to in English-language literature as "transceivers," a contraction of "transmitter" and "receiver," and translated into French as "transcepteur." Transceivers typically consist of a transmitting section and a receiving section. The transmitting section includes a light source that emits a beam of light and a first optical device configured to perform optical coupling of the beam in a first optical fiber. The receiving section includes a second optical device configured to perform coupling of a beam received by a second optical fiber onto a photodetector. In the aeronautical field in particular, these transceivers, which use two optical fibers, present certain drawbacks, notably in terms of cost, size, installation, and associated maintenance management.

[0008] To overcome these drawbacks, one solution is to couple the light beams emitted and received by the light source and the photodetector, respectively, within a single optical fiber. A common optical device for both the light source and the photodetector enables the coupling and separation of the emitted and received light beams traveling through the optical fiber.

[0009] Numerous solutions exist for creating such a common optical device. One option is to use a semi-reflective plate equipped with a dichroic filter. However, optimal optical coupling is not guaranteed, as the light source and the photodetector are located far from the end of the optical fiber, and the emitted or received light beams pass through numerous optical components (lenses, filters, etc.). Furthermore, implementing this solution requires many mechanical parts to be machined with high precision to hold the various optical components in place. In addition, the resulting transceiver is bulky.

[0010] It is possible to replace the semi-reflective plate with an optical coupler, an optical circulator, or even a wavelength multiplexer / demultiplexer. However, the resulting transceptors remain bulky. Therefore, integrating a large number of such transceptors into a confined space is not feasible.

[0011] Presentation of the invention

[0012] The present invention aims to remedy the aforementioned drawbacks.

[0013] To this end, the present invention proposes an optical transmission and reception module, referred to as the module, comprising:

[0014] - a subassembly comprising an optical fiber and a substrate for positioning the optical fiber, called a positioning substrate,

[0015] - a light source,

[0016] - a photodetector,

[0017] - an optical element.

[0018] The positioning substrate comprises a first surface, a second opposite surface and a first lateral face, and comprising a longitudinal groove, made from the first surface, for receiving the optical fiber, said longitudinal groove opening onto the first lateral face.

[0019] The optical fiber has a core with a refractive index n c , an optical axis, and presenting a first end face flush with the first lateral face of the positioning substrate.

[0020] The first lateral face of the positioning substrate and said first end face of the optical fiber together form a common face.

[0021] The optical element has an entrance face on which a dichroic filter is deposited, said entrance face being arranged to be opposite the common face. The dichroic filter is configured as follows:

[0022] - to reflect a beam of light at a first wavelength,

[0023] - to allow a light beam to pass through at a second wavelength, distinct from the first wavelength. The light source is configured to emit a light beam at the first wavelength, called the emission beam.

[0024] The photodetector is configured to receive a light beam at the second wavelength, called the receiving beam.

[0025] According to the invention, the common face has two successive flat portions: - a first flat portion, extending from the first surface of the positioning support, and defining a plane presenting an angle [3] with respect to a plane perpendicular to the optical axis of the optical fiber, and

[0026] - a second flat portion, extending from the first flat portion and the second surface of the positioning substrate, and defining a plane presenting an angle α with respect to the optical axis of the optical fiber.

[0027] The entrance face of the optical element defines a plane inclined, with respect to the optical axis of the optical fiber, at the same angle α as the second planar portion of the common face.

[0028] The second flat portion of the common face is joined to a part of the dichroic filter located opposite the second flat portion of the common face, via an adhesive layer.

[0029] The first flat portion of the common face and a part of the dichroic filter located opposite the first flat portion of the common face are not joined together, delimiting an intercalated space.

[0030] The light source is arranged opposite the intercalated space so that its emission beam, after passing through the intercalated space, is directed towards the dichroic filter, is reflected there and then redirected towards the optical fiber.

[0031] The photodetector is arranged with respect to the optical element so as to receive the receiving beam from the optical fiber, after the passing of said receiving beam through the dichroic filter and through the optical element.

[0032] The module according to the invention thus advantageously comprises only a light source, a photodetector, an optical fiber and an optical element with a dichroic filter to couple the emission beam, from the light source, in the optical fiber and to couple the reception beam, from said optical fiber, to the photodetector.

[0033] Instead of using many external optical components to achieve coupling of the different light beams (emission beam and reception beam), the optical fiber itself is used, more specifically its entrance face, and a dichroic filter arranged opposite it, with an intercalated space between a part of the entrance face and the dichroic filter.

[0034] This particularly simple configuration therefore requires no additional optical components, as the geometric arrangement ensures both the transmission and reception of the emitted and received beams. The optical fiber is advantageously positioned as close as possible to the active optical components—the light source and the photodetector—thus guaranteeing high-performance optical coupling.

[0035] This configuration allows for the creation of a compact and low-cost module according to the invention. The integration of a large number of these modules into small spaces is therefore possible.

[0036] According to particular implementation methods, the module according to the invention also meets the following characteristics, implemented separately or in each of their technically operative combinations.

[0037] In preferred embodiments of the invention, the intercalated space is filled by a filling material having a refractive index n e greater than the refractive index n c from the core of the optical fiber.

[0038] Thus, in operation, part of the rays of the emission beam is directed directly towards the dichroic filter, passing through the filled intercalated space, is reflected by the dichroic filter, and then is transmitted into the optical fiber, after a new passage through the intercalated space.

[0039] Another portion of the emission beam rays first reaches the first flat section of the common face. Since the intercalated space traversed by this portion of the emission beam rays has a higher refractive index than the core of the optical fiber, this portion of the emission beam rays is reflected by the first flat section of the common face through total internal reflection. This portion of the emission beam reflected by the first flat section of the common face is then directed toward the dichroic filter, reflected by the dichroic filter, and transmitted through the optical fiber after passing through the intercalated space again.

[0040] In preferred embodiments of the invention, the filler material is the same material as the material constituting the adhesive layer. The assembly of the optical fiber with the optical element is thus facilitated by the use of a single material.

[0041] In preferred embodiments of the invention, the light source and the photodetector are arranged in the same plane. Such an arrangement further reduces the final size of the optical transmitter-receiver module.

[0042] In preferred embodiments of the invention, the optical element is an optical prism having a refractive index greater than or equal to a refractive index of the core of the optical fiber.

[0043] In preferred embodiments of the invention, the module comprises a plurality of optical fibers, and as many light sources and photodetectors, each optical fiber being arranged in a longitudinal groove of the same positioning substrate. Each optical fiber has a first end face flush with the first lateral face of the positioning substrate. Said first lateral face of the positioning substrate and said first end face of each optical fiber together form the common face. The module comprises a single optical element dimensioned so that its input face, with the dichroic filter, is opposite the common face and so that its output face is opposite all the photodetectors. The light sources are each arranged opposite the intercalated space. The module thus forms a compact, multi-channel, bidirectional optical component.

[0044] Brief description of the figures

[0045] The invention will be better understood upon reading the following description, given by way of non-limiting example, and made with reference to the figures which represent: Figure 1 is a schematic representation of an optical transmission and reception module according to an example of an embodiment of the invention,

[0046] Figure 2 is a cross-section of the optical transmission and reception module of Figure 1 along line AA,

[0047] Figure 3 is a schematic cross-sectional representation of an optical transmission and reception module according to one embodiment of the invention.

[0048] Figure 4 is an enlargement of detail G from Figure 1, illustrating in exploded view the assembly between a sub-assembly and an optical element constituting an optical transmission and reception module,

[0049] Figure 5 is an assembled view of Figure 4. Figure 6 is a view of the assembly between the subassembly and the optical element constituting an optical transmission and reception module according to an alternative embodiment of the invention.

[0050] Figure 7 is a view of the assembly between the sub-assembly and the optical element constituting an optical transmission and reception module according to one embodiment of the invention,

[0051] Figure 8 is a view of the assembly between the sub-assembly and the optical element constituting an optical transmission and reception module according to one embodiment of the invention,

[0052] Figure 9 is a perspective view of an optical transmission and reception module according to another embodiment of the invention.

[0053] Description of the implementation methods

[0054] Figure 1 illustrates in a very schematic way an example of an optical transmission and reception module according to the invention.

[0055] In the rest of the description, the optical transmission and reception module will be referred to as module or transceiver 100.

[0056] Figure 2 represents a cross-section of module 100 from figure 1 along line AA.

[0057] Module 100 includes:

[0058] - a subassembly 90 comprising an optical fiber 10 and a substrate for positioning the optical fiber 10, called the positioning substrate 50, - a light source 20,

[0059] - a 30 photodetector,

[0060] - an optical element 40.

[0061] The positioning substrate 50 is preferably in the form of a plate. As illustrated in Figure 2, the positioning substrate 50 comprises a first surface 52, preferably flat. The positioning substrate 50 comprises a second surface 54, opposite the first surface 52, preferably flat. The positioning substrate 50 comprises lateral faces, or lateral edges, connecting the first surface 52 to the second surface 54.

[0062] The positioning substrate 50 is for example a ceramic or silicon support, preferably glass, of the borosilicate type.

[0063] The positioning substrate 50 comprises, as illustrated in Figure 2, a longitudinal groove 51 made in a thickness e s said positioning substrate. By thickness, we mean the distance between the first surface 52 and the second surface 54.

[0064] The longitudinal groove 51 is cut from the first surface 52. It extends over a depth h r .

[0065] The longitudinal groove 51 is intended to receive the optical fiber 10.

[0066] The positioning substrate 50 is shown in transparency in Figure 1 to illustrate the longitudinal groove 51 and to visualize the positioning of the optical fiber 10 of said longitudinal groove.

[0067] The longitudinal groove 51 opens onto one of the lateral faces, called the first lateral face 55, of the positioning substrate 50.

[0068] The longitudinal groove 51, for example, has a V shape, as illustrated in section AA of figure 2.

[0069] The shape and / or dimension of the longitudinal groove 51 is / are preferably adapted to the diameter of the optical fiber 10.

[0070] The optical fiber 10 conventionally comprises a core 11, as illustrated in Figures 2 and 3. The core 11 has a refractive index n c The core 11 of the optical fiber 10 is preferentially made of glass, based on silica.

[0071] Optical fiber 10 can be a single-mode optical fiber or a multi-mode optical fiber.

[0072] Preferably, optical fiber 10 is a multimode optical fiber. It therefore has a core 11 of large diameter.

[0073] An optical cladding 12 is in contact with and surrounds the core 11. The optical cladding 12 has a refractive index n g lower than the refractive index n c of the heart 11.

[0074] The optical fiber 10 has an optical axis 13 which follows the center of the core 11 of the optical fiber 10.

[0075] Only a portion of the length of optical fiber 10 is shown in Figures 1 and 3.

[0076] The optical fiber 10 has a first end face 14.

[0077] As described previously, the optical fiber 10 is placed in the longitudinal groove 51 of the positioning substrate 50. More precisely, the first end face 14 of the optical fiber 10 is flush with the first lateral face 55 of the positioning substrate 50.

[0078] The first end face 14 of the optical fiber 10 and the first side face 55 of the positioning substrate 50 together form a common face for the subassembly 90.

[0079] The optical fiber 10 is held in place in the longitudinal groove 51 for example by means of an adhesive 53. The adhesive 53 is for example a UV adhesive (ultraviolet curing adhesive).

[0080] When the optical fiber 10 is placed in the longitudinal groove 51, said optical fiber is substantially flush with the first surface 52 of the positioning support 50.

[0081] According to the invention, and as illustrated in figure 4, the common face of the subassembly 90 is neither flat nor located entirely in a plane P perpendicular to the optical axis 13 of the optical fiber 10.

[0082] The common face has two successive flat portions:

[0083] - a first flat portion 91 which extends from the first surface 52 of the positioning support 50 and which defines a plane having an angle [3 with respect to the plane P perpendicular to the optical axis 13 of the optical fiber 10, and - a second flat portion 92 which extends between the first flat portion 91 and the second surface 54 of the positioning substrate 50 and which defines a plane having an angle a with respect to the optical axis 13 of the optical fiber 10. In other words, the second flat portion 92 defines a plane having an angle y with respect to the plane perpendicular to the optical axis of the optical fiber 10. Thus, the sum of the angles a and y is 90°.

[0084] The line of intersection of the first flat portion 91 and the second flat portion 92 preferentially forms a salient and non-re-entrant edge.

[0085] The first flat portion 91 extends over a height hi of the positioning substrate 50. This height h1 is preferably less than the depth h r of the longitudinal groove 51 in the positioning substrate. For example, the height hi is at most equal to the diameter of the optical fiber 10. Preferably, the height hi is substantially equal to the diameter of the optical fiber 10. The angle [3 can be non-zero, as illustrated in figures 4 and 5, or zero, as illustrated in figure 6.

[0086] The absolute value of the angle [3 of the first plane portion 91 is strictly less than the angle a of the second plane portion 92. In the figures, the angle [3 of the first plane portion 91 is oriented positively in the direction of a clockwise direction.

[0087] The second flat portion 92 extends over a height h2 of the positioning substrate 50. The sum of the heights hi and h2 thus corresponds to the thickness e sof the positioning substrate 50.

[0088] The angle a of the second plane portion 92 is a non-zero angle.

[0089] The angle a of the second plane portion 92 can preferably be between 20° and 60°, and even more preferably between 40° and 50°. In a preferred example, the angle a is approximately equal to 45°.

[0090] In the figures, angle a of the second plane portion 92 is oriented positively in a clockwise direction.

[0091] The first flat portion 91 and the second flat portion 92 of the common face can, for example, be made by polishing or cleaving.

[0092] In module 100 according to the invention, sub-assembly 90 is assembled to optical element 40.

[0093] The optical element 40 is advantageously arranged opposite the common face, as illustrated in Figures 1, 4 to 8. Figures 4 and 5 show an enlargement of detail G of Figure 1. Figure 4 is an exploded view of the assembly of subassembly 90 with the optical element 40. Figure 5 is an assembled view of the assembly of subassembly 90 with the optical element 40.

[0094] In a preferred embodiment, the optical element 40 is an optical prism. The optical element 40 has a face, called the entrance face 41, arranged opposite the common face.

[0095] The entrance face 41 of the optical element 40 defines an inclined plane, with respect to the optical axis 13 of the optical fiber 10, at the same angle α as the second planar portion 92 of the common face.

[0096] A dichroic filter 45 is deposited on the entrance face 41 of the optical element 40. The dichroic filter 45 is configured to reflect light beams emitted at a first wavelength Xi and to allow light beams emitted at a second wavelength X2 to pass through. The wavelength X2 is distinct from the wavelength Xi.

[0097] In a preferred embodiment, the wavelength X1 is less than the wavelength X2, and the chosen dichroic filter 45 is a high-pass type filter.

[0098] In one example implementation, the wavelength Xi is 850 nm and the wavelength X2 is 940 nm. The cutoff frequency of the dichroic filter is between Xi and X2, for example at 900 nm.

[0099] In another embodiment, the wavelength Xi is greater than the wavelength X2, and the chosen dichroic filter 45 is a low-pass type filter. The cutoff frequency of the dichroic filter 45 is between Xi and X2.

[0100] The optical element 40 is assembled to the common face via an adhesive layer 80 interposed between the dichroic filter 45 and the second flat portion 92 of the common face.

[0101] Subassembly 90 is thus assembled to optical element 40 in such a way that:

[0102] - the second flat portion 92 of the common face is joined to a part of the dichroic filter 45 located opposite the second flat portion 92 of the common face, via the adhesive layer 80,

[0103] - the first flat portion 91 of the common face and part of the dichroic filter 45 of the optical element 40 opposite the first flat portion 91 of the common face are not joined together, thus delimiting an intercalary space 5.

[0104] In a first configuration of module 100, as illustrated in Figures 5 and 6, the intercalated space 5 is not filled. The intercalated space 5 is thus a hollow volume through which air circulates. Air has a refractive index lower than the refractive index n c from the core of the optical fiber.

[0105] In a second configuration of the module 100, as illustrated in Figures 7 and 8, the intercalated space 5 is filled by a filling material having a refractive index n e greater than the refractive index n cof the optical fiber core 10. In this second configuration of module 100, the filler material can be the material constituting the adhesive layer 80. The adhesive layer 80 then has a refractive index higher than the refractive index n c of the optical fiber core 10. Thus, the optical element 40 is assembled to the common face via the adhesive layer 80 interposed between the dichroic filter 45 and the first and second flat portions 91, 92 of the common face. The adhesive layer 80 has a local excess thickness between the first flat portion 91 of the common face and the part of the dichroic filter 45 opposite the first flat portion 91 of the common face.

[0106] According to the invention, the light source 20 is arranged opposite the intercalated space 5.

[0107] The light source 20 is configured to emit a beam of light, called the emission beam, in the direction of the intercalated space 5.

[0108] The light source 20 is preferably a monochromatic source. The emission beam is emitted at the first wavelength Xi.

[0109] In general, the emission beam exiting the light source 20 is a divergent beam and takes the form of a diffusion cone.

[0110] Any light source can be used for light source 20, such as, for example, light-emitting diodes (known by the acronym LED) or laser sources, such as laser diodes or vertical-cavity surface-emitting laser diodes, commonly known by the acronym VCSEL (for the English "Vertical-Cavity Surface-Emitting Laser"). However, the use of surface-emitting light sources, such as LEDs or VCSELs, will be advantageously preferred.

[0111] The light source 20 is placed at a distance from the intercalated space 5. The light source 20 is preferably placed on the side of the common face, close to it.

[0112] As described previously, the dichroic filter 45 is configured to reflect light beams emitted at a first wavelength Xi. The dichroic filter 45 is therefore suitable for reflecting the emission beam from the light source 20.

[0113] Thus, the light source 20 is arranged with respect to the gap 5 such that its emission beam, after passing through the gap 5, is directed towards the dichroic filter 45 to be reflected and then redirected towards the optical fiber 10 and subsequently propagates in the core 11 of the optical fiber 10. In Figure 3, for clarity, only one ray 21 of the emission beam is shown, specifically the one located on a central axis of said emission beam. Arrows indicate the direction of propagation of this ray 21.

[0114] The light source is positioned more or less close to the first flat portion 91 of the common face depending on the module configuration, that is, depending on whether the intercalated space 5 is filled or not by a filling material having a refractive index n e greater than the refractive index n c from the core of the optical fiber.

[0115] Indeed, it is known that the operation of a dichroic filter differs depending on whether it is placed at an air / material interface or a material / material interface. More specifically, a dichroic filter reflects a given wavelength of an incident beam only within a predefined range of beam angles. This range of angles is greater when the dichroic filter is at an air / material interface than at a material / material interface (such as, for example, glass / glass).

[0116] In the first configuration of the module, as illustrated in Figures 5 and 6, the gap 5 is not filled. The dichroic filter is then located at an air / optical element interface 40, and the angle range accepted by the dichroic filter is the largest. The light source 20 is preferentially positioned relative to the first flat portion 91 of the common face so that most or all of the rays forming the emission beam are directed towards the dichroic filter 45 and then reflected back to the optical fiber 10.

[0117] It is possible that a portion of the emission beam rays first reaches the first planar portion 91 of the common face. This portion of the emission beam rays mainly includes rays with large angles of incidence. In this case, this portion of the emission beam rays is reflected by the first planar portion 91 of the common face by partial reflection. This portion of the emission beam reflected by the first planar portion 91 of the common face is directed towards the dichroic filter 45, then reflected by said dichroic filter 45 and transmitted into the optical fiber 10, after a further passage through the gap 5. The path of this portion of the emission beam rays is called the indirect path. In the second configuration, as illustrated in Figures 7 and 8, the gap 5 is filled with a filling material having a refractive index n egreater than the refractive index n c of the core of the optical fiber. The dichroic filter 45 is then located at a material / optical element interface 40 and the angle range accepted by the dichroic filter is reduced.

[0118] The light source 20 is then preferentially positioned closer to the first flat portion 91 of the common face. Depending on the angle of incidence of the rays of the emission beam, said rays are directed towards the dichroic filter 45 either along a direct trajectory or along an indirect trajectory.

[0119] More precisely, a portion of the emission beam rays is directed straight towards the dichroic filter 45, passing through the filled gap 5, is reflected by the dichroic filter 45, and then transmitted into the optical fiber 10 after passing through the gap 5 again. The path of this portion of the emission beam rays is called the direct path. This portion of the emission beam rays mainly includes rays of the emission beam with small angles of incidence.

[0120] Another portion of the emission beam rays first reaches the first planar segment 91 of the common face. This portion of the emission beam rays mainly includes rays with large angles of incidence. The intercalated space 5 traversed by this portion of the emission beam rays, which has a higher refractive index than the core of the optical fiber, is reflected by the first planar segment 91 of the common face by total internal reflection. This portion of the emission beam reflected by the first planar segment 91 of the common face is directed towards the dichroic filter 45, then reflected by said dichroic filter 45 and transmitted into the optical fiber 10, after a further passage through the intercalated space 5. The path of this portion of the emission beam rays is called the indirect path.

[0121] Thus, regardless of the configuration of module 100, the module advantageously allows the transmission of the emission beam, emitted by the light source 20, into the optical fiber 10 with optimal coupling.

[0122] According to the invention, the photodetector 30 of the module 100 is configured to receive a light beam emitted at the second wavelength X2, referred to as the receiving beam. According to the invention, the receiving beam originates from the optical fiber 10.

[0123] As described previously, the dichroic filter 45 is configured to allow any light beam of wavelength X2 to pass through. The dichroic filter 45 is therefore suitable for allowing the receiving beam from the optical fiber 10 to pass through. The photodetector 30 is thus preferentially arranged with respect to the optical element 40 so as to receive the receiving beam from the optical fiber 10, after the receiving beam has passed through the dichroic filter 45 and then through the optical element 40.

[0124] In one embodiment, as illustrated in Figures 1 and 3, the optical element 40 has a second face, called the output face 42, arranged so as to be opposite the photodetector 30.

[0125] The optical element 40 is advantageously designed so that the receiving beam enters from its entrance face 41 and exits from its exit face 42, as illustrated in Figure 3. For clarity, only the propagation of an arbitrary ray 31 of the receiving beam is shown in this Figure 3. Arrows indicate the direction of propagation of this arbitrary ray 31.

[0126] The shape of the optical element 40 is advantageously adapted to the desired orientation of the reflected beam.

[0127] In one embodiment, the shape of the optical element 40 is adapted so that the light source 20 and the photodetector 30 are arranged in two substantially perpendicular planes, as illustrated in Figure 1. Such an arrangement of the light source 20 and the photodetector 30 helps to reduce the final size of the module 100.

[0128] In the example in Figure 1, the optical element 40 is a right-angled prism. The entrance face 41 is the flat face opposite the right angle of the prism.

[0129] In another embodiment, not shown in the figures, the shape of the optical element 40 is adapted so that the light source 20 and the photodetector 30 are arranged in the same plane. Such an arrangement of the light source 20 and the photodetector 30 also helps to reduce the overall size of the module 100.

[0130] As described previously, the photodetector 30 is arranged to receive the receiving beam, after the passing of said receiving beam through the dichroic filter 45 and the optical element 40.

[0131] More specifically, the photodetector 30 is positioned opposite the output face 42 of the optical element 40, at a distance from the output face 42.

[0132] The photodetector 30 is preferentially positioned with respect to the optical element 40, and more particularly with respect to the output face 42, so that all the rays forming the receiving beam are received in whole, or almost in whole, by said photodetector.

[0133] Thus, the receiving beam from the optical fiber 10 exits the optical fiber 10 via the first end face 14, passes through the gap 5 and the dichroic filter 45, and enters the optical element 40. The receiving beam propagates in the optical element 40, exits through its exit face 42 and is directed towards the photodetector 30.

[0134] Such an arrangement of the photodetector 30 vis-à-vis the optical element 40 allows the transmission of the receiving beam into the photodetector 30 with optimal coupling.

[0135] The optical element 40 may have substantially the same refractive index as the core 11 of the optical fiber 10 or a higher refractive index.

[0136] Optical element 40 is, for example, a glass prism.

[0137] Module 100 may include a first support 60 for positioning the light source 20. Module 100 may include a second support 62 for positioning the photodetector 30.

[0138] The module 100 may include a plate 64, allowing the optical fiber 10 to be compressed against the first surface 52 of the positioning substrate 50. Said plate is preferably interposed between the positioning substrate 50 and the first support 60. The plate 64 is also dimensioned in thickness to guarantee a predefined distance between the light source and the intercalated space 5.

[0139] An example of a method for assembling sub-assembly 90, light source 20, photodetector 30, and optical element 40 to produce module 100, is now described, by way of non-limiting example, as illustrated in Figures 1 and 2.

[0140] The optical fiber 10 is positioned and held in place in a longitudinal groove 51, for example V-shaped, previously made in a thickness e s of the positioning substrate 50.

[0141] The longitudinal groove 51 is made from the first surface 52, preferably flat, of the positioning substrate 50.

[0142] The longitudinal groove 51 is made in the positioning substrate 50 for example by laser engraving or by means of a diamond saw.

[0143] The shape and / or dimension of the longitudinal groove 51 is preferably adapted to the diameter of the optical fiber 10.

[0144] The first end face 14 of the optical fiber 10 is positioned at the level of the first lateral face 55 of the positioning substrate 50 to form the common face. At this stage of assembly, the common face is flat. It is substantially in a plane perpendicular to the optical axis 13 of the optical fiber 10. The plate 64 is then preferably positioned against the first surface 52 of the positioning substrate 50, slightly compressing the optical fiber 10 in the longitudinal groove 51. The plate 64 can be positioned offset from the common face.

[0145] In one example of implementation, plate 64 is made of electrically non-conductive polymer material or glass.

[0146] Plate 64 and optical fiber 10 are held in place, for example, by glue 53.

[0147] The optical fiber 10 and the positioning substrate 50 are then polished so that the common face presents the first and second flat portions 91, 92.

[0148] In one embodiment, the optical fiber 10 and the positioning substrate 50 are polished once so that the entire common face has an inclination of an angle α with respect to the optical axis 13 of the optical fiber 10. Then the optical fiber 10 and the positioning substrate 50 are polished again, this time so that the common face has an inclination of an angle [3 with respect to the plane perpendicular to the optical axis 13 of the optical fiber 10, from the first surface 52 of the positioning substrate 50, over a height h1.

[0149] The polishing of the common face is carried out, for example, by conventional micromachining techniques. The prism 40 is itself previously made with an entrance face 41 having an angle a.

[0150] A surface treatment is then applied to the entrance face 41 of the prism 40 to form the appropriate dichroic filter 45. This surface treatment consists, for example, of the deposition of successive thin layers. The layers and their respective thicknesses are determined conventionally by those skilled in the art. According to the first configuration of module 100, the prism 40 is then joined, by its entrance face 41, to the common face at the level of the second flat portion 92. The dichroic filter 45 is thus interposed between the entrance face 41 of the prism and the common face.

[0151] According to the second configuration of module 100, the prism 40 is then attached, by its entrance face 41, to the common face, at the level of the first flat portion 91 and the second flat portion 92. The dichroic filter 45 is thus intercalated between the entrance face 41 of the prism and the common face.

[0152] The prism 40 is held in place against the common face by gluing, the glue forming the adhesive layer 80.

[0153] In one example of the implementation, the glue is a UV glue.

[0154] The active optical components, namely the light source 20 and the photodetector 30, are mounted on the first substrate 60. The light source 20 is preferably a surface-emitting source. The first substrate 60 is preferably made of ceramic or silicon. The first substrate 60 can advantageously serve as a substrate for the electronic power supply and control circuits of the active optical components. The first substrate 60 can be a printed circuit board (PCB).

[0155] When the shape of the prism 40 is adapted so that the two active optical components are arranged in the same plane, said two active optical components are preferably glued to the first support 60.

[0156] When the shape of the prism 40 is adapted so that the two optical components are arranged in two substantially perpendicular planes, the light source 20 is preferably bonded to the first support 60, and the photodetector 30 is preferably bonded to the second support 62, arranged perpendicular to the first support 60, as illustrated in Figure 3. The second support 62 is preferably a ceramic or silicon support. In one embodiment, the adhesive is a thixotropic conductive adhesive. Such an adhesive exhibits good thermal and electrical conductivity.

[0157] The active optical components are arranged on the first support 60 in such a way that, when the first surface 52 of the positioning substrate 50 comes to be positioned opposite the first support 60:

[0158] - the light source 20 is positioned opposite the intercalated space 5 and arranged opposite the dichroic filter 45 and the prism 40, so that the emission beam is directed towards the prism 40 to be reflected by the dichroic filter 45,

[0159] - the photodetector 30 is arranged opposite the exit face 42 of the prism, so that the receiving beam, coming from the optical fiber 10, passes through the dichroic filter 45, passes through the prism 40 and heads towards the photodetector 30.

[0160] The plate 64, which compresses the optical fiber against the first surface 52 of the positioning substrate 50, is interposed between the positioning substrate 50 and the first support 60. The plate 64 has been pre-dimensioned in thickness to guarantee a predefined distance between the said active optical components and the said optical fiber 10.

[0161] The positioning substrate 50 and the first support 60 are held opposite each other, for example by an adhesive, for example a UV adhesive.

[0162] With such a module, the optical fiber 10 is as close as possible to the active optical components, thus the optical couplings are optimal.

[0163] The Module 100, as described, comprises a single optical fiber, a single light source, and a single photodetector. Such a Module 100 operates advantageously in both transmission and reception via a single optical fiber. This Module 100 can be called a single-channel, bidirectional optical transceiver.

[0164] It is also possible to consider such a module 100 with several optical fibers 10, light sources 20 and photodetectors 30 in order to create a bidirectional multi-channel optical transceptor.

[0165] In this case, the module 100 comprises as many light sources 20 and photodetectors 30 as there are optical fibers 10. Each optical fiber 10 is connected to a light source 20 and a photodetector 30. Such a module 100 advantageously comprises a single positioning substrate 50. The positioning substrate 50 comprises a plurality of longitudinal grooves 51, arranged parallel to each other. Each optical fiber 10 is positioned in one of the longitudinal grooves 51 of the positioning substrate 50. Each first end 14 of the optical fibers 10 is flush with the first lateral face 55 of the positioning substrate 50. Each first end 14 of the optical fibers and the first lateral face 55 of the positioning substrate 50 together form the common face.

[0166] Such a module 100 advantageously comprises a single optical element 40, of a size adapted so that its entrance face 41, with the dichroic filter 45, is opposite the common face and so that its output face 42 is opposite all the photodetectors 30.

[0167] The light sources 20 are arranged parallel to each other, each opposite the intercalated space 5, on the first support 60.

[0168] The photodetectors 30 are arranged parallel to each other, each opposite the optical element 40, either on the first support 60 or on the second support 62. Figure 9 illustrates an example of a module 100 comprising eight optical fibers. The positioning substrate 50 is shown in transparency to demonstrate the longitudinal grooves 50 and the positioning of the optical fibers 10 within said longitudinal grooves 51. The first support 60, the second support 62, and the active optical components 20, 30 are not shown for the sake of clarity in Figure 9. Such a module 100 thus comprises eight bidirectional communication channels.

[0169] Example of a completed project:

[0170] In this example, the light source is a VCSEL from Optowell® (reference HV85-0025M1), emitting at a wavelength of 850nm.

[0171] The photodetector is a photodiode from the company Kyosemi® (reference KPID050M), configured to detect a receiving beam with a wavelength of 940nm.

[0172] The optical fiber is a large core HCS® (Hard-Clad Silica) type optical fiber with a 400pm core and a numerical aperture of 0.37 (reference CF01493-12 from OFS).

[0173] The distance between the VCSEL and the first surface 52 of the positioning substrate 50 is 350pm.

[0174] The distance between the output face 42 of the optical element 40 and the photodiode is 10Oprn, in the optical axis 13 of the optical fiber 10.

[0175] The angle a is 45°, the angle [3 is zero, hr=h1 and A=850nm.

[0176] The depth h r the longitudinal groove 51 is 629pm.

[0177] The first flat portion 91 extends over a height hi of the positioning substrate 50 equal to 430pm.

[0178] Intercalated space 5 is not filled.

[0179] With such a configuration, a coupling performance of the emission beam emitted by the VCSEL in the optical fiber of around 94% and a coupling performance of the reception beam from the optical fiber in the photodiode of around 60% was measured.

[0180] In a preferred application of the Module 100, the module is placed in an aircraft and can be associated with equipment such as equipment known by the acronym PSU (Passenger Service Unit), allowing a passenger to trigger calls to the commercial flight crew or to turn a reading light on / off.

[0181] Module 100 can then be advantageously used both for data transmission, via Li-Fi (acronym for "Light Fidelity") technology, and for providing ambient lighting. Data transmission via Li-Fi technology can be understood as both a downward flow (towards the passenger) and an upward flow (from the passenger).

[0182] Each light source 20 of the module 100 is configured to emit the emission beam at a wavelength Xi located in the infrared range. By infrared range, we mean the range of wavelengths between 764 nm and 2 pm.

[0183] Each photodetector 30 of the module 100 is configured to detect the receiving beam at a wavelength Æ2 also located in the infrared range.

[0184] The preceding description clearly illustrates that, through its various features and their advantages, the present invention achieves its intended objectives. In particular, it provides a compact and low-cost optical transmission and reception module. This module features a simple configuration that requires no additional optical components other than a light source, a photodetector, and a prism. Polishing the optical fiber and positioning the light source, photodetector, and prism relative to the optical fiber effectively ensure the transmission and reception of light beams.

Claims

22 Demands Claim 1. Optical transmit and receive module, referred to as module (100), comprising: - a subassembly (90) comprising an optical fiber (10) and a substrate for positioning the optical fiber (10), called the positioning substrate (50), - a light source (20), - a photodetector (30), - an optical element (40), the positioning substrate (50) comprising a first surface (52), a second opposite surface (54) and a first lateral face (55), and comprising a longitudinal groove (51), made from the first surface (52), for receiving the optical fiber (10), said longitudinal groove opening onto the first lateral face (55), the optical fiber (10) comprising a core (11), with refractive index n c, an optical axis (13), and having a first end face (14) flush with the first lateral face (55) of the positioning substrate (50), said first lateral face (55) of the positioning substrate (50) and said first end face (14) of the optical fiber (10) together forming a common face, the optical element (40) comprising an entrance face (41) on which a dichroic filter (45) is deposited, said entrance face (41) being arranged to be opposite the common face, the dichroic filter (45) being configured: - to reflect a beam of light at a first wavelength (Xi), - to allow a beam of light at a second wavelength (X2), distinct from the first wavelength (Xi), the light source (20) being configured to emit a light beam at the first wavelength (Xi), called the emission beam, the photodetector (30) being configured to receive a light beam at the second wavelength (X2), called the receiving beam, characterized in that: the common face has two successive flat portions: - a first flat portion (91), extending from the first surface (52) of the positioning support (50), and defining a plane presenting an angle [3] with respect to a plane (P) perpendicular to the optical axis (13) of the optical fiber (10), and - a second flat portion (92), extending from the first flat portion (91) and the second surface (54) of the positioning substrate (50), and defining a plane presenting an angle α with respect to the optical axis (13) of the optical fiber (10), the entrance face (41) of the optical element (40) defines a plane inclined, with respect to the optical axis (13) of the optical fiber (10), at the same angle α as the second planar portion (92) of the common face, the second flat portion (92) of the common face is joined to a part of the dichroic filter (45) located opposite the second flat portion (92) of the common face, via an adhesive layer (80), the first flat portion (91) of the common face and a part of the dichroic filter (45) located opposite the first flat portion (91) of the common face are not joined together, delimiting an intercalated space (5), the light source (20) is arranged opposite the intercalated space (5) so that its emission beam, after passing through the intercalated space (5), is directed towards the dichroic filter (45), is reflected there and then redirected towards the optical fiber (10), the photodetector (30) being arranged with respect to the optical element (40) so as to receive the receiving beam from the optical fiber (10), after the passing of said receiving beam through the dichroic filter (45) and through the optical element (40). Claim 2. Module (100) according to claim 1 in which the intercalated space (5) is filled by a filling material having a refractive index n e greater than the refractive index n c of the core (11) of the optical fiber (10). Claim 3. Module (100) according to the preceding claim in which the filling material is the same material as the material constituting the adhesive layer (80). Claim 4. Module (100) according to any one of the preceding claims wherein the light source (20) and the photodetector (30) are arranged in the same plane. Claim s. Module (100) according to any one of the preceding claims wherein the optical element (40) is an optical prism having a refractive index greater than or equal to a refractive index of the core (11) of the optical fiber (10). Claim s. Module (100) according to any one of the preceding claims comprising a plurality of optical fibers (10), and as many light sources (20) and photodetectors (30), each optical fiber (10) being arranged in a longitudinal groove (51) of the same positioning substrate (50), each optical fiber (10) having a first end face (14) flush with the first lateral face (55) of the positioning substrate (50), said first lateral face (55) of the positioning substrate (50) and said first end face (14) of each optical fiber (10) together forming the common face, the module (100) comprising a single optical element (40) dimensioned so that its entrance face (41), with the dichroic filter (45), is opposite the common face and so that its exit face (42) is opposite all the photodetectors (30), the light sources (20) each being arranged opposite the intercalated space (5).

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