Optical fiber device

Abstract

The invention relates to an optical device comprising: an optical fiber, an optical component comprising: a substrate, a stack of three layers arranged on one face of the substrate: a semi-reflective layer, a diffraction layer comprising a diffraction grating, a reflective layer, and an optical element (600). The optical component is arranged and dimensioned to form an interface between the optical fiber and a light source / photodetector assembly arranged in directions perpendicular to an optical axis of the optical fiber. The stacking of the three layers and their characteristic parameters (thicknesses, refractive index of the layers) enable the optical component to achieve optical coupling of a first incident beam from the light source to the optical fiber. The optical element enables the optical component to achieve efficient optical coupling of a second incident beam from the optical fiber to the photodetector.Figure for the abbreviation: Figure 1.

Description

Title of the invention: Optical fiber device Technical field of the invention

[0001] The present invention relates to a fiber optic device for the bidirectional transmission of optical signals from a light source and / or to a photodetector. The present invention relates in particular to an optical device enabling the bidirectional transmission of signals from a light source and / or to a photodetector arranged in a direction substantially orthogonal to the optical axis of the optical fiber.

[0002] The invention finds an advantageous application in the aeronautical field, in particular for equipping an aircraft. Previous technique

[0003] In aircraft, optical fibers are increasingly used to interconnect equipment for communication purposes.

[0004] In the particular context of the distribution of Li-Fi (acronym for Light-Fidelity) type optical signals, optical fibers can be used to carry these signals bidirectionally from light sources and to photodetectors located at the level of the backs of the passenger seats.

[0005] These optical fibers run the entire length of the cabin, in areas that are difficult to access and have limited volume, generally in the ceiling, under the luggage compartments, and one of their ends arrives above the backs of the passenger seats.

[0006] An interface is then necessary between the end of an optical fiber, located above the backrest of a passenger seat, and the light source / photodetector assembly located at the level of said backrest of a passenger seat, to allow: - on the one hand, the optical coupling of a light beam, carrying optical signals, coming from the light source towards the optical fiber, - on the other hand, the optical coupling of a light beam, carrying optical signals, coming from the optical fiber to the photodetector.

[0007] Optical couplings are all the more complex as they must be made not in a direction of the optical axis of the optical fiber, but in a direction orthogonal to this optical axis, which implies the use of an angle return of the order of 90°.

[0008] In the so-called downward flow direction, that is, from the optical fiber to the photodetector, optical coupling can, for example, simply rely on the natural divergence of the light beam. A simple angle deflection, with a mirror for example, can suffice as an interface between the optical fiber and the photodetector.

[0009] However, in the so-called upward flow direction, that is, from the light source to the optical fiber, the natural divergence of the light beam emitted by the light source must be counteracted in order to capture the entire light beam emitted by the light source and then inject it into the optical fiber. A setup based on lenses and a prism or a mirror can achieve this optical coupling. However, such a setup requires meticulous implementation because the alignments must be precise to obtain optimal coupling. Furthermore, such a setup is bulky, both in terms of weight and volume, expensive, and inefficient in terms of injection into the optical fiber, making it difficult to integrate into a highly constrained environment such as that of an aircraft. Presentation of the invention

[0010] The present invention aims to remedy the aforementioned drawbacks.

[0011] To this end, the present invention proposes an optical device comprising: - an optical fiber having a core, with refractive index nc and diameter dc, and having a first end face, - an optical component comprising: • a substrate with a refractive index ns substantially equal to the refractive index nc of the optical fiber core and a thickness es substantially less than or equal to the diameter dc of the fiber core, said substrate: • comprising two faces, called the first and second faces, • extending between two opposite edges, called the first and second edges, • presenting a first longitudinal portion originating from the first edge and a second longitudinal portion originating from the second edge, • a stack of three layers arranged on the second face of the substrate, at the level of the first longitudinal portion of said substrate • a semi-reflective layer with a refractive index nsr greater than the refractive index ns of the substrate, and of thickness esr, • a diffraction layer of thickness ed, comprising, throughout its thickness, a diffraction grating of period A, • a reflective layer, • an optical element, at the level of its second longitudinal portion,

[0012] the optical fiber being arranged opposite the optical component so that the The first end face of said optical fiber is attached to the first edge of the substrate.

[0013] the semi-reflective layer and the diffraction layer being disposed between the substrate and the reflective layer, the semi-reflective layer being disposed between the substrate and the diffraction layer or between the diffraction layer and the reflective layer,

[0014] for a first incident ray, having a first given wavelength Xiet arriving on the first face of the substrate with a predetermined angle of incidence ai and defined relative to a direction normal to said first face of the substrate: The thicknesses of the semi-reflective layer and the diffraction layer are determined to generate destructive interference of the reflected rays. The diffraction grating is configured to allow the diffraction of the first incident ray within the limit of the first order of diffraction, and at a diffraction angle such that the diffracted ray propagates in the substrate, within an acceptance cone of the optical fiber, towards the first face of the optical fiber.

[0015] for a second incident ray from the optical fiber, having a second wavelength X2 distinct from the first wavelength Xb the optical element is configured to direct said second incident ray out of the substrate, perpendicular to the first face of the substrate.

[0016] The optical component advantageously forms an interface between the first end face of the optical fiber and a light source / photodetector assembly arranged in a direction substantially perpendicular to an optical axis of the optical fiber.

[0017] The optical component advantageously allows: on the one hand, to collect as many of the first incident rays as possible, forming the first incident beam from the light source, and to transmit them through the optical fiber, and on the other hand, to collect a maximum of the second incident rays forming the second incident beam coming from the optical fiber and to transmit them to the photodetector.

[0018] The stacking of the three layers, their arrangement, and their characteristic parameters (thickness, refractive index of the layers) enable the optical component to achieve efficient optical coupling of the first incident beam from the light source to the optical fiber. The natural divergence of the light beam emitted by the light source is counteracted.

[0019] The optical element enables the optical component to achieve optical coupling effective of the second incident beam coming from the optical fiber towards the photodetector.

[0020] In particular embodiments, the optical device may further comprise one or more of the following characteristics, taken individually or in all technically possible combinations.

[0021] In particular embodiments, the diffraction grating takes the form of a plurality of concentric circular arcs, centered on the first edge of the substrate, at the level of the first face of the optical fiber. Such a circular arc shape of the diffraction grating advantageously allows the rays diffracted by said diffraction grating to converge towards the first end face of the optical fiber.

[0022] In particular embodiments, the arcs of circles extend over the same angular range corresponding to a numerical aperture of the optical fiber.

[0023] In particular embodiments, the diffraction grating has materials whose refractive indices are identical to the materials of the layers arranged on either side of the diffraction layer.

[0024] In particular embodiments, the second edge of the substrate of the optical component has an inclination of an angle substantially equal to 45° with respect to a longitudinal axis of said substrate and the optical element is a mirror attached to said second edge of the substrate.

[0025] The invention also relates to an optical assembly comprising a light source, a photodetector, and an optical device according to at least one of its embodiments. The light source is arranged opposite the first face of the substrate, at the level of the first longitudinal portion, and is configured to emit the first incident ray. The photodetector is arranged opposite the first face of the substrate, at the level of the second longitudinal portion, and is positioned relative to the optical element so as to receive the second incident ray. Brief description of the figures

[0026] 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:

[0027] Figure 1 is a perspective view of an optical device according to the invention comprising, in exploded view, an optical component in a first configuration,

[0028] Figure 2 is a cross-sectional view of the optical device with the first configuration of the optical component, and illustrating the path, in the optical component, of a light ray, in the direction of the upward flow,

[0029] Figure 3 is a cross-sectional view of the optical device with a second configuration of the optical component, and illustrating the trajectory, in the optical component, of a light beam, in the direction of the upward flow,

[0030] Figure 4 illustrates the path of a light beam in the optical device in the direction of the upward flow, regardless of the component configuration.

[0031] Figure [Fig. 5] illustrates the path of a light beam in the optical device in the direction of the downward flow,

[0032] Figure 6 illustrates a top view of a diffraction layer of the optical device, with a diffraction grating in the form of concentric circular arcs. Description of embodiments

[0033] Figure 1 illustrates an example of an optical device 500 according to the invention. Said optical device comprises an optical fiber 200 and, in a semi-exploded perspective, an optical component 100 forming a resonant array, referred to as the optical component.

[0034] The optical device 500 advantageously forms part of an optical assembly 700 further comprising a light source 300 and a photodetector 400.

[0035] The light source 300 and the photodetector 400 are arranged in directions substantially perpendicular to an optical axis of the optical fiber 200.

[0036] According to the invention, the optical component 100 of the optical device is advantageously designed and configured to: - on the one hand, transmitting a light beam, called the first incident beam 310, originating from the light source 300 in the optical fiber 200, as illustrated in [Fig. 4], and - on the other hand, transmit a light beam, called second incident beam 410, from the optical fiber 200 to the photodetector 400, as illustrated in [Fig.5].

[0037] Each light beam 310, 410 is advantageously configured to transmit an optical data transmission signal, for example a modulated optical signal of the Li-Fi type.

[0038] The optical component 100 is thus advantageously intended for the bidirectional transmission of optical signals: - in a direction known as the upward flow, from the light source 300 towards the optical fiber 200, - in a direction called downward flow, from optical fiber 200 to photodetector 400.

[0039] The light source 300 is preferably a quasi-monochromatic source. The first incident beam 310 is, for example, emitted at a wavelength, called the first wavelength Xp In one embodiment, the first incident beam 310, exiting the light source 300, is a diverging beam and takes the form of a cone. diffusion, as illustrated in [Fig.4]. In an alternative not shown, a lens can be placed at the output of the light source 300, to collimate the first incident beam.

[0040] Generally, any light source can be used for the light source 300, such as, for example, light-emitting diodes (LEDs) or laser sources, such as laser diodes or vertical-cavity surface-emitting laser diodes (VCSELs). However, the use of surface-emitting light sources, such as LEDs or VCSELs, is advantageously preferred.

[0041] The photodetector 400 is configured to detect the second incident beam 410.

[0042] The second incident beam 410 has a wavelength, called the second wavelength X2, distinct from that of the first incident beam.

[0043] In one embodiment, the photodetector 400 is a photodiode.

[0044] The optical fiber 200 of the optical device 500 preferably comprises, in a conventional manner, a core 210 and an optical cladding 220, as illustrated in figures 2 and 3.

[0045] The core 210 has a refractive index nc and a diameter dc. The core 210 is preferably made of glass, based on silica.

[0046] The optical cladding 220 surrounds the core 210 and has a refractive index lower than the refractive index nc of the core.

[0047] The optical fiber 200 has a first end face 230 intended to come against the optical component 100.

[0048] The optical fiber 200 can be a single-mode optical fiber or a multi-mode optical fiber. Preferably, the optical fiber is a multi-mode optical fiber.

[0049] The optical component 100 of the optical device 500 comprises a substrate 110.

[0050] Said substrate has a first face, called lower face 113, and a second opposite face, called upper face 114.

[0051] The substrate 110 has, between said lower face and said upper face, a thickness es substantially less than or equal to, preferably less than, the diameter dc of the core 210 of the optical fiber 200.

[0052] The substrate 110 has a first edge 111 intended to be bonded to the first end face 230 of the optical fiber 200, as illustrated in Figures 1 to 5. The substrate 110 and the optical fiber 200 are preferably held together by gluing. The adhesive used to hold the first end face 230 of the optical fiber 200 against the first edge 111 of the substrate 110 preferably has the same refractive index as that of the core 210 of the optical fiber 200.

[0053] The substrate 110 further has a second edge 112 opposite to said first edge.

[0054] The substrate 110 is made of a material having a refractive index ns substantially equal, preferably equal, to the refractive index nc of the core 210 of the optical fiber 200.

[0055] The substrate 110 extends longitudinally between the first and second edges 111, 112. The substrate 110 has two distinct longitudinal portions, referred to as the first 115 and second 116 longitudinal portions. The first longitudinal portion 115 extends from the first edge 111 and the second longitudinal portion 116 extends from the second edge 112.

[0056] By extension, the first longitudinal portion 115 of the substrate will be considered as a first longitudinal portion of the optical component 100. Similarly, the second longitudinal portion 116 of the substrate will be considered as a second longitudinal portion of the optical component 100.

[0057] The first longitudinal portion of the optical component 100 is advantageously dedicated to the upward flow direction, and the second longitudinal portion is dedicated to the downward flow direction. Thus, the light source 300 is intended to be positioned opposite the lower face 113 of the substrate, at the level of said first longitudinal portion, and the photodetector 400 is intended to be positioned opposite the lower face 113 of the substrate 110, at the level of said second longitudinal portion. The light source 300 and the photodetector 400 are preferably placed at a distance from the lower face 113 of the substrate.

[0058] The first longitudinal portion 115 of the optical component 100 is preferably dimensioned to collect a maximum of the rays constituting the first incident beam 310 coming from the light source 300.

[0059] The optical component 100 comprises, at its first longitudinal portion, a stack of three layers from the upper face 114 of the substrate 110, as illustrated in Figures 1 to 3: - a layer, called the semi-reflective layer 120, - a layer, called the 130 diffraction layer, - a layer, called reflective layer 140.

[0060] The optical component 100 comprises, at the level of its second longitudinal portion, an optical element 600, as illustrated in figures 1 to 3.

[0061] The following description will first describe the operating principle of the optical component 100 in the direction of the upward flow and then, secondly, in the direction of the downward flow. Direction of upward flow

[0062] At the level of the first longitudinal portion 115, the stacking order of the three layers 120, 130, 140 on the substrate 110 is not necessarily that stated above. Nevertheless, the semi-reflective layer 120 and the diffraction layer 130 are formed necessarily included between the substrate 110 and the reflective layer 140. Thus, the optical component 100 can have two configurations at the level of said first longitudinal portion.

[0063] In a first embodiment of the optical component, shown in Figures 1 and 2, said optical component comprises, from the upper face 114 of the substrate 110, the successive stacking described above. The optical component is shown in [Fig. 1] in exploded perspective view to better understand the stacking of its constituent layers. [Fig. 2] shows a cross-sectional view of the optical component 100.

[0064] In a second embodiment of the optical component, shown in cross-sectional view in [Fig.3], said optical component comprises the following successive stacking, from the upper face 114 of the substrate: - the diffraction layer 130, - the 120 semi-reflective layer, - the reflective layer 140.

[0065] Regardless of the configuration of the optical component 100, the three layers of the optical component stack each have the following characteristics.

[0066] The semi-reflective layer 120 has a thickness esr. It is made of a material having a refractive index nsr greater than the refractive index ns of the substrate 110. The material is transparent to the first wavelength Xi of the first incident beam 310. In a preferred embodiment, the semi-reflective layer 120 is made of silicon nitride (Si3N4).

[0067] The reflective layer 140 has a thickness er. It is made of a material with a refractive index nr. It is configured to reflect the first wavelength Xi of the first incident beam 310. In a preferred embodiment example, the reflective layer 140 is a metallic layer, for example gold or silver, or several dielectric layers.

[0068] The diffraction layer 130 has a thickness ed. It includes a 131 diffraction grating, with a spatial period of A. The 131 diffraction grating is made throughout the thickness of the diffraction layer. The diffraction grating 131 is advantageously dimensioned according to the first wavelength Xidu first incident beam 310, according to Bragg's law.

[0069] The diffraction grating 131 is preferably designed for a wavelength range including the first wavelength Xidu of the first incident beam 310. Preferably, the diffraction grating 131 is designed for a wavelength range extending from ± 5 nm around the first wavelength / .|du first incident beam 310. The diffraction grating 131 is made of materials with two different refractive indices. The diffraction grating is preferentially formed from the materials of the layers located throughout the diffraction layer 130.

[0070] Thus, in the first configuration, the diffraction grating 131 is made of a material having a refractive index corresponding to the refractive index nsr of the semi-reflective layer 120 and a refractive index corresponding to the refractive index nr of the reflective layer 140. The diffraction grating 131 is made for example by etching the material of the semi-reflective layer 120 and then depositing the material constituting the reflective layer 140.

[0071] In the second configuration, the diffraction grating 131 is made of a material having a refractive index corresponding to the refractive index ns of the substrate 110 and a refractive index corresponding to the refractive index nsr of the semi-reflective layer 120. The diffraction grating 131 is made for example by etching in the material of the substrate 110 and then depositing the material of the semi-reflective layer 120.

[0072] The diffraction grating 131 is periodic along a longitudinal axis of the substrate corresponding to the extension of the optical axis of the optical fiber.

[0073] In a preferred embodiment, as illustrated in [Fig. 1], the diffraction grating 131 takes the form of a plurality of concentric circular arcs.

[0074] The circular arcs are arranged so that their focal points coincide and are located at the first end face 230 of the optical fiber. The circular arcs extend substantially within the same angular range and exhibit periodically increasing radii of curvature, as illustrated in [Fig. 6]. [Fig. 6] is a top view of the diffraction layer. The angular range corresponds preferentially to the numerical aperture of the optical fiber 200.

[0075] In the first longitudinal portion 115, the optical component 100, in particular the three layers, is advantageously dimensioned according to the first wavelength Xi of the first incident beam 310 passing through it and an angle of incidence ai of a ray of said first incident beam, called the first incident ray. The angle of incidence ai is defined relative to the direction normal to the diffraction grating 131, therefore to the direction normal to the lower face 113 of the substrate 110.

[0076] According to the invention, the angle of incidence ai of the first incident ray is preferably close to zero, for example in a range of values ​​between 0 and 20°. This range of values ​​for the angle of incidence ai is given here by way of illustration only and should not be considered limiting. The range of values ​​is variable and depends, among other things, on the first wavelength Xi of the first incident beam 310, the materials constituting the different layers constituting the optical device, characteristics of the semi-reflective layer 120 and the diffraction layer 130.

[0077] According to the invention, regardless of the configuration of the optical component, for each first incident ray, of first wavelength Xi and angle of incidence ai, the thicknesses of the semi-reflective layer 120 and the diffraction layer 130 are dimensioned so as to generate, in the substrate 110, destructive interference of the rays reflected by the two layers. The reflected rays correspond to the reflection of the first incident ray on each of the layers.

[0078] The combination of the semi-reflective layer 120 and the reflective layer 140 with the diffraction grating 131 makes it advantageous to create a resonant grating which cancels the rays reflected in the substrate 110.

[0079] As a reminder, for two rays to interfere destructively, they must be in opposite phase and in the same direction.

[0080] The calculations of the thicknesses of the semi-reflective layer 120 and the diffraction layer 130 to form a resonant network, is within the reach of a person skilled in the art.

[0081] Furthermore, according to the invention, and regardless of the configuration of the optical component, for each first incident ray, of first wavelength Xi and of angle of incidence ai, the diffraction grating 131 is configured to allow the diffraction of the first incident ray from the light source 300 in the limit of the first order of diffraction, and under a diffraction angle such that a ray diffracted by said diffraction grating 131 then propagates in the substrate 110, in an acceptance cone of the optical fiber 200, in the direction of the first edge of the substrate.

[0082] More specifically, the spatial period A of the diffraction grating 131 is chosen such that the first incident ray from the light source 300 is diffracted to the limit of first-order diffraction. To obtain a ray diffracted to the limit of first-order diffraction by the diffraction grating 131, the spatial period of said diffraction grating is advantageously chosen to be on the order of the first wavelength Xi of the first incident beam 310.

[0083] The spatial period A of the diffraction grating 131 is also chosen so that the diffracted rays of order 1 can be refracted in the substrate 110.

[0084] The previously described arc-shaped diffraction grating 131 advantageously allows the rays diffracted by the diffraction grating 131 to converge towards the first end face 230 of the optical fiber 200, as illustrated in [Fig. 6]. The dashed circle in [Fig. 6] represents the shape of the first incident beam 310, originating from the light source 300, and arriving at the diffraction grating 131.

[0085] Thus, the optical component 100 advantageously allows, at the level of the first longitudinal portion 115, the collection of a maximum of the rays from the first beam incident 310 from the light source 300, to deflect them and inject them into the optical fiber 200, as illustrated in [Fig.4].

[0086] The light source 300 is arranged with respect to the first face of the substrate such that a maximum of the rays of the first incident beam 310 enter the substrate, from the lower face 113 of the substrate 110, and pass through said substrate in order to be diffracted by the diffraction grating 131 and then transmitted in the optical fiber 200.

[0087] Such an arrangement of the optical component, whatever its configuration, thus allows the transmission of the first incident beam 310 from the light source 300 into the optical fiber 200 with optimal coupling.

[0088] By way of illustration, Figures 2 and 3 show an example of the trajectory of a ray of the first incident beam in the optical component for the two configurations of the optical component. Only a ray 10 of the first incident beam 310 is shown for clarity. In this case, and without limitation, the ray shown is that located on a central axis of said first incident beam. An arrow indicates the direction of propagation of this ray. a. First configuration of the optical component ([Fig.2])

[0089] When the ray 10 reaches the lower face 113 of the substrate 110, at an angle of incidence ai, the ray 10 generates a refracted ray 11 propagating in the substrate 110. Said ray also generates a reflected ray, not shown in [Fig.2],

[0090] When the refracted ray 11 reaches the upper face 114 of the substrate 110, the refracted ray 11 generates: - a refracted ray 12 propagating in the semi-reflective layer 120, - a reflected ray 13 in the substrate 110.

[0091] The refracted ray 12 propagates in the semi-reflecting layer 120 and reaches the diffraction grating 131. The refracted ray 12 then generates: - a diffracted ray 14 according to the first order of diffraction, - a reflected ray 15.

[0092] The diffracted ray 14 propagates in the semi-reflective layer 120 and is then refracted in the substrate 110 and travels towards the first edge 111 of the substrate, towards the first end face 230 of the optical fiber, and then into the optical fiber along a propagation direction 16. Since the refractive index of the substrate is substantially equal to that of the core of the optical fiber 200, the diffracted ray 14 propagating in the substrate then propagates in the optical fiber, without refraction and without loss by reflection.

[0093] The reflected ray 15 propagates in the semi-reflective layer 120 and then, when it reaches the upper face 114 of the substrate 110, generates a refracted ray 17 in the substrate 110. The refracted ray 17 propagates in the same direction of propagation. page that the reflected ray 13.

[0094] The reflected ray 15 is also reflected by the upper face 114 of the substrate 110 towards the diffraction grating.

[0095] The various characteristic parameters (thicknesses, refractive index of the layers) of the optical component 100 according to the invention being determined so that the phase shift between the reflected ray 13 and the refracted ray 17 (coming from the reflected ray 15) is substantially equal to II and that these two rays 13, 17 propagate in the same direction of propagation, there then results in a destructive interference between these two rays 13, 17, decreasing the luminous intensity propagating along the direction of reflection, and consequently increasing the luminous intensity of the diffracted ray 14 propagating along the direction of propagation 16 towards the optical fiber.

[0096] The optical component 100 thus forms a resonant network, by repeating the process of destructive interference of the different rays reflected in the substrate, and further strengthening the light intensity of the diffracted rays propagating along the propagation direction 16 towards the optical fiber. a. Second configuration of the optical component ([Fig. 3D]

[0097] When the ray 20 reaches the lower face 113 of the substrate 110, at an angle of incidence ai, the ray 20 generates a refracted ray 21 propagating in the substrate 110. Said ray also generates a reflected ray, not shown in [Fig.3].

[0098] When the refracted ray 21 reaches the upper face 114 of the substrate 110 and the diffraction grating 131, the refracted ray 21 generates: - a diffracted ray 22 according to the first order of diffraction, - a refracted ray 24 propagating in the semi-reflective layer 120, - a reflected ray 23 in the substrate.

[0099] The diffracted ray 22 propagates in the substrate 110 and travels towards the first edge 111 of the substrate, towards the first end face 230 of the optical fiber, and then into the optical fiber along a propagation direction 30. Since the refractive index of the substrate is substantially equal to that of the core of the optical fiber 200, the diffracted ray 22 is transmitted into the optical fiber without refraction and without loss by reflection.

[0100] The refracted ray 24 propagates through the semi-reflective layer 120 and reaches the reflective layer 140. The refracted ray 24 generates a reflected ray 25. The reflected ray 25 propagates through the semi-reflective layer 120 and then generates, when it reaches the diffraction grating 131: - a diffracted ray 28, according to the first order of diffraction, - a refracted ray 27 in the substrate 110, - a reflected ray 26 in the semi-reflective layer 120.

[0101] The diffracted ray 28 propagates in the substrate 110 and travels towards the first edge 111 of the substrate, towards the first end face 230 of the optical fiber, then in the optical fiber along the same propagation direction 30 as the diffracted ray 22.

[0102] The refracted ray 27 propagates in the same propagation direction as the reflected ray 23.

[0103] The various characteristic parameters (thicknesses, refractive index of the layers) of the optical component 100 according to the invention being determined so that the phase shift between the reflected ray 23 and the refracted ray 27 (coming from the reflected ray 25) is substantially equal to II and that these two rays 23, 27 propagate in the same direction of propagation, there then results in a destructive interference between these two rays 23, 27, decreasing the luminous intensity propagating along the direction of reflection, and consequently increasing the luminous intensity of the diffracted rays 22, 28 propagating along the direction of propagation 30 towards the optical fiber 200.

[0104] The optical component 100 thus forms a resonant network, by repeating the process of destructive interference of the different rays reflected in the substrate, and further strengthening the luminous intensity of the diffracted rays propagating along the propagation direction 30 towards the optical fiber. Direction of downward flow

[0105] At the level of the second longitudinal portion 116, the optical component 100 comprises the optical element 600.

[0106] The optical element 600 is advantageously configured to direct the second incident beam 410, that from the optical fiber 200, towards the photodetector 400, as illustrated in [Fig. 5]. More specifically, the optical element 600 is configured to direct the second incident beam 410 away from the substrate 110, in a direction substantially perpendicular to the lower face 113 of said substrate.

[0107] In other words, the optical element 600 advantageously allows an angle referral of substantially 90° to the photodetector 400.

[0108] As illustrated in [Fig.5], the photodetector 400 is preferentially positioned relative to the optical element 600 of the optical component 100, and at a distance from the lower face 113 of the substrate 110, so that a maximum of the rays forming the second incident beam 410 and deflected by the optical element 600 is received in whole, or in part, by said photodetector.

[0109] In one embodiment of the optical element 600, said optical element is a mirror attached to the second edge 112 of the substrate 110. The second edge 112 of the substrate has an inclination of a predefined angle with respect to the longitudinal axis of the substrate.

[0110] In a preferred embodiment of the optical element 600, as illustrated in Figures 2 and 3, the second edge 112 of the substrate has an inclination of an angle approximately equal to 45° with respect to the longitudinal axis of the substrate.

[0111] In another embodiment of the optical element 600, said optical element is a prism, for example a glass prism. The shape of the prism is advantageously adapted so that the second incident beam 410 is directed towards the photodetector 400.

[0112] In another embodiment of the optical element 600, said optical element comprises a stack of layers as described in the first longitudinal portion 115. The characteristic parameters of the different layers (thicknesses, refractive indices, period of the diffraction grating) of this stack of layers are, in this case, advantageously adapted to the second wavelength X2 of the second incident beam.

[0113] Thus, regardless of the optical element 600 used, the second incident beam 410, coming from the optical fiber, passes through the substrate to the optical element 600, is deflected by the optical element 600 and is directed towards the photodetector 400. The diffraction grating 131 located in the first longitudinal portion 115, being configured to be insensitive to the second wavelength X2 of the second incident beam coming from the optical fiber, said second incident beam is not deflected by this diffraction grating 131.

[0114] Such an arrangement of optical component 100 vis-à-vis the photodetector 400 allows the transmission of the second incident beam 410 into the photodetector 400 with optimal coupling.

[0115] The invention thus proposes an optical device with a compact optical component, advantageously allowing the bidirectional transmission of optical signals, via light beams, from a light source 300 and / or to a photodetector 400, both arranged in a direction substantially perpendicular to the optical axis of the optical fiber 200, with optimal coupling.

[0116] The use of a compact and substantially flat optical component allows the optical device to be installed in environments constrained in terms of volume or dimension, such as in aircraft.

[0117] Thus, in a preferred application, the optical assembly 700 is arranged in an aircraft. The optical device 500 is arranged in an aircraft cabin, with the optical component 100 located above a passenger seat. The light source 300 and the photodetector 400 are located in the passenger seat.

[0118] The optical component 100 can be placed near equipment such as equipment known by the acronym PSU (“Passenger Service Unit” in English terminology), allowing in particular a passenger to trigger calls to the commercial flight crew or to turn a reading light on / off.

[0119] The optical module can advantageously be used for data transmission, via Li-Fi technology (acronym for "Light Fidelity"). The light source 300 of the optical assembly 700 is thus configured to emit the first incident beam 310 with the first wavelength Xi located in the infrared range. By infrared range, we mean the range of wavelengths between 780 nm and 2 pm. The photodetector of the optical module is, for its part, configured to detect the second incident beam with the second wavelength ^also located in the infrared range.

Claims

Demands

1. Optical device (500) comprising: - an optical fiber (200) comprising a core (210), of refractive index nc and diameter dc, and having a first end face (230), - an optical component (100) comprising: • a substrate (110) with a refractive index ns substantially equal to the refractive index nc of the optical fiber core and a thickness es substantially less than or equal to the diameter dc of the fiber core (200), said substrate: • comprising two faces, called the first (113) and second (114) faces, • extending between two opposite edges, called the first (111) and second (112) edges, • presenting a first longitudinal portion (115) starting from the first edge (111) and a second longitudinal portion (116) starting from the second edge (112), • a stack of three layers arranged on the second face (114) of the substrate (110), at the level of the first longitudinal portion (115) of said substrate • a semi-reflective layer (120) with a refractive index nsr greater than the refractive index ns of the substrate, and of thickness esr, • a diffraction layer (130), of thickness ed, comprising, throughout its thickness, a diffraction grating (131) of period A, • a reflective layer (140), an optical element (600), at the level of its second longitudinal portion (116), the optical fiber (200) being arranged opposite the optical component (100) such that the first end face (230) of said optical fiber is attached to the first edge (111) of the substrate (110), the semi-reflective layer (120) and the diffraction layer (130) being disposed between the substrate (110) and the reflective layer (140), the semi-reflective layer (120) being disposed between the substrate (110) and the diffraction layer (130) or between the diffraction layer (130) and the reflective layer (140), for a first incident ray, having a first wavelength Xi and arriving on the first face (113) of the substrate (110) with a predetermined angle of incidence ai and defined relative to a direction normal to said first face of the substrate: • the thicknesses of the semi-reflective layer (120) and the diffraction layer (130) are determined to generate destructive interference of the reflected rays, • the diffraction grating (131) is configured to allow the diffraction of the first incident ray in the limit of the first order of diffraction,and at a diffraction angle such that the diffracted ray propagates in the substrate (110), in an acceptance cone of the optical fiber (200), towards the first face of the optical fiber, for a second incident ray from the optical fiber, having a second wavelength X2 distinct from the first wavelength I, i, the optical element (600) is configured to direct said second incident ray out of the substrate (110), perpendicular to the first face (113) of the substrate.

2. Optical device (500) according to claim 1 in which the diffraction grating (131) is in the form of a plurality of concentric circular arcs, centered on the first edge (111) of the substrate, at the level of the first face (230) of the optical fiber (200).

3. Optical device (500) according to the preceding claim in which the arcs of circles extend over the same angular range corresponding to a numerical aperture of the optical fiber (200).

4. Optical device (500) according to any one of the preceding claims wherein the diffraction grating (131) has materials whose refractive indices are identical to the materials of the layers arranged on either side of the diffraction layer (130).

5. Optical device (500) according to any one of the preceding claims wherein the second edge (112) of the substrate (110) of the optical component (100) has an inclination of an angle substantially equal to 45° with respect to a longitudinal axis of said substrate and in which the optical element (600) is a mirror attached to said second edge of the substrate.

6. Optical assembly (700) comprising a light source (300), a photodetector (400) and an optical device (500) according to any one of the preceding claims, said light source being arranged opposite the first face (113) of the substrate (110), at the level of the first longitudinal portion (115), and configured to emit the first incident ray, said photodetector being arranged opposite the first face (113) of the substrate (110), at the level of the second longitudinal portion (116), and disposed with respect to the optical element (600) so as to receive the second incident ray.

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