Fibre-optic optical assembly

Abstract

The invention relates to an optical assembly (50) comprising: - an optical fibre (200), - a support (51), - a fibre positioning substrate (52), - a beam splitter element (60), - an optical component (100) forming a resonant network, - a cover plate. The substrate (52) rests on the support and has a housing for receiving the beam splitter element and the optical component. A groove (80), made in the substrate (52) and the support (51) and opening into the housing, receives the optical fibre such that the latter faces the beam splitter element. The arrangement of the elements constituting the optical assembly with respect to one another enables bidirectional transmission of signals with a light source / photodetector assembly arranged in a direction orthogonal to an optical axis of the optical fibre, without having to dynamically align the elements with one another.

Description

[0001] Fiber optic optical assembly

[0002] Technical field of the invention

[0003] The present invention relates to a fiber optic optical assembly for the bidirectional transmission of optical signals from a light source and to a photodetector. In particular, the present invention relates to an optical assembly for the bidirectional transmission of signals from a light source and to a photodetector, the light source / photodetector assembly being arranged in a direction substantially orthogonal to the optical axis of the optical fiber.

[0004] The invention finds an advantageous application in the aeronautical field, in particular for equipping an aircraft.

[0005] Prior art

[0006] In aircraft, optical fibers are increasingly used to interconnect equipment for communications purposes.

[0007] In the particular context of the distribution of Li-Fi (acronym for Light-Fidelity) type optical signals, optical fibers can be used to route these optical signals bidirectionally from light sources and towards photodetectors, these light sources and photodetectors being housed in the backrests of passenger seats.

[0008] These optical fibers run all along the cabin, in areas that are difficult to access and have limited space, generally in the ceiling, under the luggage compartments, and one of their ends reaches above the backs of the passenger seats.

[0009] An interface is then necessary between the end of an optical fiber, located above the back of a passenger seat and the light source / photodetector assembly arranged at the level of said back of a passenger seat, to allow:

[0010] - on the one hand the optical coupling of a light beam, carrying optical signals, coming from the light source to the optical fiber,

[0011] - on the other hand the optical coupling of a light beam, carrying the optical signals, coming from the optical fiber to the photodetector. The optical couplings are all the more complex as they must be done, not in a direction of the optical axis of the optical fiber, but in a direction substantially orthogonal to this optical axis, which implies the use of an angle return of the order of 90°.

[0012] In the so-called downward flow direction, i.e. 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, may be sufficient as an interface between the optical fiber and the photodetector. However, in the so-called upward flow direction, i.e. 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. An assembly based on lenses and a prism or a mirror can, for example, make it possible to achieve this optical coupling. However, such an assembly requires careful implementation because the alignments between the different optical elements must be precise to obtain optimal coupling.Furthermore, such an assembly is cumbersome, both in terms of weight and volume, expensive and inefficient in terms of injection into the optical fiber, therefore difficult to integrate into a very constrained environment such as that of an airplane.

[0013] Presentation of the invention

[0014] The present invention aims to remedy the aforementioned drawbacks.

[0015] To this end, the present invention proposes an optical assembly comprising:

[0016] - an optical fiber, comprising an optical axis,

[0017] - a basic substrate, called support,

[0018] - a so-called fiber positioning substrate,

[0019] - a beam splitter element,

[0020] - an optical component forming a resonant network, called an optical component,

[0021] - a cover plate, the fiber positioning substrate resting on a main face of said support and comprising a lateral edge having a hollow profile forming a housing for receiving the beam splitter element and the optical component, a longitudinal groove being made in the fiber positioning substrate and the support and opening into the housing of said fiber positioning substrate, said longitudinal groove being dimensioned to receive the optical fiber, the optical fiber being positioned in the optical assembly so that a first end face of the optical fiber faces the beam splitter element, the cover plate resting on the fiber positioning substrate and pressing the optical fiber into the longitudinal groove, the optical component being configured to receive a light beam, called the first incident beam,coming from a direction substantially perpendicular to the optical axis of the optical fiber, and to transmit this first incident beam towards the optical fiber, via the beam splitter element, the beam splitter element being configured to:,

[0022] - let the first incident beam pass towards the optical fiber,

[0023] - transmit a light beam, called the second incident beam, coming from the optical fiber outside the optical assembly, in a direction substantially perpendicular to the optical axis of the optical fiber.

[0024] The arrangement of the various constituent elements of the optical assembly relative to each other advantageously allows the bidirectional transmission of signals with a light source / photodetector assembly arranged in a direction substantially orthogonal to the optical axis of the optical fiber without resorting to dynamic alignment of the elements with each other and with the light source and the photodetector.

[0025] The planar component advantageously allows a maximum of rays from the first incident beam coming from the light source to be collected and transmitted into the optical fiber, via the beam splitter element. The beam splitter element allows the second incident beam, coming from the optical fiber, to be transmitted to the photodetector.

[0026] The optical assembly thus allows efficient optical coupling of the first incident beam from the light source to the optical fiber, through the optical component and efficient optical coupling of the second incident beam from the optical fiber to the photodetector, through the beam splitter element. In particular embodiments, the optical device may further comprise one or more of the following features, taken individually or in all technically possible combinations.

[0027] In particular embodiments, the optical fiber comprises a core of refractive index n c and of diameter of, and the optical component comprises a stack comprising:

[0028] - a substrate with refractive index n s substantially equal to the refractive index n c of the core of the optical fiber and thickness e sless than or equal to the diameter of the core of the fiber, said substrate comprising two faces, called first and second faces,

[0029] - a semi-reflective layer with refractive index n S r greater than the refractive index n s of the substrate, and of thickness e S r,

[0030] - a diffraction layer, of thickness ed, comprising, throughout its thickness, a diffraction grating of period A,

[0031] - a reflective layer, the reflective layer resting on the main face of the support, the semi-reflective layer and the diffraction layer being arranged between the substrate and the reflective layer, the semi-reflective layer being arranged between the substrate and the diffraction layer or between the diffraction layer and the reflective layer, for a first incident ray of the first incident beam, having a first given wavelength λi and arriving on the first face of the substrate with a predetermined angle of incidence λai and defined relative to a direction normal to said first face of the substrate:

[0032] - the thicknesses of the semi-reflecting layer and the diffraction layer are determined to generate destructive interference of the reflected rays,

[0033] - the diffraction grating is configured to allow diffraction of the first incident ray within the limit of the first diffraction order, and at a diffraction angle such that the diffracted ray propagates in the substrate, in an angular acceptance cone of the optical fiber, towards the beam splitter element then towards the first face of the optical fiber.

[0034] The stacking of the three layers on the support, their arrangement and their characteristic parameters (thicknesses, refractive index of the layers) allow the optical component to achieve efficient optical coupling of the first incident beam coming from the light source to the optical fiber. The natural divergence of the light beam emitted by the light source is counteracted.

[0035] In particular embodiments, the diffraction grating is in the form of a plurality of concentric circular arcs, centered at the first end face of the optical fiber. Such a circular arc shape of the diffraction grating advantageously makes it possible to converge the rays diffracted by said diffraction grating towards the first end face of the optical fiber. In particular embodiments, the support, the fiber positioning substrate and the cover plate are each made of a material which allows at least the wavelengths in the ultraviolet to pass through.

[0036] In particular embodiments, the beam splitter element is a separate part from the optical component and is disposed between the first end face of the optical fiber and the optical component, the beam splitter element and the optical component having a shape complementary to the housing of the fiber positioning substrate, so as to each fit in a complementary manner in the housing of said fiber positioning substrate.

[0037] In particular embodiments, the beam splitter element is a prism splitter, for example a splitter cube.

[0038] In particular embodiments, the optical component comprises a first lateral edge having an inclination substantially equal to 45° relative to the optical axis of the optical fiber, and in which the beam splitter element is a dichroic filter attached to the first lateral edge of the optical component, the optical component having a shape complementary to the housing of the fiber positioning substrate, so as to take place in a complementary manner in the housing of said fiber positioning substrate, with the first lateral edge facing the first end face of the optical fiber.

[0039] In particular embodiments, the first end face of the optical fiber is inclined at an angle substantially equal to 45° relative to the optical axis of said optical fiber, such that the first end face of the optical fiber is attached to the dichroic filter attached to the first lateral edge of the optical component. The invention also relates to an optical assembly comprising a light source, a photodetector and an optical assembly as described above. The light source is arranged opposite the optical component and is configured to emit the first incident beam. The photodetector is arranged opposite the beam splitter element so as to receive the second incident beam. The invention also relates to a method for producing an optical assembly as described above, with the beam splitter element of the optical assembly forming a separate part from the optical component.The process comprises the steps of:

[0040] - positioning of the fiber positioning substrate on the main face of the support,

[0041] - production of the longitudinal groove in the fiber positioning substrate and the support,

[0042] - positioning of the beam splitter element and the optical component in the housing of the fiber positioning substrate,

[0043] - positioning of the optical fiber in the longitudinal groove,

[0044] - positioning of the cover plate.

[0045] The invention also relates to a method for producing an optical assembly as described above, with the optical component comprising a first lateral edge having an inclination substantially equal to 45° relative to the optical axis of the optical fiber, and with the beam splitter element forming a dichroic filter attached to the first lateral edge of the optical component. The method comprises the steps of:

[0046] - positioning of the fiber positioning substrate on the main face of the support,

[0047] - production of the longitudinal groove in the fiber positioning substrate and the support,

[0048] - positioning of the optical component in the housing of the fiber positioning substrate,

[0049] - positioning of the optical fiber in the longitudinal groove,

[0050] - positioning of the cover plate.

[0051] Brief description of the figures

[0052] The invention will be better understood on reading the following description, given by way of non-limiting example, and made with reference to the figures which represent: Figure 1 is a top view of an optical assembly according to a first embodiment,

[0053] Figure 2 is a sectional view of the optical assembly of the figure along line AA,

[0054] Figure 3 is a sectional view of the optical assembly of the figure along line BB,

[0055] Figure 4 is a sectional view of the optical assembly of the figure along line AA with a focusing lens at a beam splitter element of the optical assembly,

[0056] Figure 5 is a top view of an optical assembly according to a second embodiment,

[0057] Figure 6 is a sectional view of the optical assembly of Figure 5 along line AA,

[0058] Figure 7 is a sectional view of an optical assembly according to an alternative embodiment of the second embodiment,

[0059] Figure 8 is a sectional view of a first configuration of an optical component of the optical assembly, regardless of the embodiment of the optical assembly, Figure 9 is a sectional view of a second configuration of an optical component forming a resonant grating of the optical assembly, regardless of the embodiment of the optical assembly,

[0060] Figure 10 illustrates the trajectory, in the optical component of Figure 8, of a light ray, in the direction of the upward flow,

[0061] Figure 11 illustrates the trajectory, in the optical component of Figure 9, of a light ray, in the direction of the upward flow.

[0062] Description of the embodiments

[0063] An optical assembly 50 according to a first embodiment is described in connection with FIGS. 1 to 4 and 8 to 11.

[0064] First embodiment of the optical assembly

[0065] The optical assembly 50 according to the first embodiment comprises, as illustrated in FIGS. 1 to 4, the following constituent elements:

[0066] - a 200 optical fiber,

[0067] - a basic substrate, called support 51,

[0068] - a substrate, called fiber positioning 52, - a beam splitter element 60,

[0069] - an optical component forming a resonant network, called optical component 100,

[0070] - a cover plate 53.

[0071] In the following description, the optical assembly will be associated with an XYZ reference. The indication of the X, Y and Z axes helps to understand the said optical assembly.

[0072] The X axis designates a longitudinal axis of the optical assembly, and corresponds to a longitudinal dimension of said optical assembly. The Y axis designates an axis perpendicular to the X axis, and corresponds to a transverse direction of the optical assembly. The Z axis designates an axis perpendicular to the X and Y axes. As illustrated in FIG. 1, the Z axis designates the vertical axis. Thus, in summary, the optical assembly 50 has a length along the X axis, a width along the Y axis and a height along the Z axis.

[0073] As used in the description, the terms "horizontal", "vertical", "left", "right", "top", "bottom", "above", "below", "bottom", "upper", etc. refer, unless otherwise specified, to the orientation of the optical assembly in the figures.

[0074] Furthermore, unless otherwise indicated, the terms “substantially”, “approximately”, “in the order of” mean to within 10%, and preferably to within 5%.

[0075] In this first embodiment, the beam splitter element 60 is a physical part as such, distinct from the optical component 100.

[0076] The optical assembly 50 is intended to be associated with a light source 300 and a photodetector 400, both being arranged in directions substantially perpendicular to an optical axis 240 of the optical fiber. As illustrated in FIG. 2, the light source 300 is intended to be arranged opposite the optical component 100 and the photodetector 400 is intended to be arranged opposite the beam splitter element 60. The optical assembly, the light source 300, the photodetector 400 form an optical assembly 70.

[0077] The optical assembly 50 is advantageously intended for and configured for, as illustrated in FIG. 2:

[0078] - on the one hand, transmitting a light beam, called the first incident beam 310, coming from the light source 300 into the optical fiber 200, via the optical component 100, and - on the other hand, transmitting a light beam, called the second incident beam 410, coming from the optical fiber 200 to the photodetector 400, via the beam splitter element 60.

[0079] The first incident beam 310 and the second incident beam 410, and their direction of propagation, are each represented schematically by an arrow in FIG. 2. The two incident light beams 310, 410 are advantageously configured to transmit an optical data transmission signal, for example a modulated optical signal of the Li-Fi type.

[0080] The optical assembly 50 is thus advantageously intended for the bidirectional transmission of optical signals:

[0081] - in a so-called upward flow direction, that is to say from the light source 300 to the optical fiber 200,

[0082] - in a so-called downward flow direction, that is to say from the optical fiber 200 to the photodetector 400.

[0083] 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 λi.

[0084] In a preferred embodiment, the first incident beam 310 is at a wavelength of 940nm.

[0085] In an exemplary embodiment, the first incident beam 310, at the output of the light source 300, is a divergent beam and is in the form of a diffusion cone (not shown in the figures). Alternatively, a lens (not shown in the figures) may be arranged at the output of the light source 300, to collimate the first incident beam.

[0086] Generally, any light source may be used for the light source 300, 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 "Vertical-Cavity Surface-Emitting Laser"). However, the use of surface-emitting light sources, such as LEDs or VCSELs, will be advantageously preferred.

[0087] The photodetector 400 is configured to detect the second incident beam 410. The second incident beam 410 has a wavelength, called the second wavelength λ2, distinct from that of the first incident beam.

[0088] In a preferred embodiment, the second incident beam 410 is at a wavelength of 850nm.

[0089] In a preferred embodiment, the photodetector 400 is a photodiode.

[0090] The optical assembly 50 according to the invention is configured so that its constituent elements are arranged relative to each other so as to allow bidirectional transmission of the optical signals, without having to resort to dynamic alignment of the elements with each other and with the light source 300 and the photodetector 400.

[0091] The various elements constituting the optical assembly 50 and their arrangement relative to each other are now described.

[0092] Optical fiber 200

[0093] The optical fiber 200 preferably comprises, in a conventional manner, a core 210 and an optical cladding 220 surrounding the core 210, as illustrated in FIG. 3. The core 210 has a refractive index n c and a diameter of. The core 210 is preferably made of glass, based on silica.

[0094] The optical cladding 220 surrounds the core 210 and has a refractive index lower than the refractive index n c of the heart.

[0095] The optical fiber 200 has a first end face 230.

[0096] Preferably, the first end face 230 is straight, i.e. perpendicular to the optical axis 240 of the optical fiber 200.

[0097] The optical fiber 200 may be a single-mode optical fiber or a multi-mode optical fiber. Preferably, the optical fiber is a multi-mode optical fiber.

[0098] In a preferred embodiment, the optical fiber 200 has a diameter of 430 pm, with a core diameter of 400 pm and a cladding thickness of 30 pm.

[0099] The support

[0100] The support 51 is a transparent substrate, made for example of transparent glass. Preferably, as illustrated in FIG. 1, the support 51 is in the form of a plate.

[0101] The support 51 is preferably made of a material which allows at least the wavelengths in the ultraviolet to pass through. By ultraviolet, we mean the wavelengths between 100 nm and 400 nm.

[0102] The support 51 has a main face 51 1 for receiving the fiber positioning substrate 52, the beam splitter element 60 and the optical component 100.

[0103] Preferably, the main face 511 of the support 51 is planar and contained in an XY plane. The main face 511 of the support 51 defines a reference plane. The main face 511 receiving the fiber positioning substrate 52, the beam splitter element 60 and the optical component 100, it advantageously participates in the relative alignment, along the Z axis, of said fiber positioning substrate, said beam splitter element and said optical component.

[0104] The fiber positioning substrate

[0105] The fiber positioning substrate 52 is a transparent substrate, made for example of transparent glass.

[0106] Preferably, as illustrated in Figures 1 and 2, the fiber positioning substrate 52 is in the form of a plate.

[0107] The fiber positioning substrate 52 is preferably made of a material which allows at least the wavelengths in the ultraviolet to pass through.

[0108] Preferably, the fiber positioning substrate 52 is made of the same material as the support.

[0109] The fiber positioning substrate 52 has a first main face 521, arranged against the main face 511 of the support 51. In other words, the first main face 521 of the fiber positioning substrate 52 and the main face 511 of the support 51 are adjacent to each other.

[0110] The fiber positioning substrate 52 has a second main face 522, opposite the first main face 521. The second main face 522 is intended for receiving the cover plate 53.

[0111] Preferably, the first main face 521 and the second main face 522 of the fiber positioning substrate 52 are planar. The fiber positioning substrate 52 has, between the first main face and the second main face, a thickness e P , preferably constant. The thickness e P is substantially less than the diameter of the optical fiber. The fiber positioning substrate 52 further has a lateral edge 523 having a hollow profile forming a housing for receiving the beam splitter element 60 and the optical component 100. It is understood that the housing extends over the entire thickness e P of the fiber positioning substrate 52. In the remainder of the description, by abuse of language, the housing formed by the lateral edge 523 of the fiber positioning substrate 52 will simply be referred to as the housing of the fiber positioning substrate 52.

[0112] The shapes of the optical component 100 and the beam splitter element 60 partly have a shape complementary to the housing of the fiber positioning substrate 52, so as to each take place in a complementary manner in the housing of said fiber positioning substrate 52. The beam splitter element 60 and the optical component 100 are thus each in abutment against the lateral edge 523 of the housing of the fiber positioning substrate 52 when they are in position in the optical assembly 50.

[0113] The shape of the housing of the fiber positioning substrate 52 is advantageously adapted to allow self-centering of the beam splitter element 60 and the optical component 100.

[0114] In a preferred embodiment, the housing of the fiber positioning substrate 52 has, in an XY plane, a V-shape with the tip of the V towards an opposite lateral edge, as illustrated in FIG. 1. The housing of the fiber positioning substrate 52 is thus delimited by two lateral walls forming the lateral edge 523, between which the beam splitter element 60 and the optical component 100 are positioned. Said beam splitter element and said optical component thus each abut against the lateral walls forming the housing of the fiber positioning substrate 52 when they are in position in the optical assembly 50.

[0115] The beam splitter element 60 and the optical component 100 are preferably substantially of the same thickness as the fiber positioning substrate 52.

[0116] A longitudinal groove 80 is formed in both the fiber positioning substrate 52 and the support 51 for receiving and holding in place the optical fiber 200 in the optical assembly 50. The longitudinal groove 80 is formed from the second main face 522 of the fiber positioning substrate 52 towards the support 51. The longitudinal groove 80 passes through the thickness e P of the fiber positioning substrate 52 and partially penetrates a thickness of the support 51, as illustrated in FIG. 3.

[0117] The longitudinal groove 80, with a longitudinal axis along the X axis, extends between the two lateral edges of the fiber positioning substrate 52. The longitudinal groove 80 thus opens into the housing of the fiber positioning substrate 52. Preferably, the longitudinal groove 80 and the housing are arranged relative to each other so that the tip of the V of the housing coincides with the longitudinal axis of the longitudinal groove 80. It is understood that the tip of the V of the housing of the fiber positioning substrate 52 is truncated by the longitudinal groove 80.

[0118] The shape and / or dimension of the longitudinal groove 80 is preferably adapted to the diameter of the optical fiber 200.

[0119] The longitudinal groove 80 preferably has, in a YZ plane, a V-shaped section, as illustrated in FIG. 3.

[0120] Preferably, the longitudinal groove 80 is dimensioned so that the lower part of the core 210 of the optical fiber 200 is flush with the main face 51 1 of the support 51 . Thus, the core 210 of the optical fiber 200 is opposite the beam splitter element 60 and the optical component 100, that is to say that the core 210 of the optical fiber 200 is at the same height, along the Z axis, as the beam splitter element 60 and the optical component 100. The optical fiber 200 may substantially exceed the second main face 522 of the fiber positioning substrate 52. Advantageously, the housing of the positioning substrate 52 is dimensioned so that the opening angle of the V-shape of the housing formed by the lateral edge of the fiber positioning substrate 52 corresponds substantially to the numerical aperture of the optical fiber 200.

[0121] The cover plate

[0122] The cover plate 53 is a transparent substrate, made for example of transparent glass.

[0123] Preferably, as illustrated in Figures 1 and 3, the cover plate 53 is in the form of a plate. The cover plate 53 is preferably made of a material which allows at least the wavelengths in the ultraviolet to pass through.

[0124] The cover plate 53 is disposed against the second main face 522 of the fiber positioning substrate 52, to advantageously slightly compress the optical fiber 200 in the longitudinal groove 80.

[0125] The cover plate 53 is arranged so as not to cover the housing of the fiber positioning substrate 52.

[0126] The beam splitter element

[0127] The beam splitter element 60 has a main face 61 attached to the main face 51 1 of the support 51 .

[0128] As explained previously, the beam splitter element 60 has a shape complementary to a portion of the housing of the positioning support 52. In a preferred embodiment, when the housing has a V-shaped section in an XY plane, the beam splitter element 60 has, in this same plane, a truncated V-shaped section.

[0129] The beam splitter element 60 has a first edge 62 attached to the first end face 230 of the optical fiber 200 and a second opposite edge 63 attached to the optical component 100.

[0130] The beam splitter element 60 has two longitudinal edges 64, each being joined to a portion of one of the side walls of the housing of the fiber positioning substrate 52.

[0131] The beam splitter element 60 is configured to pass or reflect a light beam passing therethrough depending on the wavelength of said light beam.

[0132] More specifically, the beam splitter element 60 is configured to:

[0133] - allow the first incident beam 310 coming from the light source 300, and from the optical component 100, to pass towards the optical fiber 200, and

[0134] - reflect the second incident beam 410 coming from the optical fiber 200 towards the photodetector 400.

[0135] The beam splitter element 60 is thus preferentially configured to be reflective at the wavelengths of light beams associated with the downward flow direction and transparent at the wavelengths of light beams associated with the upward flow direction.

[0136] In the preferred example where the wavelength of the first incident beam 310 is at 940nm and the wavelength of the second incident beam 410 is at 850nm, the beam splitter element is for example configured to be reflective at wavelengths less than 900nm and transparent at wavelengths greater than 900nm.

[0137] In a preferred embodiment, the beam splitter element 60 is designed as a prism splitter, in particular as a splitter cube.

[0138] The beam splitter element 60 is preferably made of a material having a refractive index substantially equal, preferably equal, to the refractive index n c of the core 210 of the optical fiber 200.

[0139] In a particular embodiment, as illustrated in FIG. 4, the optical assembly 50 may comprise a lens 90 attached to a face of the beam splitter element 60, opposite the main face 61 of said beam splitter element. Such a lens 90 advantageously makes it possible to focus the second incident beam 410 onto the photodetector 400, in particular when the size of the spot of said second light beam is greater than that of the photodetector.

[0140] The beam splitter element 60 is thus configured to direct the second incident beam 410, that coming from the optical fiber 200, towards the photodetector 400, as illustrated in FIG. 2. More precisely, the beam splitter element 60 is configured to direct the second incident beam 410 out of the optical assembly, in a direction substantially perpendicular to the optical axis 240 of the optical fiber 200.

[0141] In other words, the beam splitter element 60 advantageously allows an angle return of substantially 90° towards the photodetector 400.

[0142] As illustrated in Figure 2, the photodetector 400 is preferably positioned relative to the beam splitter element 60, and at a distance from said beam splitter element, so that a maximum of the rays forming the second incident beam 410, and deflected by the beam splitter element 60, is received in full, or in part, by said photodetector.

[0143] Such an arrangement of the optical assembly 50 with respect to the photodetector 400 allows the transmission of the second incident beam 410 into the photodetector 400 with optimal coupling.

[0144] The optical component forming a resonant grating

[0145] The optical component 100 has a first main face 101 attached to the main face 511 of the support 51.

[0146] As explained previously, the optical component 100 has a shape complementary to a part of the housing of the positioning support 52.

[0147] In a preferred embodiment, when the housing has a V-shaped section in an XY plane, the optical component 100 has, in this same plane, a truncated V-shaped section.

[0148] The optical component 100 has a first lateral edge 103 attached to the second edge 63 of the beam splitter element 60. The optical component 100 has a second lateral edge 104 opposite said first lateral edge 103 of the optical component 100.

[0149] The optical component 100 has two longitudinal edges 105, each being attached to a portion of one of the side walls of the housing of the fiber positioning substrate 52.

[0150] The optical component 100 is advantageously dedicated to the direction of the upstream flow.

[0151] The optical component 100 is advantageously configured to receive the first incident beam 310 and transmit this first incident beam 310 to the optical fiber 200, via the beam splitter element 60.

[0152] The light source 300 is intended to be positioned opposite a second main face 102 opposite the first main face 101 of the optical component. The light source 300 is preferably placed at a distance from the optical component 100.

[0153] The optical component 100 is preferably sized to collect a maximum of the rays constituting the first incident beam 310 coming from the light source 300.

[0154] The optical component 100 comprises, as illustrated in figures 8 and 9, a successive stack comprising:

[0155] - a substrate 110,

[0156] - a layer, called semi-reflective layer 120,

[0157] - a layer, called diffraction layer 130, - a layer, called reflective layer 140.

[0158] The stacking order of the three layers 120, 130, 140 on the substrate 110 is not necessarily that stated above. Nevertheless, the semi-reflective 120 and diffraction 130 layers are necessarily included between the substrate 110 and the reflective layer 140. Thus, the optical component 100 can have two configurations.

[0159] In a first embodiment configuration of the optical component 100, shown in FIG. 8 in sectional view, said optical component comprises the successive stack previously described.

[0160] In a second embodiment configuration of the optical component 100, shown in FIG. 9 in sectional view, said optical component comprises the following successive stack:

[0161] - substrate 110,

[0162] - the diffraction layer 130,

[0163] - the semi-reflective layer 120,

[0164] - the reflective layer 140.

[0165] When the optical component 100 is in position in the optical assembly, the reflective layer 140 is attached to the main face 51 1 of the support 51. The substrate 1 10 of the optical component is intended to be opposite the light source 300.

[0166] Whatever the configuration of the optical component 100, the substrate 110 has a first face 113 and a second opposite face 114.

[0167] As understood, and as illustrated in FIGS. 8 and 9, the first face 113 of the substrate 110 and the second main face 102 of the optical component 100 form a single face. Thus, the light source 300 is intended to be positioned opposite the first face 113 of the substrate 110 of the optical component 100.

[0168] The substrate 110 of the optical component 100 has, between its first face 113 and its second face 114, a thickness e s substantially less than or equal to the diameter of the core 210 of the optical fiber 200.

[0169] The substrate 110 of the optical component 100 is made of a material having a refractive index n s substantially equal, preferably equal, to the refractive index n c of the core 210 of the optical fiber 200. Whatever the configuration of the optical component 100, the three layers 120, 130, 140 of the optical component each have the following characteristics.

[0170] The semi-reflective layer 120 has a thickness e S r.

[0171] It is made of a material with a refractive index n S r greater than the refractive index n sof the substrate 1 10. The material is transparent to the first wavelength Xi of the first incident beam 310.

[0172] In an exemplary embodiment, the semi-reflective layer 120 is made of silicon nitride (SiaIXk).

[0173] The reflective layer 140 has a thickness e r .

[0174] It is made of a material with a refractive index n r . It is configured to reflect the first wavelength Xi of the first incident beam 310.

[0175] In a preferred embodiment, the reflective layer 140 is a metallic layer, for example gold or silver, or several dielectric layers. The diffraction layer 130 has a thickness ed.

[0176] It comprises a diffraction grating 131, of spatial period A. The diffraction grating 131 is produced throughout the thickness of the diffraction layer 130.

[0177] The diffraction grating 131 is advantageously sized as a function of the first wavelength Xi of the first incident beam 310, according to Bragg's law.

[0178] The diffraction grating 131 is preferably designed for a wavelength range comprising the first wavelength Xi of the first incident beam 310. Preferably, the diffraction grating 131 is designed for a wavelength range extending ± 5 nm around the first wavelength Xi of the first incident beam 310.

[0179] The diffraction grating 131 is made with materials having two different refractive indices. The diffraction grating 131 is preferably formed from the materials of the layers located on either side of the diffraction layer 130.

[0180] Thus, in the first configuration of the optical component 100, the diffraction grating 131 is made of a material having a refractive index corresponding to the refractive index n S r of the semi-reflecting layer 120 and a refractive index corresponding to the refractive index n r of the reflective layer 140. The diffraction grating 131 is produced for example by etching the material of the semi-reflective layer 120 then depositing the material constituting the reflective layer 140.

[0181] In the second configuration of the optical component, the diffraction grating 131 is made of a material having a refractive index corresponding to the refractive index n s of the substrate 1 10 and a refractive index corresponding to the refractive index n Sr of the semi-reflecting layer 120. The diffraction grating 131 is produced for example by etching in the material of the substrate 110 then depositing the material of the semi-reflecting layer 120.

[0182] The diffraction grating 131 is periodic along a longitudinal axis of the optical assembly.

[0183] In a preferred embodiment, as illustrated in FIG. 1, the diffraction grating 131 is in the form of a plurality of concentric circular arcs. The circular arcs are arranged so that their focal points coincide and are located at the first end face 230 of the optical fiber 200. The circular arcs extend substantially in the same angular range and have periodically increasing radii of curvature, as illustrated in FIG. 1 (in top view). The angular range preferably corresponds to the numerical aperture of the optical fiber 200.

[0184] The optical component 100, in particular the three layers 120, 130, 140, is advantageously dimensioned as a function of the first wavelength λi of the first incident beam 310 passing through it and of an angle of incidence αi of a ray of said first incident beam, called the first incident ray. The angle of incidence αi is defined relative to the direction normal to the diffraction grating 131, therefore to the normal direction of the first face 113 of the substrate 110.

[0185] 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 for illustrative purposes only and should not be considered as limiting. The range of values ​​is variable and depends, among other things, on the first wavelength λi of the first incident beam 310, the materials constituting the different layers 120, 130, 140 constituting the optical component 100, the characteristics of the semi-reflecting layer 120 and the diffraction layer 130.

[0186] According to the invention, whatever the configuration of the optical component 100, for each first incident ray, of first wavelength λi and an angle of incidence αi, the thicknesses of the semi-reflecting layer 120 and of the diffraction layer 130 are dimensioned so as to generate, in the substrate 110, a 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.

[0187] The combination of the semi-reflective layer 120 and the reflective layer 140 with the diffraction grating 131 makes it possible to advantageously create a resonant grating making it possible to cancel the rays reflected in the substrate 110.

[0188] As a reminder, for two rays to interfere destructively, they must be in phase opposition and in the same direction.

[0189] The calculations of the thicknesses of the semi-reflecting layer 120 and of the diffraction layer 130 to form a resonant grating are within the reach of those skilled in the art. In addition, according to the invention, and whatever the configuration of the optical component 100, for each first incident ray, of first wavelength λi and an angle of incidence λi, the diffraction grating 131 is configured to allow the diffraction of the first incident ray coming from the light source 300 within the limit of the first diffraction order, and at a diffraction angle such that a ray diffracted by said diffraction grating 131 then propagates in the substrate 110, in an angular acceptance cone of the optical fiber, in the direction of the first edge of the substrate.

[0190] More precisely, the spatial period A of the diffraction grating 131 is chosen such that the first incident ray coming from the light source 300 is diffracted within the limit of the first diffraction order. To obtain a ray diffracted within the limit of the first diffraction order by the diffraction grating 131, the spatial period of said diffraction grating is advantageously chosen to be of the order of the first wavelength λi of the first incident beam 310.

[0191] The spatial period A of the diffraction grating 131 is chosen such that the diffracted rays of order 1 can be refracted in the substrate.

[0192] The previously described arc shape of the diffraction grating 131 advantageously makes it possible to converge the rays diffracted by the diffraction grating 131 towards the first end face 230 of the optical fiber 200, passing through the beam splitter element, as illustrated in FIG. 2. Thus, the optical component 100 advantageously makes it possible to collect a maximum of the rays of the first incident beam 310 coming from the light source 300, to deflect them and to inject them into the optical fiber 200, after passing through the beam splitter element, as illustrated in FIG. 2.

[0193] The light source 300 is arranged relative to the first face of the substrate such that a maximum of the rays of the first incident beam 310 penetrates into the substrate, from the first face 113 of the substrate 110, and passes through said substrate in order to be diffracted by the diffraction grating 131 then transmitted into the optical fiber 200.

[0194] Such an arrangement of the optical component 100, 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, after passing through the beam splitter element.

[0195] As an example of dimensioning, the ratio between the total thickness of the three layers 120, 130 and 140 of the optical component 100 and the thickness of the substrate 110 of the optical component 100 is 1 to 400.

[0196] The thickness of the optical component 100 is of the order of the thickness of the fiber positioning substrate 52.

[0197] For illustrative purposes only, Figures 10 and 11 represent 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 one ray 10 of the first incident beam 310 is represented for the sake of clarity. In this case, and in a non-limiting manner, the ray represented 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 (Figure 10)

[0198] When the ray 10 reaches the first face 1 13 of the substrate 1 10, at an angle of incidence ai, the ray 10 generates a refracted ray 1 1 propagating in the substrate 1 10. Said ray also generates a reflected ray, not shown in FIG. 10.

[0199] When the refracted ray 1 1 reaches the second face 1 14 of the substrate 1 10, the refracted ray 1 1 generates:

[0200] - a refracted ray 12 propagating in the semi-reflecting layer 120,

[0201] - a reflected ray 13 in the substrate 110. The refracted ray 12 propagates in the semi-reflecting layer 120 and reaches the diffraction grating 131. The refracted ray 12 then generates:

[0202] - a diffracted ray 14 according to the first order of diffraction,

[0203] - a reflected ray 15.

[0204] The diffracted ray 14 propagates in the semi-reflecting layer 120 then is refracted in the substrate 110 and heads towards the first lateral edge 103 of the optical component 100, passes through the beam splitter element 60, the first end face 230 of the optical fiber 200, then is transmitted in the optical fiber 200 in a propagation direction 16. The refractive index of the substrate 110 of the optical component 100 and that of the beam splitter element 60 being substantially equal to that of the core 210 of the optical fiber 200, the diffracted ray 14 propagating in the substrate 110 then propagates in the beam splitter element 60, then in the optical fiber 200, without refraction and without loss by reflection. The reflected ray 15 propagates in the semi-reflecting layer 120 then generates, when it reaches the second face 114 of the substrate 110, a refracted ray 17 in the substrate 110.The refracted ray 17 propagates in the same direction of propagation as the reflected ray 13.

[0205] The reflected ray 15 is also reflected by the second face 114 of the substrate 110 towards the diffraction grating 131.

[0206] The various characteristic parameters (thicknesses, refractive index of the layers) of the optical component 100 according to the invention being determined in such a way that the phase shift between the reflected ray 13 and the refracted ray 17 (coming from the reflected ray 15) is substantially equal to n and that these two rays 13, 17 propagate in the same direction of propagation, this then results in destructive interference between these two rays 13, 17, reducing the light intensity propagating in the direction of reflection, and consequently increasing the light intensity of the diffracted ray 14 propagating in the direction of propagation 16 towards the beam splitter element then the optical fiber.

[0207] The optical component 100 thus forms a resonant network, repeating the process of destructive interference of the different rays reflected in the substrate 110, and further reinforcing the light intensity of the diffracted rays propagating in the propagation direction 16 towards the optical fiber. b) Second configuration of the optical component (figure 11)

[0208] When the ray 20 reaches the first 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. 11.

[0209] When the refracted ray 21 reaches the second face 114 of the substrate 110 and the diffraction grating 131, the refracted ray 21 generates:

[0210] - a diffracted ray 22 according to the first order of diffraction,

[0211] - a refracted ray 24 propagating in the semi-reflecting layer 120,

[0212] - a reflected ray 23 in the substrate 1 10.

[0213] The diffracted ray 22 propagates in the substrate 110 and heads towards the first lateral edge 103 of the optical component, passes through the beam splitter element 60, the first end face 230 of the optical fiber 200, then is transmitted in the optical fiber 200 in a propagation direction 30. The refractive index of the substrate 110 and that of the beam splitter element 60 being substantially equal to that of the core of the optical fiber 200, the diffracted ray 22 is transmitted in the optical fiber 200, without refraction and without loss by reflection.

[0214] The refracted ray 24 propagates in the semi-reflecting layer 120 and reaches the reflecting layer 140. The refracted ray 24 generates a reflected ray 25. The reflected ray 25 propagates in the semi-reflecting layer 120 and then generates, when it reaches the diffraction grating 131:

[0215] - a diffracted ray 28, according to the first order of diffraction,

[0216] - a refracted ray 27 in the substrate 1 10,

[0217] - a reflected ray 26 in the semi-reflecting layer 120.

[0218] The diffracted ray 28 propagates in the substrate 110 and heads towards the first lateral edge 103 of the optical component 100, passes through the beam splitter element 60, the first end face 230 of the optical fiber 200, then is transmitted in the optical fiber 200 in the same propagation direction 30 as the diffracted ray 22.

[0219] The refracted ray 27 propagates in the same direction of propagation as the reflected ray 23.

[0220] The various characteristic parameters (thicknesses, refractive index of the layers) of the optical component 100 according to the invention being determined in such a way that the phase shift between the reflected ray 23 and the refracted ray 27 (coming from the reflected ray 25) is substantially equal to n and that these two rays 23, 27 propagate in the same direction of propagation, this then results in destructive interference between these two rays 23, 27, reducing the light intensity propagating in the direction of reflection, and consequently increasing the light intensity of the diffracted rays 22, 28 propagating in the direction of propagation 30 towards the optical fiber 200.

[0221] The optical component 100 thus forms a resonant network, repeating the process of destructive interference of the different rays reflected in the substrate of the optical component, and further reinforcing the light intensity of the diffracted rays propagating in the propagation direction 30 towards the optical fiber 200.

[0222] All the constituent elements of said optical assembly 50, and where appropriate the lens 90, are advantageously held in place relative to each other, for example by gluing. The glue used to hold the various elements together, in particular holding the optical fiber 200 in the longitudinal groove 80, holding the fiber positioning substrate 52 against the support 51, holding the cover plate 53 against the fiber positioning substrate 52, holding the beam splitter element 60 and the optical component 100 in the housing of the fiber positioning substrate 52 and against the support 51, is for example of the same refractive index as that of the optical cladding 220 of the optical fiber 200.

[0223] In addition, the materials of the support 51, of the fiber positioning substrate 52 and of the cover plate 53 being transparent, their assembly can advantageously be carried out by means of an adhesive suitable for polymerizing with light radiation in the ultraviolet, for example in the range 300nm to 400nm.

[0224] Second embodiment of the optical assembly

[0225] An optical assembly 50 according to a second embodiment is described in connection with FIGS. 5 to 7.

[0226] In this second embodiment, the optical assembly 50 comprises all the constituent elements of the optical assembly according to the first embodiment. The differences between the two embodiments relate to the beam splitter element 60 and to the geometric shape of the optical component 100. In this second embodiment, the beam splitter element 60 is not a separate part as such. The beam splitter element 60 is in the form of a dichroic filter placed against the first lateral edge 103 of the optical component. As for the first embodiment of the optical assembly 50, the beam splitter element 60, in the form of a dichroic filter, is configured to:

[0227] - allow the first incident beam 310 coming from the light source 300, and from the optical component 100, to pass towards the optical fiber 200, and

[0228] - reflect the second incident beam 410 coming from the optical fiber 200 towards the photodetector 400.

[0229] The dichroic filter 60 is configured to direct the second incident beam 410 out of the optical component 110, in a direction substantially perpendicular to the optical axis 240 of the optical fiber 200 towards the photodetector 400, as illustrated in FIG. 6. The dichroic filter 60 advantageously allows an angle return of substantially 90° towards the photodetector 400. The dichroic filter 60 behaves transparently for the first incident beam 310 and allows the first incident beam 310 coming from the light source 300 to pass towards the optical fiber 200. The first lateral edge 103 of the optical component 100 has an angle substantially equal to 45° relative to the optical axis 240 of the optical fiber 200, as illustrated in FIG. 6.

[0230] The first lateral edge 103 of the optical component 100 is partially pressed against the first end face 230 of the optical fiber 200, as illustrated in FIG. 6.

[0231] The remainder of the description associated with the various constituent elements of the optical assembly 50 according to the first embodiment, their characteristics and the operating mode of the optical assembly also apply to the second embodiment.

[0232] The various examples and variants according to the first embodiment of the optical assembly 50 can also be applied to the second embodiment.

[0233] In an alternative embodiment of the second embodiment of the optical assembly, illustrated in FIG. 7, the first end face 230 of the optical fiber 200 is inclined at an angle substantially equal to 45° relative to the optical axis 240 of said optical fiber, such that the entire first end face of the optical fiber is attached to the dichroic filter of the optical component.

[0234] Optical assembly production process

[0235] A method of producing an optical assembly 50 is now described, without limitation. The method will be described in the case of the first embodiment of the optical assembly.

[0236] The fiber positioning substrate 52 is positioned on the support 51.

[0237] The fiber positioning substrate 52 has been previously prepared. The housing, in particular its shape, is produced for example by conventional micromachining techniques.

[0238] The fiber positioning substrate 52 is positioned on the support 51 such that its first main face 521 is placed against the main face 511 of the support 51.

[0239] The fiber positioning substrate 52 is held in place on the support 51, for example by gluing.

[0240] Preferably, the fiber positioning substrate 52 and the support 51 being made of transparent material, the glue used can be a glue suitable for polymerizing with light radiation in the ultraviolet.

[0241] Once the fiber positioning substrate 52 is positioned on the support 51, the longitudinal groove 80 is formed in the fiber positioning substrate 52 and the support 51.

[0242] The longitudinal groove 80, in particular its shape and depth, is produced for example by conventional micromachining techniques, or by laser engraving or by means of a diamond saw.

[0243] Once the longitudinal groove 80 is made, the beam splitter element 60 and the optical component 100 are positioned in the housing of the fiber positioning substrate 52.

[0244] The beam splitter element 60 is first positioned in the housing until it abuts the side edge 523 of the fiber positioning substrate. Then the optical component 100 is positioned in the housing until it abuts the side edge 523 of the fiber positioning substrate 52 and the beam splitter element 60. More specifically, the beam splitter element 60 is positioned in the housing until its longitudinal edges 64 abut the side walls of the side edge 523 of the fiber positioning substrate 52. Then the optical component 100 is positioned in the housing until its longitudinal edges 105 abut the side walls of the side edge 523 of the fiber positioning substrate 52 and its first side edge 103 abuts the second edge 63 of the beam splitter element 60.

[0245] The beam splitter element 60 and the optical component 100 are held in place in the housing and on the support, for example by gluing.

[0246] Then, the optical fiber 200 is positioned in the longitudinal groove 80.

[0247] The optical fiber 200 is arranged in the longitudinal groove 80 such that the first end face 230 of the optical fiber 200 abuts against the first edge 62 of the beam splitter element 60.

[0248] The optical fiber 200 is held in place in the longitudinal groove 80, for example by gluing.

[0249] Once the optical fiber 200 is positioned in the longitudinal groove, the cover plate 53 is positioned.

[0250] The cover plate 53 is arranged in the assembly so as to rest only on the second main face 522 of the fiber positioning substrate 52, covering the optical fiber 200 in the longitudinal groove 80.

[0251] The cover plate 53 is held in place on the fiber positioning substrate 52, for example by gluing. Preferably, since the fiber positioning substrate 52 and the cover plate 53 are made of transparent material, the glue used may be a glue suitable for polymerizing with light radiation in the ultraviolet.

[0252] When the optical assembly is carried out according to the second embodiment, the production method differs in that the step of positioning the beam splitter element 60 and the optical component 100 in the housing of the optical component consists only of a step of positioning the optical component 100 in the housing of the fiber positioning substrate 52. The optical component 100 is previously prepared. The first lateral edge 103 of the optical component is polished to achieve the tilt angle substantially equal to 45°. The overall shape of the optical component and the polishing of the first lateral edge are carried out for example by conventional micromachining techniques.

[0253] The optical component 100 is positioned in the housing until it abuts against the lateral edge 523 of the fiber positioning substrate 52.

[0254] More specifically, the optical component 100 is positioned in the housing until its longitudinal edges 105 abut against the side walls of the side edge 523 of the fiber positioning substrate 52.

[0255] The optical component 100 is held in place in the housing and on the support, for example by gluing.

[0256] The optical fiber is then positioned in the longitudinal groove 80 so that its first end face 230 abuts against the first lateral edge 103 of the optical component 100.

[0257] The invention thus proposes an optical assembly of compact size, advantageously allowing the bidirectional transmission of optical signals, via light beams, from a light source and towards a photodetector, both arranged in a direction substantially perpendicular to the optical axis of the optical fiber, with optimal coupling. The optical assembly is configured to guarantee self-centering of the beam splitter element, of the optical component with respect to the optical fiber to ensure efficient bidirectional transfer. The optical assembly makes it possible to dispense with a dynamic alignment step between the beam splitter element, the optical component, the optical fiber, the light source and the photodetector.

[0258] The use of a compact and substantially flat optical assembly allows its installation in environments constrained in terms of volume or dimension, such as in aircraft.

[0259] Thus, in a preferred application, the optical assembly 70 is disposed in an aircraft. The optical assembly is disposed in an aircraft cabin disposed above a passenger seat. The light source and the photodetector are disposed in the passenger seat.

[0260] The optical assembly can be placed near equipment such as equipment known by the acronym PSU (Passenger Service Unit), allowing in particular a passenger to trigger calls to the cabin crew or to turn on / off a reading light.

[0261] The optical assembly may advantageously be intended for data transmission, via Li-Fi technology (acronym for “Light Fidelity”). The light source 300 of the optical assembly 70 is thus configured to emit the first incident beam 310 with the first wavelength λ located in the infrared range. By infrared range, we mean the range of wavelengths between 780 nm and 2 pm. The photodetector is, for its part, configured to detect the second incident beam with the second wavelength λ also located in the infrared range.

Claims

Claims Claim 1. Optical assembly (50) comprising: - an optical fiber (200), comprising an optical axis (240) and a core (210) of refractive index n c and diameter of, - a basic substrate, called support (51), - a so-called fiber positioning substrate (52), - a beam splitter element (60), - an optical component forming a resonant network, called an optical component (100), - a cover plate (53), the fiber positioning substrate (52) resting on a main face (51 1 ) of said support (51 ) and comprising a lateral edge (523) having a hollow profile forming a housing for receiving the beam splitter element (60) and the optical component (100), a longitudinal groove (80) being made in the fiber positioning substrate (52) and the support (51 ) and opening into the housing of said fiber positioning substrate, said longitudinal groove being dimensioned to receive the optical fiber (200), the optical fiber (200) being positioned in the optical assembly (50) so that a first end face (230) of the optical fiber (200) faces the beam splitter element (60), the cover plate (53) resting on the fiber positioning substrate and pressing the optical fiber into the longitudinal groove,the optical component (100) being configured to receive a light beam, called the first incident beam (310), coming from a direction substantially perpendicular to the optical axis (240) of the optical fiber (200), and to transmit this first incident beam (310) to the optical fiber (200), via the beam splitter element (60), the beam splitter element (60) being configured to:, - let the first incident beam (310) pass towards the optical fiber (200), - transmitting a light beam, called the second incident beam (410), coming from the optical fiber (200) out of the optical assembly, into a direction substantially perpendicular to the optical axis (240) of the optical fiber (200), characterized in that the optical component (100) comprises a stack comprising: - a substrate (110) of refractive index n s substantially equal to the refractive index n cof the core of the optical fiber and thickness e s less than or equal to the diameter of the core of the fiber (200), said substrate comprising two faces, called first (1 13) and second (1 14) faces, - a semi-reflective layer (120) of refractive index n S r greater than the refractive index n s of the substrate, and of thickness e S r, - a diffraction layer (130), of thickness ed, comprising, throughout its thickness, a diffraction grating (131) of period A, - a reflective layer (140), the reflective layer (140) resting on the main face (51 1 ) of the support (51 ), the semi-reflective layer (120) and the diffraction layer (130) being arranged between the substrate (110) and the reflective layer (140), the semi-reflective layer (120) being arranged between the substrate (1 10) and the diffraction layer (130) or between the diffraction layer (130) and the reflective layer (140), for a first incident ray of the first incident beam (310), having a first given wavelength λi and arriving on the first face (1 13) of the substrate (1 10) with a predetermined angle of incidence λai and defined relative to a direction normal to said first face of the substrate (1 10): - the thicknesses of the semi-reflecting layer (120) and of 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 within the limit of the first diffraction order, and at a diffraction angle such that the diffracted ray propagates in the substrate (110), in an angular acceptance cone of the optical fiber (200), towards the beam splitter element then towards the first face of the optical fiber. Claim 2. Optical assembly (50) according to claim 1 in which the diffraction grating (131) is in the form of a plurality of concentric circular arcs, centered at the first end face (230) of the optical fiber (200). Claim 3. Optical assembly (50) according to one of the preceding claims in which the support (51), the fiber positioning substrate (52) and the cover plate (53) are each made of a material which allows at least the wavelengths in the ultraviolet to pass. Claim 4. Optical assembly (50) according to one of the preceding claims in which the beam splitter element (60) is a separate part from the optical component (100) and is arranged between the first end face (230) of the optical fiber (200) and the optical component, the beam splitter element (60) and the optical component (100) having a shape complementary to the housing of the fiber positioning substrate (52), so as to each take place in a complementary manner in the housing of said fiber positioning substrate. Claim 5. Optical assembly (50) according to the preceding claim in which the beam splitter element is a prism splitter, for example a splitter cube. Claim 6. Optical assembly (60) according to one of claims 1 to 3 wherein the optical component (100) comprises a first lateral edge (103) having an inclination substantially equal to 45° relative to the optical axis (240) of the optical fiber, and wherein the beam splitter element (60) is a dichroic filter attached to the first lateral edge (103) of the optical component (100), the optical component (100) having a shape complementary to the housing of the fiber positioning substrate (52), so as to take place in a complementary manner in the housing of said fiber positioning substrate, with the first lateral edge (103) facing the first end face (230) of the optical fiber (200). Claim 7. Optical assembly (50) according to the preceding claim in which the first end face (230) of the optical fiber (200) is inclined at an angle substantially equal to 45° relative to the optical axis (240) of said optical fiber, such that the first end face (230) of the optical fiber is attached to the dichroic filter attached to the first lateral edge (103) of the optical component (100). Claim 8. Optical assembly (70) comprising a light source (300), a photodetector (400) and an optical assembly (50) according to one of the preceding claims, said light source being arranged opposite the optical component and configured to emit the first incident beam, said photodetector being arranged opposite the beam splitter element so as to receive the second incident beam.

Images