OPTICAL LINK FOR AEROSPACE APPLICATIONS AND CORRESPONDING ASSEMBLY METHOD

Abstract

An optical link is intended for use in aerospace applications. The optical link comprises an optical fiber (30) interconnecting two termination points. Each termination point includes a ferrule holder (11) and a ferrule (12) to which the optical fiber (30) is fixed by adhesive (41). The optical link also includes a protective element (20) with a metallic sheath (25) in which the optical fiber (30) is loosely mounted. At each termination point, the protective element (20) is mounted integrally with the ferrule holder (11) such that the optical link has a cavity (32) in the ferrule holder (11) between the ferrule (12) and the protective element (20) through which the optical fiber (30) exits the protective element (20) to be fixed to the ferrule (12). The cavity (32) is arranged so that the adhesive (41) joining the optical fiber (30) and the ferrule (11) is at a distance from the protective element (20). Figure to be published with the abbreviation: Fig. 2

Description

Title of the invention: OPTICAL LINK FOR AEROSPACE APPLICATIONS AND CORRESPONDING ASSEMBLY METHOD technical field

[0001] The present invention relates to an optical link intended for use in aerospace applications, i.e. in demanding thermal conditions which can for example range from -160°C to +135°C. STATE OF PRIOR ART

[0002] Optical links can be used in the aerospace field for opto-pyrotechnical applications, particularly for triggering ignitions. An ignition laser generates a light pulse that is then transmitted through an optical link or optical harness to one or more targets, i.e., to one or more opto-pyrotechnical initiators where a detonator triggers the ignition of an energetic material. These opto-pyrotechnical applications require precise control of line losses between the ignition laser and the opto-pyrotechnical initiator.

[0003] Optical links can also be used in the aerospace field for communication applications. These applications require perfectly controlled propagation times of light pulses or light signals.

[0004] The design of optical links for the applications mentioned above therefore aims to achieve high mechanical stability of the optical links in thermally and mechanically demanding environments: in terms of transmittance stability and dimensional variations (shrinkage / expansion of the optical link). Indeed, due to the demanding thermal conditions of space applications, which can range, for example, from -160°C to +135°C, the optical links may be subjected to mechanical stresses, such as strong vibrations, which can lead to variability in the transmission properties of these optical links.

[0005] It is therefore desirable to provide a solution which makes it possible to improve the mechanical stability of optical links, as well as their optical performance, in aerospace applications. Description of the invention

[0006] An optical link intended for use in aerospace applications is proposed herein, the optical link comprising an optical fiber interconnecting two termination points, where each termination point comprises a ferrule to which the optical fiber is fixed by adhesive and a ferrule holder, the optical link comprising A protective body is also placed around the optical fiber. The optical link is designed so that the protective body includes a metallic sheath, with the optical fiber loosely mounted within the sheath. Furthermore, at each termination point, the protective body is mounted securely to the ferrule holder, creating a cavity in the ferrule holder between the ferrule and the protective body. The optical fiber exits the protective body through this cavity and is secured to the ferrule. The cavity is positioned so that the adhesive bonding the optical fiber to the ferrule is located away from the protective body. This loose mounting and the cavity prevent tight bends in the optical fiber, both during optical link assembly and during use in aerospace applications. This improves the mechanical stability and optical performance of the optical link.

[0007] In a particular embodiment, each termination point further comprises a centering guide for guiding the optical fiber exiting the protective element into said cavity, the centering guide being assembled to the ferrule holder, the protective element being glued to the centering guide, the cavity being such that the glue assembling the optical fiber and the ferrule is also at a distance from the centering guide. Thus, the insertion of the optical fiber into the ferrule is facilitated.

[0008] In a particular embodiment, the protective element is in three parts: a first part on the side of a first termination point, including a portion of metallic sheath with a diameter equal to a first diameter value; a second part on the side of a second termination point, including a portion of metallic sheath with a diameter also equal to the first diameter value; and a third part connecting the first and second parts, including a portion of metallic sheath with a diameter equal to a second diameter value greater than the first diameter value. Furthermore, the optical link has an interlocking assembly between said first and second parts, on the one hand, and said third part, on the other.Thus, the optical link is easily adapted to small connectors while remaining flexible along the length of the third part, offering more leeway for the free mounting of the optical fiber.

[0009] In a particular embodiment, the nested assembly is held in place with adhesive joints between said portions of the metal sheath. Thus, the nested assembly is easily held in place.

[0010] In a particular embodiment, the optical fiber is coated with polyetheretherketone at the glue joints between said first and second parts, on the one hand, and said third part, on the other hand, where the optical fiber thus coated with polyetheretherketone is in free mounting in the metal sheath. Thus, the optical fiber is protected against any possible migration of glue at the joints.

[0011] In a particular embodiment, the nested assembly includes, on the outer surface of the protective element, a portion of heat-shrink tubing spanning between said third part and said first part, and between said third part and said second part. Thus, the protection of the optical fiber against moisture and its consequences under thermal conditions related to aerospace applications is reinforced at these points.

[0012] In a particular embodiment, each endpoint is included in a connector and the nested assembly is integrated into a rear housing of the connector. Thus, the nested assembly is protected from mechanical handling stresses.

[0013] In a particular embodiment, the metal sheath is coated with a polyimide material. This enhances the protection of the optical fiber against moisture and its consequences under thermal conditions associated with aerospace applications.

[0014] In a particular embodiment, the metal sheath is made of stainless steel. This enhances the protection of the optical fiber against moisture and its consequences under thermal conditions associated with aerospace applications.

[0015] An optical harness comprising one or more optical links is also proposed here according to any one of the embodiments presented above.

[0016] Also proposed here is a space vehicle using at least one optical link and / or at least one optical harness, according to any of the embodiments presented above, within the framework of an opto-pyrotechnic application.

[0017] Also proposed here is a space vehicle using at least one optical link and / or at least one optical harness, according to any of the embodiments presented above, within the framework of a communication application.

[0018] Also proposed here is a method for assembling an optical link intended to interconnect two termination points by means of an optical fiber and intended for use in aerospace applications, where each termination point comprises a ferrule and a ferrule holder, the method comprising: inserting the optical fiber into a protective element including a metallic sheath, the optical fiber being freely mounted within the metallic sheath. And for each end of the optical fiber, the ferrule being assembled to the ferrule holder: placing a drop of glue on the ferrule where the optical fiber is to be fixed; inserting the end of the optical fiber into a through hole in the ferrule holder; mounting the protective element securely to the ferrule holder so that the optical link has a cavity in the ferrule holder between the ferrule and the protective element where the optical fiber exits the protective element to be fixed to the ferrule, the cavity being arranged so that the glue assembling the optical fiber and the ferrule is at a distance from the protective element.

[0019] In a particular embodiment, the method comprises: securing the protective element with a centering device, and sliding the optical fiber into it; adding the dot of glue to an orifice of a through hole in the ferrule, through which the optical fiber must be inserted to allow subsequent optical connection; adding glue to the external surface of the centering device to ensure its subsequent attachment to the ferrule holder; and inserting the optical fiber into the ferrule, through the orifice of the through hole in the latter where the dot of glue has been deposited, and in so doing, the centering device is inserted into the ferrule holder until it stops, so as to form said cavity in the ferrule holder.

[0020] In a particular embodiment, the adhesive point undergoes polymerization cycles with increasing temperature steps. This makes it possible to obtain a high-strength adhesive bond, suitable for the extreme conditions of aerospace applications. Brief description of the drawings

[0021] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of at least one exemplary embodiment, said description being made in relation to the accompanying drawings, among which:

[0022] [Fig.lA] schematically illustrates an optical link, in a first embodiment;

[0023] [Fig.lB] schematically illustrates an optical link, in a second embodiment;

[0024] [Fig.2] schematically illustrates an optical link termination point, in a particular embodiment;

[0025] [Fig.3] schematically illustrates an assembly arrangement nested in the second embodiment;

[0026] [Fig.4] schematically illustrates a harness comprising several such optical links;

[0027] [Fig. 5] schematically illustrates a space vehicle using at least one such link optics and / or at least such a harness; and

[0028] [Fig.6] schematically illustrates a method of assembling the optical link.

[0029] DETAILED DESCRIPTION OF IMPROVEMENTS Optical link structure

[0030] An optical link intended for use in aerospace applications is disclosed below. Different embodiments of the optical link are detailed. In each of these embodiments, the optical link comprises an optical fiber interconnecting two endpoints. From one endpoint to the other, the The optical fiber is protected by a protective body that surrounds it. The protective body includes a metallic sheath, with the optical fiber being freely mounted within the metallic sheath.

[0031] The free mounting makes it possible to limit the losses induced by bends (micro- and macro-bends) of the optical fiber due to thermal and / or mechanical stresses suffered by the optical link in its context of use.

[0032] Preferably, the metal sheath is made of stainless steel.

[0033] Each termination point comprises a ferrule and a ferrule holder, which are part of a connector, for example, an 8D type ELIO 38999 connector (ELIO is a registered trademark). The optical fiber is attached to the ferrule by thermosetting epoxy adhesive, for example, EPO-TEK 353ND (EPO-TEK is a registered trademark). The ferrule holder is a support with a through hole on one side of which the ferrule is inserted and held (for example, by press fitting or by gluing) and on the other side of which is attached the protective element that protects the optical fiber between the two termination points.

[0034] At each termination point, the protective element is mounted integrally with the ferrule holder, such that the optical link has a cavity in the ferrule holder between the ferrule and the protective element. The optical fiber exits the protective element into this cavity to be attached to the ferrule, and the cavity is arranged (sized) so that the adhesive bonding the optical fiber and the ferrule is at a distance from the protective element.

[0035] To mount the protective element attached to the ferrule holder, a thermosetting epoxy type adhesive, for example EPO-TEK 353ND (EPO-TEK is a registered trademark), is preferably used.

[0036] Fig. 1A schematically illustrates an optical link, in a first embodiment (optical link 100).

[0037] The optical link 100 comprises an optical fiber interconnecting two termination points 10. From one termination point 10 to the other, the optical fiber is protected by a protective element 20 that surrounds it. The protective element 20 includes a metallic sheath 25, in which the optical fiber is freely mounted, as schematically illustrated in [Fig. 2]. For example, the diameter of the metallic sheath 25 is 1 mm or 1.2 mm, and the diameter of the optical fiber is 250 µm.

[0038] Each termination point 10 includes a ferrule holder 11 and a ferrule 12 through which the optical fiber is made accessible via the connector to which the ferrule holder 11 and the ferrule 12 belong.

[0039] In a particular embodiment, the metal sheath 25 is covered with a polyimide material, for example in the form of a self-adhesive tape, for example 3M 5413 type polyimide adhesive tape (3M is a registered trademark) or by a polyimide tube, for example of type Polyimide tubing ROTIMA (ROTIMA is a registered trademark) into which the metallic protective sheath 25 is inserted. This arrangement provides protection against moisture which, depending on the conditions of use of the optical link, could cause ice formation which would lead to unnecessary stress on the optical fiber.

[0040] Figure [1B] schematically illustrates an optical link in a second embodiment (optical link 110). The arrangement of the termination points 10 of Figure [1B] is identical to that of Figure [1A].

[0041] In this second embodiment, the protective element 20 is in three parts: - a first part 21a on the side of one of the termination points 10, including a portion of metallic sheath with a diameter equal to a first diameter value (for example, 1.2 mm); - a second part 21b on the side of the other termination point, including a portion of metallic sheath with a diameter also equal to the first diameter value; - a third part 22 linking the first part 21a and the second part 21b, including a portion of metallic sheath with a diameter equal to a second diameter value (for example, 2.3 mm) greater than the first diameter value.

[0042] Thus, on the arrangement of [Fig.2], the metal sheath 25 is also in three parts (the three portions mentioned above).

[0043] The optical link 110 has a nested assembly between said third portion 22 and each of said first 21a and second 21b portions. In a particular embodiment, the nested assembly is held in place with adhesive joints between said portions of the metal sheath 25. Adhesive suitable for bonding small mechanical assemblies may be used, such as cyanoacrylate adhesive, for example, LOCTITE 121HP (LOCTITE is a registered trademark). In a particular embodiment, the optical fiber is coated with polyetheretherketone (PEEK) at the adhesive joints between said first 21a and second 21b portions, on the one hand, and said third portion 22, on the other hand. The protective element 20 is such that, even when thus covered with polyetheretherketone, the optical fiber is freely mounted in the metal sheath 25.Such an arrangement protects the optical fiber from any possible migration of glue at the joints between said portions of the metal sheath 25.

[0044] In a particular embodiment, the nested assembly includes, on the outer surface of the protective element 20, a portion of heat-shrink tubing 23 (sleeve) straddling said third part 22 and said first part 21a, and between said third part 22 and said second part 21b. This portion of tubing Heat shrink tubing provides enhanced protection against moisture. For example, this section of heat shrink tubing is type RNF-100-1 / 8.

[0045] A particular embodiment of nested assembly is shown below in relation to [Fig.3].

[0046] In a particular embodiment, the first part 21a of the protective element 20 is dimensioned so that it can be inserted into a connector backshell. The same applies to the second part 21b of the protective element 20. Thus, the less robust elements of the optical link (junction of the metal sheath portions, junction with the termination point) are protected by the connector backshell, and the more flexible part of the optical link is left free between the connectors.

[0047] As in the case of [Fig.1A], the metal sheath 25 can be covered with a polyimide material.

[0048] Figure [Fig.2] schematically illustrates an optical link termination point 10, in a particular embodiment.

[0049] In [Fig.2], the ferrule 12 has been press-fitted into a through hole 13 of the ferrule holder 11. Alternatively, the ferrule 12 can be glued into the through hole 13. For example, the through hole 13 has a shoulder preventing the ferrule 12 from exceeding a limit position when inserted into the through hole of the ferrule holder 11, so as to ensure a cavity 32 of sufficient dimensions in the ferrule holder 11 between the ferrule 12 and the protective member 20.

[0050] The optical fiber 30 is attached to the ferrule 12 so as to provide an optical connection, the ferrule holder 11 and the ferrule 12 forming part of a connector for making this optical connection. Typically, the optical fiber 30 is inserted into a through hole in the ferrule 12 (generally in its center). The optical fiber 30 is attached to the ferrule 12 with adhesive. Preferably, the optical fiber 30 is attached with a drop of adhesive to the ferrule 12 at the opening of said through hole in the ferrule 12, which is located in the cavity 32.

[0051] The protective element 20 comprises the metal sheath 25, the optical fiber 30 being freely mounted in the metal sheath 25.

[0052] The protective element 20 is mounted securely to the ferrule holder 11, for example by means of glue, so that the optical link presents the cavity 32 in the ferrule holder 11 between the ferrule 12 and the protective element 20. The cavity 32 is dimensioned such that the glue 41 assembling the optical fiber 30 and the ferrule 12 is at a distance from the protective element 20 which surrounds the optical fiber 30. The integrity of the glue 41 is thus preserved despite any mechanical and / or thermal stresses applied to the optical link.

[0053] To facilitate the assembly of the protective element 20 and the ferrule holder 11, a centering device 31 is preferably used. The centering device 31 is mounted integrally with the protective element 20 and the ferrule holder 11. The centering device 31 guides the optical fiber 30 exiting the protective element 30 into the cavity 32. Once the centering device 31 is assembled with the ferrule holder 11, the cavity 32 is positioned such that the adhesive 41 bonding the optical fiber 30 and the ferrule 12 is also at a distance from the centering device 31.

[0054] The centering device 31 is, for example, a tube with a shoulder. The centering device 31 is inserted into the through hole 13 through the orifice opposite to that through which the ferrule 12 is inserted. The shoulder of the centering device 31, bearing against the ferrule holder 11, makes it possible to limit the insertion distance of the centering device 31 in the through hole 13 and to ensure that the cavity 32 has sufficient dimensions.

[0055] For example, the centering device 31 is mounted securely to the ferrule holder 11 using glue 42 (for example of type EPO-TEK 353ND (EPO-TEK is a registered trademark)).

[0056] For example, the protective element 20 is mounted securely to the centering device 31 by means of glue 44 (such as thermosetting epoxy glue, for example of type EPO-TEK 353ND (EPO-TEK is a registered trademark)) fixing the metal sheath 25 inside the pipe formed by the centering device 31.

[0057] The protective element 20 may include, on its outer surface, a portion of heat-shrinkable sleeve 33 at the termination point 10. This portion of heat-shrinkable sleeve 33 provides protection against moisture. For example, this portion of heat-shrinkable sleeve 33 is of type RNF-100-1 / 16, and can be attached to the shoulder of the centering device 31 using adhesive 43 suitable for bonding small mechanical assemblies (such as cyanoacrylate adhesive, for example, LOCTITE 121HP (LOCTITE is a registered trademark)).

[0058] In a particular embodiment (not shown), the metal sheath 25 is covered with a polyimide material.

[0059] In a particular embodiment, the optical fiber 30 is coated with polyetheretherketone 34 at the end of the metal sheath 25. Such an arrangement protects the optical fiber from possible migration of glue at the termination point 10.

[0060] Fig. 3 schematically illustrates an assembly arrangement nested in the second embodiment (Fig. 1B).

[0061] Figure 3 shows a portion 25a of the metal sheath 25 of the first part 21a or the second part 21b of the protective member 20 (on the side of either of the termination points 10), as well as a portion 25b of the metal sheath 25 of the third part 22 of the protective member 20. The diameter of said portion 25a has a diameter equal to the first diameter value mentioned above, and the diameter of said portion 25b has a diameter equal to the second diameter value mentioned above (which, as a reminder, is greater than said first diameter value).

[0062] Portion 25a of the metal sheath 25 penetrates portion 25b of the metal sheath 25, for example over a distance of a few centimeters. Over this distance, portions 25a and 25b of the metal sheath 25 are joined by adhesive joints (not visible in [Fig. 3]).

[0063] Figure 3 presents a particular embodiment where the junction of portions 25a and 25b of the metal sheath 25 is covered with a heat-shrinkable sleeve 51b, which is therefore straddling said third part 22 of the protective element 20 and said first part 21a (resp. second part 21b) of the protective element 20.

[0064] Furthermore, [Fig. 3] presents a particular embodiment in which portion 25a of the metal sheath 25 (termination point side 10) is covered by a heat-shrink sleeve 51a (which corresponds to portion 33 of the heat-shrink sleeve in [Fig. 1B]). Here, the heat-shrink sleeve 51b partially covers the heat-shrink sleeve 51a so as to provide a watertight seal against moisture at the junction of the first part 21a (or second part 21b) of the protective element 20 and the third part 22 of the protective element 20.

[0065] Furthermore, [Fig.3] presents a particular embodiment where the optical fiber is coated with polyetheretherketone 52 on both sides of the junction between portions 25a and 25b of the metal sheath 25 (potentially up to the termination point 10 on the side of portion 25a of the metal sheath 25).

[0066] Finally, [Fig.3] presents a particular embodiment where the portion 25b of the metal sheath 25 is covered with a polyimide material 53 to ensure protection against moisture up to the heat shrink sleeve 51b (with an overlap area of ​​the heat shrink sleeve 51b on the polyimide material 53 to complete the sealing).

[0067] In relation to Figs. IA, IB, 2 and 3, different embodiments of an optical link suitable for use in aerospace applications, i.e. in demanding thermal conditions which can for example range from -160°C to +135°C above, have been presented. Harness structure

[0068] It is also possible to construct an optical harness 400 comprising one or more such optical links, as schematically illustrated in [Fig. 4]. For example, as illustrated in [Fig. 4], the harness 400 comprises a connector 401 that brings together respective optical link termination points 10, the remaining termination points 10 of which are mounted on separate individual connectors 402. A connector 401 that brings together several optical link termination points 10 is called a "multi-way" connector (versus "single-way" connectors). It is It is therefore possible to create an optical harness with a combination of multi-way and single-way connectors on either side of the optical links. Application in space vehicles

[0069] Figure 5 schematically illustrates a space vehicle 500, such as a space launcher, using at least one optical link as previously described, in any of the detailed embodiments, and / or at least one optical harness comprising several such optical links.

[0070] In one embodiment, the Space Vehicle 500 uses said at least one optical link and / or said at least one optical harness in an opto-pyrotechnic application. Optical pulses (for example, with a power of approximately 40 W) are thus transmitted via said at least one optical link and / or said at least one optical harness to trigger explosive charges in a synchronized manner, for example, to detach elements of the Space Vehicle 500 with high temporal precision.

[0071] In one embodiment, the Spacecraft 500 uses said at least one optical link and / or said at least one optical harness in a communication application. Thus, electronic equipment, such as computers, communicates efficiently with each other. Assembly process

[0072] To assemble the optical link, an optical fiber is inserted (for example by an operator) into a protective device including a metallic sheath, the optical fiber being freely mounted in the metallic sheath.

[0073] Next, for each optical link termination point, a ferrule and ferrule holder assembly is used. For example, for each end of the optical fiber, the operator obtains a ferrule and a ferrule holder. Generally, the ferrule and ferrule holder are supplied pre-assembled, ready to be integrated into an optical connector. Otherwise, the operator assembles the ferrule and ferrule holder.

[0074] Then, a drop of glue is placed on the ferrule where the optical fiber is to be fixed. For example, the drop of glue is placed using a syringe, by inserting said syringe through an orifice of a through hole in the ferrule holder that is opposite the one through which the ferrule was forcibly inserted into said through hole.

[0075] Then, the end of the optical fiber is inserted into a hole through the ferrule holder, so as to reach the ferrule and be fixed therein to allow the optical connection to be made later.

[0076] Then, the protective element is assembled with the ferrule holder so that the optical link has a cavity in the ferrule holder between the ferrule and the protective element where the optical fiber exits the protective element to be fixed onto the ferrule, the cavity being arranged so that the glue assembling the optical fiber and the ferrule is at a distance from the protective element.

[0077] The assembly of the protective element with the ferrule holder is carried out before the glue fixing the optical fiber and ferrule has set (dried).

[0078] The cavity allows in particular that, if the optical fiber bends during the assembly of the protective element with the ferrule holder so as to form a bend, this bend can be easily removed (typically, by pulling on the optical fiber) before the glue fixing the optical fiber to the ferrule sets.

[0079] Figure 6 schematically illustrates a method for assembling an optical link, more particularly at a termination point 10, in a particular embodiment.

[0080] In a step 602, a protective element including a metallic protective sheath (for example, made of stainless steel) is secured with a centering device, and an optical fiber is slid into it, the dimensions of the optical fiber and the metallic sheath are such that the optical fiber is freely mounted in the metallic sheath.

[0081] For example, an operator secures a polyetheretherketone sheath covering a metallic sheath with a centering device, typically using glue, and slides a free-mount optical fiber into it.

[0082] In a step 604, a ferrule and a ferrule holder are joined together.

[0083] In step 606, a drop of glue is added to an orifice of a through hole in the ferrule, through which the optical fiber is to be inserted to allow for the subsequent establishment of an optical connection. This precise point on the ferrule is made accessible through a through hole in the assembly formed by the ferrule holder and the ferrule, and the drop of glue is deposited there, for example, by the operator using a syringe.

[0084] In a step 608, glue is added to the external surface of the centering device, to enable its subsequent attachment to the ferrule holder.

[0085] In a step 610, the optical fiber is inserted into the ferrule, through the orifice of the through hole in the latter where the glue dot was deposited in step 606. In doing so, the centering device is inserted into the ferrule holder until it stops, so as to form, in the ferrule holder, a cavity between the ferrule and the protective member so that the glue assembling the optical fiber and the ferrule is at a distance from the protective member.

[0086] Once the glue intended to fix the optical fiber and the ferrule has set, as well as the glue assembling the centering device with the protective element and the ferrule holder, then the termination point of the optical link is made on one side of the protective element, and the same process can be applied on the other side of the protective element for the other termination point of the optical link.

[0087] In the process described above, when components are bonded with thermosetting epoxy adhesive, for example EPO-TEK 353 ND (EPO-TEK is a registered trademark), the adhesive preferentially cures through polymerization cycles with increasing temperature steps, which provides good adhesion for use in the aerospace field. In particular, step-by-step polymerization ensures that the glass transition temperature (Tg) of the cured epoxy adhesive remains well above the product's operating temperature, thus guaranteeing a mechanically rigid bond under all operating conditions of the optical link or harness, including at high temperatures.This particular embodiment of the process is especially advantageous because the optical fiber and the ferrule are joined by a highly resistant adhesive bond, achieved through step-by-step polymerization. This contrasts with the traditional approach of filling the cavity with adhesive and achieving a cure through polymerization at a constant high temperature. For example, a polymerization cycle at +90°C is performed for 30 minutes, followed by another cycle at +150°C for the next 30 minutes.

Claims

Demands

1. An optical link (100, 110) intended for use in aerospace applications, the optical link (100, 110) comprising an optical fiber (30) interconnecting two termination points (10), wherein each termination point (10) has a ferrule (12) to which the optical fiber (30) is fixed by adhesive (41) and a ferrule holder (11), the optical link (100, 110) also comprising a protective element (20) around the optical fiber (30), characterized in that the protective element (20) includes a metallic sheath (25), the optical fiber (30) being freely mounted in the metallic sheath (25), and, at each termination point (10), the protective element (20) is mounted integrally with the ferrule holder (11) such that the optical link (100, 110) has a cavity (32) in the ferrule holder (11) between the ferrule (12) and the protective element (20) where the optical fiber (30) exits the protective element (20) to be fixed onto the ferrule (12),the cavity (32) being arranged so that the adhesive (41) joining the optical fiber (30) and the ferrule (12) is at a distance from the protective element (20).

2. The optical link (100, 110) according to claim 1, wherein each termination point further comprises a centering device (31) for guiding the optical fiber (30) out of the protective element (20) into said cavity (32), the centering device (31) being assembled to the ferrule holder (11), the protective element (20) being assembled by glue (44) with the centering device (31), the cavity (32) being such that the glue (41) assembling the optical fiber (30) and the ferrule (12) is also at a distance from the centering device (31).

3. The optical link (110) according to claim 1 or 2, wherein the protective element (20) is in three parts: - a first part (21a) on the side of a first termination point (10), including a portion of metallic sheathing with a diameter equal to a first diameter value; - a second part (21b) on the side of a second termination point (10), including a portion of metallic sheathing with a diameter also equal to the first diameter value; - a third part (22) connecting the first part (21a) and the second part (22b), including a portion of metallic sheathing diameter equal to a second diameter value greater than the first diameter value; and in which the optical link (110) has an assembly nested between said first (21a) and second (21b) parts, on the one hand, and said third part (22), on the other hand.

4. The optical link (110) according to claim 3, wherein the nested assembly is held in place with glue joints between said portions of the metal sheath.

5. The optical link (110) according to claim 4, wherein the optical fiber (30) is coated with polyetheretherketone (52) at the glue joints between said first (21a) and second (21b) parts, on the one hand, and said third part (22), on the other hand, wherein the optical fiber (30) thus coated with polyetheretherketone (52) is in free mounting in the metal sheath (25).

6. The optical link (110) according to any one of claims 3 to 5, wherein the nested assembly includes, on the outer surface of the protective element (20), a portion of heat-shrinkable sleeving (51b) straddling said third part (22) and said first part (21a), and said third part (22) and said second part (21b).

7. The optical link (110) according to any one of claims 3 to 6, wherein each termination point (10) is included in a connector (401, 402) and wherein the nested assembly is integrated into a rear shell of the connector (401, 402).

8. The optical link (100, 110) according to any one of claims 1 to 7, wherein the metal sheath (25) is covered with a polyimide material (53).

9. The optical link (100, 110) according to any one of claims 1 to 8, wherein the metal sheath (25) is made of stainless steel.

10. An optical harness (400) comprising one or more optical links (100, 110) according to any one of claims 1 to 9.

11. A space vehicle (500) using at least one optical link (100, 110) according to any one of claims 1 to 9 and / or at least one optical harness (400) according to claim 10 in the context of an opto-pyrotechnic application.

12. A spacecraft (500) using at least one optical link (100, 110) according to any one of claims 1 to 9 and / or at least

13.

14. an optical harness (400) according to claim 10 in the context of a communication application. Method for assembling an optical link (100, 110) intended to interconnect two termination points (10) by means of an optical fiber (30) and intended for use in aerospace applications, wherein each termination point (10) comprises a ferrule (12) and a ferrule holder (11), the method comprising: - insert the optical fiber (30) into a protective device (20) including a metallic sheath (25), the optical fiber (30) being freely mounted in the metallic sheath (25); and for each end of the optical fiber (30), the ferrule (12) being assembled to the ferrule holder (11): - place a dot of glue (41) on the ferrule (12) where the optical fiber (30) is to be fixed; - insert the end of the optical fiber (30) into a through hole in the ferrule holder (11); - mount the protective member (20) with the ferrule holder (11) so that the optical link (100, 110) has a cavity (32) in the ferrule holder (11) between the ferrule (12) and the protective member (20) where the optical fiber (30) exits the protective member (20) to be fixed on the ferrule (12), the cavity (32) being arranged so that the glue (41) assembling the optical fiber (30) and the ferrule (12) is at a distance from the protective member (20). A method according to claim 13, comprising: - secure (602) the protective element (20) with a centering device (31), and slide the optical fiber (30) into it; - add (606) the glue dot (41) on an orifice of a through hole in the ferrule (12), through which the optical fiber (30) must be inserted to allow subsequent optical connection; - add (608) glue (42) to the external surface of the centering device (31) to ensure its subsequent attachment to the ferrule holder (11); and - insert (610) the optical fiber (30) into the ferrule (12), through the orifice of the through hole in the latter where the glue dot (41) has been deposited, and in doing so, the centering device (31) is inserted into the ferrule holder (11) until it stops, so as to form said cavity (32) in the ferrule holder (11).

15. A method according to claim 13 or 14, wherein the glue point (41) undergoes polymerization cycles with increasing temperature steps.

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