Fiber processing tower for the manufacture of functionalized optical fiber

Abstract

Fiber drawing tower for the manufacture of a functionalized optical fiber. This fiber drawing tower includes a stabilizing support (120) adapted to limit the amplitude of vibrations of a bare optical fiber generated by a drawing furnace (42). This support includes, for this purpose, a membrane whose hardness, on the Shore A scale, is between 5 and 60. The membrane has a slot with edges adapted to rub against the bare optical fiber when this bare optical fiber passes inside a pattern inscription station (44). The vertical distance between the slot and a pattern inscription zone (66) in the bare optical fiber is less than a distance Dmax beyond which the amplitude of the vibrations of the bare optical fiber becomes greater than the diameter of the core of this bare optical fiber. Fig. 4

Description

Title of the invention: Fiber processing tower for the manufacture of a functionalized optical fiber

[0001] The invention relates to a fiber-laying tower for the fabrication of a functionalized optical fiber. The invention also relates to a stabilizing support for this fiber-laying tower and to a method for manufacturing a functionalized optical fiber using this fiber-laying tower.

[0002] A fiber-laying tower for the manufacture of a functionalized optical fiber is described in application CN109655962A. This fiber-laying tower comprises, successively from top to bottom, in particular:

[0003] - a drawing oven capable of generating, from a preform, a bare optical fiber,

[0004] - a station for writing patterns into bare optical fiber using a laser femtosecond and a phase mask,

[0005] - a station for depositing a protective coating onto the bare optical fiber, then

[0006] - a drive device capable of vertically scrolling the optical fiber in these different positions.

[0007] This fiber-laying tower has the advantage that the patterns are inscribed in the manufactured optical fiber before the protective coating is applied to the optical fiber. This reduces the number of steps required to manufacture the functionalized optical fiber. In particular, subsequent steps of removing the protective coating to proceed with pattern inscription are avoided.

[0008] However, at the inscription station, the amplitude of the vibrations of the optical fiber in a horizontal direction is significant, i.e., greater than 10 pm and generally greater than 100 pm. Thus, the relative position of the optical fiber with respect to the lens that directs the femtosecond laser pulses onto the optical fiber also varies considerably. Under these conditions, only low-resolution pattern inscription methods can be implemented. These low-resolution methods share the common characteristic of not requiring precise positioning of the lens with respect to the optical fiber. These low-resolution methods include, for example, inscription methods that use a phase mask, as described in application CN109655962A.

[0009] Conversely, in the fiber optic tower of application CN109655962A, it is not possible to implement registration methods requiring higher resolution, i.e., methods in which the relative position of the optical fiber with respect to the target varies little. For example, in the fiber optic tower of application CN109655962A, it is not possible to implement a registration method point-to-point patterns using a femtosecond laser as described in application CN115933324A.

[0010] The following prior art gives other examples of fiber-laying towers similar to that of application CN109655962A:

[0011] - W. Gao et al. : «Multi-Wavelength Ultra-Weak Fiber Bragg Grating Arraysfor Long-Distance Quasi-Distributed Sensing”, Photonic Sensors 12 (2), 2022,

[0012] - H. Guo et al. : “Ultra-weak FBG and its refractive index distribution in the drawing optical fiber”, Optics Express 23, 4 (2015).

[0013] The invention aims to provide a fiber tower that has the same advantages as the fiber tower disclosed in application CN109655962A while offering the possibility of using other pattern inscription methods and, in particular, inscription methods requiring higher resolution.

[0014] The invention therefore relates to a fiber-laying tower for the manufacture of a functionalized optical fiber, this fiber-laying tower comprising successively, from top to bottom:

[0015] - a drawing oven capable of generating, from a preform, a bare optical fiber, This bare optical fiber, generated and comprising at least a core and a cladding shaped to guide an optical signal,

[0016] - a station for writing patterns into bare optical fiber using a beam laser, this registration station comprising a laser source capable of emitting the laser beam and a lens capable of directing the emitted laser beam onto a registration area traversed by the generated bare optical fiber,

[0017] - a station for depositing a protective coating onto the sheath of the bare optical fiber generated,

[0018] - a drive device capable of vertically scrolling the bare optical fiber generated along a vertical scrolling axis that passes successively through the registration area of ​​the registration station and then through the deposit station,

[0019] in which:

[0020] - the fiber tower includes a stabilizing support capable of limiting the amplitude vibrations of the bare optical fiber are generated, this support comprising for this purpose a membrane whose hardness, on the Shore A scale, is between 5 and 60,

[0021] - the membrane has a slot through which the scroll axis passes, this slot comprising edges capable of rubbing against the bare optical fiber when this bare optical fiber passes inside the registration station, and

[0022] - the vertical distance between the slot and the inscription area is less than one distance Dmax beyond which the amplitude of the vibrations of the bare optical fiber becomes greater than the diameter of the core of that bare optical fiber.

[0023] Embodiments of this fiber tower may include one or more of the following features:

[0024] 1)

[0025] - the stabilizing support comprises a housing having side walls and a lower wall, these walls delimiting a cavity within which the inscription area is located, the lower wall having a lower hole through which the scroll axis passes and one of the side walls having a lateral opening for introducing, inside the cavity, the laser beam directed onto the inscription area, and

[0026] - the fiber tower includes an index liquid which fills the cavity of the housing so that the inscription area is located inside the index liquid, this index liquid being transparent to the laser beam and its refractive index being between 0.88*ri2 and l,l*ri2, where rn is the refractive index of the bare optical fiber cladding, and

[0027] - the membrane is fixed, without any degree of freedom, to the lower wall and seals the lower hole to retain the index liquid inside the cavity while being traversed by the bare optical fiber.

[0028] 2)

[0029] - the laser source is a femtosecond laser capable of emitting laser pulses, and

[0030] - the lens is configured to focus each laser pulse on the area inscription to generate, one after the other, patterns in the optical fiber that scrolls through this inscription zone.

[0031] 3)

[0032] - the membrane forms a lower membrane and the stabilizing support comprises in addition to a top membrane, the bottom and top membranes being located on either side of the inscription area,

[0033] - the hardness of the upper membrane, on the Shore A scale, is between 5 and 60, and the upper membrane has an upper slot through which the scroll axis passes, this upper slot having edges adapted to rub against the bare optical fiber when this bare optical fiber scrolls inside this upper slot, and

[0034] - the vertical distance between the upper slot and the inscription area is less than the distance Dmax.

[0035] 4) The fiber tower includes a plate capable of moving, with precision less than 100 pm, the stabilization support in two directions orthogonal and perpendicular to the scroll axis.

[0036] 5)

[0037] - the fiber tower includes a measuring station with a characteristic dimensional of a portion of the bare optical fiber located within an area inspection station, this measuring station being located between the drawing furnace and the deposition station, and

[0038] - the vertical distance between the slot and the inspection area is less than the distance Dmax.

[0039] 6) The vertical distance between the slot and the inscription area is between 0.5 cm and 5 cm.

[0040] The invention also relates to a stabilization support for the construction of the above-mentioned fiber-laying tower, this support being capable of limiting the amplitude of vibrations of the bare optical fiber and comprising for this purpose:

[0041] - a lower wall having a lower hole centered on a scroll axis, and

[0042] - a lower membrane fixed, without any degree of freedom, to the lower wall and sealing the lower hole,

[0043] in which:

[0044] - the hardness of the lower membrane, on the Shore A scale, is between 5 and 60, and

[0045] - the lower membrane has a lower slit through which the axis of scrolling, this lower slot having edges suitable for rubbing against the bare optical fiber when this bare optical fiber scrolls inside this slot.

[0046] Embodiments of this support may include one or more of the following characteristics:

[0047] 1)

[0048] - the stabilizing support comprises a housing having side walls and the lower wall, these walls delimiting a cavity suitable for being filled by the index liquid, within which the inscription area is located, and

[0049] - one of the side walls of the housing has a lateral opening for inserting, inside the cavity, the laser beam is directed onto the inscription area.

[0050] 2)

[0051] - the housing comprises an upper wall located on the opposite side to the lower wall, this upper wall having a top hole centered on the scroll axis, and

[0052] - the stabilizing support comprises a fixed upper membrane, without any degree of freedom, on the upper wall and sealing the upper hole, the hardness of the upper membrane, on the Shore A scale, being between 5 and 60, and

[0053] - the upper membrane has a superior slit through which the axis of scrolling, this upper slot having edges suitable for rubbing against the bare optical fiber when this bare optical fiber scrolls inside this upper slot.

[0054] 3) The thickness of each membrane is between 0.5 mm and 3 mm.

[0055] 4) The diameter of the lower hole is between 1 mm and 5 mm and the length of the the slot is greater than 0.5 mm and less than the diameter of the lower hole.

[0056] 5) Each wall, to which a membrane is fixed, comprises a set of two jaws that can be moved reversibly relative to each other between:

[0057] - a pinched state in which the jaws pinch the periphery of the membrane to fix it to the wall, and

[0058] - a relaxed state in which the jaws allow the replacement of the membrane by a new membrane.

[0059] The invention also relates to a method for manufacturing a functionalized optical fiber using the above-mentioned fiber-laying tower, this method comprising successively the following steps:

[0060] - the generation, using a drawing furnace and from a preform, of a bare optical fiber, this generated bare optical fiber comprising a core and a cladding shaped to guide an optical signal, then

[0061] - the inscription of patterns in bare optical fiber using a laser beam and a registration station comprising a laser source capable of emitting the laser beam and a lens capable of directing the emitted laser beam onto a registration area traversed by the generated bare optical fiber, then

[0062] - the application, using a deposition station, of a protective coating onto the sheath of the bare optical fiber generated, and

[0063] - the vertical scrolling, using a drive device, of the bare optical fiber generated along a vertical scrolling axis that passes successively through the registration area of ​​the registration station and then through the deposit station,

[0064] in which, in parallel with the inscription of patterns, the method includes limiting, using the stabilization support above, the amplitude of the vibrations of the bare optical fiber generated.

[0065] The invention will be better understood upon reading the following description, given solely by way of non-limiting example and made with reference to the drawings in which:

[0066] - Figures 1 to 3 are schematic and partial cross-sectional illustrations longitudinal, of three optical fibers corresponding to three different manufacturing states,

[0067] - [Fig. 4] is a schematic illustration of a fiber tower in which The three manufacturing states shown in figures 1 to 3, each including a stabilizing support, are shown.

[0068] - [Fig. 5] is a schematic illustration of a registration station on the tower of fiber layer of the [Fig.4],

[0069] - Figures 6, 7 and 10 are illustrations, in perspective and from different points from the point of view of a housing of the stabilization support of the fiber optic tower of [Fig.4],

[0070] - [Fig. 8] is a top view of the tower stabilization support housing fiber layer of the [Fig.4],

[0071] - [Fig.9] is a side view of the tower stabilization support housing fiber layer of the [Fig.4],

[0072] - [Fig. 1 1] is a top view of a membrane of the stabilizing support of the fiber spinning tower of the [Fig.4],

[0073] - [Fig.12] is a perspective illustration of the membrane of [Fig.11],

[0074] - [Fig. 13] is a schematic illustration, in vertical section, of a portion lower part of the fiber tower stabilization support of [Fig.4], and

[0075] - [Fig. 14] is a flowchart of a process for manufacturing an optical fiber functionalized using the fiber tower of [Fig.4].

[0076] In this description, the terminology, conventions, and definitions of the terms used in this text are introduced in Chapter I. Detailed examples of embodiments are then described in Chapter II with reference to the figures. Variants of these embodiments are presented in Chapter III. Finally, the advantages of the different embodiments are specified in Chapter IV.

[0077] Chapter I: Definitions, terminology and conventions:

[0078] In the figures, the same references are used to designate the same elements.

[0079] In the remainder of this description, the well-known characteristics and functions of a person skilled in the art are not described in detail.

[0080] The figures are oriented with respect to an orthogonal XYZ coordinate system, where the X and Y directions are horizontal and the Z direction is vertical. Terms such as "above", "below", "top", "bottom", "superior", "inferior" are defined with respect to the Z direction.

[0081] The symbol “*” denotes scalar multiplication.

[0082] The expression "an element made of a material A" or the expression "an element made of material A" means that material A represents 90% or 95% of the mass of that element.

[0083] An optical fiber comprises at least one portion capable of guiding an optical signal along its longitudinal axis. This portion consists of at least one core and an optical cladding that covers at least one core. The refractive index of the optical cladding is adapted so that the optical signal is confined within the core and can propagate longitudinally with limited losses. This portion of the optical fiber, whose function is to guide the optical signal, is subsequently called the "bare optical fiber." Thus, this bare optical fiber comprises at least one core and the optical cladding of the optical fiber. In contrast, the fiber bare optical fiber does not include the protective coating that covers the optical cladding to protect the bare optical fiber.

[0084] The term “coated optical fiber” refers to the bare optical fiber coated with its protective coating.

[0085] The term "optical fiber" alone is used when it is unambiguously clear from the context in which it is used whether it refers to bare optical fiber or coated optical fiber.

[0086] The protective coating forms the outer sheath of a coated optical fiber. The function of this coating is to give the optical fiber mechanical properties that allow it to be handled and used without damage. In particular, the protective coating protects the bare optical fiber:

[0087] - scratches on the surface of the optical sheath which form break initiation points; And

[0088] - environmental chemical aggressions such as gases or liquids which may lead to:

[0089] a) initiation of ruptures by oxidation of the surface of the optical cladding,

[0090] b) a degradation of the optical qualities of the bare optical fiber by the spectral absorption of diffusing compounds inside the bare optical fiber.

[0091] An optical fiber, bare or coated, is said to be "functionalized" when it has a network of patterns inscribed in its core and / or its optical cladding.

[0092] A “pattern” is a sudden change in the refractive index created in the core and / or the optical cladding using a laser pulse.

[0093] In this text, the distance Df is the distance, measured horizontally, between the longitudinal axis of the bare optical fiber and the end of the lens which directs the laser beam towards an inscription area.

[0094] An inscription zone is the area at which a pattern or a set of several patterns is generated in the bare optical fiber when this bare optical fiber passes through this inscription zone at a time when a laser pulse is emitted through the lens.

[0095] An inspection zone is the area at which a dimensional characteristic of the bare optical fiber is measured.

[0096] In this text, a "high resolution" inscription method means a method of inscribing patterns in the bare optical fiber which requires that, during the implementation of this method, the variations in the distance Df remain less than the diameter of the core of the bare optical fiber.

[0097] Conversely, a "low-resolution" inscription method is a method for inscribing patterns in bare optical fiber that does not require that, during the With the implementation of this method, the variations in the distance Df remain less than the diameter of the core of the bare optical fiber.

[0098] Chapter II: Example of an embodiment

[0099] Figure 1 represents a portion of a bare, unfunctionalized optical fiber 2. The fiber 2 is, for example, a single-mode optical fiber or SMF (Single Mode Fiber) capable of guiding an optical signal over very long distances, i.e., over distances greater than one kilometer. The optical signal is guided along a longitudinal axis 6 of the fiber 2. The wavelength of the guided optical signal is typically in the visible light range, i.e., between 380 nm and 780 nm, or in the near-infrared range, i.e., between 780 nm and 2000 nm, or in the far-infrared range, i.e., between 2 pm and 22 pm.

[0100] The fiber 2 comprises, for example, a single core 10, within which the optical signal propagates, and an optical cladding 12 which covers this core 10. The fiber 2 is, for example, made of silica. In this case, one of the core 10 and the optical cladding 12 is doped to obtain the desired refractive index, which is different from the refractive index of the other of the core 10 and the optical cladding 12. For example, the core 10 is made of germanium-doped silica, and the optical cladding 12 is then made of undoped pure silica.

[0101] Fiber 2 is uncoated. Fiber 2 is non-functionalized, meaning that the core 10 and the cladding 12 do not have any pattern inscribed by means of a laser pulse. Thus, the core 10 does not have any intentionally created defects in the core designed to reflect any part of the optical signal propagating within it.

[0102] In this embodiment example, the outside diameter Dn of the fiber 2 is equal to 125 pm and the diameter Di0 of the core 10 is equal to 10 pm.

[0103] Fig. 2 represents a functionalized bare optical fiber 20. This fiber 20 is identical to fiber 2 except that patterns 22 are inscribed in its core 10 to functionalize it.

[0104] In this embodiment, the patterns 22 are inscribed using laser pulses from a femtosecond laser. Such a pattern corresponds to a sudden change in the refractive index in the core 10. In this example, a pattern inscribed using a femtosecond laser consists of a bubble. The bubble appears at the focal point on which the laser pulse is focused. Each bubble creates a significant change in the refractive index of the core 10 in the direction of propagation of the optical signal. For this reason, the difference between the refractive index nriO of the core 10 and the refractive index nrB of a bubble is greater than 0.3 or 0.4. Here, the interior of each bubble is empty or practically empty, which corresponds to a difference between the indices nriO and nrB greater than or equal to 0.4.

[0105] Furthermore, for the change in refractive index to be abrupt, the diameter of each bubble is less than 2 pm or 500 nm and, preferably, less than 100 nm. Generally, the diameter of each bubble is also greater than 10 nm or 50 nm. Each bubble is essentially spherical. Thus, in this text, the diameter of a bubble is equal to the diameter of the smallest sphere that entirely contains that bubble. Here, this diameter is less than 100 nm.

[0106] It is emphasized that currently only laser pulses, typically femtosecond, generating nonlinear effects in the optical fiber, make it possible to obtain a pattern 22 having the above characteristics. Thus, by observing the dimensional characteristics of the pattern 22, it is possible to determine that it was created using a femtosecond laser pulse.

[0107] In this embodiment, the motifs 22 are grouped into several distinct sets of motifs 22, and the motifs 22 in each set are arranged relative to one another to form a Bragg grating. Typically, a Bragg grating consists of at least three and, preferably, at least ten motifs 22. Thus, the fiber 20 comprises a succession of Bragg gratings arranged one after the other along the axis 6.

[0108] The step A between two immediately consecutive patterns 22 along the axis of the same Bragg grating is constant and chosen to place the wavelength at which this Bragg grating reflects the incident optical signal at the desired value.

[0109] Figure 3 represents a functionalized coated optical fiber 30 identical to the fiber 20 except that it also includes a protective coating 32 that encases the entire cladding 12. The material of the coating 32 can be any material, provided it is suitable for the coating 32 to fulfill its function of protecting the bare optical fiber 20. In this context, the material of the coating 32 is chosen according to the application of the fiber 30. For example, the coating 32 is made of one of the following materials: polymer, metal, ceramic, or carbon. The following description focuses on the specific case where the coating 32 is made of polymer.

[0110] Figure 4 represents a fiber-laying tower 40 used to manufacture fiber 30. This tower 40 is similar to fiber-laying towers known for manufacturing non-functionalized optical fibers in which the bare optical fiber is silica. Thus, only the elements necessary for understanding the invention are shown in Figure 4 and described thereafter. In particular, in Figure 4, the absence of representation of certain manufacturing stations is indicated by dashed lines.

[0111] Tower 40 comprises, successively from top to bottom, the following manufacturing stations:

[0112] - a 42 drawing oven,

[0113] - a 44-point pattern entry station,

[0114] - a measuring station 46,

[0115] - a coating deposition station 48 for coating 32, and

[0116] - a 50 training device.

[0117] The furnace 42 melts a silica preform 52 to generate the silica fiber 2, which then passes through the various manufacturing stations until the fiber 30 is obtained. Here, the fiber passes through the various manufacturing stations along a vertical axis 54 of travel. The fiber passes through the various manufacturing stations at a production speed vp. The speed vp is typically greater than 50 mm / s and less than 1500 mm / s. For example, the speed vp is often equal to or close to 250 mm / s and, preferably, even greater than 120 mm / s.

[0118] Station 44 inscribes the patterns 22 into the core 10 of the fiber 2 using a laser beam, so that the fiber 20 is obtained at the output of station 44. To this end, in this embodiment, station 44 implements a high-resolution inscription method, and more specifically, a point-to-point inscription method. For this purpose, as shown in [Fig. 5], the inscription station 44 comprises a laser source 60, a stabilizer 62, and a lens 64.

[0119] The laser source 60 is here a femtosecond laser capable of emitting laser pulses with durations generally between 5 fs and 300 fs.

[0120] The lens 64 directs the emitted laser pulses onto an inscription zone 66 located at the intersection of the axis 54 and the optical axis 68 of this lens 64. Here, the lens 64 focuses the laser pulse onto this zone 66 so that the zone 66 corresponds to the focal point of the laser beam. For this purpose, the lens 64 typically includes at least one converging lens 70. Thus, when the zone 66 is traversed by the core 10 of the fiber 2 at a time when a laser pulse is emitted, this creates one of the patterns 22 in the core 10. Since the fiber 2 passes through the zone 66, the station 44 inscribes the patterns 22 one after the other in the core 10 using a temporal succession of laser pulses. The frequency of the laser pulses is set taking into account the speed vp to obtain the desired distance between two immediately consecutive patterns 22 of the same Bragg grating.Conversely, when no Bragg grating is to be inscribed in the core 10 of the fiber 2 which runs through zone 66, the generation of laser pulses is inhibited.

[0121] The stabilizer 62 stabilizes the laser beam emitted by the source 60 so that it is always correctly centered on the lens 70. To this end, it comprises:

[0122] - one or more sensors that measure a difference between the current position of the beam laser and a position reference,

[0123] - one or more actuators capable of changing the direction of the laser beam, and

[0124] - a microprocessor programmed to control the actuator(s) in such a way as to reduce the measured gaps.

[0125] The registration station also includes a plate 72 which allows the position of the zone 66 to be adjusted in a horizontal plane. For this purpose, the lens 64 is fixed, without any degrees of freedom, to this plate 72. The plate 72 allows the lens 64, and therefore the zone 66, to be moved with a precision less than the diameter Di0 and, preferably, with a precision less than Dio / 2 or Dio / 5. Here, the precision of the plate 72 is less than 1 µm. The plate 72 can be operated manually or electrically. Here, the plate 72 is used to position the zone 66 at the intersection of the axes 54 and 68.

[0126] The measuring station 46 allows for the measurement of a dimensional characteristic of the fiber 20 obtained after the inscription of a pattern 22. Here, the dimensional characteristic is a horizontal distance between the patterns 22 and the boundary between the core 10 and the cladding 12. For example, for this purpose, the station 46 includes at least one camera and an image processing module. The camera films the portion of the fiber 20 located at an inspection zone 80. The filmed images are then processed, as they are acquired, by the processing module to extract the distance between the patterns 22 and the boundary between the core 10 and the cladding 12.

[0127] The measurement performed by station 46 can be used for various purposes. For example, here, the tower 40 includes an electronic control unit 90 comprising a monitoring module 92 and a human-machine interface 94. Module 92 continuously acquires the distances measured by station 46 and compares them to pre-recorded thresholds. As soon as one of these pre-recorded thresholds is exceeded by the measured distance, module 92 commands the human-machine interface 94 to signal a manufacturing defect. Thus, in this embodiment, module 92 makes it possible to automatically signal a positioning defect of the patterns 22 relative to the longitudinal axis 6.

[0128] Position 48 includes:

[0129] - an applicator 102 for depositing the coating 32 onto the fiber 20, and

[0130] - a device 104 for fixing the coating 32 deposited on the fiber 20.

[0131] Thus, at the output of station 48, fiber 30 is obtained.

[0132] The drive device 50 advances the fiber vertically along the axis 54. For this purpose, it includes a capstan 110 which pulls the fiber 30. In addition, it includes a winder 112 which winds the fiber 30 onto a reel 114. Once the fiber 30 has been manufactured, it is fully wound onto the reel 114. The reel 114 can then be removed from the winder 112 for storage until it is used in a subsequent step to manufacture fiber sensors.

[0133] The vertical distance between the furnace 42 and the deposition station 48 is greater than several meters and, generally, greater than four or five meters. Thus, if nothing is done, The fiber hangs freely between the furnace 42 and the station 48. Therefore, as it moves between the furnace 42 and the station 48, the fiber vibrates, and the amplitude of these vibrations is significant, exceeding the diameter Di0. Such vibrations cause the distance between the objective 64 and the fiber 2 to vary, such that the core 10 may be located entirely adjacent to the inscription zone 66. In this case, the patterns 22 are not inscribed in the core 10, or are not inscribed in the fiber 2 if the fiber 2 is entirely located outside the zone 66.

[0134] To remedy this problem, the tower 40 also includes a stabilizing support 120 and a plate 122 for adjusting the position of the support 120.

[0135] The support 120 is suitable for limiting the amplitude of the vibrations of the fiber 2 at the level of the zone 66. Here, this support 120 also allows the amplitude of the vibrations of the fiber 20 to be limited at the level of the inspection zone 80.

[0136] The plate 122 allows the position of the support 120 to be adjusted in the X and Y directions. For this purpose, the support 120 is fixed, without any degrees of freedom, to this plate 122. The plate 122 allows the support 120 to be moved with an accuracy of less than 100 µm and, preferably, with an accuracy of less than 10 µm or 1 µm. The plate 122 can be operated manually or electrically. Here, the plate 122 is used to correctly position the support 120 relative to the scroll axis 54.

[0137] The support 120 will now be described in more detail with reference to figures 6 to 13 in the case where the support 120 is also suitable for containing a liquid of index 121 ( [Fig.4]).

[0138] The liquid 121 is chosen to have a refractive index close to that of the cladding 12 and to be transparent to the pulses of the femtosecond laser. The liquid 121 minimizes the refractive index differences at the interface between the refractive index liquid and the cladding 12, thereby reducing unwanted refraction and optical aberrations. Typically, the refractive index of the liquid 121 is between 0.88*ri² and 1.1*ri², where ri² is the refractive index of the cladding 12. For example, the liquid 121 can be water, a mixture of water and ethanol, an alcohol, or an oil such as silicone oil.

[0139] The support 120 includes a housing 130. The housing 130 is a hollow parallelepiped. It has four lateral walls 132 to 135, a lower wall 136 and an upper wall 137 which define an internal cavity 140.

[0140] The cavity 140 is intended to contain the liquid 121. The area 66 is located inside the cavity 140 when the support 120 is mounted on the fiber tower 40. Here, the area 66 is located in the middle of the cavity 140.

[0141] The side walls 132, 133 and 135 each extend mainly in their respective vertical planes. The side wall 134 is inclined and therefore extends mainly in an inclined plane which makes an angle α ([Fig.9]) with the vertical. The angle α is chosen so that the laser pulses reaching this wall 134 are reflected elsewhere than in the area 66. For this purpose, the angle α is greater than 1° and less than 60°. Preferably, the angle α is between 5° and 25° or between 5° and 10°. Here, the angle α is equal to 8°. The walls 136 and 137 each extend in a respective horizontal plane. Here, the walls 132 to 137 are predominantly square.

[0142] The walls 132 to 137 are made of a rigid material. For example, they are made of a thermoplastic polymer such as ABS (acrylonitrile butadiene styrene) or of a metal such as steel or aluminum.

[0143] The wall 132 has a lateral opening 142 for introducing, inside the cavity 140, the laser beam directed on the area 66. For this purpose, in this embodiment, as shown in [Fig.10], the end of the objective 64 is received inside this opening 142. In addition, a seal, not shown, ensures the liquid-tightness 121 between the objective 64 and the wall 132 while allowing movement, by the plate 72, of the objective 64.

[0144] In a preferred embodiment, the inspection zone 80 is located inside the cavity 140. Here, the zone 80 is located just below the inscription zone 66. In this case, to allow observation of the fiber 20 and its patterns 22 from outside the housing 130, the walls 133 to 135 have observation windows 144 to 146, respectively. Here, each of these windows 144 to 146 is circular and centered on an axis passing through the center of the cavity 140. Each of these windows is covered by a transparent pane of glass to ensure the housing 130 is sealed against the liquid 121 while allowing observation of the fiber passing through the cavity 140 from outside the housing 130 using the camera(s) of the measurement station 46. Advantageously, these windows 144 to 146 also allow naked-eye observation of the fiber passing through cavity 140. For example, the diameter of these windows 144 to 146 is equal to 20 mm..

[0145] The lower wall 136 has a through-hole 150 ([Fig. 9], 10 and 13) centered on the scroll axis 54. The hole 150 allows the fiber, which has entered the cavity 140, to exit. The hole 150 opens on one side into the cavity 140 and, on the opposite side, outside the housing 130. Typically, the cross-section of the hole 150 is circular and its diameter is between 1 mm and 5 mm. Here, the diameter of the hole 150 is 2 mm.

[0146] The hole 150 is sealed by a lower membrane 152 ([Fig. 11] and 12) fixed, without any degrees of freedom, to the wall 136. This membrane 152 allows the passage of the fiber 20 while limiting the amplitude of its vibrations and ensuring the seal of the cavity 140 against the liquid 121. To this end, the membrane 152 has a slot 154 ([Fig. 11] and 12) centered on the axis 54 of movement. The length of the slot 154 is at least two or three times greater than the diameter Dn and, preferably, five or seven times greater than the diameter Di2. The length of this slot 154 is also less than the diameter of the hole 150 so that it does not touch the edges of the hole 150 when fixed to the wall 136. For example, here, the length of the slot 154 is 1 mm. This slot 154 has two edges 156, 158 ([Fig. 12]) which rub together on the fiber 20 when the fiber 20 passes through this slot 154. In [Fig. 12], the deformation of the slot 154 when it is traversed by the fiber 20 has been schematically represented and exaggerated. In the absence of the fiber 20, the edges 156 and 158 are joined and extend in the plane of the membrane 152.

[0147] To ensure that the friction of the edges 156 and 158 on the fiber 20 is gentle and causes little or no damage to the fiber 20, the membrane 152 is made of a material with a Shore A hardness between 5 and 60, and preferably between 5 and 50 or between 10 and 30. The material of the membrane 152 is elastically deformable so that contact between the edges 156, 158 and the fiber 20 is maintained even if the diameter of the fiber 20 varies slightly during the manufacturing of the fiber 30. Typically, the membrane 152 is made of elastomer and, preferably, of one of the following materials or a mixture thereof: rubber, silicone, neoprene, and polyurethane. For example, here, the 152 membrane is mainly made of natural rubber possibly with a silicone filler and its hardness on the Shore A scale is between 8 and 15.

[0148] To further limit the degradation of the fiber 20, the thickness of the membrane 152 is between 0.5 mm and 3 mm. For example, here, the thickness of the membrane 152 is equal to 1.5 mm or 2 mm.

[0149] Preferably, the wall 136 includes a lower mechanism 160 ([Fig. 13]) for fixing the membrane 152 to the wall 136 which allows a simple replacement of this membrane 152 by a new membrane 152. This mechanism 160 includes a set of two jaws 162 and 164 ([Fig. 13]) movable relative to each other reversibly between a pinched state, shown in [Fig. 13], and a relaxed state. In the clamped state, the jaws 162, 164 clamp the periphery of the membrane 152 to fix it to the wall 136. In the released state, the jaws 162, 164 allow the replacement of the membrane 152 with a new membrane 152. Here, the jaw 162 is formed by a peripheral portion of the wall 136 that surrounds the hole 150. For example, in this embodiment, this peripheral portion has the shape of a disc centered on the axis 54 and pierced in its center by the hole 150.The diameter of this disc is equal to the diameter of the membrane 152 plus sufficient clearance to remove the membrane 152. The jaw 164 is also a disc centered on the axis 54 and whose center is pierced by a hole 166. The diameter of the hole 166 is between 1 mm and 5 mm and, preferably, equal to the diameter of the hole 150.

[0150] The mechanism 160 is moved between its clamped and released states by means of a screw 168 and a threaded neck 170. The neck 170 is centered on the axis 54 and has an internal thread. The neck 170 and the wall 136 form a single block of material. The upper end of screw 168 has the disc that forms the jaw 164. The screw 168 is traversed completely by the fiber 20 in the clamped state of the mechanism 160. Screw 168 has a thread that engages with the tapped thread in the neck 170. Thus, when screw 168 is screwed into the neck 170, it moves the jaw 162 until it compresses, and therefore clamps, the periphery of the membrane 152 against the jaw 162. Conversely, when screw 168 is unscrewed, the jaw 164 moves away from the jaw 162 and screw 168 is removed from the neck 170. When screw 168 is removed from the neck 170, the membrane 152 can be removed and replaced with a new one. 152.

[0151] Here, the upper wall 137 is the mirror image of the lower wall 136 with respect to a horizontal plane passing through the center of the cavity 140, except that it also has an orifice 180 for introducing the liquid 121 into the cavity 140. In particular, the upper wall 137 has an upper hole and an upper fastening mechanism identical to those described for the wall 136. The upper fastening mechanism is used to fix an upper membrane to the wall 137, identical to the membrane 152. In particular, the upper membrane has an upper slit. Thus, the membranes fixed to the walls 136 and 137 are mirror images of each other with respect to the horizontal plane passing through the center of the cavity 140. Therefore, everything described in the specific case of the membrane 152 also applies to the upper membrane.

[0152] The dimensions of the side walls 132 to 135 are adjusted so that the vertical distance between the slot 154 and the inscription area 66 is less than a distance Dmax. The distance Dmax is the distance beyond which the amplitude of the fiber vibrations 20 becomes greater than the diameter Di0. It has been observed that the amplitude of the fiber vibrations is very small, typically less than 1 pm or 100 nm, in the vicinity of the slot 154, and then the amplitude of these vibrations increases as one moves downwards from the slot 154. In the embodiment described here, it has been observed that the distance Dmax is approximately 30 cm. Here, to minimize the amplitude of vibrations at the inscription zone 66, the dimensions of the side walls 132 to 135 are chosen so that the distance between the slot 154 and the inscription zone 66 is between 0.5 cm and 5 cm.In this embodiment, the lengths of each side of walls 132 to 135 are all equal to 35 mm so that the distance between slot 154 and area 66 is equal to 9 mm.

[0153] In this embodiment, since the inspection zone 80 is located between the zone 66 and the slot 154, the amplitude of the vibrations of the fiber 20 at the level of the inspection zone 80 is also very low, which simplifies the measurement of the dimensional characteristic.

[0154] In this embodiment, the support 120 includes a base 190 on which the housing 130 is fixed without any degree of freedom. This base 190 extends horizontally beyond one of the lateral faces on the side opposite the scroll axis 54. Here, the base 190 extends beyond the face 134 in a direction parallel to the X direction. The base 190 has holes allowing it to be fixed without any degree of freedom, typically by means of screws, to the plate 122.

[0155] The manufacturing process of fibre 30 will now be described with reference to [Fig.14],

[0156] During an initialization step 200, the furnace 42 generates, from the preform 52, an initial portion of fiber 2 which is then threaded through the slots of the support 120, then through the station 48, and finally wound around the capstan 110 and the reel 114. During this initialization step, the initial portion of fiber 2 is, for example, threaded through the slots of the support 120 using a needle. For this purpose, the end of the initial portion of fiber 2 is threaded through the eye of this needle, and then the needle is pushed through the upper 152 and lower membranes 152. In this example, the passage of the needle through the membranes creates the slots in these membranes at the same time as the fiber 2 is threaded through these slots.

[0157] Once the initial portion of fiber 2 has been put in place, the needle is removed. Then, in a step 202, the furnace 42 continuously generates successive portions of fiber 2 which are driven vertically by the capstan 110 so that they pass successively through the support 120 and the stations 44, 46 and then through the station 48.

[0158] In a step 204, the support 120 limits the amplitude of the fiber vibrations so that the amplitude of these vibrations at the inscription zone 66 remains below Di0. Here, the amplitude of the fiber 2 vibrations at zone 66 is typically less than 1 pm or 500 nm. With the support 120 described here, it has been observed that the amplitude of the vibrations at zone 66 is less than the diameter of the fiber core and even five, ten, or one hundred times less than the diameter of the fiber core. Thus, when a succession of patterns 22 are inscribed one after the other in the core 10, the alignment of these patterns 22 one behind the other appears to be perfectly parallel to the longitudinal axis 6 of the fiber 20 when observed with an optical microscope.

[0159] In parallel with step 204, during a step 206, station 44 writes one after the other the motifs 22 into the core 10 of fiber 2 in order to obtain fiber 20.

[0160] Also in parallel with step 204, during a step 208, station 46 measures, at the level of zone 80, the distance between the motifs 22 and the boundary between the core 10 and the sheath 12, then transmits these measurements to the control unit 90.

[0161] During a step 210, the module 92 acquires the measured distances and compares them to pre-recorded thresholds. If the measured distances exceed one of these thresholds, the module 92 commands the human-machine interface 94 to indicate this to a human.

[0162] At the exit of stations 44 and 46, the portion of fibre enters the deposition station 48 where, during a step 212, the coating 32 is deposited on the sheath 12.

[0163] Next, the portion of fibre 30 obtained at the output of station 48 is wound, during a step 214, onto the reel 114.

[0164] Chapter III: Variants:

[0165] Variants of the stabilizing support:

[0166] It is not necessary for the inscription area 66 to be located midway between the lower and upper slots. For example, alternatively, the inscription area is closer to either the lower slot 152 or the upper slot.

[0167] Alternatively, the stabilizing support comprises a single membrane. For example, the upper membrane and the upper fastening mechanism are omitted. This is possible even when the housing 130 contains the liquid 121 because the upper membrane is not used to retain the liquid 121 in the cavity 140.

[0168] In the case where the housing 130 does not contain index liquid, it is possible to omit either the upper or lower membrane 152. It is then also possible to omit the side walls 132 to 135 and the upper wall 137. Thus, in this particularly simplified case, the stabilizing support comprises only the lower wall 136 and the lower membrane 152. The inscription area can then be located above or below this single membrane.

[0169] One or more of the side windows 144 to 146 may be omitted. If all the side windows are omitted, then the inspection area 80 may be located below the membrane 152 and therefore outside the cavity 140.

[0170] Other shapes are possible for the housing 130. For example, the inclined wall 134 can be replaced by a vertical wall. In this case, if necessary, reflections of the laser beam can be limited by covering the vertical wall with a material that absorbs the wavelength of the laser beam. Another solution is to place this vertical wall much further from the inscription area 66, for example, two or three times further away than in the case of wall 134.

[0171] The housing 130 can also have a shape other than a cube. For example, it can have the shape of a cylinder with a circular cross-section or other.

[0172] Other mechanisms for attaching the membrane 152 to the lower wall 136 are possible. For example, alternatively, the membrane 152 is glued to the wall 136 and not held in place by pinching.

[0173] Variants of the pattern registration station:

[0174] The motifs 22 are not necessarily bubbles but can be, in variants, filaments, densifications of silica or nanonetworks (“nanogratting” in English) or coloured centres resulting from the recombination of bonds between germanium and silica.

[0175] The motifs 22 are not necessarily centered on the axis 6 of the fiber 20. They can also be offset from the axis 6 while remaining in the core 10. The motifs 22 can also be inscribed in the cladding 12 near the core 10.

[0176] Alternatively, Bragg gratings are tilted fiber Bragg gratings or chirped fiber Bragg gratings. In the case of chirped fiber Bragg gratings, the step size A between the patterns of the same Bragg grating is not constant but, on the contrary, varies according to a predefined law.

[0177] The inscription station can also be used to create optical devices other than Bragg gratings in the core of the optical fiber. For example, in an alternative, the motifs 22 inscribed in the core 10 form a juxtaposition, along the axis 6, of Fabry-Perot cavities. In another alternative, at regular intervals, for example every millimeter, a motif 22 is inscribed in the core 10 continuously along its entire length.

[0178] The motifs 22 are not necessarily inscribed only in the core 10 but may also, in addition, extend into the optical cladding 12 or be only inscribed in the cladding 12.

[0179] When the laser source 60 is sufficiently stable, the laser beam stabilizer 62 can be omitted.

[0180] The plate 72 can be omitted. In this case, the position of the objective 64 relative to the tower 40 is fixed.

[0181] The registration station can also be configured to implement other high-resolution registration methods than the method described in Chapter IL. For example, it is possible to replace the femtosecond laser with a UV (Ultra-Violet) laser.

[0182] The registration station 44 can also be replaced by a registration station configured to implement a low-resolution registration method. Indeed, stabilizing the optical fiber in the registration zone 66 can also be beneficial for low-resolution registration methods. For example, combining the stabilization support with a low-resolution registration method The resolution allows patterns to be preferentially inscribed in a single core of a multi-core optical fiber. As an illustration of such a variant, the inscription station is configured to simultaneously inscribe several patterns in core 10 by implementing a method known as "phase mask scanning technique." Such methods are described, for example, in patent application US2007236796A1 or CN109655962A. These methods generally use a phase mask to create interference and thus simultaneously project onto the optical fiber core a set of beams that form the patterns of the inscribed grating from a single laser pulse. In this case, the patterns inscribed in the optical fiber core are not bubbles but simply variations in refractive indices.Furthermore, the size of these patterns is generally much larger than the size of the bubbles created using a femtosecond laser during point-to-point inscription. Thus, the pattern size in this case is typically greater than 1 pm or 10 pm and often equal to or greater than the Di0 diameter of the optical fiber core. When a phase mask is used, the laser source is not necessarily a femtosecond laser. For example, a nanosecond laser can be used. The inscription station can also be configured to implement one of the other inscription methods described in US2007236796A1.

[0183] The registration methods described in the articles by W. Gao et al. and H. Guo et al. cited in the introduction to this application may also be implemented instead of the point-to-point registration method described in Chapter II

[0184] Variants of the measuring station:

[0185] Alternatively, the measuring station includes several cameras arranged relative to each other to measure the horizontal distance between the motifs 22 and the boundary between the core 10 and the sheath 12, in different directions.

[0186] The measuring station can measure other dimensional characteristics instead of, or in addition to, the distance between the inscribed patterns and the boundary between the core 10 and the sheath 12. For example, this or these other dimensional characteristics can be chosen from the group consisting of the following dimensional characteristics:

[0187] - the size of the patterns inscribed in the core of the optical fiber, and

[0188] - the diameter of the generated bare optical fiber.

[0189] The size of the inscribed pattern is the diameter of that pattern when the pattern is a bubble. The size of a pattern is representative of the energy deposited by the laser source in the core of the optical fiber. Thus, the measured pattern size can be used to validate that the current energy of the laser pulses is appropriate. The measured size can also be used to control the pattern size based on a pre-recorded size setpoint. In this case, the difference between the measured size and the size setpoint is used. to automatically adjust the power of the laser source to reduce this difference.

[0190] It is also possible to measure a dimensional characteristic of fiber 2 or fiber 20 through the objective 64. In this case, the inspection zone 80 coincides with the inscription zone 66.

[0191] The inspection zone 80 can also be located below the slot 154 at a distance less than Dmax from this slot 154.

[0192] The fiber tower may also include several separate measurement stations. In this case, the fiber tower has several separate inspection zones. For example, one of these inspection zones is located inside the cavity 140 while another inspection zone is located below the membrane 152. Preferably, these separate measurement stations measure different dimensional characteristics of the fiber.

[0193] In a simplified variant, the measuring station 46 is omitted.

[0194] Additional measurement stations may be provided. For example, the fiber-laying tower may also include a station for measuring the diameter of the coated optical fiber.

[0195] Other variants:

[0196] Other embodiments of the fiber 2 are possible. For example, the core 10 can be made of pure silica and the optical cladding 12 of fluorine-doped silica. The core 10 can also be made of other materials capable of guiding the optical signal, such as rare-earth-doped aluminosilicates, sapphire, or organic polymers. In these latter cases, the optical cladding 12 is not necessarily made of the same material as the core 10.

[0197] Fiber 2 can be a multimode optical fiber or MMF (Multi-Mode Fiber).

[0198] The dimensions of the fiber 2 may vary. Generally, the diameter Dn of the cladding 12 is between 50 µm and 500 µm. The diameter Di0 of the core 10 is generally between 4 µm and 100 µm.

[0199] Optical fibre can also comprise several cores surrounded by the same sheath and the same protective coating.

[0200] The embodiments of the coating deposition station 48 depend on the chemical nature of the coating 32 being deposited. For example, if the coating 32 is an acrylate, then the applicator 102 is a die system for injecting the monomer onto the fiber 20 under pressure and temperature control, and the device 104 is a UV (Ultraviolet) lamp to ensure polymerization. If the coating 32 is made of polyamide, the device 104 is an oven for polymerization. If the coating 32 is a so-called "waiting" coating, the applicator 102 is a simple cup, and the device 104 is an oven for thermal annealing. Again, this depends on the chemical nature of the coating. The material used to create the coating 32 can be injected under pressure or, conversely, deposited under atmospheric pressure by the applicator 102. If the coating 32 is metallic, this station 48 is identical to that described in application US2016025925A1. If the coating 32 is ceramic, station 48 can be configured as described in application FR3137911A1. The deposition station 48 can also be configured to deposit a multilayer coating consisting of several layers deposited directly onto one another.

[0201] The fiber tower may include other manufacturing stations than those shown in [Fig. 4]. For example, tower 4 includes a station known as the "preform descent." The ratio between the speed of this preform descent and that of the stretching device determines the ratio between the diameter of the fiber 2 and that of the preform 52.

[0202] Other embodiments of the drive device 50 are possible. For example, the capstan 110 is omitted. In this latter case, the winder 112 drives the reel 114 in rotation to both stretch the optical fiber and wind it onto this reel.

[0203] Other embodiments of the control unit 90 are possible. For example, alternatively, the unit 90 controls the plate 72 to reduce a difference between the position of the patterns 22 measured by the station 46 and a pre-recorded position setpoint.

[0204] The plate 122 can be omitted. In this case, the stabilizing support 120 is fixed, without any degree of freedom, to the fiber layup.

[0205] In a simplified embodiment, the stabilizing support is used only to stabilize the bare optical fiber within the inspection zone 80 and not within the inscription zone 66. In this case, the distance between the slot 152 and the inscription zone 66 can be greater than the maximum distance Dmax. This embodiment is implemented, for example, when the inscription method is a low-resolution inscription method that does not require stabilizing the optical fiber. This embodiment can also be implemented in a fiber-layout tower without an inscription station.

[0206] Several of the variants described above can be combined in the same embodiment.

[0207] Chapter IV: Advantages of the described embodiments:

[0208] Using a membrane with a slit whose edges rub against the bare optical fiber as it exits the drawing oven limits the amplitude of the bare optical fiber's vibrations at this location. This limitation of the bare optical fiber's vibration amplitude makes it possible to use high-resolution inscription methods near this location, where the inscription area dimensions are small, typically smaller than to the diameter of the bare optical fiber core. Thus, these high-resolution inscription methods can also benefit from the advantages provided by the fact that the inscription station 44 is located before the protective coating deposition station 48. For example, as described in Chapter II, this allows the implementation, directly after the drawing oven 42, of point-to-point inscription methods of patterns in the bare optical fiber core.

[0209] It is emphasized that, in the prior art, it is accepted that the bare optical fiber must not come into contact with any element before its protective coating is applied. Indeed, it is known that such contact risks damaging the external surface of the bare optical fiber and thus degrading its breaking strength. In the present case, it has in fact been observed that friction between the edges 156, 158 of the slot 154 and the bare optical fiber reduces the breaking strength of the optical fiber compared to an identical optical fiber manufactured conventionally. Such a reduction in breaking strength is generally unacceptable for optical fibers intended for use in the field of telecommunications.However, despite this decrease in breaking strength, the breaking strength of the resulting optical fibers remains quite acceptable for functionalized fibers used in metrology. Indeed, in metrology, the lengths of functionalized optical fibers are much shorter than those of optical fibers used in telecommunications, and the mechanical stresses to which they are subjected are also much lower. Thus, in metrology, the observed decrease in breaking strength remains acceptable.

[0210] When the membrane 152 seals the lower hole 150 of the housing 130 containing the refractive index liquid, the same membrane 152 then serves both to stabilize the optical fiber and to retain the refractive index liquid inside the housing. This simplifies the construction of the fiber-laying tower in cases where a refractive index liquid is used to limit distortions of the laser beam at the interface of the optical cladding 12.

[0211] The use of the femtosecond laser 60 combined with the objective 64 received in the lateral aperture 142 of the housing 130 and the refractive index liquid 121 makes it possible to implement the point-to-point inscription method of patterns 22 in the optical fiber before the deposition of the protective coating. Moreover, in this case, the nature of the protective coating can be arbitrary and, in particular, the protective coating can be opaque to the pulses of the femtosecond laser.

[0212] The use of both lower and upper membranes located on either side of the inscription zone 66 makes it possible to further limit the amplitude of the vibrations of the optical fiber at the inscription zone.

[0213] The plate 122 for moving the support 120 allows the slot 154 to be centered precisely on the axis 54 of the scrolling and thus to balance the forces of friction exerted by each of the edges 156, 158 of the slot 154 on the optical fiber. This helps to limit the degradation of the optical fiber's breaking strength compared to the case where the slot 154 would be horizontally offset by more than 100 pm relative to the scrolling axis 54.

[0214] The fact that the distance between the slot 154 of the support 120 and the inspection zone 80 is less than Dmax, allows, using the same support 120, the bare optical fiber to be stabilized both in the registration zone 66 and in the inspection zone 80.

[0215] The fact that the inscription area 66 is located less than 5 cm from the slot 154 helps to limit the bulk of the support 120.

[0216] The fact that the thickness of each membrane is between 0.5 mm and 3 mm helps to limit the degradation of the breaking strength of the manufactured optical fiber.

[0217] The fact that the length of the slot 154 is greater than 0.5 mm and less than the diameter of the hole 150 makes it possible to further limit the degradation of the breaking strength of the manufactured optical fiber.

[0218] The fact that the diameter of the hole 150 is between 1 mm and 5 mm makes it possible to limit the deformation of the membrane 152 under the action of the weight of the index liquid and therefore to further limit the degradation of the breaking strength of the optical fiber manufactured.

Claims

Demands

1. Fiber drawing tower for manufacturing a functionalized optical fiber, this fiber drawing tower comprising successively from top to bottom: - a drawing oven (42) capable of generating, from a preform, a bare optical fiber, this generated bare optical fiber comprising at least a core (10) and a cladding (12) shaped to guide an optical signal, - a station (44) for writing patterns into the bare optical fiber using a laser beam, this writing station comprising a laser source (60) capable of emitting the laser beam and a lens (64) capable of directing the emitted laser beam onto a writing area (66) traversed by the generated bare optical fiber, - a station (48) for depositing a protective coating onto the cladding of the generated bare optical fiber,- a drive device (50) capable of vertically scrolling the generated bare optical fiber along a vertical scroll axis (54) which passes successively through the registration zone of the registration station and then through the deposition station, characterized in that: - the fiber tower includes a stabilizing support (120) capable of limiting the amplitude of the vibrations of the generated bare optical fiber, this support having for this purpose a membrane (152) whose hardness, on the Shore A scale, is between 5 and 60, - the membrane has a slot (154) through which the scroll axis (54) passes, this slot having edges (156, 158) capable of rubbing against the bare optical fiber when this bare optical fiber scrolls inside the registration station,and - the vertical distance between the slot (154) and the inscription zone (66) is less than a distance Dmax beyond which the amplitude of the vibrations of the bare optical fiber becomes greater than the diameter of the core of this bare optical fiber.

2. A lathe according to claim 1, wherein: - the stabilizing support comprises a housing (130) having side walls (132-135) and a bottom wall (136), these walls defining a cavity (140) within which the inscription area is located, the bottom wall having a lower hole (150) traversed by the scroll axis and one of the side walls having a lateral opening (142) for introducing, inside the cavity, the laser beam directed on the inscription area, and - the fiber tower includes an index liquid (121) which fills the cavity of the housing so that the inscription area is located inside the index liquid, this index liquid being transparent to the laser beam and its refractive index being between 0.88*ri2 and l.l*ri2, where ri2 is the refractive index of the cladding of the bare optical fiber, and - the membrane (152) is fixed, without any degree of freedom, on the lower wall and closes the lower hole to retain the index liquid inside the cavity while being traversed by the bare optical fiber.

3. Tower according to claim 2, wherein: - the laser source (60) is a femtosecond laser capable of emitting laser pulses, and - the objective (64) is configured to focus each laser pulse on the inscription area to generate, one after the other, patterns in the optical fiber that moves through this inscription area.

4. Tower according to any one of the preceding claims, wherein: - the membrane (152) forms a lower membrane and the stabilizing support further comprises an upper membrane, the lower and upper membranes being located on either side of the inscription area, - the hardness of the upper membrane, on the Shore A scale, is between 5 and 60, and the upper membrane comprises an upper slot through which the scroll axis passes, this upper slot having edges adapted to rub against the bare optical fiber when this bare optical fiber scrolls inside this upper slot, and - the vertical distance between the upper slot and the inscription area (66) is less than the distance Dmax.

5. Tower according to any one of the preceding claims, wherein the fiber tower comprises a plate (122) capable of moving, with an accuracy of less than 100 pm, the support (120) of stabilization in two directions orthogonal and perpendicular to the axis of movement.

6. Tower according to any one of the preceding claims, wherein: - the fiber tower includes a measuring station (46) for a dimensional characteristic of a portion of the bare optical fiber located inside an inspection zone (80), this measuring station being located between the drawing oven and the deposition station, and - the vertical distance between the slot (152) and the inspection zone (80) is less than the distance Dmax.

7. Tower according to any one of the preceding claims, wherein the vertical distance between the slot (152) and the inscription area (66) is between 0.5 cm and 5 cm.

8. Stabilizing support for the construction of a fiber-laying tower according to any one of the preceding claims, this support being capable of limiting the amplitude of the vibrations of the bare optical fiber and comprising for this purpose: - a lower wall (136) having a lower hole (150) centered on a scroll axis, and - a lower membrane (152) fixed, without any degree of freedom, on the lower wall and closing the lower hole, characterized in that: - the hardness of the lower membrane (152), on the Shore A scale, is between 5 and 60, and - the lower membrane has a lower slot (154) through which the scroll axis passes, this lower slot having edges (156, 158) capable of rubbing against the bare optical fiber when this bare optical fiber scrolls inside this slot.

9. Support according to claim 8, in which: - the stabilizing support comprises a housing (130) having side walls (132-135) and the bottom wall (136), these walls delimiting a cavity (140) suitable for being filled by the index liquid inside which the inscription area is located, and - one of the side walls of the housing has a lateral opening (142) for introducing, inside the cavity, the laser beam directed on the inscription area.

10. Support according to claim 9, wherein: - the housing includes an upper wall (137) located on the opposite side to the lower wall, this upper wall having an upper hole centered on the axis of travel, and - the stabilization support includes an upper membrane fixed, without any degree of freedom, on the upper wall and closing the upper hole, the hardness of the upper membrane, on the Shore A scale, being between 5 and 60, and - the upper membrane includes an upper slot through which the axis of travel is traversed, this upper slot having edges suitable for rubbing against the bare optical fiber when this bare optical fiber travels inside this upper slot.

11. Support according to any one of claims 8 to 10, wherein the thickness of each membrane is between 0.5 mm and 3 mm.

12. Support according to any one of claims 8 to 11, wherein the diameter of the lower hole is between 1 mm and 5 mm and the length of the slot is greater than 0.5 mm and less than the diameter of the lower hole.

13. Support according to any one of claims 8 to 12, wherein each wall (136, 137), on which a membrane is fixed, comprises a set of two jaws (162, 164) movable relative to each other reversibly between: - a pinched state in which the jaws pinch the periphery of the membrane (152) to fix it to the wall, and - a relaxed state in which the jaws allow the replacement of the membrane with a new membrane.

14. A method for manufacturing a functionalized optical fiber using a fiber drawing tower according to any one of claims 1 to 7, said method comprising successively the following steps: - the generation (202), using a drawing oven and from a preform, of a bare optical fiber, this generated bare optical fiber having a core and a cladding shaped to guide an optical signal, and then - the inscription (206) of patterns in the bare optical fiber using a laser beam and an inscription station comprising a laser source adapted to emit the laser beam and a lens adapted to direct the beam laser emitted onto an inscription area traversed by the generated bare optical fiber, then - the application (212), using a deposition station, of a protective coating onto the sheath of the generated bare optical fiber, and - the vertical scrolling (202), using a drive device, of the bare optical fiber generated along a vertical scrolling axis which passes successively through the inscription zone of the inscription station and then through the deposition station, characterized in that, in parallel with the inscription of patterns, the method includes the limitation (204), using a stabilization support according to any one of claims 8 to 13, of the amplitude of the vibrations of the bare optical fiber generated.

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