Method for manufacturing a functionalised optical fibre
Patent Information
- Application Number
- AU2025258813
- Authority / Receiving Office
- AU · AU
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-04-18
- Filing Date
- 2025-04-03
- Publication Date
- 2026-10-29
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Abstract
Description
[42] The pitch A between two immediately consecutive patterns 22 along the axis 4 of the same Bragg grating is constant and selected so as to set, to the desired value, the wavelength at which this Bragg grating reflects the incident optical signal.
[43] Figure 3 shows a functionalized optical fiber 30 identical to the fiber 20 except that the sheath 8 is replaced by a final protective sheath 32. Unlike the sheath 8, the sheath 32 is not necessarily intended to be easily removed. Thus, the sheath 32 is not necessarily made of a material that can be easily removed. Furthermore, unlike the sheath 8, the sheath 32 may be made of a material opaque to the laser pulses. In fact, the material from which the sheath 32 is made may be any material, provided that it is suitable for allowing the sheath 32 to perform its function of protecting the waveguide 4. Under these conditions, the material of the sheath 32 is selected according to the field of use of the fiber 30. For example, the sheath 32 is made of one of the following materials: metal, ceramic or carbon.
[44] Figure 4 shows a fiber drawing tower 40 used to manufacture the fiber 2. This tower 40 is similar to known fiber drawing towers for manufacturing non-functionalized optical fibers in which the waveguide is made of silica. Thus, only the elements necessary for understanding the invention are shown in Figure 4 and described below. In particular, in Figure 4, the omission of certain manufacturing stations is represented by dotted lines.
[45] The tower 40 successively comprises, proceeding in particular from top to bottom: a furnace 42 for drawing the waveguide 4, a station 44 for depositing the sheath 8, and a winder 46.
[46] The furnace 42 melts a silica preform 48 in order to obtain a silica filament 50, which then passes through different stations, not shown, until the waveguide 4 is obtained, which passes through the station 44 while moving at a production speed vp. The speed vp is typically greater than 80 mm / s and less than 350 mm / s. For example, the speed vp is often equal or close to 120 mm / s and, preferably, even greater than 120 mm / s.
[47] The station 44 comprises a vessel 52 and an annealing tunnel 54 for depositing the sheath 8 on the waveguide 4. Thus, at the outlet of the station 44, the fiber 2 is obtained.
[48] The vessel 52 makes it possible to deposit a PVA solution directly on the optical cladding 12 and all around this optical cladding 12. To this end, the vessel 52 contains the PVA solution to be deposited. The vessel 52 is shaped so that the waveguide 4 enters the vessel 52 from the top, then passes through the PVA solution, and then exits through a vertical tubular channel located at the bottom of the vessel 52. Here, the vessel 52 is shaped so that the PVA solution that it contains is at ambient temperature and ambient pressure. Thus, the station 44 does not comprise a device for heating the PVA solution or a device for pressurising the PVA solution. The ambient temperature is typically greater than 18°C and most often between 18°C and 35°C. The ambient pressure is typically between 980 hPa and 1060 hPa and, most often, between 1000 hPa and 1025 hPa, that is to say close to 1013 hPa. Under these conditions, the thickness of the PVA solution deposited on the optical cladding 12 depends essentially on the viscosity of this PVA solution. The viscosity of this solution is adjusted by adjusting the quantity of water in the solution. Here, the viscosity of the PVA solution is adjusted so that the thickness of the sheath 8 on the waveguide is between 10 pm and 20 pm. This corresponds to a mass of water in the solution between 70% and 80% of the mass of this solution, the remainder of this solution being PVA. In this embodiment, in order to obtain a sheath 8 having a thickness of 15 pm, the quantity of water in the PVA solution is set equal to 75% of the mass of the solution, such that PVA represents 25% of the mass of this solution.
[49] The tunnel 54 dries the PVA solution deposited on the waveguide 4 by the vessel 52. To this end, the sheath 8 passes through the tunnel 54 at the speed vp. The inside of the tunnel 54 is heated to a temperature sufficient for the deposited PVA solution to be completely dry at the outlet of this tunnel 54. Thus, the sheath 8 is obtained at the outlet of the tunnel. Generally, the temperature inside the tunnel 54 is greater than 200°C or 250°C. Here, the temperature inside the tunnel 54 is also maintained at or below 360°C so as not to damage the sheath 8.
[50] The winder 46 winds the fiber 2 leaving the station 44 onto a spool 58. Once manufacture of the fiber 2 has been completed, it is entirely wound onto the spool 58. The length L2 of the fiber 2 wound onto the spool 58 is typically greater than 1 km or 5 km. The spool 58 can then be removed from the winder 46 for storage until it is used during a subsequent functionalization phase. For example, the spool 58 is stored at a storage site, and the tower 40 can then be used to manufacture a new spool 58 without waiting for the stored spool 58 to be used during a functionalization phase.
[51] Figure 5 shows a line 60 for functionalizing the fiber 2, which transforms the fiber 2 into the functionalized optical fiber blank 20. For this purpose, the line 60 successively comprises, in the direction of travel of the optical fiber: an unwinder 62, a functionalization station 64 and a winder 66. In Figures 5 and 6, the direction of travel of the optical fiber is represented by an arrow.
[52] The unwinder 62 makes it possible to unwind the fiber 2 wound onto the spool 58 at an inscription speed vi, such that the fiber 2 travels through the station 64 at this speed vi.
[53] The station 64 inscribes, in the core 10, the patterns 22 as the fiber 2 travels through this station 64 at the speed vi. Thus, the fiber leaving the station 64 is the functionalized optical fiber blank 20. For this purpose, the station 64 is equipped with a femtosecond laser 68, the laser pulses of which are focused at a point located in the core 10. Thus, each laser pulse creates a bubble. Here, each pattern 22 is formed by one or more bubbles. Under these conditions, the station 64 inscribes, in the core 10, the patterns 22 one after another using a temporal succession of laser pulses while the fiber 2 travels in front of the femtosecond laser 68. The frequency of the laser pulses is adjusted taking into account the speed vi in order 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 portion of the fiber 2 travelling in front of the femtosecond laser 68, generation of the laser pulses is inhibited.
[54] Here, the laser pulses pass through the sheath 8 before reaching the core 10. Thus, the patterns 22 are inscribed through the sheath 8. This is possible because the sheath 8 is transparent to the laser pulses.
[55] The winder 66 winds, onto a spool 70, the blank 20 as it is produced at the speed vi. The length L20 of the blank 20 wound onto the spool 70 is typically close to the length L2, that is to say, for example, between 0.95*L2 and L2. Once the blank 20 has been completely manufactured, the spool 70 can then be removed from the winder 66 for storage until a subsequent phase of depositing the sheath 32.
[56] Typically, the speed vi is much lower than the speed vp and is often ten or one hundred times lower than the speed vp. For example, the speed vi is often between 0.05 mm / s and 10 mm / s. Here, the speed vi is equal to 0.1 mm / s. A low speed vi makes it possible to improve the accuracy of the pitch A of the inscribed Bragg gratings.
[57] Figure 6 shows a line 80 for depositing the final sheath 32, which transforms the blank 20 into the functionalized fiber 30. In Figure 6, only the elements necessary for understanding the invention have been shown. The line 80 successively comprises, in the direction of travel of the optical fiber: an unwinder 82, a station 84 for removing the sheath 8, a station 86 for depositing the sheath 32 and a winder 88.
[58] The unwinder 82 makes it possible to unwind the blank 20 wound onto the spool 70 at a deposition speed vd, such that the blank 20 travels through the stations 84 and 86 at this speed vd. Typically, the speed vd is greater than the speed vi and is often ten or fifty times greater than the speed vi. The speed vd is generally limited by the maximum speed at which the sheath 32 can be deposited on the waveguide 4. Generally, the speed vd is less than 340 mm / s or 240 mm / s and greater than 1 mm / s.
[59] The station 84 comprises a water bath through which the blank 20 passes. For this purpose, for example, the station 84 is arranged in a manner similar to that described with reference to Figure 3 of application US2006134324 or to one of Figures 6 and 7 of application US2016025925A1. Thus, in this embodiment, the station 84 comprises a tube in which a solvent, for example water, flows continuously. The blank 20 enters the straight tube through one end of this tube and exits this tube through the opposite end. Inside the tube, the blank 20 is directly in contact with the solvent over all or practically all of the length of the tube. The length of the tube is adjusted so that, at the speed vd, the contact time between the blank 20 and the solvent allows the sheath 8 to be completely dissolved. When the solvent is water, the contact time required to completely dissolve the sheath 8 is between 2 s and 5 s. In this case, the length of the tube is less than or equal to 1.5 m or 1 m.
[60] At the outlet of the station 84, the sheath 8 is completely removed and only the functionalized waveguide 4 remains, which enters the station 86.
[61] The station 86 deposits the sheath 32 directly on the waveguide 4 at the speed vd. When the sheath 32 is metallic, this station 86 is, for example, identical to that described in application US2016025925A1. If the sheath 32 is made of ceramic, the station 86 may be produced as described in application FR3137911A1. When the sheath 32 is made of polymer, the arrangement of the station 86 is derived from the arrangement of the station 44 described above. However, in this case, the polymer deposited on the waveguide 4 is not PVA. In this case and depending on the polymer used, in order to obtain the desired viscosity of the solution contained in the vessel, it may be necessary to heat this vessel. Furthermore, in the case of a polymer other than PVA, the solution of this polymer contained in the vessel is often pressurised, such that deposition takes place at a pressure greater than ambient pressure. The temperature and length of the drying tunnel must also be adapted to the polymer deposited.
[62] At the outlet of the station 86, the fiber 30 is obtained.
[63] As it is produced, the winder 88 winds the fiber 30 onto a spool 90. Thus, at the end of manufacture of the fiber 30, this fiber 30 is completely wound onto the spool 90, which can then be removed from the winder 88 for storage before being delivered to a customer. The length L30 of the fiber 30 wound onto the spool 90 is, for example, close to the length L20, that is to say between 0.95*L20 and L20, where L20 is the length of the blank 20 wound onto the spool 70.
[64] The method for manufacturing the fiber 30 will now be described with reference to Figure 7.
[65] The method begins with a phase 100 of producing the fiber 2. This phase 100 comprises in particular a step 102 of preparing the PVA solution to be used in the vessel 52. Here, this PVA solution is prepared by dissolving, in pure water, a PVA whose mass distribution, before dissolution, is between 30,000 g / mol and 70,000 g / mol and whose degree of hydrolysis is between 87% and 90%. It has been observed that this particular composition of the PVA before dissolution in water makes it possible to obtain a PVA solution that can be deposited at ambient temperature and ambient pressure, which is generally not the case for different PVA compositions.
[66] The mass distribution of the PVA is measured according to the SEC method. The degree of hydrolysis of the PVA can be characterised by different methods, including in particular XRD analysis (X-Ray Diffraction), DSC thermal analysis (Differential Scanning Calorimetry), or FTIR analysis (Fourier Transform Infrared Spectroscopy). FTIR analysis additionally makes it possible to demonstrate the ratio between the acetate groups (CH3COO-) and hydroxyl groups (OH-) of the PVA. These different analysis methods are described in the following article: M Hdidar et al.: “Effect of hydrolysis and mass molecular weight on the structure and properties of PVA films”, Ionics 2017, 23 3125-3155. After dissolution in water, the degree of hydrolysis of the PVA may vary. However, the degree of hydrolysis of the dissolved PVA is a function of the degree of hydrolysis of the PVA before dissolution. Thus, it is possible to determine whether the degree of hydrolysis, before dissolution, of the PVA used to obtain a PVA solution AA is between 87% and 90% by carrying out the following steps: - Step 1): The characteristics of this solution AA are measured by XRD, DSC and FTIR analysis. - Step 2): Samples BB of PVA solutions are prepared. Each sample BB is obtained by dissolving, in pure water, PVA having a known degree of hydrolysis before dissolution. The known degree of hydrolysis is different for each of the samples BB. Furthermore, for each of the samples BB, the mass distribution of the PVA is identical to that of the solution AA. - Step 3): The characteristics of the samples BB are measured by applying the same analyses as those used in Step 1). - Step 4): The characteristics measured in Step 3) are compared with the characteristics measured in Step 1). The samples BB whose characteristics are closest to the characteristics of the solution AA make it possible to estimate the degree of hydrolysis, before dissolution, of the PVA used to prepare the solution AA.
[67] It is also emphasised that it is possible to determine whether a PVA protective sheath was obtained by depositing a PVA solution as described here in the same manner as described above for the PVA solution AA. Indeed, for this purpose, the PVA sheath is dissolved in pure water in order to obtain a PVA solution.
[68] Here, during step 102, the amount of dissolved PVA represents between 20% and 30% of the mass of the solution. For example, in order to obtain a sheath 8 having a thickness of 15 pm, the amount of dissolved PVA represents 25% of the mass of the solution.
[69] Once the PVA solution has been prepared and poured into the vessel 52, a step 104 of producing the fiber 2 at the speed vp is carried out using the fiber drawing tower 40. During this step 104, the waveguide 4 travels through the PVA solution prepared during step 102 at the speed vp. During step 104, the PVA solution through which the waveguide passes is at ambient temperature and ambient pressure.
[70] At the end of this step 104, the spool 58 onto which the fiber 2 is wound is obtained. The phase 100 is then complete and the spool 58 is then stored, during a step 108, before being used during a functionalization phase 110. During step 108, the spool 58 may be stored for several hours or several days before being used during the phase 110.
[71] The phase 110 consists in functionalizing the waveguide 4 of the fiber 2 in order to obtain the functionalized optical fiber blank 20. The phase 110 is carried out by the functionalization line 60.
[72] For this purpose, just before the beginning of the phase 110, the spool 58 is supplied, that is to say, here, removed from storage, and then, during a step 112, the fiber 2 wound onto this supplied spool 58 is installed in the functionalization line 60. For this purpose, the spool 58 that has been supplied is mounted in the unwinder 62 and an empty spool 70 is mounted in the winder 66. The free end of the fiber 2 wound onto the spool 58 is then pulled so as to pass it through the inscription station 64 until it reaches the spool 70. The free end thus pulled is then fastened to the spool 70.
[73] Once the fiber 2 has been installed in the line 60, during a step 114, the unwinder 62 unwinds the fiber 2 at the speed vi and the winder 66 winds the blank 20 produced at the outlet of the inscription station 64 at the speed vi. Thus, the optical fiber passes through the inscription station 64 at the speed vi.
[74] At the same time, during a step 116, as the fiber 2 advances, the station 64 inscribes, through the sheath 8, the patterns 22 in the portion of the core 10 present in front of the femtosecond laser 68.
[75] Once the fiber 2 has been completely unwound from the spool 58, the functionalization phase 110 is complete. During a step 118, the spool 70 onto which the functionalized optical fiber blank 20 is entirely wound is then stored before being used during a phase 130 of depositing the sheath 32. During step 118, the spool 70 may be stored for several hours or several days before being used during the phase 130.
[76] The phase 130 consists in replacing the sheath 8 with the sheath 32 in order to obtain the functionalized optical fiber 30. The phase 130 is carried out by the line 80 for depositing the sheath 32.
[77] Execution of the phase 130 is, for example, initiated only when the material to be used for the sheath 32 is known. Thus, once this material is known and before execution of the phase 130 is initiated, a station capable of depositing the sheath 32 made of this material is installed in the line 80 in order to form the station 86. Thus, the phases 100 and 110 are the same regardless of the material of the sheath 32. Conversely, the phase 130 can be customised, which makes it possible to manufacture functionalized optical fibers using different materials to produce the sheath 32 while keeping the phases 100 and 110 unchanged.
[78] During a step 132, the blank 20 is installed in the line 80 for depositing the sheath 32. For this purpose, the spool 70, which was stored, is mounted in the unwinder 82 and an empty spool 90 is mounted in the winder 88. The free end of the blank 20 wound onto the spool 70 is then pulled so as to pass it through the stations 84 and 86 until it reaches the spool 90. The free end thus pulled is then fastened to the spool 90.
[79] Once the blank 20 has been installed in the line 80, during a step 134, the unwinder 82 unwinds the blank 20 at the speed vd and the winder 88 winds the fiber 30 produced at the outlet of the station 86 at the speed vd. Thus, the optical fiber successively passes through the station 84 and then the station 86 at the speed vd.
[80] At the same time, during a step 136, at the removal station 84, the blank 20 passes through a bath of solvent, for example water, which completely dissolves the sheath 8 and exposes the functionalized waveguide 4. The waveguide 4 thus exposed then enters the station 86 for depositing the sheath 32.
[81] At the station 86 for depositing the sheath 32, during a step 138, the sheath 32 is deposited on the exposed waveguide 4. Thus, the functionalized optical fiber 30 is obtained at the outlet of the station 86.
[82] Once the blank 2 has been completely unwound from the spool 70, the phase 130 of depositing the sheath 32 is complete. During a step 140, the spool 90 onto which the functionalized optical fiber 30 is entirely wound is then stored before being delivered to a customer. During step 140, the spool 90 may be stored for several hours or several days or even for several years before being conveyed to a customer.
[83] Chapter III: Variants:
[84] Variants of the manufacture of the non-functionalized optical fiber:
[85] Other formulations are possible for the PVA dissolved in water in order to obtain the solution to be deposited to form the sheath 8. For example, as a variant, the following formulation of the PVA, before dissolution, is possible in order to obtain a sheath 8 that dissolves rapidly in water: mass distribution between 146,000 g / mol and 186,000 g / mol, degree of hydrolysis between 87% and 89%, and mass concentration in water less than 10%. In the case of this latter formulation, during deposition of the sheath 8, the PVA solution is heated to between 35°C and 90°C. Likewise, the PVA solution is pressurised. The pressure is then typically between 100 kPa (1 bar) and 400 kPa (4 bar), depending on the temperature.
[86] The PVA may also comprise additives that do not modify, or modify only very slightly, its solubility in water. For example, as a variant, the PVA comprises a carbonbased additive, such as graphene or carbon nono-tubes. Such an additive improves the mechanical properties of the sheath 8.
[87] Pressurisation of the PVA solution is also possible even with the PVA formulation described in Chapter II above. Likewise, it is also possible to heat the PVA solution described in Chapter II, for example in order to adjust its viscosity and therefore the thickness of the sheath 8.
[88] The thickness of the sheath 8 is selected taking into account the deposition speed vd implemented during the phase 130 of depositing the sheath 32. Indeed, the slower the speed vd, the greater the thickness of the sheath 8 may be because the time allotted for removing the sheath 8 during the removal step 136 is longer. Thus, the thickness of the sheath 8 may be greater than 20 pm. Conversely, the higher the speed vd, the smaller the thickness of the sheath 8 must be in order for it to be completely dissolved during the removal step 136. Thus, the thickness of the sheath 8 may also be less than 10 pm. Nevertheless, the thickness of the sheath 8 will still be selected to be sufficient to impart the desired mechanical, chemical and thermal properties to the optical fiber.
[89] The production speed vp depends on the configuration of the fiber drawing tower and, for example, on its height. Thus, for fiber drawing towers 12 metres high, the speed vp may reach 1.66 m / s. In another fiber drawing tower, the speed vp may be less than 80 mm / s.
[90] The sheath 8 may be made of water-soluble materials other than PVA. For example, as a variant, the PVA is replaced with one of the waxes disclosed in application US2006134324A1 or in application US2016025925A1, or with another water-soluble polymer such as one of those cited in application US2016025925A1.
[91] The soluble sheath may also be made of a material soluble in a solvent other than water. For example, as a variant, as described in application US2016025925A1, the PVA is replaced with an acrylate soluble in acetone. The sheath 8 may also be made of a material soluble in an alcohol such as ethanol.
[92] Variants of the functionalization phase 110:
[93] Other embodiments of the inscribed Bragg gratings are possible. For example, the patterns are not necessarily bubbles but may, as variants, be filaments, densifications of the silica, nanogratings, or colour centres resulting from recombination of the bonds between germanium and silica. As a variant, the Bragg gratings are tilted fiber Bragg gratings or chirped fiber Bragg gratings. In the case of chirped fiber Bragg gratings, the pitch A between the patterns of the same Bragg grating is not constant but, conversely, varies according to a predetermined law.
[94] The functionalization phase 110 does not necessarily consist in inscribing Bragg gratings in the core of the optical fiber. In fact, the patterns 22 inscribed in the core 10 during the phase 110 may be arranged relative to one another so as to form optical devices other than Bragg gratings. For example, as a variant, the patterns 22 inscribed in the core 10 form a juxtaposition, along the axis 6, of Fabry-Perot cavities. In another variant, at regular intervals, for example every millimetre, a pattern 22 is inscribed in the core 10, continuously over the entire length of the core 10.
[95] As a variant, during the phase 110, a plurality of patterns 22 are simultaneously inscribed in the core 10. One method for doing this is known, for example, as the “phase mask scanning technique”. This method is described, for example, in application US2007236796A1. Other inscription methods mentioned in application US2007236796A1 may be used to inscribe the patterns 22 in the core 10 during the phase 110.
[96] The patterns 22 are not necessarily inscribed only in the core 10, but may also extend into the optical cladding 12.
[97] Variants of the deposition of the new protective sheath:
[98] As a variant, instead of using liquid water to remove the sheath 8, water vapour is used.
[99] Other embodiments of the station 84 for removing the sheath 8 are possible. For example, as a variant, the removal station 84 is arranged like one of those described with reference to Figures 4, 6, 7 and 8 of application US2006134324.
[100] As a variant, only part of the fiber 2 wound onto the spool 70 is unwound, such that the length of the manufactured fiber 30 is less than the length of the blank 20. In such a case, the same spool 70 may be used to manufacture a plurality of spools 90 of fibers 30.
[101] As a variant, during deposition step 138, the sheath 32 deposited is a multilayer sheath comprising a plurality of layers deposited directly on one another. The different layers may be made of the same material. In this case, the sheath 32 is a single-material multilayer sheath and the number of layers may be greater than four or eight. The different layers may also be made of different materials. In this case, the sheath 32 is a multimaterial multilayer sheath. For example, the sheath 32 may comprise one or more of the following layer alternations: - an alternation of layers comprising a ceramic layer and a carbon layer, - an alternation of layers comprising a polymer layer and a ceramic layer, and - an alternation of layers comprising a polymer layer and a carbon layer.
[102] Variants of the optical fiber:
[103] Other embodiments of the waveguide 4 are possible. For example, the core 10 may be made of pure silica and the optical cladding 12 is fluorine-doped silica. The core 10 may also be made of other materials capable of guiding the optical signal, such as, for example, rare-earth-doped aluminosilicates, sapphire or plastic. In these latter cases, the optical cladding 12 is not necessarily made of the same material as the core 10.
[104] The optical fiber may be a multimode optical fiber or MMF (Multi-Mode fiber).
[105] The optical fiber may also comprise a plurality of waveguides 4 surrounded by the same protective sheath.
[106] A plurality of the variants described above may be combined in the same embodiment.
[107] Chapter IV: Advantages of the described embodiments:
[108] Carrying out the functionalization phase 110 independently of the phase 130 of depositing the final sheath makes it possible to use, during the phase 110, a travel speed vi that is independent of the travel speed vd during the phase 130. Thus, the speeds vi and vd may be selected independently of one another. This facilitates optimization of the inscription phase 110 and the final-sheath deposition phase 130, respectively. In particular, the speed vd may be selected to be much greater than the speed vi, which makes it possible to optimize and accelerate deposition of the final sheath 32.
[109] Furthermore, the functionalized optical fiber blank 20 may be stored until the nature of the final sheath 32 of the functionalized optical fiber to be manufactured is known. This makes it possible to make the method for manufacturing functionalized optical fibers more flexible.
[110] Lastly, inscribing the patterns 22 through the temporary sheath 8 avoids having to remove this temporary sheath 8 during the inscription phase 110. Thus, the manufacturing method described here comprises a single step of removing the temporary sheath 8, that is to say the same number of removal steps as in the method of application WO9739371A1. This manufacturing method therefore remains particularly simple and limits the number of manufacturing stations.
[111] Completely removing the temporary sheath 8 solely using a solvent makes it possible to avoid recourse to mechanical action liable to damage the waveguide 4 of the optical fiber. Thus, the method described here makes it possible to manufacture functionalized optical fibers of very high quality.
[112] The fact that the solvent used is water makes it possible to avoid recourse to toxic solvents, which are more difficult to handle and recycle. Thus, the use of water as a solvent simplifies the manufacturing method.
[113] PVA is a non-toxic and biocompatible material. It is therefore unnecessary to take specific precautions when handling it. This simplifies implementation of the manufacturing method.
[114] The fact that the thickness of the PVA sheath 8 is between 10 pm and 20 pm makes it possible to ensure mechanical protection of the waveguide 4 while allowing this sheath 8 to be removed rapidly when it is immersed in water. In particular, the sheath 8 may be removed while the waveguide 4 is moving at a high speed vd for depositing the final sheath.
[115] Using PVA whose mass distribution is between 30,000 g / mol and 70,000 g / mol and whose degree of hydrolysis, before dissolution in water, is between 87% and 90% to prepare the solution used for depositing the sheath 8 makes it possible to perform this deposition at ambient pressure. Under these conditions, the thickness of the sheath 8 does not depend on the production speed vp of the waveguide 4. This simplifies implementation of the manufacturing method. Indeed, the speed vp may be freely selected.
[116] Not having to heat the PVA solution used to deposit the sheath 8 simplifies the manufacturing method.
[117] When PVA represents between 20% and 30% by mass of the solution, the viscosity of this solution makes it possible to deposit a temporary sheath having a thickness of 10 pm to 20 pm while working at ambient temperature and ambient pressure.
Claims
1. A method for manufacturing an optical fiber functionalized using laser pulses, thismethod comprising:- a step of supplying a first spool onto which a non-functionalized optical fiber is wound, this non-functionalized optical fiber comprising a waveguide capable of guiding an optical signal and a temporary protective sheath that covers the waveguide, then- a phase (110) of functionalizing the waveguide in order to obtain a functionalized waveguide, this functionalization step comprising inscribing (116) patterns in the waveguide using laser pulses, then- a phase (130) of depositing a final protective sheath on the functionalized waveguide in order to obtain the functionalized optical fiber,characterised in that:- the functionalization phase (110) comprises:- unwinding (114) the non-functionalized optical fiber wound onto the first spool in order to cause it to travel, at an inscription speed, in front of a femtosecond laser that inscribes, through the temporary protective sheath, the patterns in the nonfunctionalized waveguide as the non-functionalized optical fiber travels in front of this femtosecond laser, in order to obtain a functionalized optical fiber blank, and - winding (114) the functionalized optical fiber blank onto a second spool,- the phase (130) of depositing the final protective sheath comprises:- unwinding (134) the functionalized optical fiber blank wound onto the second spool in order to cause it to travel, at a deposition speed, successively through a temporary protective sheath removal station and then through a final protective sheath deposition station,- at the removal station, passing (136) the optical fiber blank through a bath of solvent that completely dissolves the temporary protective sheath in order to expose the functionalized waveguide, and- at the final protective sheath deposition station, depositing (138) the final protective sheath on the exposed waveguide.
2. The method according to claim 1, wherein, during the phase (130) of depositingthe final protective sheath, at the removal station, the solvent used is water only.
3. The method according to claim 2, wherein, during the supplying step, thetemporary sheath of the non-functionalized optical fiber wound onto the first spool is made of poly(vinyl alcohol).
4. The method according to claim 3, wherein, during the supplying step, the thicknessof the temporary sheath of the non-functionalized optical fiber wound onto the first spool is between 10 pm and 20 pm.
5. The method according to claim 3 or 4, wherein, before the step of supplying thefirst spool, the method comprises:- dissolving (102), in water, a poly(vinyl alcohol) whose mass distribution is between 30,000 g / mol and 70,000 g / mol and whose degree of hydrolysis, before dissolution in water, is between 87% and 90%, in order to obtain a poly(vinyl alcohol) solution, then- producing (104), at a production speed, the non-functionalized waveguide, and then causing the produced non-functionalized waveguide to travel, at the production speed, through the poly(vinyl alcohol) solution in order to form the temporary protective sheath around the non-functionalized waveguide.
6. The method according to claim 5, wherein, while the non-functionalized waveguideis travelling through the poly(vinyl alcohol) solution, the solution is at ambient pressure.
7. The method according to claim 6, wherein, while the non-functionalized waveguideis travelling through the poly(vinyl alcohol) solution, the solution is at ambient temperature.
8. The method according to any one of claims 5 to 7, wherein the solution obtainedby dissolving the poly(vinyl alcohol) in water comprises between 20% and 30%, by mass, poly(vinyl alcohol), the remainder being water.
9. The method according to claim 1, wherein, during the phase of depositing the finalprotective sheath, at the removal station, the solvent used contains an alcohol.
10. The method according to any one of the preceding claims, wherein:- during the supplying step, the waveguide of the supplied non-functionalized optical fiber comprises a non-functionalized core, and- the phase (110) of functionalizing the waveguide comprises inscribing (116) patterns in the core of the waveguide using the femtosecond laser.
11. The method according to any one of the preceding claims, wherein the final protective sheath is opaque to the laser pulses used during the functionalization phase.
12. A non-functionalized optical fiber for implementing a method according to any one of the preceding claims, this non-functionalized optical fiber comprising:- a waveguide (4) capable of guiding at least one optical signal,- a temporary protective sheath (8) that covers the waveguide in order to protect it from attack by the external environment, this temporary protective sheath being made of poly(vinyl alcohol),characterised in that the temporary sheath (8) is obtained by depositing a solution of poly(vinyl alcohol) dissolved in water on the waveguide and then drying this poly(vinyl alcohol) solution deposited on the waveguide, the poly(viny alcohol) used to obtain the poly(vinyl alcohol) solution having, before dissolution in water, a mass distribution between 30,000 g / mol and 70,000 g / mol and a degree of hydrolysis between 87% and 90%.
13. A functionalized optical fiber blank for implementing a method according to any one of claims 1 to 9, this functionalized optical fiber blank comprising:- a waveguide (4) capable of guiding at least one optical signal, and- a temporary protective sheath (8) that covers the waveguide in order to protect it from attack by the external environment, this temporary protective sheath (8) being made of water-soluble poly(vinyl alcohol),characterised in that the waveguide comprises patterns (22) inscribed using laser pulses from a femtosecond laser.