FR3064076A1 - METHOD FOR MANUFACTURING COMPOSITE OPTIC FIBER AND COMPOSITE OPTIC FIBER - Google Patents

Abstract

The invention relates to a method for manufacturing composite optical fiber (21) comprising the following steps: - manufacture of a low temperature vitreous transition glass preform having a longitudinal axis, - drilling a base of the preform parallel to its longitudinal axis to form at least one non-opening opening, - insertion of a wire (7a, 7b) into the at least one non-opening opening, thereby forming a composite preform (17), the wire having a melting temperature, - fiberizing of the composite preform (17), thus forming a composite optical fiber (21), the composite preform (17) being arranged vertically and the base being disposed upwards, the fiberizing having a fiberizing temperature, said fiberizing temperature being greater than said melting temperature of the wire. The invention also relates to a composite optical fiber.

Description

Holder (s): UNIVERSITY OF BORDEAUX Public establishment, NATIONAL CENTER OF SCIENTIFIC RESEARCH Public establishment.

Extension request (s)

Agent (s): JACOBACCI CORALIS HARLE Simplified joint-stock company.

£ 4) PROCESS FOR MANUFACTURING COMPOSITE OPTICAL FIBER AND COMPOSITE OPTICAL FIBER.

FR 3,064,076 - A1 (57) The invention relates to a process for manufacturing composite optical fiber (21) comprising the following steps:

- manufacture of a low temperature glass transition glass preform having a longitudinal axis,

- drilling a base of the preform parallel to its longitudinal axis to form at least one non-opening opening,

- insertion of a metal wire (7a, 7b) into the at least one non-opening opening, thus forming a composite preform (17), the metal wire having a melting temperature,

- fiberizing the composite preform (17), thus forming a composite optical fiber (21), the composite preform (17) being arranged vertically and the base being arranged upwards, the fiberizing having a fiberizing temperature, said fiberizing temperature being higher than said melting temperature of the metal wire.

The invention also relates to a composite optical fiber.

Technical field to which the invention relates

The present invention relates generally to the field of composite optical fibers.

It relates more particularly to a process for manufacturing a composite optical fiber.

It relates in particular to the manufacture of composite optical fibers allowing both the transmission of an electric current and a light signal.

TECHNOLOGICAL BACKGROUND

The manufacture of glass optical fibers is well known to those skilled in the art. It generally includes the manufacture of a glass preform, followed by a fiberizing step during which the preform subjected to a high temperature becomes viscous and can be stretched over several kilometers.

As part of academic research, we make glass / metal composite optical fibers comprising a glass waveguide and a metal wire, enclosed in a silica glass sheath. The glass waveguide transmits a light signal, the metal wire transmits an electric current along the composite optical fiber.

However the high fiber temperature required for silica (2000 ° C) damages the metals which are subjected to it. This is why the metallic wires are usually introduced into the silica fiber after fiberizing. We then try to insert metal wires into openings drilled before fiberizing. A disadvantage of this method is that the metal wires do not completely fill the section of the openings, leaving a space filled with air between the wires and the glass sheath. In addition, the arrangement of the metal wires relative to the sheath varies along the fiber, and also varies according to the fibers. Finally, another drawback of this type of method is that the length of the fiber is limited to a few tens of centimeters.

In such composite optical fibers, the electric current creates an electric field which theoretically makes it possible to modify the properties of the light signal. For example, we can observe non-linear optical effects, such as a change in the wavelength of the light signal.

Consequently, the difficulty in controlling the arrangement of the metallic wires in the composite optical fibers has several drawbacks. On the one hand, the air-filled space acts as an insulator from the electric field created by the electric current flowing through the metal wires. The observed nonlinear optical effects are therefore not as important as the theoretical effects.

On the other hand, the electric field created by the metallic wires crossed by a current is not homogeneous along the composite optical fiber, which makes the desired non-linear optical effects not very controllable.

Finally, the performance obtained by composite optical fiber is not reproducible for other fibers manufactured in the same way.

It is therefore currently difficult to envisage using the manufacturing methods of the prior art to industrially manufacture reliable composite optical fibers.

Thus, we seek to solve the problems posed by the prior art by developing an industrial manufacturing process for manufacturing reliable composite optical fibers comprising an electrical conductor having good contact with the glass of the fiber.

Object of the invention

In order to remedy the aforementioned drawback of the state of the art, the present invention proposes a process for manufacturing composite optical fiber comprising the following steps:

- manufacture of a low temperature glass transition glass preform having a longitudinal axis,

- drilling a base of the preform parallel to its longitudinal axis to form at least one non-opening opening,

- insertion of a metal wire into said at least one non-opening opening, thus forming a composite preform, the metal wire having a melting temperature,

- fibering of the composite preform, thus forming a composite optical fiber, the composite preform being arranged vertically and the base being arranged upwards, the fibering having a fiberizing temperature, said fiberizing temperature being higher than said wire melting temperature metallic.

Such a manufacturing process comprising a step of simultaneously fiberizing the metal wire and the preform makes it possible to obtain a composite optical fiber within which the different components have a good contact surface with one another.

More particularly, a manufacturing process is proposed according to the invention in which the fiberizing temperature is between 250 ° C. and 800 ° C.

Preferably, the fiberizing temperature is between 300 ° C. and 600 ° C.

The invention also provides a composite optical fiber having a longitudinal axis and comprising at least one conductive core housed in a glass sheath, said at least one conductive core being placed parallel to the longitudinal axis and having a low melting temperature, the glass sheath having a glass transition temperature between 100 ° C and 700 ° C.

Other non-limiting and advantageous characteristics of the composite optical fiber according to the invention, taken individually or in any technically possible combination, are the following:

the composite optical fiber further comprises an optical waveguide capable of conducting an optical wave and housed in the glass sheath, the conductive core consists of a metal. The metal is chosen from the following metals: tin, zinc, or a tin-based alloy chosen from an alloy: gold-tin, tin-silver, tin-bismuth or tin-indium, the glass sheath and / or the optical waveguide comprises at least one glass chosen from the following glasses: tellurium glass, phosphate glass, fluoride glass, chalcogenide glass, the tellurium glass comprises a glass whose chemical composition is one of the following: 80TeO ₂ -10ZnO-10Na ₂ O, 60TeO ₂ -5ZnO-20Na ₂ O-15GeO ₂ or 80TeO ₂ -5ZnO-10Na ₂ O-5ZnF ₂ .

composite optical fiber is at least one meter long.

Detailed description of an exemplary embodiment The description which follows with reference to the appended drawings, given by way of nonlimiting examples, will make it clear what the invention consists of and how it can be carried out.

In the accompanying drawings:

FIG. 1 represents a diagram illustrating the different stages of the process for manufacturing composite fibers,

FIG. 2 represents a diagram illustrating the different substeps of the process for manufacturing a preform,

FIG. 3a shows a preform having a single opening,

FIG. 3b illustrates a composite preform at an opening during the fiberizing step as well as vignettes of radial longitudinal section and cross section of the resulting composite optical fiber,

FIG. 4a illustrates a preform having three openings as well as the metal wires and the capillary before their insertion into the preform,

FIG. 4b illustrates the composite preform with three openings during the fiberizing step as well as vignettes of radial longitudinal section and cross section of the resulting composite optical fiber,

FIG. 5 represents a diagram illustrating the variation of the electrical resistance of a composite optical fiber as a function of its length,

- Figure 6 shows a diagram illustrating the variation of the electrical resistance of a composite optical fiber as a function of its temperature.

In order to facilitate understanding of the description, some definitions of technical terms are included below.

A composite optical fiber is a fiber made up of different materials and used to conduct a light signal and an electric current. The composite optical fiber materials include at least one glass and one metal.

The glasses have a glass transition temperature T _g .

The metals have a melting temperature T _m .

We define a low glass T _g (low-T _g glass or soft-T _g glass in English), a glass whose glass transition temperature T _g is between 100 ° C 700 ° C.

Composite optical fibers are also known by the names of multi-material optical fibers and hybrid optical fibers.

Process

The manufacturing method 100 of composite optical fiber, illustrated by FIG. 1, comprises the following steps:

- a first manufacturing step 110 of a solid glass preform,

a second step of piercing 120 of the preform to form at least one cylindrical opening,

a third step of insertion 130 of at least one metal wire and / or of a capillary into the opening, thereby forming a composite preform,

- A fourth fiberizing step 140 of the composite preform, thus forming a composite optical fiber. This fourth step is also called co-fiberizing.

In the first exemplary embodiment, the first manufacturing step 110 of the preform comprises several substeps, illustrated in FIG. 2.

The preform according to the present disclosure comprises a low glass T _g , for example a chalcogenide glass, a tellurium glass, a fluoride glass or a phosphate glass. The glass transition temperature ranges T _g of these glasses are grouped in table 1.

Interval of T _g (° C) Glass of chalcogenide 100 -250 Glass of tellurium 250 - 350 Phosphate glass 400 - 500 Fluoride glass 200 - 280

Table 1: Glass transition temperature ranges T _g of low glasses T _a

In the example of development developed below, we use a glass of tellurium. The tellurium glasses have good thermomechanical and chemical stability.

During a first preparation substep 112, a mass of tellurium glass is prepared by rapid tempering of a molten bath.

During a second substep 114, the mass of glass is poured into a cylindrical mold, for example made of brass, preheated beforehand to a temperature below, for example 5 ° C., at the glass transition temperature T _g (T _g -5 ° C).

During a third solidification step 116, the mass of glass is annealed for several hours in the brass mold at a lower temperature, for example 40 ° C., at the temperature cb glass transition T _g (T _g 40 ° C. ). The mass of glass can for example be recute overnight or for example for 12 hours.

At the end of this solidification step, a solid preform 1 of tellurium glass is obtained. As illustrated in FIG. 3a, the preform 1 has a cylindrical shape comprising a base 3a and another base 3b. The bases 3a, 3b have a diameter of several millimeters. The preform 1 extends over a length of several centimeters along a longitudinal axis Af.

During the second drilling step 120 of the preform 1, the base 3a of the preform is pierced, parallel to its longitudinal axis A _F to form a non-opening opening 5. The non-opening opening 5 has a bottom 51 the usefulness of which will be explained during the fiberizing step 140.

The drilling can be carried out mechanically, for example with a drill. Alternatively, drilling can be carried out with a laser.

By optimizing drilling parameters, such as the rotation speed, it is possible to pierce a plurality of non-opening openings 5, 5a, 5b in the preform 3 and thus obtain a complex pattern. The manufacturing method 100 of this disclosure is therefore not limited to the exemplary embodiments described here.

During the step of inserting a wire 130, a metal wire 7 is introduced into the non-opening opening 5 of the preform, thus forming a composite preform 9 shown in FIG. 3b.

In the embodiment, the metal wire 7 consists of a gold-tin alloy (Au-Sn). The metal wire 7 can also consist of tin-based alloys such as a tin-bismuth (Sn-Bi), tin-indium (Sn-ln), tin-silver (Sn-Ag) alloy, for example. 5% Ag-95% Sn, or even tin (Sn) or zinc (Zn). These metals and metal alloys have a low melting temperature T _m . The melting temperatures of some of the metals used in the example embodiments are grouped in Table 2.

Sn Au-Sn Sn-Ag Sn-ln Sn-Bi Zn T _m (° C) 232 280 221 120 138 420

Table 2: Melting temperature T _m of certain metals and metal alloys

The diameter of the metal wire 7 is less than that of the non-penetrating opening 5. For example, for an opening with a diameter of 1.1 mm, the diameter of the wire can be 1 mm.

The insertion 130 of the metal wire 7 into the non-opening opening 5 of the preform can be done manually.

During the fiberizing step 140 of the composite preform 9, the composite preform 9 is suspended vertically in an oven, the base 3a being arranged upwards. The oven is programmed to subject the lower end of the composite preform 9 to a fiberizing temperature Tf in order to obtain a composite optical fiber 11.

The fiber drawing temperature T _f is higher than the glass transition temperature T _g and the metal melting temperature T _m . The fiberizing temperature Tf is several hundred degrees, it is for example between 250 ° C and 800 ° C, and preferably 300 ° C to 600 ° C.

The glass transition temperature T _g of tellurium glasses is approximately 280 ° C. The glass transition temperatures of certain examples of tellurium glasses used in the exemplary embodiments are grouped in table 3. These tellurium glasses are denoted TZN (of chemical formula 80TeO ₂ 10ZnO-10Na ₂ O), TZNG (of chemical formula 60TeO2-5ZnO-20Na ₂ O-15GeO ₂ ) and TZNF (with chemical formula 80TeO ₂ -5ZnO-10Na ₂ O-5ZnF ₂ ).

TZN TZNG TZNF Tg (° C) 285 272 282

Table 3: Glass transition temperature T _g of tellurium glasses

In this first embodiment, a metal wire 7 made of a gold-tin alloy is used, the melting temperature of which is 280 ° C.

Under the effect of the fiber drawing temperature Tf, the glass of the composite preform 9 becomes viscous and the metal wire 7 becomes liquid. The composite preform 9 is stretched down under the effect of gravity and refined homothetically to form the composite optical fiber 11. This homothetic stretching makes it possible to preserve the geometry of the composite preform 9 as illustrated in FIG. 3b.

The radial longitudinal cross-section and cross-section thumbnails show that the composite optical fiber 11 has a homothetic transformation of the composite preform 9 with a conductive core 17 formed from the metal wire 7 of the composite preform and a glass sheath 13 formed at from the glass preform 1.

The average diameter of the composite optical fiber 11 thus produced is 150 μm. The average diameter of the composite optical fiber 11 is generally between 100 μm and 500 μm. The length of the composite optical fiber 11 extends over several meters. Typically the length of the composite optical fiber 11 is between approximately 1 m and a few tens of meters and preferably between 1 m and ten meters, for example between 1 m and 2 m. The diameter of the conductive core 17 is for example of the order of 12.5 μm.

This simultaneous fiberizing step 140 of all the components of the composite preform 9 allows a good contact surface between the glass sheath 13 of the composite optical fiber 11 and the conductive core 17 in the composite optical fiber 11.

During the fiberizing step 140, the viscosity of the preform 1 is kept as high as possible, in order to allow a controlled flow of the metal wire 7 which is in its liquid phase.

We understand here the interest of a non-opening opening 5. Indeed, if the preform 1 were pierced from one base 3a to the other 3b, the liquid metal would flow out of the composite optical fiber 11 during fiberizing. By limiting the depth of the opening 5, the bottom 51 prevents the flow of the liquid metal downwards.

In addition, the non-opening opening 5 laterally contains the liquid metal inside the composite optical fiber 11 by preventing it from flowing through the side of the fiber.

However, care is taken not to subject the composite preform 9 to a too high fiberizing temperature T _f , which could cause mechanical failure of the composite preform 9. According to this first embodiment, the fiberizing temperature Tf is 500 ° C. . It is a moderate temperature compared to the fiber drawing temperature T _f of the silica glasses which rises to 2000 ° C.

This solves the problems present in the prior art. In fact, in the prior art, by exposing the metals and the glasses to a fiberizing temperature Tf of the order of 2000 ° C., it causes cross-scattering phenomena between the different materials, and the vaporization of the metals which degrades the performance of the composite optical fibers thus manufactured. In addition, the methods of the prior art introduce mechanical stresses into the fibers due to the differences in thermal coefficients of the different materials used.

The manufacturing process 100 comprising a fiberizing temperature T _f at a moderate temperature makes it possible to form composite optical fibers 11 mechanically resistant and having good continuity in the transmission of electric current.

In an additional protection step, not shown, the optical fiber is coated with a protective coating. The protective coating comprises for example a polymer.

This method of manufacturing 100 of composite optical fibers is also applicable to families of glasses other than tellurium glasses. Indeed, glasses having a low glass transition temperature T _g , as well as a fiberizing temperature for example between 250 ° C and 800 ° C, and preferably between 300 ° C and 600 ° C allow obtaining 11 quality composite optical fibers. These glass families include, for example, phosphate glasses, fluoride glasses and chalcogenide glasses.

This manufacturing process 100 is simpler, faster and has a low cost.

Composite optical fibers

In the first embodiment illustrated in FIG. 3a, the preform 1 manufactured according to manufacturing step 110 has a cylindrical shape generally of circular section, extending over a length of several centimeters along a longitudinal axis A _F. The preform 1 has for example a length of a few centimeters and a diameter of the order of a centimeter. The preform 1 may for example have a length of 8 cm and bases 3a, 3b with a diameter of 8 mm.

At the end of the drilling step 120 of the base 3a, the non-opening opening 5 extends over a depth of a few centimeters, and its diameter is of the order of a millimeter. The non-opening 5 has a bottom 51 and does not open onto the other base 3b of the preform. Its depth can be for example 3 cm and its diameter can be between 0.8 mm and 1.1 mm.

At the end of the insertion step 130, a composite preform 9 is obtained comprising a metal wire 7, as illustrated in FIG. 3b.

Finally, at the end of the fiberizing step 140, a composite optical fiber 11 is obtained having a conductive core 17 housed in a glass sheath

13. The conductive core 17 is formed from the metal wire 7, and the glass sheath 13 is formed from the preform 1.

In a second example of the invention, illustrated by FIG. 4a, during the drilling step 120, a plurality of openings 5, 5a, 5b are drilled on the base 3a of the preform 1. For example, a first non-opening central opening 5 at the center of the first base 3a of the preform, and two other non-opening openings 5a, 5b placed symmetrically on either side of the first non-opening central opening 5. These non-opening openings respectively have a background 51,51a, 51b.

During the insertion step 130, a glass capillary 15 is inserted into the central non-opening opening 5.

For example, the glass capillary 15 comprises a central part 151 and an external part 153 arranged concentrically. The central part 151 located at the center of the capillary 15 comprises for example a TZNF glass. The external part 153 which envelops the central part 151 comprises for example TZNG glass.

The central part 151 and the external part 153 have different refractive indices allowing the guiding of the light by total internal reflection. The preform is for example made of TZN tellurium glass.

Alternatively, the glass capillary 15 comprises a single glass whose refractive index is greater than that of the preform 1.

Alternatively, the glass capillary 15 comprises a plurality of parts arranged concentrically and having different indices of refraction.

A metal wire 7a, 7b is respectively inserted into each of the two other non-opening openings 5a, 5b of the preform. The metal wires 7a, 7b are made of a metal such as a tin-gold alloy. The metal wires 7a, 7b more generally consist of one of the metals mentioned above.

Alternatively, the metal wire 7a may be made of a metal different from the metal wire 7b.

At the end of the insertion step 130, a composite preform 19 is obtained, illustrated in FIG. 4b.

The fiberizing step 140 is carried out as for the first example of embodiment. At the end of the manufacturing process 100, a composite optical fiber 21 is obtained, several meters long and comprising an optical waveguide 1151 of glass and conductive cores 17a, 17b housed in the glass sheath 13.

The optical waveguide 1151 is formed from the capillary 15, the conductive cores 17a, 17b are formed from the metal wires 7a, 7b respectively, and the glass sheath 13 is formed from the glass preform 1.

The optical waveguide 1151 and the conductive cores 17a, 17b have a good contact surface with the glass sheath 13 which houses them.

The distance between the optical waveguide 1151 and the conductive cores 17a, 17b is small and constant throughout the composite optical fiber 21. This distance is between 0 and several tens of micrometers, for example 40 μm. Consequently, the induced electric field has a high value in the optical waveguide 1151. The non-linear optical effects, proportional to the length of the composite optical fiber 21 and inversely proportional to the distance between the conductive cores 17a, 17b , are thus increased.

The invention is not limited to these two exemplary embodiments. A variety of composite optical fibers comprising a plurality of glass optical waveguides and / or a plurality of conductive cores can be manufactured according to manufacturing method 100 of this disclosure.

The electric field induced by the electric current passing through the conductive cores 17a, 17b easily penetrates into the optical waveguide 1151 transmitting the light signal, and thus creates non-linear optical effects.

Such a composite optical fiber 21 can for example be used to produce polychromatic lasers of the supercontinuum type.

The electric current flowing through the conductive cores 17a, 17b creates a marking effect (poling effect, in English) which makes it possible, for example, to locally change the structure of the glasses in order to make it non-centrosymmetric, this makes it possible to increase the conversion capacity. frequency. In this case, intense light is injected at a given optical frequency into the optical waveguide 1151, and a widening of the frequency band at the output of composite optical fiber 21 is obtained.

It is also possible to increase this marking effect by coupling the electrical marking with an optical marking while complexifying this marking effect by illumination with a spatially structured electric field. The presence of the conductive cores 17a, 17b housed in the same composite optical fiber 21 allows this operation to be carried out.

Tellurium glasses have excellent optical properties, particularly with regard to transmission in the infrared and non-linearity of order 2, which makes them particularly well suited to such an application.

It is also possible to initiate other optical effects within the composite optical fiber 21 such as optical switching or modal transformations by printing tunable Bragg gratings.

The conductive cores 17a, 17b can also serve as heat sinks. Indeed, when a high power light signal is injected into the composite optical fiber 21, the temperature of the optical waveguide 1151 increases sharply. The conductive cores 17a, 17b make it possible to dissipate heat more quickly.

In addition, the conductive cores 17a, 17b can serve as a reinforcement for the composite optical fiber 21, thereby improving its mechanical resistance.

Such a manufacturing process also makes it possible to manufacture composite optical fibers several meters long.

Tests on the continuity in the transmission of electric current were carried out on the composite optical fibers 11 obtained according to this manufacturing process 100.

In a first test, a current is applied to a composite optical fiber 11 and the electrical resistance of the composite optical fiber 11 is measured as a function of the length of the fiber. This first test is carried out on a fiber length of 4 m. This test is carried out at a constant temperature of 20 ° C.

Figure 5 illustrates the results of this first test. In this figure, the horizontal axis represents the length in meters of the composite optical fiber 11, and the vertical axis represents the electrical resistance in Ohm of the conductive core 17 of the composite optical fiber 11.

The electrical resistance of the conductive core 17 of the composite optical fiber 11 increases linearly as a function of its length, which confirms the continuity in the transmission of electric current.

In a second test, a composite optical fiber 11 is placed on a heating plate 23, a current is applied to the composite optical fiber 11 and the electrical resistance of the conductive core 17 is measured as a function of the temperature. In this second test, the temperature is increased to around 260 ° C. The length of the composite optical fiber is 1 m and remains constant.

Figure 6 illustrates the results of this second test. In this figure, the horizontal axis represents the temperature in degrees Celsius to which the composite optical fiber 11 is subjected, and the vertical axis its electrical resistance in Ohm.

The electrical resistance of the composite optical fiber 11 increases linearly as a function of the temperature, which confirms the continuity in the transmission of the electric current.

This manufacturing process 100 therefore makes it possible to obtain composite optical fibers 11 having good continuity in the transmission of electric current.

Claims (10)

1. A method of manufacturing (100) composite optical fiber (11, 21) comprising the following steps: manufacturing (110) of a preform (1) of low temperature glass transition glass (T _g ) and having a longitudinal axis (A _F ), - drilling (120) of a base (3a) of the preform parallel to its longitudinal axis (A _F ) to form at least one non-opening opening (5, 5a, 5b), - insertion (130) of a metal wire (7, 7a, 7b) into said at least one non-opening opening (5, 5a, 5b), thus forming a composite preform (9, 19), the metal wire (7 , 7a, 7b) having a melting temperature (T _m ), - fiberizing (140) of the composite preform (9, 19), thus forming a composite optical fiber (11, 21), the composite preform (9, 19) being arranged vertically and the base (3a) being arranged upwards, the fiber drawing having a fiber temperature (T _f ), said fiber temperature (T _f ) being higher than said melting temperature (T _m ) of the metal wire. 2. The manufacturing method according to claim 1, wherein the fiberizing temperature (Tf) is between 250 ° C and 800 ° C. 3. The manufacturing method according to claim 2, wherein the fiberizing temperature (Tf) is between 300 ° C and 600 ° C. 4. Composite optical fiber (11, 21) having a longitudinal axis (A _F ) and comprising at least one conductive core (17, 17a, 17b) housed in a glass sheath (13), said at least one conductive core (17 , 17a, 17b) being placed parallel to the longitudinal axis (A _F ) and having a low melting temperature (T _m ), the glass sheath (13) having a glass transition temperature (T _g ) of between 100 ° C and 700 ° C. 5. Composite optical fiber (11,21) according to claim 4, further comprising an optical waveguide (1151) capable of conducting an optical wave and housed in the sheath (13) of glass. 6. Composite optical fiber (11,21) according to claim 4 or 5, wherein the conductive core (17, 17a, 17b) consists of a metal. 7. A composite optical fiber (11, 21) according to claim 6, in which the conductive core (17, 17a, 17b) comprises a metal chosen from the following metals: tin, zinc, or a tin-based alloy chosen among an alloy: gold-tin, tin-silver, tin-bismuth or tin-indium. 8. Composite optical fiber (11,21) according to one of claims 4 to 7, in which the glass sheath (13) and / or the optical waveguide (15) comprises at least one glass chosen from glasses following: tellurium glass, phosphate glass, fluoride glass, chalcogenide glass. 9. Composite optical fiber (11, 21) according to claim 8, in which the tellurium glass comprises a glass whose chemical composition is one of the following: 80TeC> 2-10ZnO-10Na2O, 60TeO2-5ZnO-20Na2O-15GeC > 2 or 80TeO ₂ -5ZnO-10Na ₂ O-5ZnF ₂ . 10. Composite optical fiber (11, 21) according to one of claims 4 to 9, the composite optical fiber (11, 21) having a length of at least one meter. 1/3