Field of the Invention

The invention generally relates to measurement systems and, in particu-link optical fiber sensor devices and such devices manufacturing processes.

BACKGROUND

An optical fiber sensor comprises a measurement optical fiber whose optical characteristics are sensitive to a physical quantity. When light is injected into the optical fiber, a light signal is generated and detected by the sensor. This signal is then converted and processed to return the measured quantity. Fiber optic sensors are widely used in various types of applications, not only due to their small size (size and relatively low weight) and their insensitivity for electromagnetic-magnetic-interference, but also because they are particularly suited to the technical multiplexing and the implementation of amplifiers or distributed sensors. They also limit the intrusiveness of the sensor in the middle.

Some fiber optic sensors using Bragg gratings inscribed in the fiber. A Bragg grating is a reflector having different refractive indices alternate layers, which causes a periodic variation in the effective refractive index in the optical fiber. The fiber Bragg grating sensors are used to measure a physical quantity corresponding to a stress applied to the sensor. The stress applied to the sensor induces a variation in wavelength.

The fiber optic sensors with Bragg gratings may be passive or active (optical fiber laser sensor).

The fiber optic sensors with Bragg gratings are arranged in a protective jacket, crossing each side by the optical fiber. When mounting such a sensor, it is useful to leave an additional length of

unstretched fiber within the enclosure. Indeed, in the absence of such an additional length, the stretched optical risk of generating a stiffness in a wide operating range fiber (in particular temperature range) which is detrimental to proper functioning of the sensor. Moreover, such an additional lon-LATIONS allows the fiber filtering mechanical disturbances that may come from outside the sensor.

A known solution to realize an additional length of fiber is illustrated in Figure 1. According to this approach, at least one loop 23 is carried with the fiber 22 in the casing 20 which houses the sensor 21, which allows to generate an additional length. However, such a solution generates a bulky because of the minimum bend radius allowed for an optical fiber (of the order of cm). This solution is therefore not suitable for compact sensors.

general definition of the invention

The invention improves the situation. To this end, it proposes a method of manufacturing an optical fiber sensor device comprising a housing defining a cavity and an optical fiber sensor, the optical fiber sensor comprising an optical fiber and a holding device fixed sensor the optical fiber, the holding device being traversed by the optical fiber between two fixing points provided on the holding device. Advantageously, the method comprises the steps of:

-Position the optical fiber sensor in the housing so as to pass the fiber through the two passage openings provided on the envelope, the optical fiber extending generally along a longitudinal axis in the cavity, which delimits two portions optical fiber in the casing on either side of the holding device, each fiber portion extending between a retaining device of the attachment points and one of the passage openings of the casing, substantially in a straight line;

-maintaining the optical fiber sensor in position;

- Carry out a differential elongation of the casing relative to the optical fiber sensor in the longitudinal direction and outwardly of the casing, while the fiber optic sensor is maintained in position;

-set the optical fiber to the housing at said openings; and

- bring back the envelope in a balanced position.

According to one characteristic, the differential fiber elongation step is performed by mechanically stretching the casing in the longitudinal direction on each side of the casing outwardly of the casing, while the casing is back into the equilibrium position by releasing the envelope.

In one embodiment, the differential elongation A L of the envelope relative to the optical fiber sensor satisfies a constraint on the ambient temperature T s at the time of fixing the fiber to the envelope, the maximum temperature T max of operation of the fiber sensor, the thermal expansion coefficient A c of the optic sensor and the thermal expansion coefficient edit Chapter Ρ of the envelope.

In particular, the stress is defined by the inequality:

AL— ~^~ · λρ (Jmax ~ Ts)— . Ac (Tmax— Ts) ,

wherein A c denotes the thermal expansion coefficient of the holding device of the fiber sensor, A P thermal expansion coefficient of the envelope, L c is the length of the fiber sensor, L P denotes the length of the envelope, T s the surrounding temperature at the time of fixing the fiber to the envelope, and the maximum temperature Tmax of the sensor.

In another embodiment, the differential elongation step is performed by differential thermal expansion of the shell relative to the optical fiber sensor by increasing the temperature to a higher expansion temperature than the maximum operating temperature defined for the optical fiber sensor device, and the envelope is returned to the equilibrium position by bringing the temperature to a temperature below the expansion temperature. Specifically, the envelope is returned to the equilibrium position by bringing the temperature to a temperature in the sensor operating range that is lower than the expansion temperature.

The envelope can then be selected to have a coefficient of thermal expansion according to the equation:

wherein A c denotes the thermal expansion coefficient of the sensor holder, edit Chapter Ρ denotes the coefficient of thermal expansion of the envelope, L c is the length of the holding device, and L P is the length of the envelope.

In particular, the differential elongation A ' L of the casing may be equal to:

Si =. l R (T - T 1 ) -! . la (T - rj

wherein A c denotes the thermal expansion coefficient of the sensor, edit Chapter Ρ the coefficient of thermal expansion of the envelope, L c is the length of the holding device, L P denotes the length of the casing, operating temperature T, Ti and the expansion temperature.

According to an additional characteristic, the fiber bonding step to the casing at the level of passage openings may comprise a bonding fiber at the locking points.

The manufacturing method may further comprises the fixing of the fiber sensor to the casing at at least one connecting zone.

Attaching the sensor to the casing at at least one connection zone can in particular be carried out by gluing.

According to another characteristic, the step of positioning the fiber optic sensor may comprise longitudinal positioning of the optical fiber sensor substantially in the middle of the casing.

In one embodiment, the sensor may be a hydrophone.

The invention further provides a fiber optic sensor arrangement, comprising an envelope delimiting a cavity, an optical fiber sensor, the optical fiber sensor comprising an optical fiber and a fixed holding device of the optical fiber, the device of maintenance being traversed by the optical fiber between two fixing points provided on the holding device. Advantageously, the optical fiber passes through the envelope at two passage openings provided on the casing and extends generally along a longitudinal axis in the cavity, which delimits two portions of optical fiber lengths of data in the envelope, on either side of the holding device, each fiber portion extending between one of said holding device of the fixing points and the

In particular, the wavelength of the light passing through the optical fiber of the sensor device is a linear function of a stretch parameter corres-ponding to a stretch applied to the sensor device, the linear function having a slope discontinuity to a critical value of the stretch parameter such that the director of the linear function coefficient after the critical value is greater than the head of the linear function coefficient before the critical value.

The invention thus allows a differential stretching of the container relative to the sensor before connecting the container to the optical fiber and / or the sensor.

Description of figures

Other features and advantages of the invention will appear with the following description and the figures of the accompanying drawings:

- Figure 1 is a diagram showing an optical fiber sensor device according to one approach of the prior art;

- Figure 2 is a diagram showing an optical fiber sensor device according to some embodiments of the invention;

- Figure 3 is a diagram illustrating the differential elongation of the casing relative to the optical fiber sensor according to some embodiments of the invention;

- Figure 4 is a flowchart showing the method of manufacturing a fiber optic sensor device according to an embodiment of the invention; - Figure 5 is a flowchart showing the method of manufacturing a fiber optic sensor device according to another embodiment of the invention; and

- Figure 6 is a diagram showing variation of the wavelength depending on a stretch parameter corresponding to a stretch applied to the sensor device.

The drawings and appendices to the description may serve not only to better understanding of the description, but also contribute to the definition of the invention, if any.

detailed description

2 shows an optical fiber sensor device 1 according to some embodiments of the invention.

The optical fiber sensor device 1 comprises a casing 10 defining a cavity 3 and at least one optical fiber sensor 2 housed in the cavity 3. The invention is described below in connection with a single optical fiber sensor 2 housed in the cavity 3 by way of non-limiting example.

The optical fiber sensor 2 comprises an optical fiber 12 whose optical characteristics are sensitive to a physical quantity, and a holding device 1 1 secured to the optical fiber 12. The soaking time 1 device 1 is crossed by the optical fiber and is fixed thereto at two points of fixture 1 10 and 1 1 1 provided on said holding device. The soaking time 1 1 is configured to hold the fiber in position in the cavity 3. It may further comprise additional elements for mechanical amplification in some acoustic applications, for example.

The optical fiber sensor 2 may be any type of sensor configured to measure a physical quantity, such as for example a fiber optic hydrophone, a strain sensor, pressure, temperature, acceleration, etc. Although not limited to such applications, such a fiber sensor 2 is particularly suitable for acoustic hydrophone applications to detect acoustic pressure variations. Indeed, the electronic components do not have to be provided in the submerged part. As a result, they can be towed easily and it can be multiplexed on the same fiber more fiber optic sensor devices 1.

The envelope 10 may be configured to mechanically protect the sensor, in particular against knocks, against some stresses due to the environment (e.g., water) against corrosion, etc. The envelope 10 may for example be in the form of a rigid body such as a cylindrical tube whose generatrix line coincides substantially with the general axis of the optical fiber 12. The jacket may be formed of several assembled elements each other or have an integral structure.

3 the cavity delimited by the casing 10 may be filled with a fluid protection such as oil to optimize operation and lifetime of the sensor.

The casing may be flexible or rigid and sealed to isolate the fluid contained therein from the outside environment.

According to one aspect of the invention, the optical fiber 12 passes through the envelope 10 in a sealed manner at two passage openings 130 and 140 provided on the casing. These openings may be arranged respectively on both sides of the envelope, such as two opposite faces 13 and 14. In the cavity 3, the optical fiber extends generally following a longitudinal axis, which delimits two portions optical fibers 120 and 121 of data lengths, in the casing on either side of the support device 1 1. Each portion of fiber 120 and 121 extending between one of the passage openings of the casing 130 and 140 and the point of attachment of the holding device (10 and, respectively, 1 1 1 1) closest. Thus, the portion of fiber 120 s' of the casing 10 and the entry point in the support device 1 1 in the cavity 3 while the fiber portion 121 extends between the exit point Sm of the casing 10 and the exit point Su the support device 1 1 in the cavity 3.

The optical fiber element 12, forming the active part of the sensor 2 thus enters the cavity 3 by the E10 item and exits the cavity through the point S10, passing through the openings of passages 130 and 140.

In addition, the optical fiber 12 may include at least one Bragg grating 15 placed on the fiber and configured to transmit wavelengths sensitive to mechanical stress applied to the optical fiber 12. The measurement of these variations in lengths wave allows to derive the stress applied to the optical fiber 12 and a result of measuring a physical quantity such as acoustic pressure, for example, using a search box.

In known manner, the optical fiber 12 may consist of a tube (e.g. silica tube) one hundred microns in diameter and comprise in its center a heart forming a duct for channeling the light. The fiber can be illuminated by means of a laser beam with a periodic array of interference fringes. The one or more Bragg gratings can be photo-registered one after another on the fiber 12. In addition, the fiber 12 may comprise a protective sheath to mechanically protect the fiber.

The Bragg grating 15 may comprise a set of successive rings registered transversely in the heart of the fiber (e.g. photo-imprinting), the distance between each ring representing the pitch of the array which is representative of a given wavelength. When light is injected into the fiber 12, it can spread in the longitudinal direction (direction of the fiber) until it reaches the Bragg grating 15. Bragg grating filter then the wavelength corresponding to its not opposing the passage of the line of this wavelength and the reflectivity. The spectrum of the reflected beam can then be analyzed. A deformation of the fiber causes a change of grating pitch, and consequently a variation of the length of wave of the reflected beam around its initial value, this variation being proportional to the stretch-ing of the fiber. The analysis of the variation of the wavelength and to measure the physical magnitude which induces deformation of the fiber (e.g., the acoustic pressure).

Those skilled in the art will understand that the invention is not limited to an optical fiber 12 comprising a Bragg grating inscribed and can be applied to other types of optical fibers, such as a coiled fiber or fiber Type OWLC (Laser Sensor Optical Fiber) with a Bragg grating.

In one embodiment, the casing 10 may comprise two 13/14 faces vis-à-vis each comprising a passage opening 130/140 respectively for the passage of the optical fiber 12.

After assembly of the sensor device 1, the casing 10 is secured to the optical fiber 12 at the two openings 130 and 140 of the casing 10 and each portion 120 and 121 of the fiber 12 extends substantially along an axis (ie substantially in a straight line). The optical fiber 12 may be fixed to the casing 10 at the openings 130 and 140 by any means of rigid connection such as by welding (eg laser welding) or adhesion (eg by gluing or by coating polyamide adhesive Epoxy) . In the embodiment of Figure 3, the attachment at the crossing points 130 and 140 between the fiber 12 and the jacket is carried out using glue dots 170.

In addition, the support device 1 1 of the sensor 2 can be fixed to the casing 10 at connection points 171.

According to one aspect of the invention, the portions of the optical fiber 120 and 121 located inside the cavity 3 on either side of the soaking time 1 device 1 include a distension performed by differential elongation of the casing 10 (also known as "differential stretch" below) relative to the optical fiber prior to attachment of the fiber to the shell 10 at the openings 130 and 140 of the casing 10.

As used herein, the term "distension" of fiber means that the fiber length of each portion 120 and 121 within the cavity 3 is larger than the geometrical distance ([E 0 In] and [SuS -io]) between the input point E 0 (or respectively the exit point Sm) of the optical fiber 12 into the cavity 3 bounded by the casing 10 and the entry point (or respectively the point of exit Su) of the optical fiber 12 in the holding device 1 1 ([Ei 0 in] LCAC (Equation 2)

During thermal expansion, the sensor 2 is maintained in position within the cavity 3 or by prior fixing of the support device 1 1 to the casing 10 at the points of connection 1 71, either by using suitable tooling to maintain in position the holding device 1 1 (integral with the fiber) during expansion.

In this embodiment, the fixation of the fiber 12 to the casing 1 0 at the openings 1 30 and 140 and / or the fixing of the optical fiber sensor 2 to the casing 1 at 0 points coupling 1 71 may be advantageously performed at a temperature above the maximum temperature of use of the sensor device 1.

Throughout the temperature range of operation, portions of fiber 1 20 and 1 21 are so loose due to the differential retraction of the casing 10 relative to the sensor 2.

Considering that the fixation of the fiber 1 2 to the casing 1 0 (e.g., by gluing) to the level of the passage openings is effected at a temperature ΤΊ, variation A ' L of the fiber can be obtained by thermal expansion to an operating temperature T <ΤΊ according to the following equation:

A'L = ^ . P (T - T1) - if . c(T - rj (Equation 3)

L c , L P , A ' L may particularly be expressed in meters, and T ΤΊ can be expressed in degrees Celsius (° C) and A c and edit Chapter Ρ in reciprocal degrees Celsius (° C "1 ).

For fiber portions 1 20 and 1 21 loose within the cavity 3 bounded by the casing 1 0, the change in length A ' L defined in equation 3 meets A' L <0 whatever the temperature T in the operating range of the sensor, which is to select the materials of the sensor 2 and the envelope 1 0 so as to satisfy equation 2.

4 illustrates the manufacturing process of the optical fiber sensor device 1 according to the first embodiment or the differential stretching is carried out mechanically before the fixation of the fiber and the casing at the level of passage openings 1 30 and 140.

At step 400, the optical fiber sensor 2 is assembled and incorporated into the casing 1 0 so that the fiber 12 passes through the passage openings 1 30 and 140, without being fixed thereto and each portion fiber 1 20 and 1 21 extend substantially straight. In this phase, the fiber sensor 2 can be positioned substantially in the middle of the cavity 3.

At step 401, the optical fiber sensor 2 is maintained in position. In one embodiment, it may be held in position by fixing the holding device 1 1 of the sensor 2 to the casing at the connection points 171, for example by gluing. Alternatively, the optical fiber sensor 2 can be held in position using a suitable tooling.

At step 402, a differential stretching of the envelope 1 0 relative to the sensor 2 is performed mechanically according to the longitudinal axis 1 6 at each end face 13 and 14 of the envelope 1 on which is 0 arranged one of the openings of Run 1 30 and 140, outwardly of the casing 10 (according to arrows 41 and 42 shown in Figure 3), using for example a stretching device which is fastened on either side of the casing 10 at each opposite end 1a 3 and 14.

At step 403, the fiber 1 2 is fixed to the casing at each opening of Run 1 30 and 140, for example by gluing. Assuming that the fixing of the fiber 1 2 to the casing 1 0 is performed at a temperature T s , the mechanical stretching of the envelope is such that the casing undergoes an elongation A L according to equation 1.

In the embodiments where the sensor 2 is maintained in position in step 401, without mounting the sensor 2 to the casing at the points of connection 1 71, the method may include the step 404 of attachment of the device holding the sensor 1 1 2 1 0 to the casing at the connection points 1. 71 Alternatively, this step of attaching the support device 1 1 of the sensor 2 to the casing 10 may be performed before or during step 403.

At step 405, the envelope 1 0, to which are fixed the fiber portions 120 and 1 21 at the passage openings and the retaining device of the sensor 2, is released so that the envelope back in position. This results in distension on each fiber of Portion 1 20 and 21 January.

The optical fiber sensor device 1 thus obtained can then be used in any operating environment where the temperature is less than T max .

5 illustrates the manufacturing method according to the second embodiment where the stretching of the fiber is performed by thermal expansion.

At step 500, the optical fiber sensor 2 is assembled and incorporated into the casing 10 so that the fiber 12 passes through the passage openings 130 and 140, without being fixed thereto and each fiber portion 120 and 121 extends substantially in a straight line as described in connection with step 400 of Figure 4.

At step 501, the optical fiber sensor 2 is maintained in position as described in connection with step 401 of Figure 4 (by means of a holding jig or by prior fixing of the sensor support device 1 1 to the casing 10).

At step 502, pre-assembled elements of the optic sensor device 1 are exposed to a temperature T greater than the maximum operating temperature T max of the sensor device 1, using a heating system. The heating system is switched between an initial temperature T 0 and the temperature is increased until the temperature stabilizes at the ΤΊ temperature.

By increasing the operating temperature gradually to ΤΊ temperature while maintaining in position the optical fiber sensor 2, the casing 10 expands more than the sensor 2, which generates a differential elongation of the casing 10 relative the sensor 2.

At step 503, the fiber 12 is fixed to the casing at each passage opening 130 and 140, for example by gluing. Assuming that the fixing of the fiber 12 to the casing 10 is carried out at ΤΊ temperature, the heat expansion process allows to obtain a differential elongation A ' L of the envelope relative to the sensor, according to equation 3 . It thus appears distension at each portion of fiber 120 and 121, which depends on this differential elongation.

In the embodiments where the sensor 2 is maintained in position in step 501, without mounting the sensor 2 to the casing at the connection points 171, the method may comprise a step 504 for fixing the holding device 1 1 of the sensor 2 to the casing 10 at the connection points 171. Alternatively, this step of attaching the support device 1 1 of the sensor 2 to the casing 10 can be performed at any time before, during or after step 503.

At step 505, the envelope is reduced to a temperature lower than T1 (e.g. ambient temperature), which can be restored to an equilibrium position.

The optical fiber sensor device 1 thus obtained can then be used in any operating environment where the temperature is lower than

The various embodiments proposed thus possible to obtain a stretching of the optical fiber portions 120 and 121 on either side of the sensor 2, prior to attachment of the fiber to the shell at the level of the passage openings. The extra length of fiber thus obtained makes it possible to limit the risk of stiffness of the tensioned fiber regardless of the operating range (in particular irrespective of the temperature range) while filtering mechanical disturbances that may come from outside the sensor fiber 12.

The optical fiber sensor device 1 thus obtained is characterized by a particular law of variation of the wavelength with respect to a stretching applied to the device, as illustrated in Figure 6, regardless of the applied stretching process ( thermal expansion, by mechanical stretching) and independently of the drawing process applied during manufacture of the sensor device 1. Specifically, the wavelength of the light passing through the optical fiber of the sensor device 1 is a linear function of a stretch parameter corresponding to a stretching applied to said sensor means, the linear function having a slope of rupture for a critical value of the stretch parameter.

Thus, if a progressive stretching is applied to the sensor device 1 (after manufacturing), represented by a stretch parameter S, it was observed that the λ wavelength increases in function of the stretching to a S value

SO critical according to a first growing right 50 and, after the critical value SO according to an increasing second straight line 51, the director of the second right coefficient being greater than the slope of the first line 50. The break in slope (change from the first straight 50 to the second line 51) is thus produced at the point sO which may correspond substantially to the bonding temperature of the fiber to the shell 10 or to the maximum stretching of the casing 10 according to the embodiment of the manufacturing process . Once the breaking point is reached, the fiber 12, within the cavity 3, is stretched.

The various embodiments of the invention permit therefore to obtain a good operation of the optical fiber sensor device 1 in a wide range of use, especially temperature, by introducing such an overlength fiber between the 2 sensor and its casing 10, during the manufacturing process of the device 1. Such a solution has no impact on the volume of the cavity 3 bounded by the casing 10. In addition, various embodiments of the invention reduces the risk of breakage of the optical fiber. Indeed, fiber displacements are very small, the elongation of the fiber during the manufacturing process does not cause buckling of the optical fiber can cause a breakage of the fiber 12. In performing the

The invention is not limited to the embodiments described above by way of example. It encompasses all the variants that may be envisaged by the skilled person. In particular, the invention is not limited to a particular number of connection zones between the sensor 2 and

the casing 10. In addition, it is not limited to a particular application or sensor to a particular form of casing. In some embodiments particularly, the casing 10 may be made of different materials and various elements assembled together to form an envelope.

Furthermore, although the invention has been described in connection with an embodiment where the casing 10 comprises a single fiber sensor 2, it can also be applied to a plurality of sensors connected in parallel (all sensors can be for example held by a common holding device 1 1) or in series.

claims

1. A method of making a fiber optic sensor device (1) comprising a casing (10) delimiting a cavity (3) and an optical fiber sensor (2), said optical fiber sensor comprising an optical fiber (12) and a sensor holder (1 1) integral with the optical fiber, said holder being traversed by the optical fiber between two fixing points provided on said holder, characterized in that it comprises the steps of :

- positioning the optical fiber sensor (2) in the casing (1 0) so as to passing the fiber (1 2) through two passages (1 30 and 140) provided on the casing (1 0) , the optical fiber extending generally along a longitudinal axis into said cavity (3), which delimits two optical fiber portions in the casing on either side of the holding device (1 1), each portion fiber extending between one of said mounting points of the holding device and said passage openings of the casing, substantially in a straight line;

- maintaining the fiber optic position sensor;

- perform a differential elongation of the casing (1 0) with respect to the optical fiber sensor (2) in the longitudinal direction and outwardly of the casing (1 0), while the optical fiber sensor remains held in position;

- fixing the optical fiber to the casing (10) at said passage openings; and

- returning the casing (1 0) in an equilibrium position.

2. The manufacturing method according to claim 1, characterized in that said differential fiber elongation step is performed by mechanically stretching the envelope (10) in said longitudinal direction on each side of the casing (1 0 ), outwardly of the casing, and in that the envelope is returned to said equilibrium position by releasing the envelope.

3. The manufacturing method according to claim 2, characterized in that the differential elongation A L of the envelope (1 0) with respect to the optical fiber sensor (2) satisfy a constraint on the ambient temperature T s at the time fixing the fiber to the shell (10), the maximum temperature T max of operation of the sensor fiber (2), the thermal expansion coefficient A c of the sensor fiber (2) and the thermal expansion coefficient edit Chapter Ρ of the casing (10).

4. The manufacturing method according to claim 3, characterized in that said stress is defined by the inequality:

AL— ~^~ · λρ (Jmax ~ Ts)— . Ac (Tmax— Ts) ,

wherein A c denotes the coefficient of thermal expansion of the fiber sensor (2) edit Chapter Ρ the coefficient of thermal expansion of the envelope, L c is the length of the fiber sensor (2), L P denotes the length of the casing (10), T s the surrounding temperature at the time of fixing the fiber to the shell (10), and T max the maximum operating temperature of the sensor.

5. The manufacturing method according to claim 1, characterized in that said differential elongation step is performed by differential thermal expansion of the shell (10) relative to the optical fiber sensor (2) by increasing the temperature up at a higher expansion temperature than the maximum operating temperature set for the fiber optic sensor device (1), and in that the envelope is brought in said position of equilibrium by reducing the temperature to a temperature below the expansion temperature.

6. The manufacturing method according to claim 5, characterized in that the envelope 10 is chosen to have a coefficient of thermal expansion according to the equation:

wherein A c denotes the thermal expansion coefficient of the sensor holder (2), A P thermal expansion coefficient of the envelope, L c is the length of the holding device (1 1), and L P denotes the length of the casing (10).

7. The manufacturing method according to claim 6, characterized in that the differential elongation of the casing (10) is equal to:

Si =. l R (T - T 1 ) -! . la (T - rj

wherein A c denotes the thermal expansion coefficient of the sensor (1 1), edit Chapter Ρ the coefficient of thermal expansion of the envelope, L c is the length of the holding device (1 1), L P denotes the length of the casing (10), T is the operating temperature, and ΤΊ the expansion temperature.

8. Manufacturing process according to one of the preceding claims, characterized in that the fiber bonding step to the casing at the level of openings comprises a bonding fiber at the locking points.

9. Manufacturing process according to one of the preceding claims, characterized in that it further comprises attaching the sensor fiber (2) to the casing (10) at at least one connection zone (171 ).

10. The manufacturing method according to claim 9, characterized in that the fastening of the sensor (2) to the casing (10) at at least one connection zone (171) is realized by gluing.

January 1. Production method according to one of the preceding claims, characterized in that the step of positioning the fiber optic sensor includes the longitudinal positioning of the optical fiber sensor substantially in the middle of the casing.

12. Manufacturing process according to one of the preceding claims, characterized in that the sensor is a hydrophone.

13. An optical fiber sensor (1) comprising a casing (10) delimiting a cavity (3), an optical fiber sensor (2), said optical fiber sensor comprising an optical fiber (12) and a device maintaining (1 1) integral with the optical fiber, said holder being traversed by the optical fiber between two fixing points provided on said holder, characterized in that the optical fiber (12) passes through the envelope at two passage openings (130, 140) provided on the casing (10) and extends generally along a longitudinal axis into said cavity (3), which delimits two portions of optical fiber lengths of data in the envelope, on either side of the holding device (1 1), theshell (10) being secured to the optical fiber (12) at both openings (130, 140) of the envelope, and in that each fiber portion extends between one of said attachment points of the device holding (1 1) and the passage opening (130, 140) of the casing (10) situated on the same side of the optical fiber sensor (2) and is substantially straight, each fiber portion comprising a distention so that the length of each fiber portion extending between a fixing point of the holding device and an opening of the envelope is greater than the geometrical distance between said point of attachment of the retaining device (1 1) and said passage opening.extends between one of said holding device of the fixing points (1 1) and the passage opening (130, 140) of the casing (10) situated on the same side of the optical fiber sensor (2) and is substantially straight line, each fiber portion comprising a distension so that the length of each fiber portion extending between a fixing point of the holder and a passage opening of the envelope is greater than the geometrical distance between said point fixing the holding device (1 1) and said passage opening.extends between one of said holding device of the fixing points (1 1) and the passage opening (130, 140) of the casing (10) situated on the same side of the optical fiber sensor (2) and is substantially straight line, each fiber portion comprising a distension so that the length of each fiber portion extending between a fixing point of the holder and a passage opening of the envelope is greater than the geometrical distance between said point fixing the holding device (1 1) and said passage opening.each fiber portion comprising a distension so that the length of each fiber portion extending between a fixing point of the holder and a passage opening of the envelope is greater than the geometrical distance between said point of attachment of holding device (1 1) and said passage opening.each fiber portion comprising a distension so that the length of each fiber portion extending between a fixing point of the holder and a passage opening of the envelope is greater than the geometrical distance between said point of attachment of holding device (1 1) and said passage opening.

14. A sensor device as claimed in claim 13, characterized in that the wavelength of the light passing through the optical fiber of the sensor device is a linear function of a stretch parameter corresponding to a stretching applied to the sensor device said linear function having a slope of rupture to a critical value of the stretch parameter such that the director of the linear function coefficient after said critical value is greater than the head of the linear function coefficient prior to said critical value.