ES2357388A1 - Optical biparametric sensor based on brillouin effect. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Optical sensor for measuring temperature and elongation in a structure, comprising: an optical flue (1) configured to emit an optical pump signal; at least one optical transducer (6) comprising a first waveguide (14) and a second waveguide (15) connected in series, wherein the first waveguide (14) is configured to provide a spectral response at a frequency brillouin and the second waveguide (15) is configured to offer a spectral response to another brillouin frequency; - an optical input/output device (10) to allow the passage of the optical pump signal to said optical transducer (6) and to allow the passage of a counter-propagating optical signal from said optical transducer (6) towards a coupler optical (7). The at least one optical transducer (6), the optical input/output device (10) and the optical coupler (7) form a ring resonant cavity. When the optical pump signal is injected into the transducer (6), a brillouin effect is generated in each of the waveguides (14, 15) which causes an optical signal centered at a respective brillouin frequency. The optical coupler (7) is capable of reinjecting the optical signals centered at said brillouin frequencies in the ring optical cavity. The measurement of these two frequencies (vb1, vb2) allows to discriminate the elongation and temperature of the structure. (Machine-translation by Google Translate, not legally binding)

Description

Biparameter optical sensor based on effect brillouin.

Field of the Invention

The present invention belongs to the field of techniques and devices for measuring parameters in structures. In concrete, refers to the techniques to measure and monitor in real time elongation and temperature of a structure Dadaist.

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Background of the invention

Various techniques and devices are known to measure parameters in engineering structures, civil works and building. A usual form of deformation sensing in structures is by fiber optic. Thus, the US patent  US4927232 describes a fiber optic system to monitor the possible deformations in a structure analyzing characteristics such as the attenuation or phase of an optical signal transmitted to through that fiber, while European patent EP0404242 B1 proposes a system based on interferometry of optical signals, the possible deformations being reflected as variations of the optical path traveled by the light that propagates through a optical fiber.

Measurement systems have also been developed of tension in structures, such as the one presented in 1994 by D. Inaudi, A. Elamari and S. Vurpillot at the 2nd European Conference on Smart Structures and Materials (Glasgow), which is based on low coherence interferometry for the monitoring of civil engineering structures "). In this The transducer system consists of two fibers terminated in two mirrors, which constitute the two "arms" of a Michelson interferometer.

Within sensing systems, they are known distributed sensing systems based on scattering Brillouin in optical fibers, as proposed in the patent British GB2289331: This technique proposes fiber injection of two radiations against propagators, separated in frequency a value equivalent to \ nu_ {B} for said fiber. In this way, it induces the stimulated Brillouin dispersion process in the fiber (SBS) and, analyzing the intensity of the radiation received after this process, temperature conditions can be deduced or elongation in the fiber. In addition, it proposes the use of signals pulsed in order to perform a distributed sensing and to know these conditions at any point along the fiber.

The international patent application WO03 / 078932 A1 presents another technique based on spectral analysis of light scattered by Brillouin dispersion in a fiber. This technique proposes the use of a trunk fiber from which they leave several sensor fibers towards the different sectors of the structure that you want to monitor. The Brillouin dispersion is driven back by the fiber itself and taken to the detector to through the trunk fiber. It also proposes the use of pulses of different widths to perform analysis with greater or lesser resolution, all in the optical domain. Likewise, the use of a non-tensioned fiber to compensate for temperature effect.

Another sensor based on spontaneous Brillouin dispersion is that provided by US Pat.
US7283216 B1. This sensor incorporates a Brillouin ring laser as a local oscillator in heterodyne detection. The sensor fiber is not part of the resonant cavity, which is 10-20 m long. The laser signal generated in said cavity is used either as a pump to generate the Brillouin scattering in the sensor fiber, or as a reference for the beating with the signal coming from the sensor fiber. Thus, heterodyne detection can be performed at a low frequency (100-500 MHz), which allows detectors with lower bandwidth and greater sensitivity to be used, as well as the ability to process data in real time with the available technology.
commercially

The US patent application US2008 / 0068586 A1 describes an SBS based sensing system that you don't need a manual adjustment of the intensity of the light injected into the fiber, with an elongation measurement accuracy of up to 200 \ mu \ varepsilon.

On the other hand, ring lasers by effect Brillouin have been very developed in recent years and offer very narrow emission lines, which is beneficial in Certain applications U.S. Patent US7272160 B1 proposes a technique to generate an effect ring laser Brillouin with an electronic stability control, a cavity of 10-40 m long and one line width per below 200 Hz.

Carlos Galíndez et al . describe in Temperature sensing in multiple zones based on Brillouin fiber ring laser , Journal of Physics: Conference Series 178 (2009) 012017, a system for sensing a single parameter - in this case the temperature - in multiple zones based on a laser Brillouin The sensing system is based on a fiber optic transducer, where using different fiber sections of different characteristics different areas are represented in which the measurement is allowed. The presence of a single fiber in each zone allows to determine a single parameter (elongation or temperature) in that zone.

On the other hand, O. Fraz \ tilde {a} or et al . describe in Brillouin fiber laser discrete sensor for simultaneous strain and temperature measurement , Applied Physics B, Lasers and Optics 86, pages 555-558 (2007), a tension and temperature sensor consisting of a Fabry-Perot cavity with 20 m of fiber optics between two Bragg networks ( Fiber Bragg Grating FBG).

This sensor has some drawbacks, such as the need to use two Bragg networks, which are devices sensitive to other parameters, which complicates the implementation of sensor, reducing measurement accuracy. In addition, the sensor Fraz \ tilde {a} or requires the length of the optical fiber to be fixed.

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Summary of the Invention

The present invention seeks to solve the problems mentioned above through a sensor system to measure temperature and elongation integrally between two points.

Specifically, in a first aspect of the present invention, an optical sensor for measuring temperature and elongation in a structure is provided, comprising: an optical source configured to emit an optical pumping signal; at least one optical transducer comprising a first waveguide and a second waveguide connected in series; and an optical input / output device configured to allow the passage of the optical pumping signal to said optical transducer and to allow the passage of a counter-propagating optical signal from said optical transducer to an optical coupler. The first waveguide of the optical transducer is configured to offer a spectral response to a given Brillouin frequency and the second waveguide of the optical transducer is configured to deliver a spectral response to a given Brillouin frequency different from the previous one. The at least one optical transducer, the optical input / output device and the optical coupler form a ring resonant cavity, so that when the optical pump signal is injected into the transducer, it is generated in each of the waveguides The transducer forms a Brillouin effect that causes an optical signal centered at a respective Brillouin frequency. The optical coupler is able to reinject into the optical ring cavity, through the optical input / output device, the optical signals centered at the respective Brillouin frequencies. The measurement of these two frequencies allows to discriminate the two parameters, elongation and temperature of the
structure.

Preferably, the sensor further comprises: means for combining the optical pumping signal and the optical signals centered at Brillouin frequencies; a photodetector for convert optical signals into electrical signals; and means for process the electrical signals and determine, from frequency shift between these signals, temperature and elongation to which at least one of the waveguides is subjected.

Preferably, the sensor further comprises a optical amplifier located between the optical source and the optical input / output device to amplify said signal pumping optics

Preferably, the sensor further comprises means for optically isolating the optical source.

Preferably, the optical device of input / output is an optical circulator.

Preferably, the transducer comprises the minus a polarization controller to regulate polarization of the light entering the transducer.

Preferably, each waveguide of the transducer is fixed to a structure at two points of anchor separated a certain distance, along which The temperature and elongation can be measured.

In a possible embodiment, one of the two guides wave is slightly tensioned between the two points of anchor and the other waveguide is longer than that distance, with so that it is only affected by the temperature, staying insensitive to elongation. In another possible embodiment, the two waveguides are tensioned between the two points of anchorage.

In a possible embodiment, the sensor comprises a plurality of transducers connected in series.

In another possible embodiment, the sensor it comprises: a plurality of ring resonant cavities, each one of them formed by an optical transducer, a device optical input / output and an optical coupler; and means for split the optical pump signal generated by the optical source e inject into each ring resonant cavity a part of said split optical signal

Optionally, the at least one transducer It comprises a protective cover.

Preferably, the waveguides that form the At least one transducer is optical fibers.

In another aspect of the invention, a method of sensing temperature and / or elongation is provided, comprising: generating an optical pump signal by an optical source; injecting the optical signal into an optical transducer through an optical input / output device, where the transducer comprises a first waveguide and a second waveguide connected in series, where the first waveguide is configured to provide a response spectral at a given Brillouin frequency and the second waveguide is configured to offer a spectral response to a given Brillouin frequency different from the previous one; spontaneously generate a stimulated Brillouin effect on the transducer, forming an optical signal centered at a Brillouin frequency in each of the waveguides that form the transducer; reinject through an optical coupler the optical signals centered at two Brillouin frequencies into an optical ring cavity formed by the transducer, the optical input / output device and the optical coupler itself, obtaining a backscattered optical signal; extracting said backscattered optical signal from the ring resonant cavity; mix the backscattered optical signal with the optical pump signal; convert the resulting signal to the electrical domain; calculate the temperature and / or elongation between two points to which the transducer has been connected from the Brillouin parameters of the signals
detected.

The advantages of the invention will become apparent. in the following description.

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Brief description of the figures

In order to help a better understanding of the characteristics of the invention, according to an example preferred practical implementation thereof, and to complement This description is accompanied as an integral part of it, a game of drawings, whose character is illustrative and not limiting. In these drawings:

Figure 1 shows a basic scheme of proposed sensor system according to an embodiment of the invention.

Figure 2 shows the structure of the optical transducer according to an embodiment of the invention.

Figure 3 shows a scheme of a system muti-transducer sensor according to a embodiment of the invention.

Figure 4 shows an outline of the three parts of a multitransducer sensor system with N transducers placed in parallel according to an embodiment of the invention.

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Detailed description of the invention

The following describes a bi-parametric active sensor system capable of comprehensively measuring in real time the temperature and total elongation between two points along a structure, regardless of distance. As explained below, between these points are conveniently located optical waveguides in which Brillouin dispersion is generated. The sensor is based on the dependence of Brillouin dispersion effect with the parameters to be measured and with the physical properties of the optical guides. This effect (Brillouin dispersion effect) is stimulated and amplified using a ring resonant cavity, of which the aforementioned guides are part (which can be, for example, optical fibers). Waveguides are the basis of an optical transducer, which is detailed more
ahead.

When an optical (pumping) radiation that propagates through a specific waveguide exceeds a threshold, non-linear scattering of Brillouin can occur; thus a counter-propagating wave is generated whose frequency is shifted by a value called Brillouin frequency (\ nu_ {B}, central value of the Brillouin gain spectrum). That is, the anti-propagating signal is centered on a different optical frequency from the one that originated it. The characteristics of the generated Brillouin dispersion signal depend on the properties of the material that make up the waveguide, such as density, geometric shape, physical structure of the material, among others. Similarly, the frequency of Brillouin also depends on the temperature and elongation conditions ( strain ) to which the waveguide is subjected. If the waveguide is included within a ring-shaped resonant cavity, the Brillouin interaction is reinforced or stimulated by the same light spontaneously dispersed by the material and a more intense and selective Stokes signal can be generated. That is, a Brillouin (SBS) signal is obtained whose spectral bandwidth (Brillouin gain bandwidth) (\ Delta \ nu_ {B}) is very narrow (typical values close to 30 MHz, which over a wavelength 1500 nm equals approximately 0.05 pm). This selectivity in the output signal results in high resolutions in the measure of the variations of the Brillouin frequency, and therefore in the variations in temperature and elongation to which the waveguides are subjected. The temperature and elongation to which the transducer is subjected are determined by the measurement and proper processing of the generated radiations, specifically analyzing the displacement of the Brillouin frequency of each fiber. These two measures allow the correct discrimination of both parameters.

Radiation is reinforced at re-inject them into the ring resonant cavity formed by the aforementioned guides anti-propagating the pumping signal. For the Thus, anti-propagating radiation is made resonate by emitting laser radiation (Brillouin laser) very narrow whose spectral bands depend on the properties of the guides, pumping, temperature and elongation at that the aforementioned guides are submitted.

Figure 1 shows a basic scheme of the proposed sensor system. It is a bi-parametric and integral waveguide sensor comprising an opto-electronic unit A, a channel B and one or more transducers C. The scheme of Figure 1 represents a single transducer, referenced as 6. Other embodiments include several
transducers

The opto-electronic unit A generates and processes optical radiation to induce the effect Brillouin in transducer or transducers 6, detects it, treats it And measure it. The opto-electronic unit A in the figure 1 comprises the following elements: a coherent optical source 1, which is protected by an optical isolator 2 located at the exit of the source; an optical amplifier 4; a device 10 that allows the input and output of optical signals from / to the device transducer 6; and an analyzer system 9 of the optical signal 9. The opto-electronic unit A also needs others optical devices 3 7 8 optical signal distributors, which divide or combine the light depending on the function that is needed inside the sensor These elements 3 7 8 can be realized by optical couplers Preferably, the device 10 is implemented by a spinner or optical circulator. Alternatively, device 10 can be implemented by a optical coupler

Optical source 1 must be chosen that:

i.

the pumping signal must have a density of enough energy to generate the Brillouin effect in the transducer waveguides 6.

ii.

must be protected from possible retro-dispersions that interfere with the generation of the Brillouin effect and / or damage it.

In addition, the optical device 10 must allow the input of the optical signals to the transducer device 6 and collect the scatter signal from the device transducer 6.

Channel B is composed of sections of guides wave and connect the opto-electronic unit with the o the transducers 6. These two waveguides are implemented so that the Brillouin effect is not present.

The resonant cavity A is created by the device 10, optical coupler 7 and transducer 6. As has been said, the device 10 is preferably implemented by a optical circulator 10. Circulator 10 directs the signals from the coupler 3 located at the input of the amplifier optical 4 towards transducer 6 and those coming from the latter towards the coupler 7.

Figure 2 shows an implementation preferred of the optical transducer 6. The transducer 6 is formed by two sections of waveguides 14 15 of different characteristics physical (such as, for example, doping, index profile, etc.), in order to obtain different spectral responses with different frequencies of Brillouin (\ nu_ {B1}, \ nu_ {B2}).

The waveguides are preferably fibers Optical More preferably, it is implemented with two single mode fibers of different characteristics. Also preferably, the transducer 6 further comprises one or more devices 5 polarization controllers to regulate optical polarization of the signals entering the ring cavity. Controllers of polarization 5 serve to optimize the interaction between the two anti-propagating optical signals in the two guides cool.

The signal to noise ratio of the two sections of waveguides 14 15 is improved if they are part of a cavity in ring thanks to amplification. In other words, the cavity is used to generate the stimulated dispersion of Brillouin and said dispersion is used as an amplification and filtering element Very selective optical.

In transducer 6, so many signals originate by Brillouin effect (at different Brillouin frequencies \ nu_ {B1}, \ nu_ {B2}) as different guides (14, 15) have been used. Simultaneously, all radiation lines generated (\ nu_ {B1}, \ nu_ {B2}) in transducer 6 (signals per effect Brillouin) are mixed (in the coupling element 8) with a sample of the light radiation of the pumping laser 1 (figure 1), the which are detected in real time. The emission lines in optical frequencies are transferred to electrical frequencies (photodetector 11 of figure 1) determining in real time their values using an electric spectrum analyzer, frequency meters or similar equipment 9. By algorithmic methods of processing, which are not part of the present invention, are determine in real time the elongation and the temperature at which submit each of the guides of each transducer assembly, as well as of other variables that may derive from elongation ("strain") and / or temperature.

As stated, waveguides 14 15 are preferably implemented by optical fibers. Consequence of the properties of SBS in optical fibers, the different lines emitted by each fiber of the transducers are very selective, what which contributes to improve resolution and accuracy to the extent of frequency shift and consequently in resolution and temperature accuracy and / or elongation.

A form of implementation is proposed using a transducer device comprising two guides of wave 14 15, for example optical fibers. The guides 14 15 are located between the points whose elongation or "strain" is to be measured, being able to be either integrated in the structure or pre-tensioned between the two separate ends a distance L by means of an anchoring element 13. The guides are fix the structure at two points that coincide with the point of beginning of the first fiber and the end point of the second fiber and vice versa. With this configuration the measurement of both the temperature as of the elongation to which the transducer units, such as the one outlined in Figure 2. The guides 14 15 respond to elongation and temperature between anchoring elements 13 since the frequency of the line of emission by Brillouin effect (signals by Brillouin effect) in them It depends on these factors. The correct characterization of the guides 14 15 in temperature and elongation and the correct processing of the emission lines by Brillouin effect through data matrices crossed allows discrimination of temperature and elongation in the transducer. A sample of the optical signal with the that the Brillouin effect has been generated can be used as local oscillator to beat with Stokes signals (or lines of emission by Brillouin effect) from the transducer. This is reflected in figure 1 since the line that joins 3 and 8 is the path by the one that takes this sample up to 8 where the milkshake takes place, or mixing, with the emission lines by Brillouin effect coming of the transducer 6.

In a specific implementation of the transducer implemented in optical fiber, which should be considered illustrative and not limiting, one of the optical fibers is lax to discriminate the effect of temperature, while the other fiber is tensioned to provide elongation information, such as This is the case in Figure 2. Alternatively, since the two fibers have different physical characteristics, an arrangement can be used in which both fibers are tensioned. In this case, both temperature and elongation ( strain ) can be measured in both waveguides. In the example of Figure 2, the fibers are optically connected in series and are anchored between two separate points a distance L, which corresponds to the length of the transducer.

The transducer can optionally incorporate a protective cover 16, which can be rigid or flexible, to in order to detect both elongations and curvatures in the structure.

The transducer of Figure 2 has the following features:

i.

comprises two fibers optically connected in series, which are part of a resonant cavity (ring in this case).

ii.

The optical waveguides 14 15 should have the lengths suitable for generating the Brillouin effect (\ nu_ {B1}, \ nu_ {B2}) sufficient depending on the powers Pumping to interrogate them.

iii.

The length of the optical waveguide does not it must necessarily be the same for both waveguides (ex. Fibers) 14 15 that constitute the transducer.

iv.

The optical waveguides 14 15 must be optically connected

v.

The protective cover 16 must not insulate the transducer of external temperature changes or elongation of the fiber.

saw.

The polarization of the optical field that enters and leaves of the transducer must be controlled and maximized in order to obtain an efficient gain value from Brillouin, since this phenomenon is dependent on polarization.

An example is provided below. concrete implementation of the sensor device in technology fiber optic, according to the scheme in figure 1. This example It should be considered illustrative and not limiting. The optical source 1 is a laser that generates the signal for pumping and the local oscillator using coupler 3. The light that is injected into the cavity is previously amplified using an optical amplifier 4, which in this Example is an EDFA. The signal enters the cavity through a optical circulator 10, which in turn serves to extract the signal of spontaneously generated Brillouin dispersion (at frequencies \ nu_ {B1}, \ nu_ {B2}) and reinjected by the opposite end of the fiber, thereby closing the fiber ring (cavity in ring). With transducer polarization controllers 5 (see figure 2) the polarization of the light is regulated in order to Maximize the Brillouin effect. 1% of Stokes signal is extracted of the cavity using a coupler 7 (I could be of coupling ratio, RA, 99: 1 although other coupling ratios are possible) which is whipped with a sample of the initial laser signal using a coupler 8 (may be RA 50:50 although other coupling relationships are possible). This optical signal is converted into an electrical signal using a photodetector 11 and can be measured 9, for example, by means of an analyzer of electrical spectra (AEE) or meter of the frequency in the electrical domain. The detection and analysis of the backscattered signal can be made by heterodining or through homodinaje.

Figure 3 shows a possible implementation of a multi-transducer sensor system with a opto-electronic unit A, one channel B and one plurality of N transducers C. The N transducers 6.1 6.2 ... 6.N they are optically connected in series and are interrogated simultaneously through a single unit opto-electronics A made with a single laser one.

Figure 4 shows another possible implementation of a multitransducer sensor system with N transducers 6.1 6.2 ... 6.N placed in parallel, forming N cavities and N its subsystems demodulation and using the signal from a single laser 1. Element 12 is responsible for dividing the laser output into N identical optical signals. Element 12 is therefore a coupler or optical splitter.

The examples in Figures 3 and 4 allow, Using the same optical source, get 2N signals to measure the temperature and / or elongation in N sections of a structure.

The described sensor device can be implemented with fiber optic technology and used for Real-time monitoring of a wide variety of structures. The sensor, simple to implement, is able to measure in real time variations in integral temperature and total elongation between two points The separation distance between the points can be in a range that includes tens of meters and tens of kilometers; therefore the spectrum of structures in which it You can implement it is very varied.

The invention is applicable, among other domains, to the typical structures of engineering, civil works and construction, as well as in any other domain where required monitor in real time the elongation or temperature of a given structure. In addition, elongation and temperature measurements they can be used to determine other variables indirectly, Like mechanical tension. Transducers and optical channels can be both embedded and properly located in the surface of the structure to be monitored.

Claims (14)

1. An optical sensor to measure temperature and elongation in a structure, comprising: - an optical source (1) configured to emit an optical pumping signal; - at least one optical transducer (6) that comprises a first waveguide (14) and a second waveguide (15) connected in series; - an optical input / output device (10) configured to allow the passage of the pumping optical signal towards said optical transducer (6) and to allow the passage of a signal anti-propagating optics from said transducer optical (6) towards an optical coupler (7); where the optical sensor is characterized in that the first waveguide (14) of the optical transducer (6) is configured to offer a spectral response to a certain Brillouin frequency (nu B1) and the second waveguide (15) of the optical transducer (6) is configured to offer a spectral response to a certain Brillouin frequency (nu B2) different from the previous one, and where said at least one optical transducer (6), said optical input / output device ( 10) and said optical coupler (7) form a ring resonant cavity, so that when said optical pumping signal is injected into the transducer (6), it is generated in each of the waveguides (14, 15) that the transducer (6) forms a Brillouin effect that causes an optical signal centered at a respective Brillouin frequency (\ nu_ {B1}, \ nu_ {B2}), and where said optical coupler (7) is able to reinject into the optical cavity in ring, through the optical input device gives / outputs (10), said optical signals centered at said respective Brillouin frequencies (\ nu_ {B1}, \ nu_ {B2}), allowing the measurement of these two frequencies (\ nu_ {B1}, \ nu_ {B2}) discriminate the two parameters, elongation and temperature, of said structure. 2. The sensor of claim 1, which It also includes: - means (3, 8) for combining the optical signal of pumping and optical signals centered at frequencies Brillouin; - a photodetector (11) to convert said optical signals in electrical signals; Y - means (9) for processing said signals electrical and determine, from frequency offset between said signals, the temperature and elongation to which it is subjected at least one of said waveguides (14,15). 3. The sensor of any of the claims 1 or 2, further comprising an optical amplifier located between the optical source (1) and the optical device of input / output (10) to amplify said optical signal of pumping. 4. The sensor of any of the previous claims, further comprising means (2) for optically isolate said optical source (1). 5. The sensor of any of the previous claims, wherein said optical device of input / output (10) is an optical circulator. 6. The sensor of any of the previous claims, wherein said transducer (6) comprises at least one polarization controller (5) to regulate the polarization of the light entering the transducer (6). 7. The sensor of any of the previous claims, wherein each waveguide (14, 15) of said transducer (6) is fixed to a structure in two anchor points (13) separated a certain distance (L), at along which the temperature and elongation can be measured. 8. The sensor of claim 7, wherein a of the two waveguides (14) is slightly tensioned between the two anchor points (13) and where the other waveguide (15) is longer than said distance (L), so that only is affected by the temperature, remaining insensitive to the elongation. 9. The sensor of claim 7, wherein the two waveguides (14, 15) are tensioned between the two anchor points (13). 10. The sensor of any of the previous claims, comprising a plurality of transducers (6.1, 6.2, ..., 6.N) connected in series. 11. The sensor of any of the claims 1-9, comprising: - a plurality of ring resonant cavities, each formed by an optical transducer (6.1,
6.2, ..., 6.N), an optical input / output device (10) and an optical coupler (7); Y - means (12) for dividing the optical signal of pumping generated by the optical source (1) and inject into each cavity ring resonant a part of said split optical signal. 12. The sensor of any of the previous claims, wherein said at least one transducer (6) It comprises a protective cover (16). 13. The sensor of any of the previous claims, wherein said waveguides (14, 15) forming said at least one transducer (6) are optical fibers. 14. A method of temperature sensing and elongation, which comprises: - generate an optical pump signal by an optical source (1); - injecting said optical signal into a transducer optical (6) through an optical input / output device (10), wherein said transducer (6) comprises a first waveguide (14) and a second waveguide (15) connected in series, where the first waveguide (14) is configured to offer a spectral response to a given Brillouin frequency (\ nu_ {B1}) and the second waveguide (15) is configured to offer a spectral response at a certain frequency Brillouin (\ nu_ {B2}) different from the previous one; - generate an effect spontaneously Brillouin stimulated in said transducer (6), forming a signal optics centered at a Brillouin frequency (\ nu_ {B1}, \ nu_ {B2}) in each of the waveguides (14, 15) that form the transducer (6); - reinject through an optical coupler (7) said optical signals centered at two Brillouin frequencies (\ nu_ {B1}, \ nu_ {B2}) in an optical ring cavity formed by the transducer (6), the optical input / output device (10) and the optical coupler itself (7), obtaining an optical signal backscattered; - extracting said backscattered optical signal from the ring resonant cavity; - mixing (8) said backscattered optical signal with the optical pumping signal; - convert the signal to the electrical domain (9) resulting; - calculate the temperature and elongation between two points to which the transducer (6) has been connected from the measurements of the two Brillouin frequencies (\ nu_ {B1}, \ nu_ {B2}) of the detected signals.