CN114777823A - FLRD sensor system and FLRD sensing device based on phase drift - Google Patents
FLRD sensor system and FLRD sensing device based on phase drift Download PDFInfo
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Abstract
The invention discloses an FLRD sensor system and an FLRD sensing device based on phase drift, belonging to the technical field of optical fiber sensing, wherein the system comprises: signal light generating means for generating signal light and reference light; the FLRD sensor is arranged on a propagation light path of the signal light and used for sensing the quantity to be detected so that the signal light carries the information of the quantity to be detected; the signal light detection module is arranged on an output light path of the FLRD sensor and used for detecting information signal light carrying the quantity to be detected and converting the information signal light into a first electric signal; the reference light detection module is arranged on a propagation light path of the reference light and is used for detecting the reference light and converting the reference light into a second electric signal; and a demodulator for extracting the phases of the two paths of electric signals respectively and calculating the phase difference
Then according to
When calculatingThe constant of decay τ is varied to complete the measurement; preferably, the signal light and the reference light are extracted via the same modulator. The invention can improve the measurement precision of the PS-FLRD system.
Description
Technical Field
The invention belongs to the technical field of optical fiber sensing, and particularly relates to an FLRD sensor system and an FLRD sensing device based on phase drift.
Background
The Cavity Ring-Down (CRD) technique is a spectrum detection technique, and compared with the conventional spectrum detection technique, the Cavity Ring-Down (CRD) technique can transmit signal light circularly in a Cavity, thereby greatly enhancing the absorption of a substance to light and greatly improving the detection sensitivity. And because the CRD technology measures the decay rate of the signal, not the decay value of the signal, the influence of the light source jitter on the result is avoided. The earliest CRD technique employed a cavity consisting of two high-reflectivity mirrors, coupling sine-wave modulated light into the cavity, and measuring the intra-cavity loss by detecting the change in the phase of the input and output light. However, the cavity formed by the high-reflection mirror needs to be aligned strictly, and the problems of mode matching and the like exist. And the optical fiber has low loss and is easy to couple with the optical fiber, so that the optical fiber is introduced into a CRD system, and a fiber ring cavity ring-down technology is provided.
The phase-shifting fiber loop attenuation (PS-FLRD) method is that two couplers with high coupling ratio are connected to form a loop. The optical signal can repeatedly pass through a detection area in the optical fiber loop, the intensity and phase change of the signal caused by attenuation can be accumulated in the loop, and the loss in the loop cavity can be demodulated by detecting the phase change of input light and output light. In the PS-FLRD, on one hand, as the light repeatedly passes through the detection region, the influence of the loss of the optical fiber is amplified, resulting in very high sensitivity of the whole system, and on the other hand, since the loss is obtained by measuring the phase drift, the detection result is not affected by the fluctuation of the laser power, and the whole system is more stable.
Based on the above advantages, PS-FLRD has been widely used for biochemical measurements such as gas absorption and solution concentration, but there are some problems, mainly expressed in the following two aspects:
(1) the PS-FLRD system demodulates the concentration of gas mainly by detecting the phase shift, while the laser and Photo Detector (PD) are very sensitive to the phase shift, and since the half-wave voltage of the modulator shifts during long-time operation, the phase of the modulated light also shifts accordingly, which greatly affects the stability of the PS-FLRD system. Therefore, the sensitivity of the system to the phase is seriously related to the measurement range, stability and resolution of the system to the gas concentration.
(2) The mapping from phase drift to loss is derived theoretically, the existing method further demodulates the fiber loss by using a formula in a PS-CRD system after the phase drift is obtained by calculation, the calculation and derivation process adopts an approximate continuous cavity length condition, and in practical application, the cavity length is several meters to dozens of even hundreds of meters in the PS-FLRD and cannot be ignored, so that the cavity length can be output only through light of integral multiple of the loop length, and the result obtained by demodulation by the existing method has inherent errors and influences the loss detection precision.
Disclosure of Invention
In view of the shortcomings and needs in the art, the present invention provides an FLRD sensor system and a phase drift based FLRD sensing device, which aims to improve the measurement accuracy of PS-FLRD system.
To achieve the above objects, according to one aspect of the present invention, there is provided an FLRD sensor system including: the device comprises a signal light generating device, an FLRD sensor, a signal light detection module, a reference light detection module and a demodulation device;
signal light generating means for generating reference light and signal light; the reference light and the signal light are modulated sinusoidal light and are generated by the same light source;
the FLRD sensor is arranged on a propagation light path of the signal light and used for sensing the quantity to be detected so that the signal light carries the information of the quantity to be detected;
the signal light detection module is arranged on an output light path of the FLRD sensor and used for detecting information signal light carrying the quantity to be detected and converting the information signal light into an electric signal which is recorded as a first electric signal;
the reference light detection module is arranged on a propagation light path of the reference light, is used for detecting the reference light and converting the reference light into an electric signal, and records the electric signal as a second electric signal;
a demodulation device connected with the signal light detection module and the reference light detection module for respectively extracting the phases of the first electrical signal and the second electrical signal and calculating the phase difference
Then according to
Calculating a time decay constant tau to finish the measurement of the quantity to be detected;
where L represents the loop length in the FLRD sensor, Ω represents the angular modulation frequency, v represents the speed of light in the fiber, Δ t represents the additional travel time compared to the travel time in the fiber, and n represents the number of turns that the signal light has traveled along the FLRD sensor.
Further, the signal light generating device includes: a light source, a signal generator, a modulator and a first coupler;
a light source for generating an original light beam;
a signal generator for generating a modulation signal;
the modulator is arranged on an output optical path of the light source, connected with the signal generator and used for modulating the original light beam into sinusoidal light according to the modulation signal;
the first coupler is arranged on an output light path of the modulator and is used for dividing the sinusoidal light output by the modulator into two parts, wherein the sinusoidal light of the larger part serves as signal light, and the sinusoidal light of the smaller part serves as reference light.
Furthermore, the signal light detection module and the reference light detection module are photodetectors of the same type.
Furthermore, the demodulation device comprises a phase-locked amplifier and a demodulation module;
a phase-locked amplifier connected with the signal light detection module and the reference light detection module for respectively extracting the phases of the first electrical signal and the second electrical signal and calculating the phase difference
A demodulation module for demodulating a signal based on
The time decay constant tau is calculated and,to complete the measurement of the quantity to be detected.
Further, the FLRD sensor includes: the sensing unit comprises a first coupler, a second coupler, a third coupler and a sensing unit; the second coupler and the third coupler are both 1 × 2 couplers;
a port 1 of the second coupler is connected with a port 1 of the third coupler, and a high coupling ratio end of the second coupler and a high coupling ratio end of the third coupler are respectively connected with two ends of the sensing unit;
the low coupling ratio end of the second coupler is used as the input end of the FLRD sensor, and the low coupling ratio end of the third coupler is used as the output end of the FLRD sensor.
In accordance with another aspect of the present invention, there is provided a phase drift based FLRD sensing device, comprising: the device comprises a light source, a signal generator, a modulator, a first coupler, an FLRD sensor, a signal light detection module, a reference light detection module and a phase difference calculation module;
a light source for generating an original light beam;
a signal generator for generating a modulation signal;
the modulator is arranged on an output optical path of the light source, connected with the signal generator and used for modulating the original light beam into sinusoidal light according to the modulation signal;
the first coupler is arranged on an output light path of the modulator and is used for dividing the sine light output by the modulator into two parts, wherein the sine light of the larger part is used as signal light, and the sine light of the smaller part is used as reference light;
the FLRD sensor is arranged on a propagation light path of the signal light and is used for sensing the quantity to be detected so that the signal light carries the information of the quantity to be detected;
the signal light detection module is arranged on an output light path of the FLRD sensor and used for detecting information signal light carrying the quantity to be detected and converting the information signal light into an electric signal which is recorded as a first electric signal;
the reference light detection module is arranged on a propagation light path of the reference light, is used for detecting the reference light and converting the reference light into an electric signal, and records the electric signal as a second electric signal;
phase difference calculation module forConnected with the signal light detection module and the reference light detection module, and used for respectively extracting the phases of the first electric signal and the second electric signal and calculating the phase difference
Further, the signal light detection module and the reference light detection module are photodetectors with the same model.
Furthermore, the phase difference calculation module is a phase-locked amplifier.
Further, the FLRD sensor includes: the sensing unit comprises a first coupler, a second coupler, a third coupler and a sensing unit; the second coupler and the third coupler are both 1 × 2 couplers;
a port 1 of the second coupler is connected with a port 1 of the third coupler, and a high coupling ratio end of the second coupler and a high coupling ratio end of the third coupler are respectively connected with two ends of the sensing unit;
the low coupling ratio end of the second coupler is used as the input end of the FLRD sensor, and the low coupling ratio end of the third coupler is used as the output end of the FLRD sensor.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) the invention is based on the transmission characteristic of light in the FLRD, namely, because the cavity length of the FLRD can not be ignored and only the light which is output by integral multiple of the loop length can be output, the light output by the FLRD is discrete rather than continuous, and the relation between the phase and the loss under the discontinuous condition is derived, namely, the relation between the phase and the loss under the discontinuous condition is obtained
The phase difference of the signal light relative to the reference light is obtained through calculation
Then, further according to the formula
The demodulation obtains the optical fiber loss and completes the measurement of the quantity to be detected, because of the demodulation method in the inventionThe method conforms to the transmission characteristic of light in the FLRD, so that the inherent error existing when the traditional PS-CRD formula is applied to the PS-FLRD can be reduced, and the measurement precision of the PS-FLRD system is effectively improved.
(2) The invention divides the modulated light output by the modulator into the signal light and the reference light, because the two lights pass through the same modulator, the drift of the whole system under long-time work caused by the half-wave voltage drift of the modulator can affect the signal light and the reference light simultaneously, and the changes are counteracted when calculating the phase difference.
(3) The invention utilizes the photoelectric detectors with the same model to complete the detection of the signal light and the reference light, so that the background noise of the photoelectric detectors has the same effect on the signal light and the reference light, thereby eliminating the influence of the background noise of the photoelectric detectors on the measurement result in the process of calculating the phase difference, further improving the measurement precision and effectively improving the stability of the system.
(4) The invention utilizes the Lock-in amplifier (LIA) to extract the phases of two paths of signals and calculate the phase difference, and can quickly and accurately complete the calculation of the phase difference.
Drawings
FIG. 1 is a schematic diagram of an FLRD sensor system provided by an embodiment of the present invention;
FIG. 2 is a schematic diagram of an FLRD sensing device based on phase drift according to an embodiment of the present invention;
the same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
the device comprises a 0-signal light generating device, a 1-light source, a 2-signal generator, a 3-modulator, a 4-first coupler, a 5-second coupler, a 6-third coupler, a 7-sensing unit, an 8-first photoelectric detector, a 9-second photoelectric detector, a 10-phase-locked amplifier, an 11-demodulation module and a 12-demodulation device.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
In order to solve the technical problem that the existing PS-FLRD system continues to use a demodulation formula in the PS-CRD system, and has inherent errors, so that the measurement precision is not high, the invention provides an FLRD sensor system and an FLRD sensing device based on phase drift, and the overall thought is as follows: based on the transmission characteristic of light in the FLRD, namely because the cavity length of the FLRD can not be ignored and only light of integral multiple of the loop length can be output, the light output by the FLRD is discrete rather than continuous, the relation between the phase and the loss under the discontinuous condition is obtained by derivation, after the phase difference between the signal light and the reference light is obtained by calculation, the optical fiber loss is demodulated based on the relation between the phase and the loss under the discontinuous condition, thereby the inherent error in the traditional demodulation equation is eliminated and the measurement precision is improved; on the basis, the optical path structure is adjusted, so that the reference light and the signal light are led out through the same modulator, the phase drift caused by the electro-optical modulator is reduced, the measurement precision is further improved, and the stability of the system is improved.
Before explaining the technical solution of the present invention in detail, the principle related to signal demodulation of the present invention is briefly introduced as follows:
assuming that the modulated optical signal is expressed as
Iout0(t)＝I0(1+γsin(Ωt))
In which I0Is the DC component of the output light, Ω represents the angular modulation frequency, γ represents the modulation depth, and t is the optical fiberThe propagation time of (2). In PS-CRD, the cavity length is continuous and the total output light can be written as:
τ is the time decay constant caused by the sensing module and Δ t is the additional propagation time of the light compared to t. However, in the PS-FLRD, the cavity length cannot be ignored, and only light passing through an integer multiple of the loop length can be output. The output light should be discrete rather than continuous. The extra time Δ t is replaced by the following equation:
n represents the number of turns the light has propagated, L represents the loop length, v represents the speed of light in the fiber, and the time decay constant depends on two components:
wherein, tauOptical fiberRepresenting the time decay constant, τ, of the fibreCouplerRepresents the coupler time decay constant; 1/tauOptical fiberRelated to the loss of one turn of transmission in the optical fiber ring, and 1/tauCouplerOnly in relation to the number of passes. When the loss in the optical fiber changes, the attenuation brought by the coupler is not influenced. Thus, α is defined as the transmission of light through one revolution, instead of the decay time constant:
α＝αoptical fiber·αCoupler
Wherein alpha isOptical fiberDenotes the optical fiber transmittance, αCouplerRepresenting coupler transmittance;
based on the above definitions, the total output light formula of PS-FLRD obtained after considering the dispersion of the output light is:
in order to facilitate the derivation of the relationship between the phase and the loss under the discontinuous condition, let:
namely:
therefore, K can be usednCalculating a phase difference
The concrete expression is as follows:
wherein Im (K)n) And Re (K)n) Respectively represents KnThe imaginary and real parts of (c);
because of
Therefore, the first and second electrodes are formed on the substrate,
since in FLRD α <1, the above formula can be simplified as:
based on the above calculation, under discontinuous conditions, the attenuation caused by the sensing unit can be induced by phase shift
The calculation method is consistent with the transmission characteristic of light in the FLRD, inherent errors existing when the demodulation method of the PS-CRD is applied to the PS-FLRD system are eliminated, and the measurement accuracy of the PS-FLRD system is effectively improved.
The following are examples.
Example 1:
an FLRD sensor system, as shown in fig. 1, comprising: the device comprises a signal light generating device 0, an FLRD sensor, a first photoelectric detector 8, a second photoelectric detector 9 and a demodulating device 12;
a signal light generating means 0 for generating reference light and signal light; the reference light and the signal light are modulated sinusoidal light and are generated by the same light source;
the FLRD sensor is arranged on a propagation light path of the signal light and used for sensing the quantity to be detected so that the signal light carries the information of the quantity to be detected;
the second photoelectric detector 9 is arranged on an output light path of the FLRD sensor, and is used for detecting information signal light carrying the quantity to be detected and converting the information signal light into an electric signal which is recorded as a first electric signal;
the first photoelectric detector 8 is arranged on a propagation light path of the reference light, is used for detecting the reference light and converting the reference light into an electric signal, and is recorded as a second electric signal;
a demodulation device 12 connected to the signal light detection module and the reference light detection module for respectively extracting the phases of the first electrical signal and the second electrical signal and calculating the phase difference
Then according to
And calculating a time decay constant tau to finish the measurement of the quantity to be detected.
Based on the foregoing analysis, the phase difference of the two paths of signals is calculated and obtained in the embodiment
Then, the signal demodulation formula adopted, i.e.
The method reflects the relation between the phase and the loss under the discontinuous condition, so that compared with the method for demodulating by directly using a demodulation formula of the PS-CRD, the embodiment can effectively improve the measurement precision.
Referring to fig. 1, in the present embodiment, the signal light generating device 0 includes: a light source 1, a signal generator 2, a modulator 3 and a first coupler 4;
a light source 1 for generating an original light beam;
a signal generator 2 for generating a modulation signal;
the modulator 3 is arranged on an output optical path of the light source 1, connected with the signal generator 2 and used for modulating the original light beam into sinusoidal light according to the modulation signal;
the first coupler 4 is arranged on an output light path of the modulator 3 and is used for dividing the sinusoidal light output by the modulator 3 into two parts, wherein the sinusoidal light of the larger part serves as signal light, and the sinusoidal light of the smaller part serves as reference light;
in the embodiment, the reference light and the signal light are led out through the same modulator, so that the phase drift caused by the electro-optic modulator can be reduced, the measurement precision is further improved, the stability of the system is improved, and the precision and the stability of the system can be obviously improved especially in the application of long-time measurement of optical fiber loss and the like in an environment of strong radiation measurement; in order to further eliminate the influence caused by the environment, it is preferable that the first photodetector 8 and the second photodetector 9 are photodetectors of the same type in this embodiment, so that the influence of the background noise of the photodetectors on the measurement accuracy can be eliminated.
Referring to fig. 1, in the present embodiment, the demodulation apparatus 12 includes a lock-in amplifier 10 and a demodulation module 11;
a lock-in amplifier 10 connected to the signal light detection module and the reference light detection module for respectively extracting the phases of the first electrical signal and the second electrical signal and calculating the phase difference
The phase-locked amplifier can quickly and accurately complete phase extraction and phase difference calculation;
a demodulation module 11 for demodulating the signal according to
And calculating a time decay constant tau to finish the measurement of the quantity to be detected.
Referring to fig. 1, in the present embodiment, the FLRD sensor includes: a second coupler 5, a third coupler 6 and a sensing unit 7; the second coupler 5 and the third coupler 6 are both 1 × 2 couplers; one side of the 1 multiplied by 2 coupler is provided with two ports which are respectively a high coupling ratio end and a low coupling ratio end, and the optical signal energy of the high coupling ratio end is greater than that of the low coupling ratio end; the other side of the 1 x 2 coupler has only one port, namely 1 port;
a port 1 of the second coupler 5 is connected with a port 1 of the third coupler 6, and a high coupling ratio end of the second coupler 5 and a high coupling ratio end of the third coupler 6 are respectively connected with two ends of the sensing unit 7; the sensing unit 7 must be placed at one side where the high coupling ratio ends of the second coupler 5 and the third coupler 6 are connected, and because the sensing unit 7 needs to be disconnected when the initial phase is measured, if the sensing unit 7 is placed at the other side of the ring cavity, the initial phase cannot be measured;
the low coupling ratio end of the second coupler 5 is used as the input end of the FLRD sensor, and the low coupling ratio end of the third coupler 6 is used as the output end of the FLRD sensor; the low coupling ratio end of the third coupler 6 acts as an output to introduce light so that most of the light can circulate in the ring cavity.
Example 2:
a phase drift based FLRD sensing device, as shown in fig. 2, comprising: the device comprises a light source 1, a signal generator 2, a modulator 3, a first coupler 4, an FLRD sensor, a first photoelectric detector 8, a second photoelectric detector 9 and a phase difference calculation module;
a light source 1 for generating an original light beam;
a signal generator 2 for generating a modulation signal;
the modulator 3 is arranged on an output optical path of the light source 1, connected with the signal generator 2 and used for modulating the original light beam into sinusoidal light according to the modulation signal;
the first coupler 4 is arranged on an output light path of the modulator 3 and is used for dividing the sinusoidal light output by the modulator 3 into two parts, wherein the sinusoidal light of the larger part serves as signal light, and the sinusoidal light of the smaller part serves as reference light;
the FLRD sensor is arranged on a propagation light path of the signal light and used for sensing the quantity to be detected so that the signal light carries the information of the quantity to be detected;
the second photoelectric detector 9 is arranged on an output light path of the FLRD sensor, and is used for detecting information signal light carrying the quantity to be detected, converting the information signal light into an electric signal and recording the electric signal as a first electric signal;
the first photoelectric detector 8 is arranged on a propagation light path of the reference light, is used for detecting the reference light and converting the reference light into an electric signal, and records the electric signal as a second electric signal;
a lock-in amplifier 10 connected to the signal light detection module and the reference light detection module for respectively extracting the phases of the first electrical signal and the second electrical signal and calculating the phase difference
In the embodiment, the reference light and the signal light are led out through the same modulator, so that the phase drift caused by the electro-optic modulator can be reduced, the measurement precision is further improved, the stability of the system is improved, and the precision and the stability of the system can be obviously improved especially in the application of long-time measurement of optical fiber loss and the like in an environment of strong radiation measurement; in order to further eliminate the influence caused by the environment, it is preferable that the first photodetector 8 and the second photodetector 9 are photodetectors of the same type in this embodiment, so that the influence of the background noise of the photodetectors on the measurement accuracy can be eliminated.
Referring to fig. 2, in the present embodiment, the FLRD sensor includes: a second coupler 5, a third coupler 6 and a sensing unit 7; the second coupler 5 and the third coupler 6 are both 1 × 2 couplers;
a port 1 of the second coupler 5 is connected with a port 1 of the third coupler 6, and a high coupling ratio end of the second coupler 5 and a high coupling ratio end of the third coupler 6 are respectively connected with two ends of the sensing unit 7;
the low coupling ratio end of the second coupler 5 is used as the input end of the FLRD sensor, and the low coupling ratio end of the third coupler 6 is used as the output end of the FLRD sensor.
The FLRD sensing device based on the phase drift provided by the embodiment is an integrated, miniaturized and high-sensitivity sensing device, and has a good application prospect in the sensing field; in practical application, the sensing unit 7 can be designed according to different quantities to be detected, so that the quantities to be detected can be measured.
For example, in a spatially isointense radiation environment, the optical fiber loss is increased due to the radiation attenuation (RIA) effect, which seriously affects the application of the optical fiber in the radiation environment, and in order to evaluate the effect of the RIA effect, the optical fiber loss needs to be accurately measured. A common method for measuring RIA is Optical Time Domain Reflection (OTDR), but because of its inherent attenuation blind area, it is not possible to detect a short length of optical fiber, the FLRD sensor system provided in this embodiment can be used to realize accurate measurement of optical fiber loss in a strong radiation environment, at this time, the erbium-doped optical fiber is used as a sensing unit, and the FLRD sensor is placed in an irradiation chamber, the RIA effect is a slow process, it takes tens of thousands to thousands of hours to completely exhaust the optical fiber, which requires the system to remain stable for a long time.
In other applications, sensing may be designed at the sensing unit according to different utility requirements. If the highly doped optical fiber is placed at the sensing unit, the loss caused by the optical fiber under the strong radiation environment can be detected; a gas chamber can be arranged at the sensing unit, and different gases or gases with different concentrations are introduced into the gas chamber for gas sensing; a common optical fiber can be placed at the sensing unit, and then pressure is increased on the sensing unit for stress sensing; the sensing unit part can be placed with liquid for refractive index measurement; magnetic field measurement, temperature measurement, and the like can also be realized.
It will be understood by those skilled in the art that the foregoing is only an exemplary embodiment of the present invention, and is not intended to limit the invention to the particular forms disclosed, since various modifications, substitutions and improvements within the spirit and scope of the invention are possible and within the scope of the appended claims.
Claims (9)
1. An FLRD sensor system, comprising: the device comprises a signal light generating device, an FLRD sensor, a signal light detection module, a reference light detection module and a demodulation device;
the signal light generating device is used for generating reference light and signal light; the reference light and the signal light are modulated sinusoidal light and are generated by the same light source;
the FLRD sensor is arranged on a propagation light path of the signal light and used for sensing a quantity to be detected so that the signal light carries information of the quantity to be detected;
the signal light detection module is arranged on an output light path of the FLRD sensor, and is used for detecting information signal light carrying the quantity to be detected and converting the information signal light into an electric signal which is recorded as a first electric signal;
the reference light detection module is arranged on a propagation light path of the reference light, and is used for detecting the reference light and converting the reference light into an electric signal which is recorded as a second electric signal;
the demodulation device is connected with the signal light detection module and the reference light detection module and used for respectively extracting the phases of the first electric signal and the second electric signal and calculating the phase difference
Then according to
Calculating a time decay constant tau to complete the measurement of the quantity to be detected;
where L represents a loop length in the FLRD sensor, Ω represents an angular modulation frequency, v represents a speed of light in an optical fiber, Δ t represents an additional propagation time compared to a propagation time in an optical fiber, and n represents a number of turns the signal light has propagated along the FLRD sensor.
2. The FLRD sensor system of claim 1, wherein the signal light generating means comprises: a light source, a signal generator, a modulator and a first coupler;
the light source is used for generating an original light beam;
the signal generator is used for generating a modulation signal;
the modulator is arranged on an output optical path of the light source, is connected with the signal generator and is used for modulating the original light beam into sinusoidal light according to the modulation signal;
the first coupler is arranged on an output light path of the modulator and is used for dividing the sinusoidal light output by the modulator into two parts, wherein the larger part of the sinusoidal light is used as the signal light, and the smaller part of the sinusoidal light is used as the reference light.
3. The FLRD sensor system according to claim 1 or 2, wherein the signal light detection module and the reference light detection module are the same type of photodetector.
4. The FLRD sensor system according to claim 1 or 2, wherein the demodulating means comprises a lock-in amplifier and a demodulating module;
the lock-in amplifier is connected with the signal light detection module and the reference light detection module and is used for respectively extracting the phases of the first electric signal and the second electric signal and calculating the phase difference
The demodulation module is used for demodulating the data according to
And calculating a time decay constant tau to finish the measurement of the quantity to be detected.
5. The FLRD sensor system of claim 1 or 2, wherein the FLRD sensor comprises: the sensing unit comprises a first coupler, a second coupler, a third coupler and a sensing unit; the second coupler and the third coupler are both 1 × 2 couplers;
a port 1 of the second coupler is connected with a port 1 of the third coupler, and a high coupling ratio end of the second coupler and a high coupling ratio end of the third coupler are respectively connected with two ends of the sensing unit;
the low coupling ratio end of the second coupler is used as the input end of the FLRD sensor, and the low coupling ratio end of the third coupler is used as the output end of the FLRD sensor.
6. A phase drift based FLRD sensing device, comprising: the device comprises a light source, a signal generator, a modulator, a first coupler, an FLRD sensor, a signal light detection module, a reference light detection module and a phase difference calculation module;
the light source is used for generating an original light beam;
the signal generator is used for generating a modulation signal;
the modulator is arranged on an output optical path of the light source, connected with the signal generator and used for modulating the original light beam into sinusoidal light according to the modulation signal;
the first coupler is arranged on an output light path of the modulator and is used for dividing the sinusoidal light output by the modulator into two parts, wherein the larger part of the sinusoidal light is used as the signal light, and the smaller part of the sinusoidal light is used as the reference light;
the FLRD sensor is arranged on a propagation light path of the signal light and used for sensing a quantity to be detected so that the signal light carries information of the quantity to be detected;
the signal light detection module is arranged on an output light path of the FLRD sensor, and is used for detecting information signal light carrying the quantity to be detected and converting the information signal light into an electric signal which is recorded as a first electric signal;
the reference light detection module is arranged on a propagation light path of the reference light, and is used for detecting the reference light and converting the reference light into an electric signal which is recorded as a second electric signal;
the phase difference calculation module is connected with the signal light detection module and the reference light detection module and used for respectively extracting the phases of the first electric signal and the second electric signal and calculating the phase difference
7. The phase-drift-based FLRD sensing device of claim 6, wherein said signal light detection module and said reference light detection module are the same type of photo-detector.
8. The FLRD sensing device of claim 6 or claim 7, wherein the phase difference calculation module is a lock-in amplifier.
9. The phase drift based FLRD sensing device of claim 6 or 7, wherein the FLRD sensor comprises: the sensing unit comprises a first coupler, a second coupler, a third coupler and a sensing unit; the second coupler and the third coupler are both 1 × 2 couplers;
a port 1 of the second coupler is connected with a port 1 of the third coupler, and a high coupling ratio end of the second coupler and a high coupling ratio end of the third coupler are respectively connected with two ends of the sensing unit;
the low coupling ratio end of the second coupler is used as the input end of the FLRD sensor, and the low coupling ratio end of the third coupler is used as the output end of the FLRD sensor.
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