CN117928654A - Ocean temperature and refractive index double-parameter measurement sensing system and measurement method thereof - Google Patents
Ocean temperature and refractive index double-parameter measurement sensing system and measurement method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of ocean multi-parameter measurement, and provides an ocean temperature and refractive index dual-parameter measurement sensing system and a measurement method thereof, wherein the ocean temperature and refractive index dual-parameter measurement sensing system comprises the following components: a pulsed laser; the 01 port of the first coupler is connected with the pulse laser; the photoelectric converter is connected with the 02 port of the first coupler; the incident light port of the inclined grating is connected with the 03 port of the first coupler, and the transmission light port of the inclined grating is connected with the 04 port of the first coupler; the broadband light source is connected with an incident light port of the inclined grating through the second coupler; the spectrum analyzer is connected with the transmission light port of the inclined grating through a third coupler and connected with the pulse laser through a circuit driving module; a D/A converter connected to the photoelectric converter; and the computer is connected with the D/A converter. By the technical scheme, temperature and refractive index dual-parameter measurement can be realized, complex and tedious spectrum processing is avoided, calculation resources are saved, and monitoring instantaneity and efficiency are improved.
Description
Technical Field
The invention relates to the technical field of ocean multi-parameter measurement, in particular to an ocean temperature and refractive index dual-parameter measurement sensing system and a measurement method thereof.
Background
The method is characterized in that the method is used for exploring rich resources of ocean, researching the protection of the marine ecological environment, predicting and early warning natural disaster, performing offshore military operations and the like, and is very relevant to the marine environment, and the marine environment monitoring is very important.
However, in the prior art, different sensing probes are generally used for respectively monitoring temperature and refractive index, when the refractive index is monitored, the influence of interference factors such as temperature is not considered, the monitoring accuracy is poor, the spectrum of the sensor is generally directly processed, however, the spectrum is complex, the data processing is difficult, and the real-time performance is difficult to ensure.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art or related art.
Therefore, the invention aims to provide the ocean temperature and refractive index dual-parameter measurement sensing system and the ocean temperature and refractive index dual-parameter measurement sensing method, which can realize temperature and refractive index dual-parameter measurement, eliminate the influence of temperature and other interference factors, have high monitoring accuracy, utilize the relationship between ring-down time and refractive index, avoid the processing of complex and tedious spectrums to a certain extent, save calculation resources and improve monitoring instantaneity and efficiency.
In order to achieve the above object, a first aspect of the present invention provides a marine temperature and refractive index dual parameter measurement sensing system, comprising: a pulsed laser; the 01 port of the first coupler is connected with the pulse laser; a photoelectric converter connected to the 02 port of the first coupler; the incident light port of the inclined grating is connected with the 03 port of the first coupler, and the transmission light port of the inclined grating is connected with the 04 port of the first coupler; the broadband light source is connected with an incident light port of the inclined grating through the second coupler; the spectrum analyzer is connected with the transmission light port of the inclined grating through a third coupler and is connected with the pulse laser through a circuit driving module so as to adjust the wavelength of pulse laser emitted by the pulse laser; a D/A converter connected to the photoelectric converter; and the computer is connected with the D/A converter.
In the technical scheme, the broadband light source and the pulse laser provide incident light for the inclined grating, on one hand, the broadband light source displays a transmission spectrum for the incident light on the spectrum analyzer through the inclined grating, the peak wavelength of the fiber core film can be determined by using the broadband light source, the temperature value can be determined, meanwhile, the peak deviation change of the fiber core film is tracked, and the wavelength of the pulse laser is subjected to feedback regulation and control. On the other hand, the laser emitted by the pulse laser is pulsed, runs in a discontinuous mode, and can leave enough ring-down time, so that the ocean refractive index can be accurately measured through the ring-down time, the processing of complex and tedious spectrums is avoided to a certain extent, and the real-time performance and the accuracy are high.
When pulse laser enters the first coupler through the 01 port, light is split according to the splitting ratio of the first coupler, one part of light enters the 02 port, the other part of light enters the 03 port, loss is generated through the inclined grating, the lost light reenters the first coupler through the 04 port, and the repetition is performed in this way, so that ring-down is generated, and the refractive index of the ocean position where the inclined grating is located can be determined through the ring-down time.
In the above technical solution, preferably, the inclined grating includes a core and a cladding, and the inclined angle of the inclined grating is 3 ° to 12 °.
In this technical scheme, the inclined grating includes fiber core and covering, and its inclination is 3 to 12, can realize the monitoring to the temperature through the fiber core membrane, realizes the monitoring to the refracting index through the covering membrane, has high sensitivity moreover, can effectively avoid ocean impurity to the interference of test result.
In any one of the above solutions, preferably, the ocean temperature and refractive index dual parameter measurement sensing system further includes: the first optical fiber isolator is connected between the 03 port of the first coupler and the second coupler, and incident light enters the inclined grating through the 03 port of the first coupler, the first optical fiber isolator and the second coupler; and the second optical fiber isolator is connected between the 04 port of the first coupler and the third coupler, and the transmitted light from the inclined grating enters the 04 port of the first coupler through the third coupler and the second optical fiber isolator.
In the technical scheme, the unidirectional light is guaranteed to pass through the arrangement of the first optical fiber isolator and the second optical fiber isolator, so that signal interference and noise caused by a ground loop are effectively avoided, and the anti-interference capability and stability of the system are improved.
In any one of the above solutions, preferably, the ocean temperature and refractive index dual parameter measurement sensing system further includes: a first filter connected between the third coupler and the second fiber isolator; and the second filter is connected between the third coupler and the spectrum analyzer.
In the technical scheme, through the setting of the filter, interference signals can be filtered, and monitoring accuracy is further improved.
In any of the above embodiments, preferably, the first coupler has a split ratio of 50:50, the interface parameter is 2 x 2; the interface parameters of the second coupler and the third coupler are 1*2.
The technical scheme of the second aspect of the invention provides a ocean temperature and refractive index double-parameter measurement method, which adopts the ocean temperature and refractive index double-parameter measurement sensing system in the technical scheme and comprises the following steps:
Immersing the inclined grating into seawater, analyzing a transmission spectrum obtained after the broadband light source enters the inclined grating by using a spectrum analyzer, and determining the current peak wavelength of the fiber core film;
Determining the current ocean temperature according to the current peak wavelength of the fiber core membrane and a pre-stored relationship diagram of the peak wavelength and the temperature of the fiber core membrane;
comparing the current peak wavelength of the fiber core film with the original peak wavelength, and determining the peak wavelength drift amount;
According to the peak wavelength drift amount, the wavelength of the pulse laser is controlled in a feedback mode, the designated trough of the low-order wave is tracked, and the current ring-down time is determined;
And determining the current ocean refractive index according to the current ring-down time and a pre-stored relation diagram of the ring-down time and the refractive index.
According to the technical scheme, the transmission spectrum obtained after the broadband light source is analyzed to enter the inclined grating is utilized, on one hand, the current ocean temperature can be determined, and on the other hand, the peak wavelength drift amount can be obtained, so that the wavelength of pulse laser can be controlled through the circuit driving module by utilizing the peak wavelength drift amount, the wavelength of the pulse laser is locked at the low-order trough value of the cladding film, and the phenomenon that the low-order trough of the cladding film cannot be determined due to wavelength drift caused by temperature is effectively avoided. The discontinuity of the pulse laser is utilized to leave enough ring-down time, further, the designated trough of the low-order wave can be tracked, the current ring-down time is determined, the current ocean refractive index is determined by utilizing the current ring-down time, the processing of complex and tedious spectrums is avoided to a certain extent, and the real-time performance and the accuracy are high.
In the above technical solution, preferably, the pre-stored relationship graph between peak wavelength and temperature of the fiber core film is obtained by specifically adopting simulation software OptiGrating of fiber grating to simulate TFBG spectral characteristics under different external environment temperatures, and setting simulated parameters: the core diameter is 8 μm and the refractive index is 1.46; the cladding diameter was 125 μm and the refractive index was 1.45; the inclination angle is 8 degrees, and transmission spectrums at different external environment temperatures are obtained; analyzing transmission spectrums under different external environment temperatures, drawing a relation diagram of peak wavelength and temperature of the fiber core membrane, and pre-storing the relation diagram.
In the above technical solution, preferably, the step of feedback controlling the wavelength of the pulse laser according to the peak wavelength drift amount, tracking the designated trough of the low-order wave, and determining the current ring-down time specifically includes the following steps: adding and calculating the original pulse laser wavelength and the peak wavelength drift amount to obtain a new pulse laser wavelength, keeping the light intensity unchanged, and continuing to output; the designated trough of the low-order wave is tracked, and the time taken for the light intensity of the wave to decay to 1/e is determined and is recorded as the current ring-down time.
In the above technical solution, preferably, the pre-stored relationship graph between ring-down time and refractive index is obtained by using simulation software OptiGrating of fiber bragg grating to simulate TFBG spectral characteristics in solutions with different refractive indexes, and setting simulated parameters: the core diameter is 8 μm and the refractive index is 1.46; the cladding diameter was 125 μm and the refractive index was 1.45; the inclination angle is 8 degrees, and the transmission spectrum of the solutions with different refractive indexes is obtained; tracking the appointed trough of the low-order wave in the transmission spectrum, respectively determining the ring-down time for the light intensity of the low-order wave in the solutions with different refractive indexes to decay to 1/e, drawing a relation diagram of the ring-down time and the refractive indexes, and pre-storing the relation diagram.
The ocean temperature and refractive index dual-parameter measurement sensing system and the ocean temperature and refractive index dual-parameter measurement sensing method have the following beneficial technical effects:
(1) The ocean temperature and refractive index double-parameter measurement sensing system and the ocean temperature and refractive index double-parameter measurement sensing method can realize temperature and refractive index double-parameter measurement, eliminate the influence of temperature and other interference factors, and are high in monitoring accuracy.
(2) The ocean temperature and refractive index dual-parameter measurement method provided by the invention realizes refractive index monitoring by adopting the relation between ring-down time and refractive index, avoids complex and tedious spectrum processing to a certain extent, saves calculation power resources and improves monitoring instantaneity and efficiency.
(3) According to the ocean temperature and refractive index dual-parameter measurement sensing system and the ocean temperature and refractive index dual-parameter measurement sensing method, the peak wavelength is obtained by utilizing the transmission spectrum of the inclined grating fiber core film, and the wavelength of the pulse laser is controlled by utilizing the peak wavelength offset, so that the wavelength of the pulse laser is locked at the low-order trough value of the cladding film, measurement errors can be effectively avoided, and the accuracy and instantaneity for determining the refractive index by utilizing the ring-down time are improved.
(4) The ocean temperature and refractive index dual-parameter measurement sensing system provided by the invention adopts the inclined grating, the inclined grating cladding film is very sensitive to the refractive index, has high sensitivity, can effectively avoid the interference of ocean impurities on a test result, and can realize the monitoring of the temperature through the inclined grating fiber core film and the ocean temperature and refractive index dual-parameter measurement.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 shows a schematic diagram of a marine temperature and refractive index dual parameter measurement sensing system according to an embodiment of the present invention;
FIG. 2 shows simulated transmission spectra of a tilted grating at different ambient temperatures;
FIG. 3 shows a plot of peak wavelength of the core film versus temperature;
FIG. 4 shows simulated transmission spectra of tilted gratings in solutions of different refractive indices;
FIG. 5 is a graph showing simulated ring-down curve results for a tilted grating at different ambient temperatures;
Figure 6 shows a plot of ring down time versus refractive index,
The correspondence between the reference numerals and the components in fig. 1 is:
102. The pulse laser, 104 first coupler, 106 photoelectric converter, 108 inclined grating, 110 broadband light source, 112 second coupler, 114 spectrum analyzer, 116 third coupler, 118 circuit driving module, 120D/A converter, 122 computer, 124 first fiber isolator, 126 second fiber isolator, 128 first filter, 130 second filter.
Detailed Description
In order that the above-recited objects, features and advantages of the present application will be more clearly understood, a more particular description of the application will be rendered by reference to the appended drawings and appended detailed description. It should be noted that, without conflict, the embodiments of the present application and features in the embodiments may be combined with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those described herein, and therefore the scope of the present invention is not limited to the specific embodiments disclosed below.
A marine temperature and refractive index dual parameter measurement sensing system and a measurement method thereof according to an embodiment of the present invention will be described in detail with reference to fig. 1 to 6.
As shown in fig. 1, the ocean temperature and refractive index dual parameter measurement sensing system according to an embodiment of the present invention includes: a pulsed laser 102, a first coupler 104, a photoelectric converter 106, a tilted grating 108, a broadband light source 110, a spectrum analyzer 114, a D/a converter 120, a computer 122, etc. The 01 port of the first coupler 104 is connected to the pulse laser 102, the 02 port is connected to the photoelectric converter 106, the 03 port is connected to the incident light port of the inclined grating 108, and the 04 port is connected to the transmission light port of the inclined grating 108. When the pulse laser enters the first coupler 104 through the 01 port, light is split according to the splitting ratio of the first coupler 104, one part of the light enters the 02 port, the other part of the light enters the 03 port, loss is generated through the inclined grating 108, the lost light reenters the first coupler 104 through the 04 port, and the repetition is performed to generate ring-down, so that the refractive index of the ocean position where the inclined grating 108 is located can be determined through the ring-down time.
The broadband light source 110 is connected with an incident light port of the inclined grating 108 through the second coupler 112; the spectrum analyzer 114 is connected with the transmission light port of the inclined grating 108 through the third coupler 116, the spectrum analyzer 114 is connected with the pulse laser 102 through the circuit driving module 118 to adjust the wavelength of the pulse laser emitted by the pulse laser 102, the broadband light source 110 displays the transmission spectrum on the spectrum analyzer 114 for the incident light through the inclined grating 108, the peak wavelength of the fiber core film can be determined by using the transmission spectrum, the temperature value can be determined, and meanwhile, the peak deviation change of the fiber core film is tracked, so that the wavelength of the pulse laser 102 is subjected to feedback regulation. A D/a converter 120 connected to the photoelectric converter 106; the computer 122 is connected to the D/a converter 120, and the photoelectric converter 106 can receive the transmitted optical signal and convert it into a corresponding electrical signal, and the D/a converter 120 can convert the digital signal into an analog signal, and display the result on the computer 122.
Further, the inclined grating 108 includes a fiber core and a cladding, and the inclined angle of the inclined grating 108 is 3 ° to 12 °, so that the temperature can be monitored through the fiber core film, the refractive index can be monitored through the cladding film, and the sensor has high sensitivity, and can effectively avoid the interference of marine impurities on the test result.
Further, as shown in fig. 1, the first fiber isolator 124 is connected between the 03 port of the first coupler 104 and the second coupler 112, and the incident light enters the inclined grating 108 through the 03 port of the first coupler 104, the first fiber isolator 124, and the second coupler 112; a second fiber isolator 126 connected between the 04 port of the first coupler 104 and the third coupler 116, and the transmitted light from the inclined grating 108 enters the 04 port of the first coupler 104 through the third coupler 116 and the second fiber isolator 126. Therefore, unidirectional light passing is guaranteed, signal interference and noise caused by a ground loop can be effectively avoided, and the anti-interference capability and stability of the system are improved.
Further, as shown in fig. 1, a first filter 128 is connected between the third coupler 116 and the second fiber isolator 126; the second filter 130 is connected between the third coupler 116 and the spectrum analyzer 114. Therefore, interference signals can be filtered, and monitoring accuracy is further improved.
Further, the split ratio of the first coupler 104 is 50:50, the interface parameter is 2 x 2; the interface parameters of the second coupler 112 and the third coupler 116 are 1*2.
According to the ocean temperature and refractive index double-parameter measurement method, the ocean temperature and refractive index double-parameter measurement sensing system is adopted, and the ocean temperature and refractive index double-parameter measurement sensing method comprises the following steps of:
s202, immersing the inclined grating into seawater, analyzing a transmission spectrum obtained after a broadband light source enters the inclined grating by using a spectrum analyzer, and determining the current peak wavelength of a fiber core film;
s204, determining the current ocean temperature according to the current peak wavelength of the fiber core membrane and a pre-stored relationship diagram of the peak wavelength and the temperature of the fiber core membrane;
s206, comparing the current peak wavelength of the fiber core film with the original peak wavelength, and determining the peak wavelength drift amount;
s208, the wavelength of the pulse laser is controlled in a feedback mode according to the peak wavelength drift amount, the designated trough of the low-order wave is tracked, and the current ring-down time is determined;
S210, determining the current ocean refractive index according to the current ring-down time and a pre-stored relation diagram of ring-down time and refractive index.
The transmission spectrum obtained after the broadband light source is analyzed to enter the inclined grating is utilized, on one hand, the current ocean temperature can be determined, and on the other hand, the peak wavelength drift amount can be obtained, so that the wavelength of pulse laser can be controlled through the circuit driving module by utilizing the peak wavelength drift amount, the wavelength of the pulse laser is locked at the low-order trough value of the cladding film, and the phenomenon that the low-order trough of the cladding film cannot be determined due to wavelength drift caused by temperature is effectively avoided. The discontinuity of the pulse laser is utilized to leave enough ring-down time, further, the designated trough of the low-order wave can be tracked, the current ring-down time is determined, the current ocean refractive index is determined by utilizing the current ring-down time, the processing of complex and tedious spectrums is avoided to a certain extent, and the real-time performance and the accuracy are high.
Further, a pre-stored relation diagram of peak wavelength and temperature of the fiber core film is obtained specifically through the following steps of simulating TFBG spectral characteristics under different external environment temperatures by adopting simulation software OptiGrating of a fiber grating, and setting simulated parameters: the core diameter is 8 μm and the refractive index is 1.46; the cladding diameter was 125 μm and the refractive index was 1.45; the inclination angle is 8 degrees, and transmission spectrums at different external environment temperatures are obtained; analyzing transmission spectrums under different external environment temperatures, drawing a relation diagram of peak wavelength and temperature of the fiber core membrane, and pre-storing the relation diagram.
Specifically, the simulation software OptiGrating of the fiber bragg grating is adopted to simulate the spectrum characteristics of the TFBG under different external environment temperatures. The simulation results are shown in fig. 2, in which the intensity is not changed but the wavelength is shifted with the increase of the temperature. The transmission spectrum of fig. 2 under different external environment temperatures is analyzed to obtain the relationship between the peak wavelength and the temperature of the fiber core film, which is shown in fig. 3. So that the current ocean temperature can be monitored based on the peak wavelength of the core film.
Further, according to the peak wavelength drift amount, the wavelength of the pulse laser is feedback controlled, the designated trough of the low-order wave is tracked, and the current ring-down time is determined, specifically comprising the following steps:
s2082, adding and calculating the original pulse laser wavelength and the peak wavelength drift amount to obtain a new pulse laser wavelength, keeping the light intensity unchanged, and continuing to output;
S2084, tracking the appointed trough of the low-order wave, and determining the time for the light intensity to decay to 1/e, and recording as the current ring-down time.
It should be noted that, the determination of the pulse laser wavelength is a cyclic repetition process, and when the ocean temperature changes, the peak wavelength drift amount is used to correct the original pulse laser wavelength, so as to ensure that the pulse laser wavelength is locked at the low-order trough value of the cladding film, thereby effectively avoiding the occurrence of the phenomenon that the low-order trough of the cladding film cannot be determined due to wavelength drift caused by temperature.
Further, a pre-stored ring-down time and refractive index relation chart is obtained specifically through the following steps of adopting simulation software OptiGrating of fiber bragg gratings to simulate TFBG spectral characteristics in solutions with different refractive indexes, and setting simulated parameters: the core diameter is 8 μm and the refractive index is 1.46; the cladding diameter was 125 μm and the refractive index was 1.45; the inclination angle is 8 degrees, and the transmission spectrum of the solutions with different refractive indexes is obtained; tracking the appointed trough of the low-order wave in the transmission spectrum, respectively determining the ring-down time for the light intensity of the low-order wave in the solutions with different refractive indexes to decay to 1/e, drawing a relation diagram of the ring-down time and the refractive indexes, and pre-storing the relation diagram.
Specifically, simulation software OptiGrating of fiber gratings is adopted to simulate the spectrum characteristics of TFBG in solutions with different refractive indexes. As a result of the simulation, as shown in fig. 4, the intensity becomes linearly weak as the refractive index increases, the loss of light through the inclined grating becomes large, but the wavelength drift and the intensity change of the core film do not occur. As shown in fig. 2, when the temperature changes, the low-order wave shifts, and if the intensity of a certain wavelength of the low-order wave changes, an error is caused, and the certain wavelength trough cannot be always tracked. Therefore, the wavelength of the pulse laser is controlled according to the shift amount of the peak wavelength of the fiber core film, the wavelength shift of a certain trough of the low-order wave is regulated, and the trough is locked.
The data of ring-down results were taken by using a 50x 50 coupler, the incident intensity of the pulsed laser was 34dB, and the tilted grating lost 10% of the intensity in a solution with a refractive index of 1.367. When the incident light enters the 01 port, passes through the coupler, 17dB enters the 02 port, 17dB enters the 03 port, 10% of the inclined grating loss is caused, and the rest 15.3dB enters the 04 port, and then passes through the coupler, the above process is repeated. Eight sets of data were taken and fitted. The tilted grating lost 20% of the light intensity in the 1.376 index solution, 30% in the 1.385 index solution, 40% in the 1.394 index solution, and 50% in the 1.403 index solution, and the ring down results are shown in fig. 5. The ring-down curve results in i=i 0e-t/τ where τ is defined as the ring-down time, i.e., the time it takes for the output light pulse to decay to 1/e maximum intensity. The ring down times for the five groups of solutions were found to be: τ 1.367= 1.232、τ1.376=1.089、τ1.385= 0.953、τ1.394= 0.831、τ1.403 =0.723, and as shown in fig. 6, a relationship between the refractive index and the ring-down time with good fitting is obtained.
The steps in the method can be sequentially adjusted, combined and deleted according to actual needs.
The units in the device can be combined, divided and deleted according to actual needs.
Those of ordinary skill in the art will appreciate that all or part of the steps of the various methods of the above embodiments may be implemented by a program that instructs associated hardware, the program may be stored in a computer readable storage medium including Read-Only Memory (ROM), random access Memory (Random Access Memory, RAM), programmable Read-Only Memory (Programmable Read-Only Memory, PROM), erasable programmable Read-Only Memory (Erasable Programmable Read Only Memory, EPROM), one-time programmable Read-Only Memory (OTPROM), electrically erasable programmable Read-Only Memory (EEPROM), compact disc Read-Only Memory (Compact Disc Read-Only Memory, CD-ROM) or other optical disk Memory, magnetic disk Memory, tape Memory, or any other medium that can be used for carrying or storing data.
In the present invention, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more, unless expressly defined otherwise. The terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; "coupled" may be directly coupled or indirectly coupled through intermediaries. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In the description of the present invention, it should be understood that the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "rear", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or units referred to must have a specific direction, be constructed and operated in a specific direction, and thus should not be construed as limiting the present invention.
In the description of the present specification, the terms "one embodiment," "some embodiments," "particular embodiments," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A marine temperature and refractive index dual parameter measurement sensing system comprising: a pulsed laser; the 01 port of the first coupler is connected with the pulse laser; a photoelectric converter connected to the 02 port of the first coupler; the incident light port of the inclined grating is connected with the 03 port of the first coupler, and the transmission light port of the inclined grating is connected with the 04 port of the first coupler; the broadband light source is connected with an incident light port of the inclined grating through the second coupler; the spectrum analyzer is connected with the transmission light port of the inclined grating through a third coupler and is connected with the pulse laser through a circuit driving module so as to adjust the wavelength of pulse laser emitted by the pulse laser; a D/A converter connected to the photoelectric converter; and the computer is connected with the D/A converter.
2. The ocean temperature and refractive index dual parameter measurement sensing system of claim 1, wherein the tilted grating comprises a core and a cladding, the tilted grating having a tilt angle of 3 ° to 12 °.
3. The ocean temperature and refractive index dual parameter measurement sensing system of claim 1, further comprising: the first optical fiber isolator is connected between the 03 port of the first coupler and the second coupler, and incident light enters the inclined grating through the 03 port of the first coupler, the first optical fiber isolator and the second coupler; and the second optical fiber isolator is connected between the 04 port of the first coupler and the third coupler, and the transmitted light from the inclined grating enters the 04 port of the first coupler through the third coupler and the second optical fiber isolator.
4. The ocean temperature and refractive index dual parameter measurement sensing system of claim 3, further comprising: a first filter connected between the third coupler and the second fiber isolator; and the second filter is connected between the third coupler and the spectrum analyzer.
5. The ocean temperature and refractive index dual parameter measurement sensing system of any one of claims 1-4, wherein the first coupler has a split ratio of 50:50, the interface parameter is 2 x 2; the interface parameters of the second coupler and the third coupler are 1*2.
6. A method for measuring ocean temperature and refractive index by using the ocean temperature and refractive index dual-parameter measurement sensing system according to any one of the claims 1 to 5, comprising the steps of:
Immersing the inclined grating into seawater, analyzing a transmission spectrum obtained after the broadband light source enters the inclined grating by using a spectrum analyzer, and determining the current peak wavelength of the fiber core film;
Determining the current ocean temperature according to the current peak wavelength of the fiber core membrane and a pre-stored relationship diagram of the peak wavelength and the temperature of the fiber core membrane;
comparing the current peak wavelength of the fiber core film with the original peak wavelength, and determining the peak wavelength drift amount;
According to the peak wavelength drift amount, the wavelength of the pulse laser is controlled in a feedback mode, the designated trough of the low-order wave is tracked, and the current ring-down time is determined;
And determining the current ocean refractive index according to the current ring-down time and a pre-stored relation diagram of the ring-down time and the refractive index.
7. The method for measuring ocean temperature and refractive index according to claim 6, wherein the pre-stored peak wavelength versus temperature chart of the fiber core film is obtained by,
Simulation software OptiGrating of fiber bragg gratings is adopted to simulate the spectrum characteristics of the TFBG under different external environment temperatures, and simulated parameters are set: the core diameter is 8 μm and the refractive index is 1.46; the cladding diameter was 125 μm and the refractive index was 1.45; the inclination angle is 8 degrees, and transmission spectrums at different external environment temperatures are obtained;
analyzing transmission spectrums under different external environment temperatures, drawing a relation diagram of peak wavelength and temperature of the fiber core membrane, and pre-storing the relation diagram.
8. The method for measuring ocean temperature and refractive index according to claim 6, wherein the step of feedback controlling the wavelength of the pulsed laser, tracking the designated trough of the lower-order wave, and determining the current ring-down time according to the peak wavelength drift amount comprises the steps of:
adding and calculating the original pulse laser wavelength and the peak wavelength drift amount to obtain a new pulse laser wavelength, keeping the light intensity unchanged, and continuing to output;
The designated trough of the low-order wave is tracked, and the time taken for the light intensity of the wave to decay to 1/e is determined and is recorded as the current ring-down time.
9. The method for measuring ocean temperature and refractive index according to claim 6, wherein the pre-stored plot of ring-down time versus refractive index is obtained by,
Simulation software OptiGrating of fiber bragg gratings is adopted to simulate the spectrum characteristics of TFBG in solutions with different refractive indexes, and simulated parameters are set: the core diameter is 8 μm and the refractive index is 1.46; the cladding diameter was 125 μm and the refractive index was 1.45; the inclination angle is 8 degrees, and the transmission spectrum of the solutions with different refractive indexes is obtained;
tracking the appointed trough of the low-order wave in the transmission spectrum, respectively determining the ring-down time for the light intensity of the low-order wave in the solutions with different refractive indexes to decay to 1/e, drawing a relation diagram of the ring-down time and the refractive indexes, and pre-storing the relation diagram.
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