Marine temperature and refractive index dual-parameter measurement sensing system and measurement method

Abstract

The present invention relates to the technical field of marine multi-parameter measurement. Provided are a marine temperature and refractive index dual-parameter measurement sensing system and measurement method. The sensing system comprises: a pulsed laser; a first coupler, a port 01 of which is connected to the pulsed laser; a photoelectric converter, which is connected to a port 02 of the first coupler; a tilted grating, an incident light port of which is connected to a port 03 of the first coupler, and a transmitted light port of which is connected to a port 04 of the first coupler; a broadband light source, which is connected to the incident light port of the tilted grating by means of a second coupler; a spectrum analyzer, which is connected to the transmitted light port of the tilted grating by means of a third coupler, wherein the spectrum analyzer is connected to the pulsed laser by means of a circuit drive module; a D / A converter, which is connected to the photoelectric converter; and a computer, which is connected to the D / A converter. By means of the technical solution of the present invention, temperature and refractive index dual-parameter measurement can be achieved, thereby preventing the processing of complex and tedious spectra, saving on computational resources, and improving the real-time performance and efficiency of monitoring.

Description

Ocean temperature and refractive index dual parameter measurement sensing system and measurement method Technical Field

[0001] The present invention relates to the technical field of ocean multi-parameter measurement, and in particular to an ocean temperature and refractive index dual-parameter measurement sensing system and a measurement method thereof. Background Art

[0002] Exploring the rich resources in the ocean, studying the protection of the marine ecological environment, predicting and warning of natural disasters, and maritime military activities are all closely related to the marine environment, and marine environmental monitoring is of vital importance.

[0003] However, in the existing technology, different sensor probes are generally used to monitor temperature and refractive index separately. When monitoring the refractive index, the influence of interference factors such as temperature is not taken into account, and the monitoring accuracy is poor. In addition, the sensor's spectrum is generally processed directly. However, the spectrum is complex, data processing is relatively difficult, and it is difficult to ensure real-time performance. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] To this end, the purpose of the present invention is to provide an ocean temperature and refractive index dual-parameter measurement sensing system and a measurement method thereof, which can realize the dual-parameter measurement of temperature and refractive index, and eliminate the influence of interference factors such as temperature, with high monitoring accuracy. By utilizing the relationship between the decay time and the refractive index, the processing of complex and tedious spectra is avoided to a certain extent, computing power resources are saved, and the real-time and efficiency of monitoring are improved.

[0006] To achieve the above-mentioned objectives, the technical solution of the first aspect of the present invention provides an ocean temperature and refractive index dual-parameter measurement sensing system, comprising: a pulsed laser; a first coupler, wherein the 01 port of the first coupler is connected to the pulsed laser; a photoelectric converter, connected to the 02 port of the first coupler; a tilted grating, wherein the incident light port of the tilted grating is connected to the 03 port of the first coupler, and the transmitted light port of the tilted grating is connected to the 04 port of the first coupler; a broadband light source, connected to the incident light port of the tilted grating via a second coupler; a spectrum analyzer, connected to the transmitted light port of the tilted grating via a third coupler, the spectrum analyzer being connected to the pulsed laser via a circuit driving module to adjust the wavelength of the pulsed laser emitted by the pulsed laser; a D / A converter, connected to the photoelectric converter; and a computer, connected to the D / A converter.

[0007] In this technical solution, a broadband light source and a pulsed laser provide incident light for the tilted grating. On the one hand, the broadband light source transmits the incident light through the tilted grating, displaying the transmission spectrum on a spectrum analyzer. This spectrum can be used to determine the peak wavelength and temperature of the core coating. It also tracks changes in the core coating's peak offset and provides feedback control over the pulsed laser's wavelength. On the other hand, the pulsed laser emits pulsed light and operates in an intermittent mode, allowing sufficient decay time to accurately measure the ocean's refractive index. This, to a certain extent, avoids the need for complex and tedious spectral processing, resulting in high real-time and accuracy.

[0008] When the pulsed laser enters the first coupler through port 01, it is split according to the splitting ratio of the first coupler. Part of the light enters port 02, and the other part enters port 03. After passing through the tilted grating, loss occurs. The lost light then re-enters the first coupler through port 04. This process is repeated, resulting in ring-down. Therefore, the refractive index of the ocean location where the tilted grating is located can be determined by the ring-down time.

[0009] In the above technical solution, preferably, the tilted grating includes a core and a cladding, and the tilt angle of the tilted grating is 3° to 12°.

[0010] In this technical solution, the tilted grating includes a core and a cladding, and its tilt angle is 3° to 12°. It can monitor the temperature through the core membrane and the refractive index through the cladding membrane. It has high sensitivity and can effectively avoid interference with test results caused by marine impurities.

[0011] In any of the above technical solutions, preferably, the ocean temperature and refractive index dual-parameter measurement sensing system also includes: a first optical fiber isolator, connected between the O3 port of the first coupler and the second coupler, and the incident light enters the tilted grating through the O3 port of the first coupler, the first optical fiber isolator, and the second coupler; a second optical fiber isolator, connected between the O4 port of the first coupler and the third coupler, and the transmitted light from the tilted grating enters the O4 port of the first coupler through the third coupler and the second optical fiber isolator.

[0012] In this technical solution, the provision of the first optical fiber isolator and the second optical fiber isolator ensures unidirectional light passage, thereby effectively avoiding signal interference and noise caused by ground loops and improving the anti-interference capability and stability of the system.

[0013] In any of the above technical 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 optical fiber isolator; and a second filter connected between the third coupler and the spectrum analyzer.

[0014] In this technical solution, the interference signal can be filtered out by setting the filter, further improving the monitoring accuracy.

[0015] In any of the above technical solutions, preferably, the splitting ratio of the first coupler is 50:50, and the interface parameter is 2*2; the interface parameters of the second coupler and the third coupler are 1*2.

[0016] The technical solution of the second aspect of the present invention provides a method for measuring the dual parameters of ocean temperature and refractive index, which adopts the dual parameter measurement sensing system of ocean temperature and refractive index in the above technical solution, including the following steps: immersing the tilted grating in seawater, and using a spectrum analyzer to analyze the transmission spectrum obtained after the broadband light source enters the tilted grating, to determine the current peak wavelength of the core membrane; based on the current peak wavelength of the core membrane, according to the pre-stored relationship diagram between the peak wavelength of the core membrane and the temperature, the current ocean temperature is determined; comparing the current peak wavelength of the core membrane with the original peak wavelength, to determine the peak wavelength drift; based on the peak wavelength drift, feedback control the wavelength of the pulsed laser, track the specified trough of the low-order wave, and determine the current decay time; based on the current decay time, according to the pre-stored relationship diagram between the decay time and the refractive index, the current ocean refractive index is determined.

[0017] This technical solution uses the transmission spectrum obtained after analyzing a broadband light source entering a tilted grating to determine both the current ocean temperature and the peak wavelength drift. This peak wavelength drift can then be used to control the wavelength of the pulsed laser through a circuit driver module, locking it to the low-order trough of the cladding film. This effectively avoids the phenomenon of wavelength drift caused by temperature that prevents the determination of the low-order trough of the cladding film. By exploiting the discontinuity of the pulsed laser, sufficient decay time is allowed, allowing the detection of specific low-order troughs to be tracked and the current decay time to be determined. This decay time is then used to determine the current ocean refractive index, thus avoiding the need for complex and tedious spectral processing and achieving high real-time and accuracy.

[0018] In the above technical solution, preferably, the pre-stored relationship diagram between the core membrane peak wavelength and the temperature is obtained specifically by the following steps: using the fiber Bragg grating simulation software OptiGrating, the TFBG spectral characteristics under different external ambient temperatures are simulated, and the simulation parameters are set as follows: the core diameter is 8 μm, the refractive index is 1.46; the cladding diameter is 125 μm, the refractive index is 1.45; the tilt angle is 8°, and the transmission spectra under different external ambient temperatures are obtained; the transmission spectra under different external ambient temperatures are analyzed, and the relationship diagram between the core membrane peak wavelength and the temperature is drawn and pre-stored.

[0019] In the above technical solution, preferably, the wavelength of the pulsed laser is feedback-controlled according to the peak wavelength drift, the designated trough of the low-order wave is tracked, and the current ring-down time is determined, which specifically includes the following steps: the original pulsed laser wavelength and the peak wavelength drift are added and calculated to obtain a new pulsed laser wavelength, and the light intensity is kept unchanged and continued to be output; the designated trough of the low-order wave is tracked to determine the time taken for its light intensity to decay to 1 / e, which is recorded as the current ring-down time.

[0020] In the above technical solution, preferably, the pre-stored relationship diagram between the ring-down time and the refractive index is obtained specifically by the following steps: using the fiber Bragg grating simulation software OptiGrating, simulating the TFBG spectral characteristics in solutions with different refractive indices, and setting the simulation parameters as follows: the core diameter is 8 μm, the refractive index is 1.46; the cladding diameter is 125 μm, the refractive index is 1.45; the tilt angle is 8°, and the transmission spectra of solutions with different refractive indices are obtained; tracking the specified troughs of low-order waves in the transmission spectrum, and determining the ring-down time used for the light intensity to decay to 1 / e in solutions with different refractive indices, and drawing the relationship diagram between the ring-down time and the refractive index, and pre-stored.

[0021] The ocean temperature and refractive index dual-parameter measurement sensor system and its measurement method proposed in the present invention have the following beneficial technical effects: (1) The ocean temperature and refractive index dual-parameter measurement sensor system and its measurement method proposed in the present invention can realize the dual-parameter measurement of temperature and refractive index, and eliminate the influence of interference factors such as temperature, and have high monitoring accuracy.

[0022] (2) The dual-parameter measurement method of ocean temperature and refractive index proposed in the present invention uses the relationship between decay time and refractive index to realize refractive index monitoring, which to a certain extent avoids the processing of complex and tedious spectra, saves computing resources, and improves the real-time performance and efficiency of monitoring.

[0023] (3) The ocean temperature and refractive index dual parameter measurement sensing system and its measurement method proposed in the present invention use the tilted grating core membrane transmission spectrum to obtain its peak wavelength, and use the peak wavelength offset to control the wavelength of the pulsed laser, so that the wavelength of the pulsed laser is locked at the low-order trough value of the cladding membrane, which can effectively avoid measurement errors and improve the accuracy and real-time performance of determining the refractive index using the ring-down time.

[0024] (4) The dual-parameter ocean temperature and refractive index measurement sensing system proposed in the present invention uses a tilted grating. The tilted grating cladding film is very sensitive to the refractive index and has high sensitivity, which can effectively avoid the interference of ocean impurities on the test results. At the same time, the temperature can also be monitored by the tilted grating core film, which can realize the dual-parameter measurement of ocean temperature and refractive index.

[0025] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments in conjunction with the following drawings, in which: FIG1 is a schematic structural diagram of a dual-parameter ocean temperature and refractive index measurement sensing system according to an embodiment of the present invention; FIG2 is a diagram showing simulated transmission spectra of a tilted grating at different ambient temperatures; FIG3 is a diagram showing the relationship between the core film peak wavelength and temperature; FIG4 is a diagram showing simulated transmission spectra of a tilted grating in solutions with different refractive indices; FIG5 is a diagram showing simulated ring-down curves of a tilted grating at different ambient temperatures; and FIG6 is a diagram showing the relationship between the ring-down time and the refractive index. The corresponding relationship between the reference numerals and components in FIG1 is as follows: 102 pulsed laser, 104 first coupler, 106 photoelectric converter, 108 tilted grating, 110 broadband light source, 112 second coupler, 114 spectrum analyzer, 116 third coupler, 118 circuit driver module, 120 D / A converter, 122 computer, 124 first fiber isolator, 126 second fiber isolator, 128 first filter, 130 second filter. DETAILED DESCRIPTION

[0027] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0029] The ocean temperature and refractive index dual-parameter measurement sensing system and its measurement method according to an embodiment of the present invention will be described in detail below with reference to FIG. 1 to FIG. 6 .

[0030] As shown in Figure 1, a dual-parameter ocean temperature and refractive index 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, and a computer 122. Port 01 of first coupler 104 is connected to pulsed laser 102, port 02 is connected to photoelectric converter 106, port 03 is connected to the incident light port of tilted grating 108, and port 04 is connected to the transmitted light port of tilted grating 108. When pulsed laser light enters first coupler 104 through port 01, it is split according to the splitting ratio of first coupler 104. Part of the light enters port 02, and the remaining part enters port 03. After passing through tilted grating 108, the lost light re-enters first coupler 104 through port 04. This cycle repeats, generating ring-down. Therefore, the refractive index of the ocean at the location where tilted grating 108 is located can be determined based on the ring-down time.

[0031] A broadband light source 110 is connected to the incident light port of the tilted grating 108 via a second coupler 112. A spectrum analyzer 114 is connected to the transmission light port of the tilted grating 108 via a third coupler 116. Spectrum analyzer 114 is connected to the pulsed laser 102 via a circuit driver module 118 to adjust the wavelength of the pulsed laser light emitted by the pulsed laser 102. The broadband light source 110 displays a transmission spectrum on spectrum analyzer 114 for incident light passing through tilted grating 108. This spectrum can be used to determine the peak wavelength and temperature of the core film, while also tracking changes in the peak offset of the core film and providing feedback control over the wavelength of the pulsed laser 102. A D / A converter 120 is connected to the photoelectric converter 106. A computer 122 is also connected to the D / A converter 120. The photoelectric converter 106 can receive the transmitted optical signal and convert it into a corresponding electrical signal. The D / A converter 120 can convert the digital signal into an analog signal, and the result can be displayed on computer 122.

[0032] Furthermore, the tilted grating 108 includes a core and a cladding, and the tilt angle of the tilted grating 108 is 3° to 12°, so that the temperature can be monitored through the core membrane and the refractive index can be monitored through the cladding membrane. It has high sensitivity and can effectively avoid interference of marine impurities on the test results.

[0033] Furthermore, as shown in FIG1 , a first fiber isolator 124 is connected between the O3 port of the first coupler 104 and the second coupler 112. Incident light enters the tilted grating 108 via the O3 port of the first coupler 104, the first fiber isolator 124, and the second coupler 112. A second fiber isolator 126 is connected between the O4 port of the first coupler 104 and the third coupler 116. Transmitted light from the tilted grating 108 enters the O4 port of the first coupler 104 via the third coupler 116 and the second fiber isolator 126. This ensures unidirectional light transmission, effectively avoids signal interference and noise caused by ground loops, and improves the system's anti-interference capability and stability.

[0034] 1 , the first filter 128 is connected between the third coupler 116 and the second fiber isolator 126, and the second filter 130 is connected between the third coupler 116 and the spectrum analyzer 114. Thus, interference signals can be filtered out, further improving monitoring accuracy.

[0035] Furthermore, the splitting ratio of the first coupler 104 is 50:50, and the interface parameter is 2*2; the interface parameters of the second coupler 112 and the third coupler 116 are 1*2.

[0036] According to an embodiment of the present invention, a method for measuring the dual parameters of ocean temperature and refractive index adopts the above-mentioned dual parameter measurement sensing system of ocean temperature and refractive index, including the following steps: S202, immersing the tilted grating in seawater, and using a spectrum analyzer to analyze the transmission spectrum obtained after the broadband light source enters the tilted grating, to determine the current peak wavelength of the core membrane; S204, based on the current peak wavelength of the core membrane, according to a pre-stored relationship diagram between the peak wavelength of the core membrane and the temperature, determine the current ocean temperature; S206, comparing the current peak wavelength of the core membrane with the original peak wavelength, and determining the peak wavelength drift; S208, based on the peak wavelength drift, feedback-controlling the wavelength of the pulsed laser, tracking the specified trough of the low-order wave, and determining the current decay time; S210, based on the current decay time, according to a pre-stored relationship diagram between the decay time and the refractive index, determine the current ocean refractive index.

[0037] By analyzing the transmission spectrum obtained after a broadband light source enters a tilted grating, the current ocean temperature can be determined, and the peak wavelength drift can be obtained. This peak wavelength drift can then be used to control the wavelength of the pulsed laser through the circuit driver module, locking it to the low-order trough value of the cladding film. This effectively avoids the phenomenon of wavelength drift caused by temperature and the inability to determine the low-order trough value of the cladding film. By taking advantage of the discontinuity of the pulsed laser and allowing sufficient decay time, the specific trough of the low-order wave can be tracked and the current decay time can be determined. This current decay time can then be used to determine the current ocean refractive index. This avoids the need for complex and tedious spectral processing, and achieves high real-time and accuracy.

[0038] Furthermore, the pre-stored relationship diagram between the core membrane peak wavelength and temperature is obtained by the following steps: using the fiber Bragg grating simulation software OptiGrating, the TFBG spectral characteristics under different external ambient temperatures are simulated, and the simulation parameters are set as follows: the core diameter is 8μm, the refractive index is 1.46; the cladding diameter is 125μm, the refractive index is 1.45; the tilt angle is 8°, and the transmission spectra under different external ambient temperatures are obtained; the transmission spectra under different external ambient temperatures are analyzed, and the relationship diagram between the core membrane peak wavelength and temperature is drawn and pre-stored.

[0039] Specifically, using the fiber Bragg grating (FBG) simulation software OptiGrating, the spectral characteristics of TFBGs at different ambient temperatures were simulated. The simulation results, shown in Figure 2, show that as temperature increases, the intensity remains unchanged, but the wavelength shifts. By analyzing the transmission spectra at different ambient temperatures in Figure 2, the relationship between the core membrane peak wavelength and temperature is derived, as shown in Figure 3. This allows the current ocean temperature to be monitored based on the core membrane peak wavelength.

[0040] Furthermore, based on the peak wavelength drift, the wavelength of the pulsed laser is feedback-controlled, the designated trough of the low-order wave is tracked, and the current decay time is determined, which specifically includes the following steps: S2082, the original pulsed laser wavelength and the peak wavelength drift are added together to calculate a new pulsed laser wavelength, and the light intensity is kept unchanged and continued to be output; S2084, the designated trough of the low-order wave is tracked, and the time taken for its light intensity to decay to 1 / e is determined, which is recorded as the current decay time.

[0041] It should be noted that the determination of the pulsed laser wavelength here is a cyclic and repetitive process. When the ocean temperature changes, the peak wavelength drift will be used to correct the original pulsed laser wavelength to ensure that the pulsed laser wavelength is locked at the low-order trough value of the cladding film, thereby effectively avoiding the occurrence of wavelength drift caused by temperature and the inability to determine the low-order trough value of the cladding film.

[0042] Furthermore, the pre-stored relationship diagram between the decay time and the refractive index is obtained specifically through the following steps: using the fiber Bragg grating simulation software OptiGrating, the spectral characteristics of the TFBG in solutions with different refractive indices are simulated, and the simulation parameters are set as follows: the core diameter is 8 μm, the refractive index is 1.46; the cladding diameter is 125 μm, the refractive index is 1.45; the tilt angle is 8°, and the transmission spectra of solutions with different refractive indices are obtained; the specified troughs of the low-order waves in the transmission spectrum are tracked, and the decay time taken for the light intensity to decay to 1 / e in solutions with different refractive indices is determined respectively, and a relationship diagram between the decay time and the refractive index is drawn and pre-stored.

[0043] Specifically, the fiber Bragg grating (FBG) simulation software, OptiGrating, was used to simulate the spectral characteristics of TFBGs in solutions with different refractive indices. The simulation results, shown in Figure 4, show that as the refractive index increases, the intensity decreases linearly, and the light loss through the tilted grating increases. However, the core membrane exhibits no wavelength drift or intensity change. As shown in Figure 2, when the temperature changes, the low-order waves shift. Tracking the intensity changes of a specific wavelength of the low-order waves will result in errors, making it impossible to consistently track a specific wavelength valley. Therefore, we control the pulsed laser wavelength based on the drift of the core membrane's peak wavelength, adjusting the wavelength drift of a specific low-order wave valley to lock onto this valley.

[0044] The data of the ring-down results were taken using a 50*50 coupler, the incident light intensity of the pulsed laser was 34dB, and the tilted grating lost 10% of the light intensity in a solution with a refractive index of 1.367. When the incident light enters port 01 and passes through the coupler, 17dB enters port 02, and 17dB enters port 03. After passing through the tilted grating and losing 10%, the remaining 15.3dB enters port 04, and then passes through the coupler and repeats the above process. Eight sets of data were taken for fitting. The tilted grating lost 20% of the light intensity in a solution with a refractive index of 1.376, 30% of the light intensity in a solution with a refractive index of 1.385, 40% of the light intensity in a solution with a refractive index of 1.394, and 50% of the light intensity in a solution with a refractive index of 1.403. The ring-down results are shown in Figure 5. The ring-down curve result is I=I0e -t / τ Where τ is defined as the ring-down time, which is the time it takes for the output light pulse to decay to 1 / e of the maximum intensity. The ring-down time of the five groups of solutions is: τ 1.367 =1.232, τ 1.376 =1.089, τ 1.385 =0.953, τ 1.394 =0.831, τ 1.403 =0.723, as shown in FIG6 , a relationship between the refractive index and the ring-down time with good fitting is obtained.

[0045] The steps in the method of the present invention can be adjusted in sequence, combined, or deleted according to actual needs.

[0046] The units in the device of the present invention can be combined, divided and deleted according to actual needs.

[0047] Those skilled in the art will appreciate that all or part of the steps in the various methods of the above embodiments can be completed by instructing related hardware through a program. The program can be stored in a computer-readable storage medium, and the storage medium includes a read-only memory (ROM), a random access memory (RAM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), a one-time programmable read-only memory (OTPROM), an electronically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, magnetic disk storage, magnetic tape storage, or any other computer-readable medium capable of carrying or storing data.

[0048] In the present invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "plurality" refers to two or more, unless expressly limited otherwise. Terms such as "installed," "connected," "connected," and "fixed" should be interpreted broadly. For example, "connected" can mean a fixed connection, a detachable connection, or an integral connection; "connected" can mean a direct connection or an indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0049] In the description of the present invention, it should be understood that the directions or positional relationships indicated by terms such as "up", "down", "left", "right", "front" and "back" are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0050] Throughout this specification, terms such as "one embodiment," "some embodiments," and "specific embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0051] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A dual-parameter ocean temperature and refractive index measurement sensing system, characterized in that: include: Pulsed lasers; A first coupler, wherein the 01 port of the first coupler is connected to the pulse laser; a photoelectric converter, connected to the 02 port of the first coupler; a tilted grating, wherein the incident light port of the tilted grating is connected to the 03 port of the first coupler, and the transmitted light port of the tilted grating is connected to the 04 port of the first coupler. When the pulse laser enters the first coupler through the 01 port, it will be split according to the splitting ratio of the first coupler. Part of the light enters the 02 port, and the other part of the light enters the 03 port. After passing through the tilted grating, loss occurs, and the lost light re-enters the first coupler through the 04 port. This process is repeated to generate ring-down, and the refractive index of the ocean position where the tilted grating is located is determined by the ring-down time; a broadband light source, connected to the incident light port of the tilted grating through the second coupler; a spectrum analyzer, connected to the transmitted light port of the tilted grating through the third coupler, and the spectrum analyzer is connected to the pulse laser through a circuit driving module to adjust the wavelength of the pulse laser emitted by the pulse laser; a D / A converter, connected to the photoelectric converter; and a computer, connected to the D / A converter. The tilted grating includes a core and a cladding, and the tilt angle of the tilted grating is 3° to 12°. A first optical fiber isolator is connected between the O3 port of the first coupler and the second coupler, and the incident light enters the tilted grating through the O3 port of the first coupler, the first optical fiber isolator, and the second coupler; The second optical fiber isolator is connected between the O4 port of the first coupler and the third coupler. The transmitted light from the tilted grating enters the O4 port of the first coupler through the third coupler and the second optical fiber isolator. a first filter connected between the third coupler and the second optical fiber isolator; a second filter connected between the third coupler and the spectrum analyzer, The splitting ratio of the first coupler is 50:50, and the interface parameter is 2*2; The interface parameters of the second coupler and the third coupler are 1*2.

2. A method for measuring ocean temperature and refractive index dual parameters, characterized in that: The ocean temperature and refractive index dual parameter measurement sensing system according to claim 1 comprises the following steps: Immerse the tilted grating in seawater and use a spectrum analyzer to analyze the transmission spectrum obtained after the broadband light source enters the tilted grating to determine the current peak wavelength of the core film. Determine the current ocean temperature according to the current peak wavelength of the core membrane and a pre-stored relationship diagram between the peak wavelength of the core membrane and temperature; Comparing the current peak wavelength of the fiber core film with the original peak wavelength to determine the peak wavelength drift; According to the peak wavelength drift, the wavelength of the pulsed laser is feedback-controlled, the designated trough of the low-order wave is tracked, and the current ring-down time is determined; According to the current ring-down time, the current ocean refractive index is determined according to the pre-stored relationship diagram between the ring-down time and the refractive index.

3. The method for measuring ocean temperature and refractive index dual parameters according to claim 2, wherein: The pre-stored relationship diagram between the core membrane peak wavelength and temperature is obtained by the following steps: The fiber Bragg grating (FBG) simulation software OptiGrating was used to simulate the TFBG spectral characteristics under different ambient temperatures. The simulation parameters were set as follows: core diameter of 8 μm, refractive index of 1.46; cladding diameter of 125 μm, refractive index of 1.45; tilt angle of 8°. Transmission spectra under different ambient temperatures were obtained. Analyze the transmission spectra under different external ambient temperatures, draw the relationship diagram between the core membrane peak wavelength and temperature, and save it in advance.

4. The method for measuring ocean temperature and refractive index dual parameters according to claim 2, wherein: Based on the peak wavelength drift, the wavelength of the pulsed laser is feedback-controlled, the designated trough of the low-order wave is tracked, and the current ring-down time is determined. Specifically, the following steps are included: The original pulse laser wavelength and the peak wavelength drift are added together to calculate the new pulse laser wavelength, and the light intensity is kept unchanged and the output is continued; Track the specified trough of the low-order wave and determine the time it takes for its light intensity to decay to 1 / e, which is recorded as the current ring-down time.

5. The method for measuring ocean temperature and refractive index dual parameters according to claim 2, wherein: The relationship between the ring-down time and the refractive index is obtained by the following steps: The fiber Bragg grating simulation software OptiGrating was used to simulate the spectral characteristics of TFBG in solutions with different refractive indices. The simulation parameters were set as follows: core diameter of 8 μm, refractive index of 1.46; cladding diameter of 125 μm, refractive index of 1.45; tilt angle of 8°. The transmission spectra of solutions with different refractive indices were obtained. Track the specified trough of the low-order wave in the transmission spectrum, determine the ring-down time used for the light intensity to decay to 1 / e in solutions with different refractive indices, draw a relationship graph between the ring-down time and the refractive index, and save it in advance.

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