A multi-parameter measuring optical fiber temperature-salt sensor and a method of using the same

Abstract

The application discloses a kind of multi-parameter measurement optical fiber temperature salt sensor and its use method, including broadband light source, optical fiber coupler and spectrometer and circulator, salinity interferometer and temperature interferometer;Broadband light source is connected with the first end of circulator communication;The second end of circulator is bidirectionally connected with salinity interferometer communication;The third end of circulator is connected with the first end of optical fiber coupler communication;The second end of optical fiber coupler is connected with the first end of temperature interferometer communication;The second end of temperature interferometer is connected with the third end of optical fiber coupler communication;The fourth end of optical fiber coupler is connected with spectrometer communication.The application is combined by circulator to produce vernier effect by two kinds of interferometer cascade, realize the accurate measurement of temperature and salinity change and the synchronous measurement of temperature and salinity double parameter, improve the measurement precision and measurement sensitivity of optical fiber temperature salt sensor;Optical fiber sensor has higher anti-electromagnetic interference ability, improves the running stability in complex environment.

Description

Technical Field

[0001] This invention relates to the field of fiber optic temperature and salinity sensing, and more particularly to a multi-parameter fiber optic temperature and salinity sensor and its usage method. Background Technology

[0002] Currently, marine monitoring equipment mainly relies on electrical sensors or fiber optic sensing technology for data acquisition. Among them, electrical sensors are characterized by mature technology and wide application, and can provide relatively stable measurement data. In the field of fiber optic sensing, FBG coating technology is a commonly used salinity sensing method. By changing the grating structure of the optical fiber through coating, it can achieve a sensitive response to salinity, and is supplemented by bare fiber gratings for temperature compensation. This fiber optic sensing technology has the advantages of low cost and simple manufacturing.

[0003] However, although electrical sensors are technologically mature, they suffer from high costs, complex maintenance requirements, and limitations such as electromagnetic interference and seabed power supply. These limitations increase the scope of electrical sensors in marine monitoring and restrict their widespread adoption. In comparison, although FBG coating technology has certain advantages in salinity sensing, its sensitivity is relatively limited and it is difficult to meet the requirements of high-precision measurement. Especially in complex and variable marine environments, its measurement accuracy and stability are often challenged. Summary of the Invention

[0004] This invention provides a fiber optic temperature and salinity sensor for multi-parameter measurement and its usage method, which aims to improve the sensor's measurement accuracy of temperature and salinity, enhance its anti-interference capabilities, and reduce the sensor's operation and maintenance costs and complexity.

[0005] To address the aforementioned technical problems, embodiments of the present invention provide a fiber optic temperature and salinity sensor for multi-parameter measurement, comprising a broadband light source, a fiber optic coupler, a spectrometer, a circulator, a salinity interferometer, and a temperature interferometer;

[0006] The broadband light source is communicatively connected to the first end of the circulator;

[0007] The second end of the circulator is bidirectionally connected to the salinity interferometer.

[0008] The third end of the circulator is communicatively connected to the first end of the fiber optic coupler;

[0009] The second end of the fiber optic coupler is communicatively connected to the first end of the temperature interferometer;

[0010] The second end of the temperature interferometer is communicatively connected to the third end of the fiber optic coupler;

[0011] The fourth end of the fiber optic coupler is communicatively connected to the spectrometer.

[0012] The fiber optic temperature-salinity sensor provided by this invention comprises two interferometers. By cascading these two interferometers, a vernier effect is generated, amplifying the influence of temperature and salinity changes on the sensing signal, thereby improving the sensor's measurement accuracy for temperature and salinity. Since the two interferometers in the fiber optic temperature-salinity sensor provided by this invention are sensitive to different measurement parameters—the salinity interferometer is sensitive to both salinity and temperature changes, while the temperature interferometer is sensitive to temperature changes—this invention uses a circulator to cascade these two interferometers to generate a vernier effect, thus amplifying temperature and salinity changes and achieving precise measurement of these changes, improving the measurement accuracy and sensitivity of the fiber optic temperature-salinity sensor provided by this invention. Furthermore, because the two interferometers respond differently to temperature and salinity, by constructing a sensitivity coefficient matrix, the fiber optic temperature-salinity sensor provided by this invention can achieve simultaneous measurement of both temperature and salinity parameters, improving measurement accuracy and efficiency.

[0013] In addition, the fiber optic sensor provided by this invention has better resistance to electromagnetic interference compared to point sensors, thus exhibiting higher operational stability in complex environments. Furthermore, compared to existing electrical sensors, fiber optic sensors are less expensive and simpler to maintain. Therefore, the fiber optic temperature and salinity sensor provided by this invention reduces the maintenance cost and complexity of sensors.

[0014] As a preferred example, the salinity interferometer is a Fabry-Perot interferometer.

[0015] The salinity interferometer used in this invention is a Fabry-Perot interferometer, which is sensitive not only to changes in salinity but also to changes in temperature, meaning that the interferometer has high sensitivity to changes in temperature and salinity.

[0016] As a preferred example, the salinity interferometer consists of two single-mode optical fibers and polyimide; wherein:

[0017] The two single-mode optical fibers have their end faces aligned and a gap exists between them, with the polyimide filling the gap.

[0018] The salinity interferometer provided by this invention consists of two single-mode optical fibers and polyimide filling the space between the two single-mode optical fibers. Since polyimide is sensitive to salinity and has a much larger coefficient of thermal expansion than single-mode optical fibers, filling the gap between the single-mode optical fibers with polyimide can significantly improve the sensitivity of the sensor when the temperature changes, thus providing more accurate data for environmental monitoring.

[0019] As a preferred example, the temperature interferometer is a Sagnac interferometer.

[0020] The temperature interferometer used in this invention is a Sagnac interferometer, which has high sensitivity to temperature changes.

[0021] As a preferred example, the temperature interferometer is composed of polarization-maintaining optical fibers that form the Sagnac loop.

[0022] As a preferred example, the fiber coupler is a 2x2 single-mode fiber coupler.

[0023] The optical fiber coupler used in this invention is a 2x2 single-mode optical fiber coupler, which can distribute and couple the optical signal output from the circulator according to a certain ratio, such as 50:50. Accordingly, this invention also provides a method for using a multi-parameter fiber optic temperature and salinity sensor, applied to any of the multi-parameter fiber optic temperature and salinity sensors described above. The method includes the following steps:

[0024] A first optical signal is sent to the first end of the circulator via a broadband light source. The first optical signal is transmitted to the salinity interferometer through the second end of the circulator. The salinity interferometer processes the first optical signal and feeds back the processed second optical signal to the circulator.

[0025] The circulator receives the second optical signal fed back by the salinity interferometer and transmits the second optical signal fed back to the fiber coupler through the third end;

[0026] The fiber optic coupler transmits the second optical signal to the temperature interferometer, which processes the second optical signal and feeds back the processed third optical signal to the fiber optic coupler.

[0027] The fiber optic coupler transmits the feedback third optical signal to the spectrometer for spectral analysis.

[0028] As a preferred example, the fiber optic coupler transmits the feedback third optical signal to a spectrometer for spectral analysis, including:

[0029] When the spectrometer is in salinity monitoring mode, the salinity interferometer is determined to be a sensing interferometer, the temperature interferometer is determined to be a reference interferometer, and the spectrometer obtains the salinity to be measured by the change in the spectral envelope wavelength in the third optical signal.

[0030] When the spectrometer is in temperature monitoring mode, the salinity interferometer is determined to be the reference interferometer, the temperature interferometer is determined to be the sensing interferometer, and the spectrometer obtains the temperature to be measured based on the change in the spectral envelope wavelength in the third optical signal.

[0031] When the spectrometer is in different modes, it will adjust the positioning of the two interferometers accordingly. When the spectrometer is in salinity monitoring mode, it will identify the salinity interferometer as the primary interferometer, i.e., the sensing interferometer. That is, the spectral data output by this interferometer is the primary sensing data, while the corresponding temperature interferometer is the reference interferometer. The spectral data output by the corresponding reference interferometer is the reference data. This means that the spectrometer will adjust the primary sensing data based on the reference data.

[0032] As a preferred example, when the spectrometer is in salinity monitoring mode, the spectrometer determines the wavelength corresponding to the salinity interferometer in the third optical signal as the main wavelength and the wavelength corresponding to the temperature interferometer as the reference wavelength. After determination, the spectrometer performs spectral analysis on the spectral envelope wavelength in the third optical signal based on the determination result to obtain the salinity to be measured.

[0033] As a preferred example, when the spectrometer is in temperature monitoring mode, the spectrometer determines the wavelength corresponding to the temperature interferometer in the third optical signal as the main wavelength and the wavelength corresponding to the salinity interferometer as the reference wavelength. After determination, the spectrometer performs spectral analysis on the spectral envelope wavelength in the third optical signal based on the determination result to obtain the temperature to be measured. Attached Figure Description

[0034] Figure 1 : A structural diagram of one embodiment of the multi-parameter measurement fiber optic temperature and salinity sensor provided by the present invention;

[0035] Figure 2 : A flowchart illustrating an embodiment of the method for using the multi-parameter measurement fiber optic temperature and salinity sensor provided by the present invention;

[0036] Among them, 1. Broadband light source; 2. Circulator; 3. Single-mode optical fiber; 4. Polyimide; 5. Fiber optic coupler; 6. Temperature interferometer; 7. Spectrometer. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1

[0039] Please refer to Figure 1This is a structural diagram of an embodiment of the multi-parameter measurement fiber optic temperature and salinity sensor provided by the present invention, including a broadband light source, a fiber optic coupler and a spectrometer, as well as a circulator, a salinity interferometer and a temperature interferometer;

[0040] The broadband light source is communicatively connected to the first end of the circulator;

[0041] The second end of the circulator is bidirectionally connected to the salinity interferometer.

[0042] The third end of the circulator is communicatively connected to the first end of the fiber optic coupler;

[0043] The second end of the fiber optic coupler is communicatively connected to the first end of the temperature interferometer;

[0044] The second end of the temperature interferometer is communicatively connected to the third end of the fiber optic coupler;

[0045] The fourth end of the fiber optic coupler is communicatively connected to the spectrometer.

[0046] The fiber optic temperature-salinity sensor provided in this invention comprises two interferometers. By cascading these two interferometers, a vernier effect is generated, amplifying the influence of temperature and salinity changes on the sensing signal, thereby improving the sensor's measurement accuracy for temperature and salinity. Since the two interferometers in the fiber optic temperature-salinity sensor provided by this invention are sensitive to different measurement parameters—the salinity interferometer is sensitive to both salinity and temperature changes, while the temperature interferometer is sensitive to temperature changes—this invention uses a circulator to cascade these two interferometers to generate a vernier effect, thus amplifying temperature and salinity changes and achieving accurate measurement of these changes, improving the measurement accuracy and sensitivity of the fiber optic temperature-salinity sensor provided by this invention. Furthermore, since the two interferometers respond differently to temperature and salinity, by constructing a sensitivity coefficient matrix, simultaneous measurement of both temperature and salinity parameters can be achieved, improving measurement accuracy and efficiency.

[0047] In addition, the fiber optic sensor provided by this invention has better resistance to electromagnetic interference compared to point sensors, thus exhibiting higher operational stability in complex environments. Furthermore, compared to existing electrical sensors, fiber optic sensors are less expensive and simpler to maintain. Therefore, the fiber optic temperature and salinity sensor provided by this invention reduces the maintenance cost and complexity of sensors.

[0048] In this embodiment, see details. Figure 1 , Figure 1The ASE (Amplified Spontaneous Emission) light source in this embodiment is the broadband light source 1, 2 is a circulator, 2 is a single-mode fiber, 3 is a polyimide, 4 is a fiber coupler, 5 is a temperature interferometer, 6 is a spectrometer, and 7 is a spectrometer.

[0049] Among them, by Figure 1 Thus, the three ports of circulator 2 are respectively connected to broadband light source 1, single-mode fiber 3, and fiber coupler 5 for transmitting the optical signal output by broadband light source 1. While fiber coupler 5 is connected to circulator 2, it is also connected to temperature interferometer 6 and spectrometer 7.

[0050] Specifically, the salinity interferometer described in this embodiment is a Fabry-Perot interferometer.

[0051] The salinity interferometer used in this invention is a Fabry-Perot interferometer, which is sensitive not only to changes in salinity but also to changes in temperature, meaning that the interferometer has high sensitivity to changes in temperature and salinity.

[0052] Furthermore, the salinity interferometer described in this embodiment consists of two single-mode optical fibers and polyimide; wherein:

[0053] The two single-mode optical fibers have their end faces aligned and a gap exists between them, with the polyimide filling the gap.

[0054] The salinity interferometer provided by this invention consists of two single-mode optical fibers and polyimide filling the space between the two single-mode optical fibers. Since polyimide is sensitive to salinity and has a much larger coefficient of thermal expansion than single-mode optical fibers, filling the gap between the single-mode optical fibers with polyimide can significantly improve the sensitivity of the sensor when the temperature changes, thus providing more accurate data for environmental monitoring.

[0055] In this embodiment, the salinity interferometer consists of two single-mode optical fibers 3 with their end faces aligned and filled with polyimide 4 within the gap formed by the two single-mode optical fibers 3. Since a small gap remains between the end faces of the two single-mode optical fibers 3 after alignment and merging, the gap needs to be filled with polyimide 4. For the salinity interferometer provided in this embodiment, the user can adjust the cavity length of the salinity interferometer to ensure the measurement stability and accuracy during the sensing and measurement process, thereby further improving the measurement precision of the salinity interferometer.

[0056] Specifically, the temperature interferometer described in this embodiment is a Sagnac interferometer.

[0057] The temperature interferometer used in this invention is a Sagnac interferometer, which has high sensitivity to temperature changes.

[0058] Furthermore, the temperature interferometer described in this embodiment is composed of polarization-maintaining optical fibers that form the Sagnac loop.

[0059] In this embodiment, the temperature interferometer 6 is composed of a Sagnac loop formed by polarization-maintaining optical fiber. For the temperature interferometer 6 provided in this embodiment, the user can adjust the arm length of the temperature interferometer 6 to ensure the measurement stability and accuracy of the temperature interferometer 6 during the measurement process, and at the same time, further improve the measurement accuracy of the temperature-salt sensor.

[0060] Regarding the cavity length of the salinity interferometer and the 6-arm length of the temperature interferometer provided in this embodiment, it is preferable that the free spectral ranges of the two interferometers are similar but not equal, thereby further improving the measurement accuracy of the temperature and salinity sensor in this embodiment.

[0061] In addition, the cascading of the two interferometers provided in this embodiment generates a vernier effect, which further improves the measurement accuracy and sensitivity of the temperature-salinity sensor to temperature and salinity changes. Since the salinity interferometer (Fabry-Perot interferometer) provided in this embodiment has high sensitivity to temperature and salinity changes, and the temperature interferometer (Sagnac interferometer) has high sensitivity to temperature changes, by cascading the different characteristics of these two interferometers, a sensitivity measurement matrix is ​​constructed. Therefore, the temperature-salinity sensor provided in this embodiment, also known as a dual-parameter measurement interferometer, can achieve simultaneous high-precision measurement of temperature and salinity.

[0062] Furthermore, the fiber optic coupler provided in this embodiment is a 2x2 single-mode fiber optic coupler.

[0063] The fiber optic coupler used in this embodiment is a 2x2 single-mode fiber optic coupler, which can distribute and couple the optical signal output from the circulator according to a certain ratio, such as 50:50. In summary, the core working mechanism of the temperature-salt ratio sensor provided in this embodiment lies in its unique spectral envelope characteristic, which is formed by the precise multiplication of the spectra independently generated by the two interferometers. The optical signal output from the width light source 1, after passing through the dual filtering effect of the two interferometers, results in a clear periodic interference pattern in the sensor's spectrum. These fringes can be further combined to form a periodic spectral envelope, thereby significantly improving the sensor's measurement sensitivity.

[0064] Accordingly, see Figure 2 , Figure 2 This is a flowchart illustrating an embodiment of the method for using the multi-parameter measurement fiber optic temperature and salinity sensor provided by the present invention. Figure 2 As shown, the method of use includes the following steps:

[0065] A first optical signal is sent to the first end of the circulator via a broadband light source. The first optical signal is transmitted to the salinity interferometer through the second end of the circulator. The salinity interferometer processes the first optical signal and feeds back the processed second optical signal to the circulator.

[0066] The circulator receives the second optical signal fed back by the salinity interferometer and transmits the second optical signal fed back to the fiber coupler through the third end;

[0067] The fiber optic coupler transmits the second optical signal to the temperature interferometer, which processes the second optical signal and feeds back the processed third optical signal to the fiber optic coupler.

[0068] The fiber optic coupler transmits the feedback third optical signal to the spectrometer for spectral analysis.

[0069] In this embodiment, the working principle of the temperature and salinity sensor specifically includes: the light signal emitted by the broadband light source 1 first enters the first end of the circulator 2, and then the light output from the port of the second end of the circulator enters the salinity interferometer. The salinity interferometer processes the received light signal and reflects the processed light signal back to the second end of the circulator 2. The reflected light signal will re-enter the circulator 2 and be output from the third end of the circulator 2 to the fiber optic coupler 5.

[0070] In fiber optic coupler 5, the optical signal is first split into two beams of equal intensity, and the two beams will propagate in opposite directions. When these two beams of equal intensity pass through temperature interferometer 6... Figure 1 In the Sagnac circuit shown, a phase difference arises due to the birefringence of the polarization-maintaining fiber. Therefore, when these two beams of light pass through fiber coupler 5 again, fiber coupler 5 couples the two beams together to achieve interference, and outputs the coupled and interfered optical signal to spectrometer 7 for spectral analysis. Specifically, in this embodiment, the fiber coupler transmits the feedback third optical signal to the spectrometer for spectral analysis, including:

[0071] When the spectrometer is in salinity monitoring mode, the salinity interferometer is determined to be a sensing interferometer, the temperature interferometer is determined to be a reference interferometer, and the spectrometer obtains the salinity to be measured based on the change in the spectral envelope wavelength in the third optical signal.

[0072] When the spectrometer is in temperature monitoring mode, the salinity interferometer is determined to be the reference interferometer, the temperature interferometer is determined to be the sensing interferometer, and the spectrometer obtains the temperature to be measured based on the change in the spectral envelope wavelength in the third optical signal.

[0073] When the spectrometer is in different modes, it will adjust the positioning of the two interferometers accordingly. When the spectrometer is in salinity monitoring mode, it will identify the salinity interferometer as the primary interferometer, i.e., the sensing interferometer. That is, the spectral data output by this interferometer is the primary sensing data, while the corresponding temperature interferometer is the reference interferometer. The spectral data output by the corresponding reference interferometer is the reference data. This means that the spectrometer will adjust the primary sensing data based on the reference data.

[0074] Furthermore, when the spectrometer described in this embodiment is in salinity monitoring mode, the spectrometer determines the wavelength corresponding to the salinity interferometer in the third optical signal as the main wavelength and the wavelength corresponding to the temperature interferometer as the reference wavelength, and performs spectral analysis on the third optical signal based on the determination result.

[0075] Furthermore, when the spectrometer described in this embodiment is in temperature monitoring mode, the spectrometer determines the wavelength corresponding to the temperature interferometer in the third optical signal as the main wavelength and the wavelength corresponding to the salinity interferometer as the reference wavelength, and performs spectral analysis on the third optical signal based on the determination result.

[0076] In this embodiment, when the spectrometer 7 is in temperature monitoring mode, the temperature-salinity sensor of this embodiment determines the temperature interferometer 6 as the sensing interferometer, responsible for sensitively responding to changes in the external environment, while the salinity interferometer acts as the reference interferometer, providing a stable reference signal. As the ambient temperature fluctuates, the polarization-maintaining fiber of the temperature interferometer 6 undergoes changes in length and the refractive index difference between the fast and slow axes due to the combined effects of thermal expansion and thermo-optical effects. This change causes a wavelength drift in the temperature interferometer 6, which is directly reflected in the spectral envelope of the sensor, thereby achieving high-precision temperature measurement.

[0077] Accordingly, when the spectrometer 7 is in salinity monitoring mode, the temperature interferometer 6 in this embodiment becomes a reference interferometer providing a stable reference signal, while the corresponding salinity interferometer transforms into a sensing interferometer. When the salt solution concentration in which the salinity interferometer is located increases, the polyimide material it contains shrinks in volume due to the release of water molecules, resulting in a decrease in the cavity length of the salinity interferometer. Simultaneously, the refractive index of the polyimide in the interferometer also changes. These combined effects cause a wavelength shift in the salinity interferometer, thereby altering the spectral envelope of the sensor and achieving high-precision salinity measurement.

[0078] In summary, this invention provides a fiber optic temperature-salinity sensor for multi-parameter measurement and its usage method, comprising a broadband light source, a fiber optic coupler, a spectrometer, a circulator, a salinity interferometer, and a temperature interferometer. The broadband light source is communicatively connected to a first end of the circulator; the second end of the circulator is bidirectionally communicatively connected to the salinity interferometer; the third end of the circulator is communicatively connected to a first end of the fiber optic coupler; the second end of the fiber optic coupler is communicatively connected to a first end of the temperature interferometer; the second end of the temperature interferometer is communicatively connected to a third end of the fiber optic coupler; and the fourth end of the fiber optic coupler is communicatively connected to the spectrometer. This invention utilizes a circulator to cascade two interferometers to generate a vernier effect, achieving precise measurement of temperature-salinity changes and simultaneous measurement of both temperature and salinity parameters, thus improving the measurement accuracy and sensitivity of the fiber optic temperature-salinity sensor. The fiber optic sensor also exhibits high resistance to electromagnetic interference, enhancing its operational stability in complex environments.

[0079] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A fiber optic temperature and salinity sensor for multi-parameter measurement, wherein, The fiber optic temperature-salt sensor includes a broadband light source, a fiber optic coupler, and a spectrometer. It is characterized in that the fiber optic temperature-salt sensor further includes a circulator, a salinity interferometer, and a temperature interferometer; the salinity interferometer is composed of two single-mode optical fibers and polyimide; the end faces of the two single-mode optical fibers are aligned, and a gap exists between the two single-mode optical fibers, with the polyimide filling the gap; the temperature interferometer is composed of polarization-maintaining optical fibers forming a Sagnac loop. The broadband light source is communicatively connected to the first end of the circulator; The second end of the circulator is bidirectionally connected to the salinity interferometer. The third end of the circulator is communicatively connected to the first end of the fiber optic coupler; The second end of the fiber optic coupler is communicatively connected to the first end of the temperature interferometer; The second end of the temperature interferometer is communicatively connected to the third end of the fiber optic coupler; The fourth end of the fiber optic coupler is communicatively connected to the spectrometer. The method of using the fiber optic temperature-salt sensor includes the following steps: A first optical signal is sent to the first end of the circulator via a broadband light source. The first optical signal is transmitted to the salinity interferometer through the second end of the circulator. The salinity interferometer processes the first optical signal and feeds back the processed second optical signal to the circulator. The circulator receives the second optical signal fed back by the salinity interferometer and transmits the second optical signal fed back to the fiber coupler through the third end; The fiber optic coupler transmits the second optical signal to the temperature interferometer, which processes the second optical signal and feeds back the processed third optical signal to the fiber optic coupler. The fiber optic coupler transmits the feedback third optical signal to the spectrometer for spectral analysis.

2. The fiber optic temperature and salinity sensor for multi-parameter measurement as described in claim 1, characterized in that, The salinity interferometer is a Fabry-Perot interferometer.

3. The fiber optic temperature and salinity sensor for multi-parameter measurement as described in claim 1, characterized in that, The temperature interferometer is a Sagnac interferometer.

4. The fiber optic temperature and salinity sensor for multi-parameter measurement as described in claim 1, characterized in that, The fiber optic coupler is a 2x2 single-mode fiber optic coupler.

5. The fiber optic temperature and salinity sensor for multi-parameter measurement as described in claim 1, characterized in that, The fiber optic coupler transmits the feedback third optical signal to a spectrometer for spectral analysis, including: When the spectrometer is in salinity monitoring mode, the salinity interferometer is determined to be a sensing interferometer, the temperature interferometer is determined to be a reference interferometer, and the spectrometer obtains the salinity to be measured by the change in the spectral envelope wavelength in the third optical signal. When the spectrometer is in temperature monitoring mode, the salinity interferometer is determined to be the reference interferometer, the temperature interferometer is determined to be the sensing interferometer, and the spectrometer obtains the temperature to be measured by the change in the spectral envelope wavelength in the third optical signal.

6. The fiber optic temperature and salinity sensor for multi-parameter measurement as described in claim 5, characterized in that, When the spectrometer is in salinity monitoring mode, the spectrometer determines the wavelength corresponding to the salinity interferometer in the third optical signal as the main wavelength and the wavelength corresponding to the temperature interferometer as the reference wavelength. After determination, the spectrometer performs spectral analysis on the spectral envelope wavelength in the third optical signal based on the determination result to obtain the salinity to be measured.

7. The fiber optic temperature and salinity sensor for multi-parameter measurement as described in claim 5, characterized in that, When the spectrometer is in temperature monitoring mode, the spectrometer determines the wavelength corresponding to the temperature interferometer in the third optical signal as the main wavelength and the wavelength corresponding to the salinity interferometer as the reference wavelength. After determination, the spectrometer performs spectral analysis on the spectral envelope wavelength in the third optical signal based on the determination result to obtain the temperature to be measured.

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