Probe type multi-parameter ocean sensor based on seven-core optical fiber

Abstract

The invention provides a probe type multi-parameter ocean sensor based on a seven-core optical fiber. The device is characterized by comprising a broadband light source, a seven-core optical fiber fan-in and fan-out device, a circulator, a spectrograph and a seven-core optical fiber probe, wherein the seven-core optical fiber probe is formed by sequentially welding two capillary tubes with different inner diameters on a seven-core optical fiber. A probe fiber end is ground into a cone frustum, the grinding surface of the cone frustum is plated with a nanogold film, a fiber end capillary tube is filled with transparent elastic colloid, the side faces of three side cores of a seven-core optical fiber are polished and then plated with metal nanofilms, and a fiber grating is written into a central core of the seven-core optical fiber corresponding to the polishing and grinding area of the side cores. Therefore, measurement of salinity, pressure intensity, temperature, heavy metal concentration and biochemical molecules in an ocean sensing application scene can be realized. The optical fiber sensor is flexible and tight in structure and can be widely applied to the optical fiber sensing application fields such as ocean exploration, water body safety and biomedicine.

Description

(I) Technical field

[0001] The present invention relates to a probe-type multi-parameter ocean sensor based on seven-core optical fiber, which can be used to measure salinity, pressure, temperature, heavy metal concentration and biochemical molecules in ocean sensing application scenarios. It can be widely used in optical fiber sensing application fields such as ocean exploration, water safety, biomedicine, etc., and belongs to the field of optical fiber sensing technology. (II) Background technology

[0002] Marine exploration is of great significance to human society as a prerequisite for understanding marine ecology, studying marine environment and developing marine resources. In recent years, the marine detection network technology composed of multifunctional small sensors has become a hot spot for the development of marine exploration due to its unique advantages such as wide detection range, low cost and real-time monitoring. Fiber optic sensors are emerging as an innovative sensing technology with advantages such as versatility, miniaturization, anti-electromagnetic interference, easy waterproofing and easy integration into fiber optic communication networks. They are gradually replacing traditional electronic sensors and are recognized as a key component of marine network detection technology. In marine research, there are many parameters that need to be detected, among which salinity, temperature and air pressure can calculate key factors such as ocean density, depth and dynamics to achieve real-time analysis of ocean currents, tides and stratification. Heavy metal concentrations and biochemical molecules are important parameters for judging water safety.

[0003] The complex environment of seawater poses a greater challenge to fiber optic sensors. Currently, most fiber optic sensors can only be used to measure one or two parameters of seawater. Single parameter monitoring limits the practicality of the sensor, and mainstream fiber optic sensors are based on transmission structures, which not only limits their usage scenarios, but also makes their application more challenging.

[0004] Patent CN202410327442.0 provides a D-type cavity fiber seawater temperature sensor based on parallel cursor and its manufacturing method. The overall structure is divided into a sensing Fabry-Perot interferometer (SFPI) and a reference Fabry-Perot interferometer (RFPI). In SFPI, femtosecond laser micromachining technology is used to write a D-type microcavity on a hollow-core optical fiber, and a curable fluid temperature-sensitive material is filled in it to form a temperature sensing area; in RFPI, femtosecond laser micromachining technology is used again to write a pair of reflectors on a single-mode optical fiber to achieve precise control of the length between the reflective surfaces, which can achieve high-precision measurement of seawater temperature, but the sensor cannot achieve multi-parameter ocean sensor measurement.

[0005] Patent CN202410208772.8 discloses an in-situ high-sensitivity optical fiber seawater salinity sensing device and method. During the seawater salinity measurement process, the optical signal forms a sensing arm and a reference arm for transmission along a dual-path optical fiber. The entire device has ultra-high salinity sensitivity at the turning point, but the sensor cannot achieve multi-parameter measurement, and the transmission structure also limits its ease of use.

[0006] Patent CN201710114769.X provides a disposable all-fiber seawater temperature and depth profile sensor, which includes a long-period fiber grating coated with a sensitization film for measuring seawater temperature and a fiber Bragg grating for measuring seawater depth, so as to achieve high sensitivity to the seawater temperature and depth profile and independently measure and reasonably allocate the spectral range, realize single-optical path cascade and synchronous detection of FBG-LPG, but due to the insensitivity of FBG to the refractive index, the sensor is limited to the measurement of seawater salinity.

[0007] In order to overcome the shortcomings of the above-mentioned prior art, the present invention discloses a probe-type multi-parameter ocean sensor based on seven-core optical fiber. The sensor integrates five measurement channels: the three side cores of the seven-core optical fiber are polished and coated with metal nanofilms to form three surface plasmon resonance (SPR) sensing channels, and the transparent elastic colloid is injected into the fiber end of the capillary structure to form FPI to measure pressure and temperature. The fiber grating (FBG) is engraved on the central core of the seven-core optical fiber in the corresponding side core polishing area as a temperature compensation component. In terms of structural design, the stepped inner diameter capillary structure effectively simplifies the process of filling the elastic colloid and improves the repeatability of sensor preparation. The core reflection structure effectively guides the SPR transmission spectrum based on the side core polishing of the seven-core optical fiber to the diagonal side core of the seven-core optical fiber. This method effectively prevents crosstalk between channels and significantly reduces the complexity of demodulating multi-parameter measurement results. As a probe-type optical fiber sensor with multi-parameter measurement and easy demodulation, it can be effectively used in the fields of ocean exploration and underwater environment perception. (III) Summary of the invention

[0008] The object of the present invention is to provide a probe-type multi-parameter ocean sensor based on seven-core optical fiber which has a compact and flexible structure and can be mass-produced.

[0009] The specific implementation of the present invention is as follows:

[0010] The probe-type multi-parameter ocean sensor system based on seven-core optical fiber consists of a broadband light source, a circulator, a seven-core optical fiber fan-in and fan-out device, a probe-type multi-parameter ocean sensor and a spectrometer. The probe-type multi-parameter ocean sensor based on seven-core optical fiber is a seven-core optical fiber that welds the first-stage capillary optical fiber and the second-stage capillary optical fiber in sequence. The end of the second-stage capillary optical fiber is ground into a conical truncated cone and a nano-gold film is plated on the ground surface to realize the core coupling transmission of the optical signal. The capillary structure is filled with a transparent elastic colloid, and the FP air cavity formed is used to measure temperature parameters and pressure parameters; the three side cores of the seven-core optical fiber are polished and plated with metal nano-films to form three surface plasmon wave (SPW) sensitive areas; fiber gratings (FBGs) are engraved on the corresponding side core polishing positions on the central core of the seven-core optical fiber for temperature compensation during parameter measurement. The optical fiber sensing system can meet the needs of measuring salinity, temperature, pressure, heavy metal concentration and biochemical molecules in ocean sensing application scenarios.

[0011] Figure 1 and Figure 2 The working principle of the probe-type multi-parameter ocean sensor based on seven-core optical fiber is explained.

[0012] like Figure 1 As shown, first, the broadband light source 1 is coupled to the single-mode optical fiber 3, and after passing through the broadband circulator 4, the broadband light is transmitted to the core of the seven-core optical fiber through the special seven-core optical fiber fan-in and fan-out device 5. A short section of stepped capillary optical fiber is welded to the end of the seven-core optical fiber, and the end of the capillary optical fiber is ground into a conical truncated cone 8 by end face grinding. A nano-gold film is plated on the ground surface of the conical truncated cone 8 by a magnetron sputtering device, and a transparent elastic colloid is filled inside the capillary. Since the intensity of the capillary effect is inversely proportional to the aperture size, the elastic colloid only exists in the second-level capillary, and forms an FP air cavity 9 with the first-level capillary air cavity. After the three side cores of the seven-core optical fiber are polished, a metal nano-film is plated to form the sensing areas SPR1, SPR2 and SPR3, and FBG1, FBG2, and FBG3 are respectively engraved on the corresponding polished areas on the central core of the seven-core optical fiber for temperature compensation during parameter measurement.

[0013] For the sake of clarity, Figure 2 As shown, the light propagation in the sensor probe is divided into three stages. Stage I is that the light entering the middle core corresponds to the light signal of the FBG reflection spectrum and is reflected back and read by the spectrometer 2 for temperature crosstalk compensation; stage II is that the light entering the central core waveguide of the seven-core optical fiber is coupled into the resonant cavity of the first-level capillary optical fiber 25; stage III is that the seven-core optical fiber waveguide SPR light signals 22, 23, and 24 are reflected by the cone frustum into the diagonal waveguide, and are transmitted back to the spectrometer 2 after passing through the fan-in and fan-out device. 27, 28, and 29 are the waveguide combinations for the transmission of the SPR light signal in the seven-core optical fiber.

[0014] The fan-in and fan-out device for realizing interconnection and coupling between a single-mode optical fiber and a seven-core optical fiber is characterized in that each fiber core of the seven-core optical fiber can realize independent coupling and transmission with the corresponding single-mode optical fiber.

[0015] The grinding technology of the cone truncated cone can grind the first-stage capillary fiber end into a cone truncated cone, and control the electric control displacement stage to adjust the contact angle between the capillary fiber end and the grinding table surface, that is, the sensor fiber end is made into a reflection angle of 45 O Cone frustum of cone.

[0016] The probe-type multi-parameter ocean sensor based on seven-core optical fiber provided by the present invention can simultaneously measure temperature, pressure, salinity, heavy metal concentration and biochemical molecules in the sensing environment. Compared with the prior art, the sensor adopts a fan-in fan-out device and combines multi-core optical fiber space division multiplexing technology to effectively avoid mutual crosstalk during parameter measurement. The structure is compact and flexible, meeting the needs of multi-parameter measurement in ocean sensing scenarios. (IV) Description of the drawings

[0017] Figure 1 This is a system diagram of a probe-type multi-parameter ocean sensor based on seven-core optical fiber. The sensing system includes: a wide-spectrum light source 1, a spectrometer 2, a single-mode optical fiber 3, a broadband optical fiber circulator 4, a seven-core optical fiber fan-in and fan-out device 5, a probe-type multi-parameter ocean sensor 6, a seven-core optical fiber 7, a conical truncated cone with a nano-gold film on the surface 8, and a FP air cavity 9.

[0018] Figure 2 This is a schematic diagram of the SPR excitation and temperature and pressure sensing principle of a multi-parameter optical fiber sensor probe. The seven-core optical fiber 21 excites surface plasma waves 22, 23, 24, the FP resonant cavity 25, the second-stage capillary 26 filled with transparent elastic colloid, and the polished surface 27 coated with nano-gold film, 28, 29, 30 are the waveguide combination when exciting SPR.

[0019] Figure 3 31, 32, 33, 34, 35, 36 are the side cores of the seven-core optical fiber, 37 is the central core of the seven-core optical fiber, and 38 is the cladding of the seven-core optical fiber.

[0020] Figure 4 41 is the cladding of the first-stage capillary fiber, 42 is its air cavity, 43 is the cladding of the second-stage capillary fiber, and 44 is its air cavity.

[0021] Figure 5It is a schematic diagram of sensing measurement by a probe-type multi-parameter ocean sensor system based on seven-core optical fiber. The probe-type multi-parameter ocean sensor system based on seven-core optical fiber in this embodiment includes: a broadband light source 51, a spectrometer 52, a single-mode optical fiber 53, a broadband optical fiber circulator 54, a seven-core optical fiber fan-in fan-out device 55, an injection pump 56, a sensing area 57, a waste liquid tank 58, a multi-parameter ocean sensor 59, and a computer 60. (V) Specific implementation methods

[0022] The present invention will be further described below in conjunction with specific embodiments.

[0023] The cross-sectional diagram of the seven-core optical fiber of this embodiment is as follows: Figure 3 31, 32, 33, 34, 35, 36 are symmetrical side cores of the seven-core optical fiber, 37 is the middle core of the seven-core optical fiber, and 38 is the cladding of the seven-core optical fiber.

[0024] The cross-sectional schematic diagram of the capillary optical fiber of this embodiment is as follows: Figure 4 41 is the cladding of the first-stage capillary fiber, 42 is its air cavity, 43 is the cladding of the second-stage capillary fiber, and 44 is its air cavity.

[0025] The geometric dimensions of the single-mode optical fiber selected in this embodiment are: cladding diameter of 125um, core diameter of 9um, and numerical aperture of the core of 0.12; the geometric dimensions of the seven-core optical fiber selected are: cladding diameter of 125um, core diameter of 9um, and distance between cores of 37.5um; the cladding diameter of the first-stage capillary selected is 125um, and the inner diameter of the air cavity is 50um; the cladding diameter of the second-stage capillary selected is 125um, and the inner diameter of the air cavity is 20um; the dopant types of the selected optical fibers are all germanium.

[0026] The seven-core optical fiber was welded to a capillary optical fiber with a stepped inner diameter, and the fiber grating (FBG1, FBG2, FBG3) was written on the central core of the corresponding edge core polishing area of ​​the seven-core optical fiber by using the phase mask method; the side cores 31, 33, and 35 of the seven-core optical fiber were polished and coated with a metal nanofilm, and a conical frustum was made at the end of the second-stage capillary optical fiber by using a conical frustum grinding system. In this system, the stepper motor was adjusted to modulate the contact angle between the capillary fiber end and the polishing table to 45 O , a nano-gold film is plated on the polished surface to guide the SPR transmission spectrum of the seven-core optical fiber side core side throw to the diagonal side core of the seven-core optical fiber. The probe-type multi-parameter ocean sensor based on the seven-core optical fiber can meet the needs of pressure, salinity, temperature, heavy metal concentration, and biochemical molecule measurement in the application scenario of ocean sensing.

[0027] When the probe-type multi-parameter ocean sensor system based on the seven-core optical fiber of this embodiment implements sensor measurement, first, the probe-type multi-parameter sensor is connected to the measurement system. The sensing area 57 is injected with liquid containing the substance to be detected by the injection pump 56, and is connected to the waste liquid pool 58 to collect the waste liquid generated by the implementation. The broadband light output by the broadband light source 51 is coupled to the single-mode optical fiber 53, and after passing through the broadband optical fiber circulator 54, the broadband light is coupled to the seven-core optical fiber core through a special seven-core optical fiber fan-in fan-out device. Secondly, the optical signal entering the FP resonant cavity is reflected back and read out by the spectrometer 52 to realize the measurement of temperature and pressure in the sensing area. At the same time, after the three edge cores of the seven-core optical fiber are polished, a metal nanofilm is coated, and the incident light beam excites a surface plasma wave (SPW) at the boundary between the gold film and the medium, and the SPR optical signal containing the substance to be detected is reflected back to the diagonal core by the cone truncated cone, and then transmitted back to the spectrometer 52 after the fan-in fan-out device. The spectrometer is connected to the computer 60 to analyze the sensor signals collected by the spectrometer to meet the requirements of pressure, salinity, temperature, heavy metal concentration, and biochemical molecule measurement. The FBG optical signal reflected back to the spectrometer 52 is analyzed to achieve temperature crosstalk compensation during parameter measurement.

[0028] The probe-type multi-parameter ocean sensor system based on seven-core optical fiber provided in the embodiment of the present invention can realize multi-parameter measurement in ocean sensing application scenarios. Compared with the prior art, since the core of the seven-core optical fiber is fully utilized, its structure is compact and flexible, and channel crosstalk during multi-parameter measurement is effectively avoided.

[0029] The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician in the field can make various changes and modifications to the present invention based on the spirit and scope of the present invention, which should be included in the protection scope of the claims of the present invention.

Claims

1. A probe-type multi-parameter ocean sensor system based on seven-core optical fiber, Its characteristics are: The optical fiber sensor system consists of a broadband light source, a circulator, a seven-core optical fiber fan-in and fan-out device, a spectrometer and a probe-type multi-parameter ocean sensor based on the seven-core optical fiber. The multi-parameter ocean sensor is composed of a section of seven-core optical fiber welded to a section of stepped inner diameter capillary structure, wherein the fiber end of the capillary structure is ground into a conical truncated cone, and a nano-gold film is plated on the ground surface of the truncated cone to form core coupling of the optical signal, and a transparent elastic colloid is filled in the capillary optical fiber structure to form a Fabry-Perot interferometer (FPI) to measure the temperature and pressure parameters of the sensing area, and the three side cores of the seven-core optical fiber are polished and plated with metal nano-films to form three surface plasmon resonance (SPR) sensing channels, and a fiber grating (FBG) is written on the central core of the seven-core optical fiber corresponding to the side core polishing area to compensate for the temperature crosstalk during parameter measurement.

2. In the seven-core optical fiber-based probe-type multi-parameter ocean sensor system according to claim 1, a stepped inner diameter capillary structure for achieving precise filling of transparent elastic colloid, Its characteristics are: The structure consists of a first-stage capillary and a second-stage capillary. The inner diameter of the first-stage capillary is tens of microns larger than that of the second-stage capillary. Since the strength of the capillary effect is inversely proportional to the inner diameter of the capillary, the filled elastic colloid only remains in the second-stage capillary, that is, the length of the FP air cavity at the fiber end is the same as that of the first-stage capillary, and the length of the elastic sensitive membrane is the same as that of the second-stage capillary, which improves the repeatability and accuracy of the production of the FP resonant cavity.

3. According to the seven-core optical fiber probe-type multi-parameter ocean sensor system of claim 1, a reflection angle of 45° is formed at the second-stage capillary fiber end by a conical frustum grinding technique. O The core-to-core reflective cone frustum effectively guides the SPR transmission spectrum based on the side-core side-throw of the seven-core optical fiber into the diagonal side core of the seven-core optical fiber.

4. According to claim 1, the probe-type multi-parameter ocean sensor based on seven-core optical fiber adopts three sensing principles of SPR, FPI and FBG respectively, and is combined with multi-core optical fiber space division multiplexing technology to independently demodulate the measurement results of each channel. This design effectively prevents crosstalk between channels and significantly reduces the complexity of demodulating multi-parameter measurement results.

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