Method for measuring temperature of high-resolution optical fiber microsphere resonant cavity based on PDH technology
Through PDH technology combining ultra-narrow linewidth light source and demodulation module optical fiber microsphere resonant cavity system, the problem of insufficient resolution of traditional echo wall microcavity fiber sensors is solved, high-sensitivity temperature and humidity detection is achieved, simplifying the preparation process and improving the yield rate.
Patent Information
- Application Number
- CN202510414720.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-02
- Publication Date
- 2025-07-04
AI Technical Summary
The resolution of the existing echo wall microcavity fiber sensors in temperature measurement is limited by the resolution of the spectrometer or tunable laser demodulator, and the traditional resonant mode has a large half-high peak width at limited resolution, making it difficult to achieve high-resolution temperature measurement.
The fiber microsphere resonant cavity system based on PDH technology is adopted, and the modulation optical signal is generated using an ultra-narrow linewidth light source and modulation module. It receives and demodulates the fiber optical sensor structure module through the echo wall microcavity fiber sensor structure module, and realizes high-resolution temperature measurement in combination with the demodulation module and the output module. It uses a narrow linewidth laser to lock the resonant peak of the higher order mode to monitor the resonant peak drift.
High sensitivity detection of physical quantities such as temperature and humidity is achieved, reducing the preparation requirements for microspheres, improving yield, and simplifying the preparation process.
Smart Images
Figure CN120252995A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of fiber optic sensing, and particularly relates to a high-resolution fiber optic microsphere resonator temperature measurement method based on PDH technology. Background Art
[0002] Since the emergence of fiber optic sensing technology in the 1970s, after decades of rapid development, it has gradually played a key and even indispensable role in various application scenarios. Among them, the fiber grating-based strain sensor, as an important branch of fiber optic sensing technology, has the characteristics of small size, high stability, anti-electromagnetic interference, mature manufacturing process, and easy multiplexing. Thanks to the rapid development of modern optics and optical communication technology, it has continuously improved in terms of sensor performance indicators, engineering practicability, and stability, and has been widely used in various application scenarios such as vibration measurement, smart materials, and structural health detection.
[0003] At the same time, optical microcavities based on the whispering gallery mode have received extensive attention and are increasingly applied in the field of fiber optic sensing. The whispering gallery microsphere confines light in a very small cavity region by total internal reflection, and has the characteristics of high quality factor and small mode volume, and is widely used in the fields of nonlinear optics, high-sensitivity sensing, and cavity mechanics. In patent CN114894745A, a whispering gallery microcavity fiber optic humidity sensor is disclosed, which uses the refractive index change brought by the humidity-sensitive material on the surface of the whispering gallery microcavity to detect the humidity change by analyzing the projection spectrum. This scheme obtains the sensing signal by detecting the spectral change of the whispering gallery microcavity, and the resolution is limited by the resolution of the spectrometer or the tunable laser demodulator. Moreover, the traditional resonance mode is the outer envelope of the high-order mode under the spectrometer with limited resolution, and the full width at half maximum is much larger than the high-order resonance mode in the envelope. Summary of the Invention
[0004] The purpose of the present invention is to provide a high-resolution fiber optic microsphere resonator temperature measurement method based on PDH technology to solve at least one of the above technical problems.
[0005] To solve the above technical problems, the specific technical solution of the present invention is as follows:
[0006] In some embodiments of the present application, a high-resolution fiber optic microsphere resonator temperature measurement method based on PDH technology is provided, including:
[0007] An ultra-narrow linewidth light source and a modulation module, and a modulated optical signal is generated in the ultra-narrow linewidth light source and the modulation module;
[0008] A whispering gallery microcavity fiber optic sensor structure module, which receives the optical signal and generates an interference signal;
[0009] A demodulation module, which is connected to the whispering gallery mode fiber optic sensor structure module through a first polarization-maintaining fiber and demodulates the interference signal;
[0010] An output module, which detects and stores the demodulated interference signal.
[0011] In some embodiments of the present application, the ultra-narrow linewidth light source and the modulation module include: an ultra-narrow linewidth fiber laser, a phase modulator, and second and third polarization-maintaining fibers for connection;
[0012] Among them, the phase modulator is respectively connected to the ultra-narrow linewidth fiber laser and the whispering gallery mode fiber optic sensor structure module through the second and third polarization-maintaining fibers, and is electrically connected to a signal generator. The optical signal generated in the ultra-narrow linewidth light source is modulated by the phase modulator and then transmitted to the whispering gallery mode fiber optic sensor structure module.
[0013] In some embodiments of the present application, the whispering gallery mode fiber optic sensor structure module includes: a whispering gallery mode and a fused taper fiber; among them, the whispering gallery mode is formed by stripping the coating layer from a single-mode fiber and firing it with a fiber fusion splicer, and the fused taper fiber is connected to the whispering gallery mode, and its two ends are respectively connected to the third polarization-maintaining fiber and the first polarization-maintaining fiber.
[0014] In some embodiments of the present application, the diameter of the taper part of the fused taper fiber is 1μm - 10μm.
[0015] In some embodiments of the present application, the demodulation module includes: a balanced photodetector and an AD8333 circuit board; among them, the balanced photodetector is connected to the first polarization-maintaining fiber and is electrically connected to the AD8333 circuit board, and the AD8333 circuit board is also electrically connected to the signal generator.
[0016] In some embodiments of the present application, the output module includes: an FPGA and a PC; among them, the FPGA is electrically connected to the AD8333 circuit board and is also electrically connected to the PC. According to the captured error signal in the AD8333 circuit board, a corresponding voltage is generated and an interaction is carried out with the PC.
[0017] Compared with the prior art, the beneficial effects of the present invention are that the present invention uses a narrow linewidth laser as the system light source, monitors the drift of the resonant peak by locking the resonant peak of the high-order mode, and realizes the detection of temperature, humidity, magnetic field and other physical quantities, so it has higher sensitivity. And compared with the high requirements for the microspheres used in the existing common whispering gallery mode fiber optic sensors, the present system locks the resonant peak of the high-order mode, so the requirements for the sphere are lower, making the preparation process simpler and greatly improving the yield. Description of the Drawings
[0018] Upon reading the following detailed description of the preferred embodiments, various other advantages and benefits will become apparent to those of ordinary skill in the art. The drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:
[0019] Figure 1 It is a schematic diagram of the system solution provided by the embodiment of the present invention;
[0020] Figure 2 It is a schematic diagram of the structure of the fused taper fiber and the whispering gallery microcavity provided by the embodiment of the present invention;
[0021] Figure 3 It is a schematic diagram of the modulated signal provided by the embodiment of the present invention;
[0022] Figure 4 It is a schematic diagram of the temperature measurement results of the embodiment and the comparative temperature sensor provided by the embodiment of the present invention. Specific Embodiments
[0023] The following will further describe in detail the specific embodiments of the present invention in conjunction with the drawings and embodiments. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.
[0024] In order to better understand the purpose, structure and function of the present invention, the following will further describe the present invention in detail in conjunction with the drawings.
[0025] Embodiment 1
[0026] Referring to the attached Figure 1 - attached Figure 4 As shown, in the embodiment of the present application, it includes an ultra-narrow linewidth light source and a modulation module 1, a whispering gallery microcavity fiber sensing structure module 2, a demodulation module 3, and an output module 4.
[0027] The modulated light output of the ultra-narrow linewidth light source and the modulation module 1 is directly connected to the whispering gallery microcavity fiber sensing structure module 2 through the third polarization-maintaining fiber 104.
[0028] The whispering gallery microcavity fiber sensing structure module 2 is connected to the photodetector 301 through the first polarization-maintaining fiber 001.
[0029] The photodetector 301 is an anti-aliasing balanced photodetector with smoothing filtering.
[0030] The AD8333 circuit board 302 directly receives the sine signal from the signal generator 002. At the same time, it receives the signal from the photodetector 301 for demodulation.
[0031] The FPGA 401 generates corresponding voltages based on the captured error signals, interacts with the PC 402, sets parameters to control the system, and stores the detection results.
[0032] Among them, the ultra-narrow linewidth light source and the modulation module 1 are composed of an ultra-narrow linewidth fiber laser 101, a phase modulator 103, a second polarization-maintaining fiber 102 for connection, and a third polarization-maintaining fiber 104. The laser output by the ultra-narrow linewidth fiber laser 101 is input to the whispering gallery microcavity fiber sensing structure module 2 after passing through the phase modulator 103. The oscillation signal generated by the signal generator 002 provides a modulation signal for the phase modulator 103. After being modulated by the phase modulator 103, the phase of the light source amplitude is modulated and becomes:
[0033]
[0034] In the formula, Ω M is the phase modulation frequency, whose value is between 1 MHz and 40 MHz, and β is the modulation depth.
[0035] The whispering gallery microcavity 201 refers to a whispering gallery mode optical microcavity with dimensions in the micron range. In the whispering gallery microcavity 201, due to the total reflection effect at the interface between the high refractive index medium and the low refractive index medium, when the closed path of the light field satisfies the phase coherent superposition, a stable standing wave field can be formed, and thus the light can be confined in the cavity to generate oscillation.
[0036] Next, an example is given for the preparation process of the whispering gallery microcavity fiber sensing structure shown in Figure 2 which may include the following steps:
[0037] 1) Prepare the encapsulation body:
[0038] Use ultraviolet curing glue to encapsulate two short sides and one long side of the glass slide.
[0039] 2) Prepare the fused taper fiber 202:
[0040] Specifically, heat a section of the fiber with the coating removed using a hydrogen-oxygen flame, and stretch the fiber towards both ends with a motor to make the fused taper fiber 202. Here, the thickness of the taper part of the fused taper fiber 202 prepared in the embodiment of the present invention is not limited.
[0041] 3) Fix the fused taper fiber 202:
[0042] Place the fused taper fiber 202 in the groove formed in the center of the two short sides of the encapsulation body, make the taper part suspended, and fix the fused taper fiber 202 by dispensing glue, and the dispensing position avoids the taper part of the fused taper fiber 202.
[0043] 4) Prepare the whispering gallery microcavity 201:
[0044] Specifically, the end face of one end of the single-mode optical fiber with the coating layer removed is discharged multiple times to fabricate the whispering gallery microcavity 201.
[0045] 5) Fix the whispering gallery microcavity 201:
[0046] Use the micro-operation adjustment stage to move the whispering gallery microcavity 201 to a suitable position. The single-mode optical fiber carrying the whispering gallery microcavity 201 is perpendicular to the long side of the package, and the whispering gallery microcavity 201 is close to the fused taper fiber 202. The distance between the whispering gallery microcavity and the tapered portion satisfies a preset condition; the preset condition is that when light is transmitted in the fused taper fiber, the light of the tapered portion is coupled into the whispering gallery microcavity through the distance and resonance will occur.
[0047] The demodulation module 3 demodulates the error signal according to the PDH technology. Among them, a reference signal with the same frequency and phase as the input to the phase modulator 103 is generated by the signal generator 002, and is jointly input into the AD8333 302 together with the electrical signal converted by the balanced photodetector 301. After multiplication and low-pass filtering processing, the DC term is retained, and the corresponding signal is obtained and input into the FPGA 401.
[0048] The demodulation module 3 has the following demodulation steps:
[0049] 1) After being converted by the balanced photodetector 301, the optical signal is converted into an electrical signal, and the signal P in satisfies the following formula:
[0050]
[0051] In the formula, P DC is the DC term of the input signal, P0 is the gain intensity, which is related to the input laser intensity, F(ω) is the transmission function of the resonant cavity, and Ω M is the phase modulation frequency.
[0052] 2) The reference signal sent by the signal generator 002 and the electrical signal obtained via the balanced photodetector 301 are simultaneously input into the AD8333 circuit board 302. The AD8333 circuit board 302 is used as the key I / Q demodulator IC in the system to generate the required I / Q signals.
[0053] 3) The signal after passing through the AD8333 circuit board 302 is sent to the FPGA 401 in the output module 4 for subsequent processing.
[0054] The balanced optoelectronic detector 301 converts the detected optical signal into an electrical signal. During the signal processing process, methods such as phase-locked amplification technology and Fourier transform can also be used to collect, analyze, and process the electrical signal, and extract the change information of optical characteristics such as the resonance wavelength, quality factor, and mode intensity of the high-order mode. Through the established multi-parameter measurement model and combined with the signal processing algorithm, the values of the measured quantities (such as temperature, pressure, refractive index, etc.) are demodulated.
[0055] The output module 4 described above is specifically: including FPGA 401 and PC 402.
[0056] The FPGA 401 generates a corresponding voltage according to the captured error signal, interacts with the PC 402, and sets parameters to control the system and store the detection results.
[0057] The FPGA 401 generates a corresponding voltage according to the captured error signal, interacts with the PC 402, and sets parameters to control the system and store the detection results.
[0058] Through the above technical solutions, the technical effects generated in the embodiments of the present application are as follows:
[0059] By combining the PDH demodulation technology with the whispering gallery microcavity fiber sensing system. Different from the existing whispering gallery microcavity fiber sensors, most of which use broadband light sources and lock the resonance peaks of the fundamental mode; in this embodiment, a narrow linewidth laser is used as the system light source. By locking the resonance peaks of the high-order mode and monitoring the drift of the resonance peaks, the detection of other physical quantities such as temperature, humidity, and magnetic field is realized, thus having higher sensitivity. And compared with the high requirements for the microspheres used in the existing common whispering gallery microcavity fiber sensors, since this system locks the resonance peaks of the high-order mode, the requirements for the sphere are lower, making the preparation process simpler and greatly improving the yield.
[0060] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application.
[0061] The terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "plurality" is two or more.
[0062] In the description of the present application, it should be noted that unless otherwise clearly specified or limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.
[0063] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part.
[0064] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A high-resolution fiber microsphere resonator temperature measurement method based on PDH technology, characterized in that Comprising: An ultra-narrow linewidth light source and a modulation module, which generate a modulated optical signal in the ultra-narrow linewidth light source and modulation module; A whispering gallery mode fiber optic sensor structure module, which receives the optical signal and generates an interference signal; A demodulation module, which is connected to the whispering gallery mode fiber optic sensor structure module through a first polarization-maintaining fiber and demodulates the interference signal; An output module, which detects and stores the demodulated interference signal.
2. The high-resolution optical fiber microsphere resonator temperature measurement method based on the PDH technology according to claim 1, characterized in that The ultra-narrow linewidth light source and modulation module includes: an ultra-narrow linewidth fiber laser, a phase modulator, and second and third polarization-maintaining fibers for connection; Wherein, the phase modulator is respectively connected to the ultra-narrow linewidth fiber laser and the whispering gallery mode fiber optic sensor structure module through the second and third polarization-maintaining fibers, and is electrically connected to a signal generator. The optical signal generated in the ultra-narrow linewidth light source is modulated by the phase modulator and then transmitted to the whispering gallery mode fiber optic sensor structure module.
3. A high-resolution fiber microsphere resonator temperature measurement method based on PDH technology according to claim 1, characterized in that The whispering gallery mode fiber optic sensor structure module includes: a whispering gallery mode and a fused taper fiber; wherein, the whispering gallery mode is formed by stripping the coating layer from a single-mode fiber and firing it with an optical fiber fusion splicer, and the fused taper fiber is connected to the whispering gallery mode, and its two ends are respectively connected to the third polarization-maintaining fiber and the first polarization-maintaining fiber.
4. A high-resolution fiber microsphere resonator temperature measurement method based on PDH technology according to claim 3, characterized in that The diameter of the taper part of the fused taper fiber is 1μm - 10μm.
5. A high-resolution fiber microsphere resonator temperature measurement method based on PDH technology according to claim 1, characterized in that, The demodulation module includes: a balanced photodetector and an AD8333 circuit board; wherein, the balanced photodetector is connected to the first polarization-maintaining fiber and is electrically connected to the AD8333 circuit board, and the AD8333 circuit board is also electrically connected to the signal generator.
6. A high-resolution fiber microsphere resonator temperature measurement method based on PDH technology according to claim 1, characterized in that The output module includes: an FPGA and a PC; wherein, the FPGA is electrically connected to the AD8333 circuit board and is also electrically connected to the PC. According to the error signal captured in the AD8333 circuit board, a corresponding voltage is generated and an interaction is carried out with the PC.