High-sensitivity distributed optical fiber temperature sensor based on PDMS / glycerin film
By coating PDMS/glycerol film on the surface of the fiber, using optical frequency domain reflection technology, the shortcomings of traditional fiber temperature sensors under the requirements of high sensitivity and high spatial resolution are solved, and high sensitivity and low cost temperature measurement effects are achieved.
Patent Information
- Application Number
- CN202411814445.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-11
- Publication Date
- 2025-03-18
AI Technical Summary
Traditional fiber optic temperature sensors perform poorly in situations where high sensitivity and high spatial resolution are required, and their structural complexity and cost are high, which affects their wide application.
By using optical frequency domain reflection technology based on PDMS/glycerol film, the light propagation characteristics of the optical fiber are significantly changed and the sensitivity of temperature response is improved.
It realizes temperature measurements that maintain high sensitivity over a wide temperature range, reduces cost and structural complexity, simplifies application processes, and is suitable for distributed temperature monitoring.
Smart Images
Figure CN119642999A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of optical fiber sensing technology, in particular to a high-sensitivity distributed optical fiber temperature sensor based on PDMS / glycerol film. The sensor aims to provide a new temperature measurement solution with high sensitivity and reliability. Background Art
[0002] Temperature measurement and monitoring technology plays an indispensable role in modern industrial production and scientific research. Whether it is temperature control in chemical reactions or real-time monitoring of the operating status of electronic equipment, accurate temperature information is the key to ensuring safe and efficient operation of the system. Traditional temperature sensors, such as thermocouples and resistance temperature detectors (RTDs), provide reliable data support in many fields with their mature technology and wide application. However, with the development of science and technology and changes in social needs, these traditional sensors seem to be unable to cope with distributed temperature monitoring tasks. Especially in situations where high sensitivity and high spatial resolution are required, traditional sensors are difficult to achieve ideal results due to physical size limitations and susceptibility to electromagnetic interference.
[0003] In this context, fiber optic temperature sensors have gradually become a new hotspot for research and application due to their unique advantages. The optical fiber itself has many advantages such as small diameter, light weight, high sensitivity, anti-electromagnetic interference, and corrosion resistance, making it possible to use it in harsh environments. In particular, with the rapid development of distributed optical fiber sensing technology, the application of optical fiber temperature sensors has ushered in new breakthroughs. Using the optical fiber itself as a sensing element can not only achieve real-time monitoring of long-distance temperature changes, but also provide high-precision spatial positioning information, greatly expanding the means and methods of temperature field analysis.
[0004] Although fiber optic temperature sensors have shown great potential in many fields, they still face some challenges in practical applications. Current fiber optic temperature sensors mainly rely on the physical properties of optical fibers to sense temperature changes, which to a certain extent limits the improvement of their sensitivity and resolution. For example, traditional single-point temperature sensors often require multiple arrangements and complex installation processes, especially when monitoring temperature over long distances, the arrangement is cumbersome and it is difficult to ensure accuracy. At the same time, although the methods of special optical fibers, special structure optical fibers, and metal-coated optical fibers can improve sensitivity, they bring about increased structural complexity and cost, affecting the widespread application of sensors.
[0005] In order to solve this problem, a new coated optical fiber temperature sensor based on optical frequency domain reflection technology is proposed. By coating a specific PDMS / glycerol thin film material on the surface of the optical fiber, the sensor significantly changes the light propagation characteristics of the optical fiber and improves the sensitivity of the temperature response. The PDMS / glycerol material has a good temperature adaptability range and can stably work in the temperature range of -40℃ to 150℃. Combined with the high-resolution measurement capability of optical frequency domain reflection technology, this new sensor can not only maintain high sensitivity over a wide temperature range, but also achieve accurate measurement of long-distance temperature changes. In addition, the sensor based on optical frequency domain reflection technology has a simple structure and low price, which greatly reduces the cost and simplifies the application process, becoming a powerful supplement in the field of temperature monitoring. It provides strong technical support for industrial production optimization, disaster warning and other fields. Summary of the invention
[0006] In view of some problems existing in the prior art, a high-sensitivity distributed optical fiber temperature sensor based on PDMS / glycerol film is provided. PDMS is a flexible material with good optical transparency and excellent chemical stability. In the application of temperature sensors, PDMS is often used as an optical sensing material. Combined with glycerol, the application of PDMS / glycerol film in optical fiber sensors is expected to significantly improve the sensitivity and measurement accuracy of the sensor. This new film can not only effectively improve the temperature response characteristics of optical fiber sensors, but also maintain stable performance under different environmental conditions, thereby meeting the needs of high-precision and high-sensitivity temperature measurement.
[0007] A high-sensitivity distributed optical fiber temperature sensor based on PDMS / glycerol film, characterized in that it includes a distributed optical fiber sensing structure of an optical frequency domain reflection system, a conducting optical fiber, a sensing optical fiber and a signal demodulation system, wherein the conducting optical fiber is a single-mode optical fiber including a core and a cladding, and the sensing optical fiber includes a single-mode optical fiber and a PDMS / glycerol film.
[0008] The invention provides a high-sensitivity distributed optical fiber temperature sensing system of a PDMS / glycerol film based on an optical frequency domain reflection technology, comprising an optical frequency domain reflection system, a PDMS / glycerol film optical fiber sensor and a signal demodulation.
[0009] The optical frequency domain reflection system, in this embodiment, uses a pre-installed optical frequency domain reflection distributed optical fiber measurement structure, and all the components and structures used are commercially available.
[0010] The PDMS / glycerol film optical fiber sensor is prepared by coating a single-mode optical fiber with a PDMS / glycerol film. In this embodiment, the length of the single-mode optical fiber coated with a PDMS / glycerol film is 0.3 m.
[0011] The core diameter of the single-mode optical fiber is 8-9 μm, and the cladding diameter is 125 μm.
[0012] The PDMS / glycerol film coated single-mode optical fiber has a thickness of 300 μm.
[0013] In the present invention, the preparation process of the high-sensitivity distributed optical fiber temperature sensor is as follows: Figure 4 As shown, the method includes:
[0014] Take out a 1m long single-mode optical fiber, with one end as the head and the other end as the tail. Use optical fiber strippers to strip off 0.3m of the protective layer of the single-mode optical fiber near its tail. Then use cotton balls and alcohol to wipe it to get a smooth and neat single-mode optical fiber.
[0015] The Sylgard184-A component and the Sylgard184-B component purchased from Dow Corning were fully mixed at a mass ratio Q of 10:1 to obtain PDMS, and then the obtained PDMS was mixed with glycerol at a mass ratio M of 12:1, and then an ultrasonic oscillator and a magnetic stirrer were used to fully mix the solution and remove bubbles, and then a pressure injection device was used to evenly inject the solution into a mold containing a single-mode optical fiber, and then heated and cured to obtain a PDMS / glycerol thin film optical fiber temperature sensor.
[0016] The following is an explanation of the high temperature sensitivity sensing mechanism of this example:
[0017] In an optical frequency domain reflection system, an external perturbation of the optical fiber at a given position causes a local change in the refractive index profile or the length of the optical fiber. This in turn causes a shift in the optical spectrum of the Rayleigh backscattering (RBS) in the local segment. RBS-based optical fiber sensing has the same working principle as FBG sensors, so during the sensing process, the RBS optical frequency is sensitive to strain and temperature changes, which can be described as formula (1):
[0018]
[0019] In formula (1), v is the optical frequency of RBS, δυ is the displacement under the action of strain and temperature change (ΔT), and α is the thermal expansion coefficient of the optical fiber, which is 0.55×10 -6 ξ is the thermal optical coefficient of the optical fiber, which is 8.3×10 -6 When a polymer coating is added to the optical fiber, the strain change caused by the thermal expansion of the polymer coating and the optical fiber can be expressed as (2):
[0020]
[0021] In formula (2), P eis the photoelastic coefficient, Δε is the induced strain. The coating polymer is PDMS / glycerol film, and its thermal expansion coefficient α = 303.7×10 -6 , which is three orders of magnitude higher than that of silica optical fiber, as shown in formula (3);
[0022] Δε=AT*α P_G (3)
[0023] It is assumed that the induced strain in the optical fiber is caused by PDMS / glycerol and is proportional to its thermal expansion in a limited temperature range. Considering that the thermo-optic coefficient is linearly dependent on temperature in a limited range, while the photoelastic constant is independent of temperature. Then, the normalized temperature sensitivity of the PDMS / glycerol coated optical fiber is given by equation (4):
[0024]
[0025] The temperature sensitivity of PDMS / glycerol coated single-mode optical fiber is higher than that of uncoated single-mode optical fiber.
[0026] The present invention improves the sensitivity of the optical fiber temperature sensor through a coating process, while avoiding the shortcomings of the prior art. It has the advantages of simple structure, high precision, fast measurement speed, corrosion resistance, etc., can realize distributed optical fiber sensing, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 The figure is a schematic diagram of the structure of a high-sensitivity distributed optical fiber temperature sensor system based on PDMS / glycerol film in the present invention.
[0028] Figure 2 This is a liquid injection diagram of a high-sensitivity distributed optical fiber temperature sensor based on PDMS / glycerol film.
[0029] Figure 3 It is a highly sensitive distributed optical fiber temperature sensor based on PDMS / glycerol film.
[0030] Figure 4 This is a diagram of the preparation process of a high-sensitivity distributed optical fiber temperature sensor based on PDMS / glycerol film.
[0031] Figure 5 Figure 2 shows the temperature drift diagram of three distributed optical fiber temperature sensors.
[0032] Figure 6 Temperature sensitivity diagram of three distributed optical fiber temperature sensors.
[0033] Among them, 1. single-mode optical fiber core, 2. single-mode optical fiber cladding, 3. PDMS / glycerol thin film coating layer, 4. 3D printing mold, 5. mold injection port, 6. mold exhaust port. DETAILED DESCRIPTION
[0034] like Figure 1 As shown, the tunable laser source (TLS) outputs a linear scanning laser, which is then transmitted to the main and auxiliary interferometers. The main interferometer is a Mach-Zehnder interferometer. The scattered light in the sensing fiber interferes with the local light to produce a beat signal, which is transmitted to a balanced detection structure to reduce interference noise. The signal is split into two orthogonal polarizations (p and s) by a polarization beam splitter and detected by a photodetector. The signal is then converted into an analog-to-digital format by a signal acquisition card. The auxiliary interferometer provides an external clock to the signal acquisition card for triggering and resampling the main interferometer signal at equal time intervals to compensate for the nonlinearity of the source frequency scan. The prepared PDMS / glycerol film fiber temperature sensor is placed in a constant temperature heating box with a temperature range of 20°C (reference temperature) to 85°C, with an increase of 5°C in each step. Subsequently, a cross-correlation demodulation algorithm is used to analyze the spectral offset between the reference signal and the measured signal to draw a temperature sensitivity curve. Figure 5 and Figure 6 It includes the temperature drift and sensitivity experimental diagram of a high-sensitivity distributed optical fiber temperature sensor based on PDMS / glycerol film. The sensitivity of the distributed optical fiber temperature sensor based on PDMS / glycerol film is 17.14pm / ℃, which is about 1.7 times that of single-mode optical fiber.
Claims
1. A high-sensitivity distributed optical fiber temperature sensor based on PDMS / glycerol film, mainly for optical fiber temperature sensor preparation and temperature demodulation, can realize distributed measurement of temperature, characterized by: The preparation process includes the following steps: (1) Take out the prepared 1m long single-mode optical fiber and use Miller pliers to strip off 0.3m of the protective layer. Be careful to ensure that the surface of the optical fiber is smooth; (2) Clean the measuring cylinder and beaker, then mix deionized water and anhydrous ethanol in a ratio of 1:1 to make a cleaning solution, then pour it into the beaker containing the optical fiber and place it in an ultrasonic oscillator for cleaning, and finally dry it for later use; (3) Sylgard 184-A component and Sylgard 184-B component purchased from Dow Corning were fully mixed at a mass ratio Q of 10:1 to obtain PDMS; (4) mixing the obtained PDMS and glycerol in a mass ratio M of 12:1; (5) using an ultrasonic oscillator and a magnetic stirrer to uniformly mix the solution; (6) using a pressure perfusion device to uniformly inject the uniformly mixed solution into a 3D printed mold containing a single-mode optical fiber; (7) The mold is then placed in a constant temperature heating box, and the thermal curing temperature is preferably 60° C. and the time is preferably 3 h; (8) The cured PDMS / glycerol film optical fiber is fused by an optical fiber cutting machine and an optical fiber fusion splicing machine, and then fused into the sensing optical fiber of the optical frequency domain reflection system; (9) An optical frequency domain reflectometer system is used to collect temperature signals and perform cross-correlation demodulation. The sensitivity curve is plotted and compared with the optical fiber sensor before coating.
2. The high-sensitivity optical fiber temperature sensor according to claim 1, characterized in that: The thickness of the PDMS / glycerol film is 300 μm.
3. The high-sensitivity optical fiber temperature sensor according to claim 1, characterized in that: The mixture is mixed in a mass ratio M of 12:1, and the thermal curing temperature is preferably 60° C. and the time is preferably 3 hours.
4. The high-sensitivity distributed optical fiber temperature sensor measurement method based on PDMS / glycerol film according to claim 1 is characterized in that: The temperature of the constant temperature heating box ranges from 20°C to 85°C, and the signal is collected by increasing by 5°C each time.