CN106197741A - Temperature-detecting device based on micro-nano long-period fiber grating sensor and method - Google Patents

Abstract

The invention discloses a temperature detection device and method based on a micro-nano long-period fiber grating sensor. A broadband light source sends a laser signal into the micro-nano long-period fiber grating sensor, and outputs a frequency-shifted modulation signal after being modulated by an acousto-optic modulator. The signal is divided into two beams of signal light by the first coupler, respectively enters the second coupler through the first optical fiber and the second optical fiber for combination, and then outputs the laser signal to be analyzed. The laser signal to be analyzed is converted into an electrical signal by a photodetector. The signal intensity information of the electrical signal is measured by the signal processing unit, and the temperature information to be measured is obtained by referring to the previously calibrated intensity information and the quantitative relationship between temperature. The present invention utilizes the high sensitivity of the central wavelength of the micro-nano long-period fiber grating sensor to temperature. When the temperature changes, the wavelength of the micro-nano long-period fiber grating sensor changes, and the phase difference between the first optical fiber and the second optical fiber changes. The temperature information to be measured is obtained by measuring the intensity change of the output signal of the detection system, which can accurately detect the temperature information, and has the advantages of low cost and simple structure.

Description

Temperature detection device and method based on micro-nano long-period fiber grating sensor

technical field

The invention relates to an optical fiber sensor, in particular to a temperature detection device and method based on a micro-nano long-period optical fiber grating sensor.

Background technique

The long-period fiber grating sensor refers to the introduction of periodic changes in the refractive index in the core of the optical fiber, and the period is on the same order of magnitude as the infrared wave, usually hundreds of microns. The long-period fiber grating sensor couples the light of a certain frequency band in the guided wave to the cladding and loses it. Its transmission characteristics will change due to external stress, temperature and other factors. The sensing information is obtained by tuning the resonance wavelength. It has the advantages of anti-electromagnetic interference, anti-corrosion, electrical insulation, high sensitivity, low cost, and good compatibility with ordinary optical fibers, and is suitable for precise and accurate measurement. Compared with ordinary Bragg gratings, long-period fiber gratings are more sensitive to environmental changes, and have the advantages of low reflection and simple measurement methods, so they are ideal sensing elements. Therefore, high-sensitivity fiber grating sensors are an important direction for the development of modern sensors. Long-period fiber gratings are used for sensing, and there are technical reports. In 2012, Bai Yukun and other researchers proposed the invention patent of cascaded long-period photonic crystal fiber grating temperature sensor, application number 201210525114.9. For substances, the grating period can be determined by the actual selected band. By controlling the temperature of the heat-sensitive material, the effective refractive index of the grating coupling mode is changed, thereby changing the central wavelength of the grating transmission spectrum, so that the temperature change is reflected in the shift of the transmission line, and the wavelength-tunable temperature sensing characteristics are realized. In the same year, Qiao Xueguang and other researchers proposed the invention patent of dual-period fiber grating temperature and humidity sensor, application number 201210088050.0. The effective refractive index and grating period change, the resonant wavelength changes, and the refractive index changes. By detecting the transmission wavelength of the temperature-sensitive long-period fiber grating and the moisture-sensitive long-period fiber grating, the temperature and humidity information of the environment can be obtained to realize Simultaneous measurement of two parameters; in 2013, Yang Yuqiang and other researchers proposed an invention patent for a temperature sensor based on long-period grating demodulation of ordinary fiber gratings, application number 201310316860.1, this invention effectively eliminates the influence of light source power fluctuations on the demodulation accuracy of fiber grating sensors . In 2015, researchers such as M.Najaria proposed a temperature and stress sensing system based on micro-nano long-period fiber grating sensors (Najari M, Javan A M, Amiri N. Hybrid all-fiber sensor forsimultaneous strain and temperature measurements based on Mach–Zehnderinterferometer [J].Optik-International Journal for Light and Electron Optics,2015,126(19):2022-2025.); In 2016, researchers such as Jia Shi proposed the temperature and refractive index of long-period fiber grating cascaded polarization-maintaining fibers Detection system (Shi J, Su G, Xu D, et al.A Dual-Parameter Sensor Usinga Long-Period Grating Concatenated With Polarization Maintaining Fiber in Sagnac Loop[J].IEEE Sensors Journal,2016,16(11):4326-4330 .).

Due to the large resonant bandwidth of the long-period fiber grating sensor of ordinary single-mode fiber, it is difficult to accurately measure the central wavelength, resulting in low temperature detection accuracy; in addition, due to the relatively large bandwidth of the transmission spectrum, if the resolution of the spectrometer is relatively low during measurement , it will introduce a relatively large wavelength reading error, which limits the measurement resolution of the long-period grating sensor of ordinary single-mode fiber. It is for these reasons that it is very inaccurate to directly measure the transmission peak of the long-period fiber grating sensor of ordinary single-mode fiber to obtain temperature information, and it appears that the measurement accuracy is not enough and has the disadvantages of large errors in the actual implementation of applications. Wait.

Contents of the invention

Purpose of the invention: The purpose of the present invention is to provide a temperature detection device and method based on a micro-nano long-period fiber grating sensor to improve the temperature detection accuracy.

Technical solution: The present invention provides a temperature detection device based on a micro-nano long-period fiber grating sensor, including a broadband light source connected in sequence, a micro-nano long-period fiber grating sensor, an acousto-optic modulator, a first coupler, an optical fiber, a second Two couplers, a photodetector and a signal processing unit, the optical fiber includes a first optical fiber and a second optical fiber, and the first coupler is connected to the second coupler through the first optical fiber and the second optical fiber respectively.

In order to increase the range of the temperature to be detected, the broadband light source is a broadband light source amplified by spontaneous emission in the 1525nm-1565nm band.

Further, the first optical fiber and the second optical fiber are one or both of single-mode optical fiber, dispersion-shifted optical fiber and highly nonlinear optical fiber.

Further, the photodetector is a balanced detector, and the response wavelength is consistent with the wavelength band of the broadband light source, so as to improve the measurement accuracy.

A temperature detection method based on a micro-nano long-period fiber grating sensor. A broadband light source sends out a laser signal that enters the micro-nano long-period fiber grating sensor. After modulation, the modulator outputs a frequency-shifted modulated signal. The modulated signal is divided into two beams of signal light by the first coupler, and enters the second coupler through the first optical fiber and the second optical fiber respectively for combination and then outputs the laser signal to be analyzed. The laser signal is converted into an electrical signal by the photodetector, and the signal intensity information of the electrical signal is measured by the signal processing unit, and the temperature information to be measured is obtained by referring to the quantitative relationship between the intensity information and the temperature calibrated in advance.

Further, the change of temperature causes the change of the transmission wavelength of the micro-nano long-period fiber grating sensor, and the phase difference between the first optical fiber and the second optical fiber changes, which causes the change of the optical power entering the photodetector, so that the output power of the photodetector The intensity of the signal changes, and the temperature to be measured is obtained by measuring the change in the intensity of the electrical signal.

Beneficial effects: the present invention utilizes the high sensitivity of the center wavelength of the micro-nano long-period fiber grating sensor to temperature, when the temperature changes, the wavelength of the micro-nano long-period fiber grating sensor changes, and the phase difference between the first optical fiber and the second optical fiber The temperature information to be measured is obtained by measuring the intensity change of the output signal of the detection system caused by the measurement, which can accurately detect the temperature information, and has the advantages of low cost and simple structure.

Description of drawings

Fig. 1 is the structural representation of device of the present invention;

Fig. 2 is the transmission spectrum of the micro-nano long-period fiber grating sensor in the embodiment;

Fig. 3 is the frequency spectrum schematic diagram of temperature change in the embodiment;

Fig. 4 is a schematic diagram of the signal intensity relationship under different temperature conditions in the embodiment.

detailed description

The technical solutions of the present invention will be described in detail below, but the protection scope of the present invention is not limited to the embodiments.

Example:

Embodiment 1: A temperature detection device based on a micro-nano long-period fiber grating sensor, as shown in FIG. , a first optical fiber 104 , a second optical fiber 105 , a second coupler 106 , a photodetector 107 and a signal processing unit 108 . The broadband light source 100, the micro-nano long-period fiber grating sensor 101, the acousto-optic modulator 102 and the first coupler 103 are connected in sequence, and the first coupler 103 is respectively connected to the second optical fiber 104 and the second optical fiber 105 through two optical paths. The coupler 106 is connected to the photodetector 107 and the signal processing unit 108 in turn. In this embodiment, the broadband light source 100 is an Amonics ALS-18 light source with an output power of 18dBm and a wavelength range of 1528 to 1564nm. The sensor 101 is to engrave 20 micro-nano long-period micro-nano fiber grating sensors with a grating pitch of 100 μm on a common single-mode micro-nano fiber by using a _CO2 pulsed laser. The transmission spectrum of the micro-nano optical fiber with a diameter of 6.2 μm is shown in Figure 2. It can be seen that its central wavelength is 1537.5 nm. The broadband laser enters the input port of the acousto-optic modulator 102Gooch&Housego Fiber-Q through another port output of the micro-nano long-period fiber grating sensor 101, and the laser signal modulated by the acousto-optic modulator 102 is output from the output port of the acousto-optic modulator 102 , the output frequency-shifted modulated signal is divided into two beams of signal light by the first coupler 103 of 3dB, and one beam of signal light enters the input of the second coupler 106 of 3dB after the length is 2km through the first optical fiber 104 common single-mode optical fiber end, another beam of signal light enters the input end of the second coupler 106 after passing through the second optical fiber 105 ordinary single-mode fiber, and the length is 2.1 km. Output signal light, the signal light enters the input end of the photodetector 107, the photodetector 107 is the Finisar XPDV21x0RA of 50GHz, the response wavelength is 1528～1564nm, the electric signal after being converted by the photodetector 107 enters the signal processing unit 108, through After processing by the signal processing unit 108 , temperature change information on the micro-nano long-period fiber grating sensor 101 is obtained.

The principle of the above temperature detection method is that the change of temperature causes the change of the transmission wavelength of the micro-nano long-period fiber grating sensor 101, and the phase difference between the first optical fiber 104 and the second optical fiber 105 changes, thereby causing the light entering the photodetector 107 to change. The change of power causes the intensity of the electrical signal output by the photodetector 107 to change. Since the intensity information has a quantitative relationship with temperature, it can be calibrated in advance. During temperature detection, the temperature to be measured can be obtained by measuring the change of the intensity of the electrical signal.

The frequency spectrum of the specific output temperature change is shown in Figure 3. It can be seen that the center frequency of the signal is 199.92MHz, and the signal strength at a temperature of 35°C is higher than that at 30°C. The relationship between temperature and signal strength is shown in the figure 4, it can be seen from Figure 4 that with the increase of temperature, the intensity of the signal increases linearly, and its slope is 0.46a.u/°C. Therefore, after calibration according to this law, the output signal of the photodetector 107 can be measured intensity to obtain the temperature information sensed by the micro-nano long-period fiber grating sensor 101.

Embodiment 2: The temperature detection device and method are substantially the same as in Embodiment 1, except that the first optical fiber 104 is a 1.8km high nonlinear optical fiber, and the second optical fiber 105 is a 1.2km dispersion-shifted optical fiber.

Claims (6)

1. a temperature-detecting device based on micro-nano long-period fiber grating sensor, it is characterised in that: include being sequentially connected with Wideband light source (100), micro-nano long-period fiber grating sensor (101), acousto-optic modulator (102), the first bonder (103), optical fiber, the second bonder (106), photodetector (107) and signal processing unit (108), described optical fiber includes One optical fiber (104) and the second optical fiber (105), the first bonder (103) is respectively by the first optical fiber (104) and the second optical fiber (105) the second bonder (106) it is connected to.

Temperature-detecting device based on micro-nano long-period fiber grating sensor the most according to claim 1, its feature exists In: described wideband light source (100) is the wideband light source of the spontaneous radiation amplification of 1525nm ~ 1565nm wave band.

Temperature-detecting device based on micro-nano long-period fiber grating sensor the most according to claim 1, its feature exists In: described first optical fiber (104) and the second optical fiber (105) they are in single-mode fiber, dispersion shifted optical fiber and highly nonlinear optical fiber One or both.

Temperature-detecting device based on micro-nano long-period fiber grating sensor the most according to claim 1, its feature exists In: described photodetector (107) is balanced detector, and response wave length is consistent with wideband light source (100) wave band.

5. a temperature checking method based on micro-nano long-period fiber grating sensor, it is characterised in that: wideband light source (100) Send laser signal and enter micro-nano long-period fiber grating sensor (101), from micro-nano long-period fiber grating sensor (101) The laser signal of output enters acousto-optic modulator (102), exports the modulated signal of shift frequency after acousto-optic modulator (102) is modulated, Modulated signal is divided into two bundle flashlights through the first bonder (103), respectively through the first optical fiber (104) and the second optical fiber (105) Entering after the second bonder (106) merges and export laser signal to be analyzed, laser signal to be analyzed is through photodetection Device (107) is converted to the signal of telecommunication, and the signal of telecommunication measures the strength information of its signal through signal processing unit (108), with reference to mark in advance The quantitative relationship of fixed strength information and temperature obtains temperature information to be measured.

Temperature checking method based on micro-nano long-period fiber grating sensor the most according to claim 5, its feature exists Cause the change of micro-nano long-period fiber grating sensor (101) transmission peak wavelength in: the change of temperature, the first optical fiber (104) and Phase contrast between second optical fiber (105) changes, and causes the change of the luminous power entering photodetector (107) so that The intensity of photodetector (107) the output signal of telecommunication changes, and treats testing temperature by measuring the change acquisition of its electrical signal intensity.