| The optical fiber sensing system based on ultra-weak fiber Bragg gratings can realize quasi-distributed fiber grating sensing with long distance,high capacity and high spatial resolution.It has a wide application prospects in multi-parameter and multi-channel distributed fiber transmission systems,which is an important research hotspot in the field of optical fiber sensing.However,due to ultra-weak fiber Bragg grating has a very low reflectivity(?0.1%),the accuracy and sensitivity of the optical detection plays a very critical role in the sensor demodulation system,which determines the performance,scale,multiplexing capability of the entire sensing system.Therefore,research on the photoelectric detection module of the ultra-weak fiber Bragg grating sensing system has important practical significance for the improvement of the sensing system performance and the large scale application.Based on the research of ultra-weak fiber grating sensing system,this paper presents a design method of photoelectric detection circuit which meets the requirements of grating demodulation system.The main work is as follows:1.Used APD instead of PIN photodiode as a photodetector to increase the gain of the circuit.Selecting OPA657 as an operational amplifier to improve the circuit gain while reducing the introduction of noise;2.Added RC filter circuit after pre-amplifier circuit to improve the signal to noise ratio;3.Calculated the reflected signal optical power range is-25dBm?-33dBm,and designed 10k times magnification of the preamplifier circuit.To ensure the circuit bandwidth more than 100 megahertz at the same time to ensure the magnification,designed secondary cascade main amplifier circuit,and selected the optimal feedback resistor and vibration capacitance for each level circuit;4.Simulated and debugged the circuit by using TINA-TI,fabricated and tested the photoelectric detection system.Experiments show that the designed photoelectric detection circuit meets the demodulation requirements. |
PDF Full Text Request