Research On Wavelength Demodulation Instrument Based On Chirped Fiber Grating

At present,there is no a product of the wavelength demodulation scheme based on chirped Fiber Bragg Grating in the market,but its potential advantages cannot be ignored,such as all-optical structure,which can improve the demodulation rate without mechanical tuning.Wavelength demodulation measurement accuracy and dynamic range can be adjusted according to demand,concatenation and parallel network topologies both be supported and low cost etc.The demodulation scheme is based on the principle of intensity measurement.There is a one-to-one relationship between light intensity and wavelength,but it is easily influenced by the temperature sensitivity of the optical device.The key problem is to solve the poor temperature stability of the system.The research topic of this paper is a wavelength demodulator instrument using a chirped Fiber Bragg Grating and the design goal is to control the temperature stability within 10 nm in the range of 0 to 50? etc.This thesis includes:1)A wavelength demodulation system based on chirped fiber grating is designed.The optical isolator is added in the system,which greatly reduces the influence of the reflected light on the stability of the output power of the light source.The optical and circuit devices are packaged in the form of welding,making it convenient to compensate the temperature in the closed space,and reduce the influence of temperature variation on the overall performance of the device.According to the influence of temperature variation on the optical coupler,the correction scheme of three-way light intensity demodulation is adopted,the transmitted light of the chirped Fiber Bragg Grating is added to the calculation to ensure the accuracy of the denominator in the calculation and to reduce measurement error.The experiment adopts the temperature control device to make multiple detections and take the average value of the demodulator in the same center wavelength of the measurement results.To reduce to 8pm of the maximum temperature change in the range of 0~50?,which is about 50% before compensation.The temperature stability of the wavelength demodulator can reach to 8pm.2)The chirped Fiber Bragg Grating developed by the team is designed as the core demodulation device,and the performance prototype of the wavelength demodulator is developed.By evaluating the dynamic range of the system to design the photoelectric conversion,signal processing circuit and the device selection,it is to achieve a series of complete circuit solution.Using these devices to build a three-way optical intensity correction wavelength demodulation system based on chirped Fiber Bragg Grating and the results show that the designed wavelength demodulator can realize the wavelength dynamic range of 1514.39~1524.51 nm,single-channel demodulation wavelength accuracy of the minimum 1.9pm,the maximum value of 16.4pm,multi-channel wavelength accuracy of 6.78 pm.The innovation of the paper is to use the chirped Fiber Bragg Grating developed by the team as the demodulator to make the performance of the wavelength demodulator.In the design,the temperature sensitivity of the optical device,such as the temperature drift of the optical coupler is taken into account,and a three-way optical intensity correction wavelength demodulation system is proposed.While ensuring the improvement of the temperature stability,the system can dynamically adjust the measurement path and demodulation precision according to the actual demand so that the whole system can reach or approach the design target level on each index.The research work of this paper are of practical value for the research of the Fiber Bragg Grating sensing technology which adopts chirped Fiber Bragg Grating as the wavelength demodulation scheme in the laboratory stage and large-scale application.