新型波长解调技术在干涉型光纤传感器输出解调中的应用

提出了一种改进型边缘滤波波长解调技术,解决干涉型或谐振型光纤传感器输出的干涉谱波长的快速解调问题。该波长解调技术基于啁啾光栅和长周期光栅的光谱特点,以啁啾光栅作为矩形滤波器,提取传感器输出干涉谱的一个干涉峰;以长周期作为边缘滤波器,将干涉峰的波长信息转化为光强信息进行检测。该波长解调技术波长解调范围为传感器输出干涉谱的一个自由光谱范围(FSR),解调速度快,克服了当前波长解调技术中存在的测量范围与测量速度难以同时提高的问题,同时还具有系统成本低,体积小,能够灵活多路扩展的特点。详细介绍了解调系统的工作原理以及系统结构,并将其实际应用于一种干涉型光纤电流传感器输出干涉谱的波长解调中。通过实验证明电流传感器工作在工频及脉冲电流(脉冲宽度25μs)情况下,该解调系统对传感器输出干涉谱具有准确、快速的解调效果。该研究对推进干涉或谐振型光纤传感器的实际工程化水平的提高具有重要意义。

A Novel Wavelength Demodulation Technique for Interferometric Fiber Optic Sensor

A novel edge-filter wavelength demodulation technique based on the special spectral characteristics of chirped fiber grating and long-period fiber grating was proposed in this paper,which offers a fast wavelength demodulation method for inter-ferometric and resonance fiber-optic sensors.In this wavelength demodulation system,the chirped fiber grating acts as a rectan-gular filter,which extracts one interferometric peak out of the periodic interference spectrum;The long-period fiber grating acts as an edge filter,whose transmission profile is shown to be nearly linear over a sufficiently wide range,converting the wave-length variation into optical power in a linear relationship,that the wavelength can be acquired through optical power measure-ment.The demodulation range can go up to one free spectrum range (FSR)and the demodulation speed is determined by the re-sponse of the photodetector theoretically.This demodulation technique has practical significance with the fast demodulation speed,wide demodulation range,low cost,small size,and the convenience to multichannel extension.The principle and struc-ture of the demodulation system were illustrated in detail,and the experiment was setup through applying the demodulation sys-tem to an interferometric fiber optic current sensor.Experiment result showed the system could demodulate accurately and fast when the sensor was under power current and pulse current.This paper is of great significance for promoting the engineering practical level of interference and resonance fiber optic sensors.