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提出了一种基于马赫-曾德干涉仪(MZI)的温度与折射率同步测量的光纤传感器。本文传感器结构由两个球形结构级联一个锥结构组成,球形结构激发高阶包层模,锥结构扩大了倏逝场穿透深度范围。其原理是当纤芯中传输的光通过第1个球形结构时,一部分光进入包层中传输形成包层模,另一部分光继续在纤芯中传输形成纤芯模,由于纤芯与包层具有不同的折射率,因而纤芯模和包层模之间产生光程差,当两部分光到达另一端的球形结构时,在包层中传输的光耦合进入纤芯,从而与纤芯中传输的光在另一球出射处发生干涉,当外界环境(如温度、折射率等)发生改变,影响光程差,则干涉谱也将随之改变。实验结果表明,本文传感器结构的透射谱中,干涉峰对温度和折射率具有不同的响应灵敏度,因此可以利用矩阵法实现对温度和折射率的同步测量。在10~100℃和1.343 2~1.402 6RIU(refractive index unity)的测量范围内,强度解调可以达到约0.22℃和1×10~(-4) RIU温度和折射率分辨率。同时发现,波长解调可以达到0.37℃温度分辨率。本文传感器结构简单紧凑、成本低,可适用于多领域实现温度和折射率的双参量同步测量。
A fiber optic sensor based on Mach-Zehnder Interferometer (MZI) is proposed to synchronously measure the temperature and refractive index. The sensor structure is composed of two spherical structures cascaded with a cone structure. The spherical structure excites high-order cladding modes, and the cone structure expands the evanescent field penetration depth range. The principle is that when the light transmitted in the core passes through the first spherical structure, part of the light enters the cladding to form a cladding mode and the other part of the light continues to propagate in the core to form a core mode. As the core and the cladding Has a different refractive index so that a difference in optical path length occurs between the core and the cladding, and when the two parts of light reach the spherical structure at the other end, the light transmitted in the cladding is coupled into the core so as to be in the core The transmitted light interferes at the exit of the other ball. When the external environment (such as temperature, refractive index, etc.) changes and affects the optical path length difference, the interference spectrum will also change. Experimental results show that in the transmission spectrum of the sensor structure, the interference peak has different response sensitivities to temperature and refractive index, so that the matrix method can be used to measure the temperature and refractive index simultaneously. In the measurement range of 10 ~ 100 ℃ and 1.343 2 ~ 1.402 6RIU (refractive index unity), the intensity demodulation can reach about 0.22 ℃ and 1 × 10 ~ (-4) RIU temperature and refractive index resolution. Also found that wavelength demodulation can reach 0.37 ℃ temperature resolution. This sensor structure is simple and compact, low cost, can be applied to many fields to achieve temperature and refractive index of the two-parameter synchronous measurement.