In this experiment, the optical parameters of optical fiber sensing measurements with the wavelength division multiplexer (WDM) and Fiber Bragg grating have obtained in temperature-controlled cabinet. The wavelength division multiplexer device not only make different wavelength illuminant input at the same time be possible, but also can achieve multi-channel output based on the feature of WDM. We design and put forward a new method which can realize various parameters measured at the same time, such as temperature and the refractive index or stress measurement. In addition, it can measure the same parameters with different wavelengths of laser at the same time. The contrast analysis results of different wavelengths of illuminant on the same parameter sensitivity and reliability of the measurement will use to provide reference to design the same illuminant with different parameter measurements.
Application of high temperature fiber sensing system is very extensive. It can be mainly used in high temperature test aerospace, such as, materials, chemicals, and energy. In recent years, various on-line optical fiber interferometric sensors based on modular interference of single-mode-multimode-single-mode(SMS) fiber have been largely explored in high temperature fiber sensor. In this paper we use the special fiber of a polyimide coating, its sensor head is composed of a section of multimode fiber spliced in the middle of Single-mode fiber. When the light is launched into the multimode fiber(MMF) through the lead-in single-mode fiber(SMF), the core mode and cladding modes are excited and propagate in the MMF respectively. Then, at the MMF-SMF spliced point, the excited cladding modes coupled back into the core of lead-out SMF interfere with SMF core mode. And the wavelength of the interference dip would shift differently with the variation of the temperature. By this mean, we can achieve the measurement of temperature. The experimental results also show that the fiber sensor based on SMS structure has a highly temperature sensitivity. From 30℃ to 300℃, with the temperature increasing, the interference dip slightly shifts toward longer wavelength and the temperature sensitivity coefficient is 0.0115nm/℃. With high sensitivity, simple structure, immunity to electromagnetic interferences and a good linearity of the experimental results, the structure has an excellent application prospect in engineering field.