Photonic Crystal Fiber Temperature Based On Phase Modulation Principle, The Research Techniques Of Stress Sensor

The demand of high-precision test, persistence work and automatic measurement in structural health monitoring of large civil engineering, energy industry and other fields is increasingly high. It put forward higher requirements for the accuracy and reliability of sensors, but the traditional electrical type sensors in these harsh environments subject to certain restrictions, therefore the fiber-based sensor for measuring physical quantities developed rapidly. It not only has advantages of light weight, high sensitivity, electromagnetic interference resistant, and also can realize real-time online monitoring, to make it become widely accepted.As a kind of optical fiber sensors, optic fiber interferometric sensors generate phase modulation by using interferometry in order to obtain high sensitivity and resolution, they are used to monitor various measurand with an extremely broad development prospects. In this paper, we presented two kinds of phase modulation sensors based on fiber-optic Michelson interference and F-P interference and verified the sensing characteristic by theoretical analysis and experimental verification.On the base of photonic crystal fiber optical characteristics, combined with the basic principle of Michelson interferometer and F-P interferometer and phase modulation mechanism, the paper designed a fiber Michelson interferometer based on polarization-maintaining photonic crystal fiber avoiding the use of3dB coupler and demonstrated its feasibility by experiments. Experimental research results showed that extinction ratio of interference fringes is achieved5dB without offset splicing fusion, and has a wide range of strain response, a strain sensitivity of-1.3pm/με is obtained in the range from Oμε to2000με. A torsion sensitivity of-19.17pm/deg and a good linearity of99.168%is obtained at the torsion range from24deg to96deg. A temperature sensitivity of9.9pm/℃is measured under100℃.A miniature Fabry-Perot interferometer is fabricated by alignment splicing a short section of double-core photonic crystal fiber (DC-PCF) to the lead-in single mode fiber (SMF) and experimentally demonstrated for measurement. Due to pure silica, a well-defined interference spectrum is obtained based an approximate72.3μm-long cavity. Experimental results indicate that the proposed sensor has a considerable temperature sensitivity of13.9pm/℃in the measurement range of30℃to900℃. The proposed sensor has advantages of small size and high stability, etc, making it a good candidate in hash high temperature environment with limited-space.