An intrinsic optical fiber hydrogen sensor based on polarization-maintaining photonic crystal fiber (PM-PCF) Sagnac interferometer was proposed. The facing target sputtering technique with special Pd/Ag plate target structure was developed to deposit Pd/Ag composite film on PM-PCF. The characteristic of Pd/Ag film was measured and analyzed. An experimental setup for hydrogen sensing was built. The wavelength at different hydrogen concentration and the temperature interference were tested. The results showed the sensitivity was higher at low concentration range and good repeatability was obtained within measuring range of 4%. And the temperature affect was weak with special PM-PCF.
In order to improve accuracy of critical contacting position in measurement of micro-scale using aiming and triggering method, delay error of triggering signal, sampling delay error of sensor and length measuring device(double frequency laser interferometer) impact on accuracy are analyzed, compensation methods of solving nodal equation through establishing piecewise fitting function based on least square polynomial fitting and compute threshold triggering points through computing delay time are put forward. With this method, the measured diameter of micro-hole with nominal diameter <i>Φ</i> 0.3mm and depth 1.0mm is compensated. Results indicate that diameter of micro-hole after compensation increases 0.12 μm, closer to nominal value, and experimental standard deviation reduces by 0.069 μm. Therefore the measuring repeatability is improved, which demonstrates that the method is correct and effective.