提出了一种基于Sagnac干涉仪的保偏光子晶体光纤(PM-PCF)氢气传感器，建立了传感模型并进行了实验研究和验证。采用对靶磁控溅射技术将钯银(Pd/Ag)合金快速均匀地沉积在保偏光子晶体光纤侧面，并利用Pd吸收氢气后的形变调制保偏光子晶体光纤的双折射，通过测量Sagnac干涉仪输出光谱峰值的变化实现氢气浓度的测量。实验结果表明该传感器可检测的氢气浓度范围为0%~4%，且具有良好的重复性。室温下对低浓度氢气具有较高的灵敏度，氢气浓度由0%变化到1%时的波长偏移量达1.307 nm。采用双折射温度不敏感的保偏光子晶体光纤，可很好地抑制外界温度变化对传感器的干扰。

A polarization-maintaining photonic crystal fiber (PM-PCF) hydrogen sensor based on Sagnac interferometer is proposed. A sensing model is established and experimentally studied and tested. With the facing target sputtering process, Pd/Ag composite film is deposited on PM-PCF fast and uniformly. The birefringence of PM-PCF can be modified by the deformation of film after absorbing hydrogen, realizing the measurement of hydrogen concentration by detecting the wavelength shift of one specific valley. The results show that good repeatability is obtained within the measuring range of 4%. This sensor′s sensitivity is higher at low hydrogen concentration and the wavelength shift is 1.307 nm when the hydrogen concentration increases from 0% to 1%. The birefringence of the PM-PCF is not sensitive to temperature, restraining the interference brought up by the fluctuation of environment temperature.