在一段8 cm长的保偏光纤两端分别熔接两段普通的单模光纤, 在保偏光纤的侧面均匀地镀上一层聚二甲基硅氧烷材料, 聚二甲基硅氧烷材料经该段保偏光纤接入到一个光纤耦合器中, 从而形成一个光纤Sagnac干涉仪.聚二甲基硅氧烷材料吸附挥发性有机物分子时, 会引起聚二甲基硅氧烷材料体积上的膨胀, 导致Sagnac干涉波长的漂移, 通过对Sagnac干涉光波长漂移的测量即可实现对挥发性有机物气体的检测.实验测量了传感器对挥发性有机物浓度的响应, 结果表明, 在0~6 000 ppm浓度范围内, 传感器的灵敏度为1.03 pm/ppm, 由光谱仪的最小分辨率为 0.02 nm 可知, 该传感器对挥发性有机物的检测下限约为19.4 ppm.该传感器相比聚二甲基硅氧烷材料与光纤光栅结合的传感器, 灵敏度提高了4 300倍.

To fabricate the Sagnac interferometer sensor, a polarization-maintaining fiber with the length of 8 cm was spliced between two single-mode fibers, and the polydimethylsiloxane material was coated on the polarization-maintaining fiber, then the polydimethylsiloxane functionalized polarization-maintaining fiber was integrated into a fiber coupler to form a Sagnac loop. When the polydimethylsiloxane absorbs volatile organic compounds, the polydimethylsiloxane will be swelled and the wavelength of interference peak will shift, so that the concentration of volatile organic compounds can be measured by monitoring wavelength shift. The response of the sensor to the concentration of volatile organic compounds was measured experimentally, and the results show that the sensitivity of the sensor is 1.03 pm/ppm when the concentration ranges from 0 ppm to 6 000 ppm. The optical spectrum analyzer with a 0.02 nm measurement precision was used in experiments, so the precision could reach about 19.4 nm in the concentration range from 0 to 6 000 ppm. The sensor′s sensitivity improves 4 300 times which compared to grating fiber with polydimethylsiloxane material sensor.