In the work, a cholesteric liquid crystal film coated side polished fiber (CLCFC-SPF) is demonstrated to sense the volatile organic compound (VOC) gas. In the CLCFC-SPF, the wavelength selectively coupling from the SPF to the cholesteric liquid crystal film (CLCF) results in the resonant dips in the transmitted spectrum. It is found that the pitch of the CLCF increases with VOC gas concentration, which reduces the refractive index (RI) of CLCF and results in a blue shift of the resonant dips. By tracing the blue shift of the resonant dips, the VOC gas sensing characteristic of the CLCFC-SPF were investigated experimentally. For tetrahydrofuran, acetone and methanol gas, the sensitivities of the CLCFC-SPF are respectively measured as 7.08 nm⋅L/mmol, 3.46 nm⋅L/mmol, 0.52 nm⋅L/mmol. Using the wavelength selectively coupling theory, gaseous-optic coefficient of the CLC can also be obtained and were measured in the experiment as 6.6 × 10^-4 RIU⋅L/mmol, 2.9 × 10^-4 RIU⋅L/mmol, 0.6 × 10^-4 RIU⋅L/mmol, respectively, for tetrahydrofuran, acetone, and methanol gas. Additionally, the experimental results also show that both the sensitivity of CLCFC-SPF and the gaseous-optic coefficient of the CLCF increase with the molar mass of the VOC gas. The work provides a way to incorporate the sensitive liquid crystal onto the fiber for implementation of liquid-crystal-based fiber sensors.

在工作中，已证明胆甾型液晶薄膜涂覆的侧面抛光纤维（CLCFC-SPF）可感测挥发性有机化合物（VOC）气体。在CLCFC-SPF中，从SPF选择性耦合到胆甾型液晶膜（CLCF）的波长会导致透射光谱出现共振下降。发现CLCF的间距随着VOC气体浓度的增加而增加，这降低了CLCF的折射率（RI），并导致谐振凹陷的蓝移。通过追踪共振凹陷的蓝移，实验研究了CLCFC-SPF的VOC气体感测特性。对于四氢呋喃，丙酮和甲醇气体，CLCFC-SPF的灵敏度分别测量为7.08 nm·L / mmol，3.46 nm·L / mmol，0.52 nm·L / mmol。利用波长选择性耦合理论，对于四氢呋喃，丙酮和甲醇气体，分别为^-4 RIU·L / mmol，2.9×10 ^-4 RIU·L / mmol，0.6×10 ^-4 RIU·L / mmol。此外，实验结果还表明，CLCFC-SPF的灵敏度和CLCF的气体光学系数均随VOC气体的摩尔质量而增加。这项工作提供了一种方法，可以将敏感的液晶结合到光纤上，以实现基于液晶的光纤传感器。