Mizuno Yosuke, Matsutani Natsuki, Hayashi Neisei, Lee Heeyoung, Tahara Masaki, Hosoda Hideki, Nakamura Kentaro
Opt Express. 2018 Oct 15;26(21):28030-28037. doi: 10.1364/OE.26.028030.
To date, most distributed Brillouin sensors for structural health monitoring have employed glass optical fibers as sensing fibers, but they are inherently fragile and cannot withstand strains of >3%. This means that the maximal detectable strain of glass-fiber-based Brillouin sensors was ~3%, which is far from being sufficient for monitoring the possible distortion caused by big earthquakes. To extend this strain dynamic range, polymer optical fibers (POFs) have been used as sensing fibers. As POFs can generally withstand even ~100% strain, at first, Brillouin scattering in POFs was expected to be useful in measuring such large strain. However, the maximal detectable strain using Brillouin scattering in POFs was found to be merely ~5%, because of a Brillouin-frequency-shift hopping phenomenon accompanied by a slimming effect peculiar to polymer materials. This conventional record of the strain dynamic range (5%) was still far from being sufficient. Here, we have thought of an idea that the strain dynamic range can be further extended by employing a POF with its whole length slimmed in advance and by avoiding the Brillouin-frequency-shift hopping. The experimental results reveal that, by applying 3.0% strain to a slimmed POF beforehand, we can achieve a >25% strain dynamic range, which is >5 times the conventional value and will greatly extend the application fields of fiber-optic Brillouin sensing.
迄今为止，大多数用于结构健康监测的分布式布里渊传感器都采用玻璃光纤作为传感光纤，但它们本质上很脆弱，无法承受超过3%的应变。这意味着基于玻璃光纤的布里渊传感器的最大可检测应变约为3%，这远远不足以监测大地震可能造成的变形。为了扩展这个应变动态范围，聚合物光纤（POF）已被用作传感光纤。由于POF通常甚至可以承受约100%的应变，起初，人们期望POF中的布里渊散射可用于测量如此大的应变。然而，由于聚合物材料特有的变细效应伴随的布里渊频移跳变现象，发现使用POF中的布里渊散射的最大可检测应变仅约为5%。这种应变动态范围的传统记录（5%）仍然远远不够。在此，我们想到了一个主意，即通过预先使POF的整个长度变细并避免布里渊频移跳变，可以进一步扩展应变动态范围。实验结果表明，通过预先对变细的POF施加3.0%的应变，我们可以实现大于25%的应变动态范围，这是传统值的5倍多，将极大地扩展光纤布里渊传感的应用领域。
