This study is intended to develop long period fibre grating sensors for potential applications in environmental and durability monitoring of coastal structures. High-quality helical long period fibre gratings (HLPFGs) are inscribed in different types of small-core single mode fibre (SMF) by use of hydrogen-oxygen flame heating technique. A detailed investigation of the effect of core diameter on their transmission spectrum and optimum length of the HLPFG has been pursued. A longer length is required to achieve the same coupling attenuation in a smaller-core SMF than that of a larger-core fibre. The strain, torsion and refractive index (RI) properties of the HLPFG is investigated experimentally to develop a high-sensitivity sensor. The experimental results show that the strain sensitivity could be enhanced by means of employing a larger-core diameter SMF. Moreover, the HLFPGs are also sensitive to the torsion and external RI. Hence, such HLFPGs have great potential for sensing applications.

这项研究旨在开发长期的光纤光栅传感器，用于沿海结构的环境和耐久性监测的潜在应用。通过使用氢氧火焰加热技术，将高质量的螺旋长周期光纤光栅（HLPFG）刻在不同类型的小芯单模光纤（SMF）中。已对铁芯直径对其传输光谱和HLPFG最佳长度的影响进行了详细研究。与较大芯光纤相比，在较小芯SMF中实现相同的耦合衰减需要更长的长度。通过实验研究了HLPFG的应变，扭转和折射率（RI）特性，以开发高灵敏度传感器。实验结果表明，采用较大芯径的SMF可以提高应变敏感性。此外，HLPFG还对扭转和外部RI敏感。因此，这种HLFPG在传感应用方面具有巨大的潜力。