基于侧面抛磨锗芯光纤的折射率传感器

通过抛磨单模-多模-单模(Single mode-Multimode-Single mode,SMS)光纤结构,设计制作一种光纤折射率传感器。多模光纤选用的是纤芯直径为16μm的锗芯光纤,纤芯直径较小,使制作的传感器尺寸较小,从而在传感应用中具有较高的样品利用率。单模光纤纤芯直径为8.4μm,可确保抛磨至多模光纤纤芯附近时单模光纤的纤芯不被破坏。SMS被AB胶固定在玻璃槽内,使得侧面抛磨光纤具有很好的鲁棒性,可重复使用性。制备并侧面抛磨了锗芯光纤长度分别为0μm、23μm、70μm、690μm、2 mm的SMS光纤结构。对产生的传输光谱进行测量,发现前4个样品随着周围环境折射率的增加,谐振波长向长波长处偏移;而前3个样品的折射率测量灵敏度随着锗芯光纤长度的增加而提高。当锗芯光纤长度为70μm时,在1.333~1.367折射率区间内,灵敏度可以达到623.5 nm/RIU。然而,过长的锗芯光纤导致折射率测量灵敏度降低。当锗芯光纤长度为2 mm时,抛磨过程中激发产生了包层模,导致传输光谱复杂、不稳定,而且长波处产生了较大的插入损耗。

Refractive Index Sensor based on Side Polished Ge-doped Fiber

A single mode-multimode-single mode(SMS)fiber structure is polished to design and manufacture an optical fiber refractive index sensor.The multimode fiber is a germanium-doped fiber(GDF)with a core diameter of 16μm.The smaller core diameter results in a smaller sensor size and thus a higher sample utilization in sensing applications.The single mode fiber core diameter is 8.4μm,which can ensure that the core of single mode fiber polished to the vicinity of the multimode fiber core is not damaged.SMS is fixed in the grooved glass with AB glue,making the side polished fiber very robust and reusable.SMS fiber structures with germanium core fiber lengths of 0μm,23μm,70μm,690μm and 2 mm are prepared and polished on the side.The transmission spectrum generated is measured,finding that the resonance wavelength of the first 4 samples is shifted to longer wavelengths as the refractive index of the surrounding environment increases;while the sensitivity of the refractive index measurement of the first 3 samples is increased as the length of the germanium core fiber increases.When the length of the germanium core fiber is 70μm,the sensitivity can reach 623.5 nm/RIU in the refractive index range of 1.333~1.367.However,an excessively long germanium core fiber causes a decrease in refractive index measurement sensitivity.When the length of the germanium core fiber is 2 mm,the cladding mode is generated during the polishing process,which results in a complex and unstable transmission spectrum and a large insertion loss at long wavelengths.