Preparation and sensing characteristics of long-period fiber gratings based on periodic microchannels

Long-period fiber gratings have the advantages of small size, corrosion resistance, anti-electromagnetic interference, and high sensitivity, making them widely used in biomedicine, the power industry, and aerospace. This paper develops a long-period fiber grating sensor based on periodic microchannels. First, a series of linear structures were etched in the cladding of a single-mode fiber by femtosecond laser micromachining. Then, the laser-modified region was selectively eroded by selective chemical etching to obtain the periodic microchannel structure. Finally, the channels were filled with polydimethylsiloxane (PDMS) to improve the spectral quality. The experimental results show that the sensor has good sensitivity in the measurement of various parameters such as temperature, stress, refractive index (RI), and bending. It has a temperature sensitivity of -55.19 pm/degrees C, a strain sensitivity of -3.19 pm/mu epsilon, a maximum refractive index sensitivity of 540.28 nm/RIU, and a bending sensitivity of 2.65 dB/m-1. All of the measurement parameters show good linear responses. The sensor has strong application prospects in the field of precision measurement and sensing.