Stress Induced Long Period Fiber Grating And Its Temperature Sensing Application In 1650nm-band

The resonance wavelength and transmission of long period grating(LPG) is sensitive to environmental parameters. There is no back-reflection and no isolator in the LPG sensing. It also possesses the advantages, such as low weight, immunity against electromagnetic interference. The temperature, bend, twist, concentration or refractive index sensitivity of LPG sensing is better than that of FBG sensing. It has found many applications in the optical sensing.In the paper, we take the method about theory and experiment and research the linear characteristics of LPG and its experiment for temperature sensing in 1650nm-band.In the aspect of theory, through discretized coupled-mode theory, quantitatively analysis and fast Fourier transform, we simulate the spectra, dispersion, multimode and temperature characteristics of LPG in 1650nm-band. When the coupling intensity isπ/4 andπ/2, the spectra of LPG and LPGs are presented. At the same time, the characteristics of the LPG temperature sensing about different cladding calorescence coefficient or grating period are showed.In the aspect of experiment, we design a mechanically induced LPG fabricated by pressing a plate with periodic grooves. And do the experiments about the stress induced LPG and its temperature sensing in 1650-nm band. In order to show the stability of the sensing, we setup a control experiment. The experiments show that the temperature sensitivity of the sensing is 0.4nm/℃. It accords with the theory. The inserting loss, extinction and temperature sensing and refractive index of the experiments is also studied.This paper can be used for optical fiber sensing in 1650nm-band referring to the experiment results.