The dual-wavelength ratio temperature measurement through helical long-period gratings

Abstract

Helically twisted long-period fiber gratings (H-LPFG) of the single-mode fiber provided by Yofc inc is spiral processed by commercial welding machine. There is an obvious second-order resonant dip near 1526 nm coupling between the fundamental mode and the LP15 cladding mode when the pitch length is about 757 μm. The half peak width is about 15 nm, and the resonant dip is about -28 dB. The transmission intensity ratio of 10lg(I1523.4nm/I1537nm) and 10lg(I1523.4nm/I1551.1nm) versus temperature are measured, which show linearly with temperature. The radio sensitivity of I1523.4nm/I1537nm is about 0.023/C° compared with the wavelength sensitivity of about 45 pm/C°. This can be applied in temperature sensor.