Tunable overlapping long-period fiber grating and its bending vector sensing application

A novel overlapping long-period fiber grating (OLPFG) is proposed and experimentally demonstrated in this paper. The OLPFG is composed of two partially overlapping long-period fiber gratings (LPFG). Based on the coupled model theory and transfer matrix method, it is found that the phase shift LPFG and LPFGs interference are two special situations of the proposed OLPFG. Moreover, the confirmation experiments verified that the proposed OLPFG has a high bending sensitivity in opposite directions, and the temperature crosstalk can be compensated spontaneously.