Sandwiched long-period fiber grating filter based on periodic SU8-thick photoresist technique.

A loss-tunable sandwiched long-period fiber grating (SLPFG) filter is proposed in this Letter. This SLPFG utilized thick SU8 photoresist layers to induce refractive index modulations, and ultrahigh period precision was hence achieved. The external force required to tune this SLPFG filter is about 0.3942 N with the deepest loss attenuation 31.29 dB at 1534 nm wavelength. This process not only improves the overall performance of traditional long period fiber grating but also cuts down the facility cost by 50%. The proposed SLPFG has great potential for low-cost and compact force transducer applications.