Abstract:The optical filter based on mechanically-induced π-phase-shifted Long-Period Gratings(LPGs) formed by pressing a bend-insensitive fiber from two sides with two identical periodically grooved plates are investigated. The influence of the sub-grating number and pressure on the spectrum characteristics of the π-phase-shifted LPG are investigated experimentally, together with the Polarization Dependent Loss(PDL). The results show that the depth of the two lateral rejection bands varies with the strength of pressure applied to the fiber; the pass-band width of the grating depends strongly on the number of the sub-grating, while the central wavelength of the pass-band is independent of it. For LP13 mode coupling, the pass band width varies from 8.2 nm to 53.8 nm when N increases from 2 to 9. A maximum PDL of about 6.86 dB for LP13 cladding mode is measured. It is believed that the mechanically-induced π-phase-shifted Long Period Fiber Gratings(LPFGs) with the merits of reconstructable, simple and easy operation have potential applications in fields of fiber-optic communications and fiber-optic sensing.