The mechanically-induced long period fiber grating(LPFG) is formed by pressing a single mode fiber from double sides with two identical periodically grooved plates.The polarization dependent loss(PDL)of the LPFG is investigated experimentally,together with effects of the spacing period of the grooved plates and the pressure on the transmission spectrum.The results show that the characteristics of the LPFG can be modified by adjusting the pressure and a peak transmission loss of 24.6 dB has been ...