The transmission spectra of multiply π phase shifted long period fiber gratings (LPFG’s) are analyzed by a combination of coupled mode theory and the fundamental matrix method. The theoretical simulation shows that the LPFG’s can act as novel bandpass filters with two dominant pass bands when multiple π phase shifts are introduced at particular locations along the grating. The theoretical simulation shows that the LPFG’s can act as novel bandpass filters with two dominant pass bands (LPFG’s) are analyzed by a combination of coupled mode theory and the fundamental matrix method when multiple π phase shifts are introduced at particular locations along the grating.