The characteristics of the transmission spectrum of the Long-period fiber gratings (LPFGs) based on the coupling of core mode to a higher order cladding mode (HE mode) are investigated using the coupled mode theory. This kind of LPFGs is different from that based on the coupling of core mode to a lower order cladding mode because of the effect of the coupling of core mode to EH cladding mode. When the cladding mode order is higher, the coupling coefficients of core mode to HE and EH cladding mod
