The modal cutoff properties and exciting conditions of higher order resonant modes for Ge-doped photonic crystal fiber Bragg grating(PCFBG) are investigated using beam propagation method(BPM).The results show that the normalized frequency V of PCFBG depends on both the normalized pitch Λ/λ and the normalized hole-size d/Λ.And the single-mode-multi-mode boundary profile of the Ge-doped PCF shifts to the low normalized holesize side contrasting to the pure-silica solid core photonic crystal fiber(pure-solid P...