Patent ID: 7333266

Claim:
A coarse wavelength division multiplex filter comprising a first portion and a second portion, the first portion including at least two Fabry-Perot cavity structures, the second portion including a non λ/4 multi-layer structure which has a plurality of alternately superposed high refraction index layers and low refraction index layers on the first portion thereof, wherein the thicknesses of the non λ/4 layers are randomly produced as per a pre-set wavelength range which takes 1470 nm as the center wavelength thereof by computer, and the at least two Fabry-Perot resonance cavity structures of the first portion obey the following rule: (LH) 3 6L(HL) 3 H(LH) 3 2L(HL) 3 H(LH) 4 6L(HL) 4 H(LH) 3 4L(HL) 3 H(LH) 4 6L (HL) 4 H(LH) 3 4L(HL) 3 H(LH) 4 6L(HL) 4 H(LH) 3 2L(HL) 3 H(LH) 3 6L(HL) 2 H/N S ; wherein, N S represents for the substrate thereof, L represents for low refraction index layer with a thickness of λ/4, H represents for high refraction index layer with a thickness of λ/4, and λ O represents for the center wavelength thereof.