Patent ID: 7389050

Claim:
A wavelength multiplexing and demultiplexing device for combining and/or splitting a 3-wavelength multiplexed light, including three bands of wavelengths, in which if central wavelengths of said three bands are denoted as λ1, λ2 and λ3, λ1 and λ2 are relatively close in value, λ3 is isolated from λ1 and λ2, and said bands are configured to satisfy following conditions where: 0.92≦λ2/λ1≦1.08, and 0.20≦λ3/λ1≦0.92 or 1.08≦λ3/λ1≦5.00, said wavelength multiplexing and demultiplexing device comprises an optical edge filter, an optical band-pass filter, and at least one optical substrate to support the optical edge filter and/or the optical band-pass filter, wherein said 3-wavelength multiplexed light is led to the optical edge filter for splitting said 3-wavelength multiplexed light into light of a band of λ3 and a 2-wavelength multiplexed light of λ1 and λ2, and said 2-wavelength multiplexed light subsequently passes to the optical band-pass filter for splitting said 2-wavelength multiplexed light into light of a band of λ1 and light of a band of λ2.