Patent ID: 6904240

Claim:
An optical multiplexing apparatus for multiplexing a plurality of optical signals having different wavelengths, comprising: first optical multiplexing means for multiplexing, among a plurality of optical signals that are input with directions of linear polarization of neighboring wavelengths being differed to each other and are successively given wavelength numbers depending upon the wavelengths, optical signals corresponding to odd wavelength numbers, while maintaining their polarization states; second optical multiplexing means for multiplexing optical signals corresponding to even wavelength numbers among said plurality of optical signals, while maintaining their polarization states; and third optical multiplexing means including: a first input unit filtering the optical signals multiplexed by said first optical multiplexing means in accordance with filter characteristics that include a transmission wavelength band with the wavelengths of odd numbers as centers, and having a band width of said transmission wavelength band which is narrower than the band width of transmission wavelength band of filter characteristics of said first optical multiplexing means; a second input unit filtering the optical signals multiplexed by said second optical multiplexing means in accordance with filter characteristics that include a transmission wavelength band with the wavelengths of even numbers as centers, and having a band width of said transmission wavelength band which is narrower than the band width of transmission wavelength band of filter characteristics of said second optical multiplexing means; and an output unit multiplexing the optical signals output from said first input unit and the optical signals output from said second input unit to output the multiplexed signal light; wherein said third optical multiplexing means comprises an interleaver including a first input port which corresponds to said first input unit and a second input port which corresponds to said second input unit, and including one output port corresponding to said output unit, and having periodic filter characteristics for each of said first and second input ports, and wherein a band width of each transmission wavelength band in the periodic filter characteristics of said first input port of said interleaver is narrower than the band width of the transmission wavelength band in the filter characteristics of said first optical multiplexing means, and a band width of each transmission wavelength band in the periodic filter characteristics of said second input port of said interleaver is narrower than the band width of the transmission wavelength in the filter characteristics of said second optical multiplexing means.