Patent ID: 7539417

Claim:
A CWDM (Coarse Wavelength Division Multiplexing) optical transmission system, comprising: an optical transmitter including a non-temperature controlled direct modulation light source, said optical transmitter outputting signal light in a signal wavelength band; an optical receiver receiving the signal light outputted from said optical transmitter; an optical fiber transmission line for transmitting the signal light outputted from said optical transmitter as a transmission medium provided between said optical transmitter and said optical receiver, said optical fiber transmission line having a positive chromatic dispersion at an operation wavelength of said direct modulation light source; and at least one non-temperature controlled dispersion compensator provided on an optical path between the signal outputting end of said optical transmitter and the signal entering end of said optical fiber transmission line, wherein, at the signal emitting end of said optical fiber transmission line, the accumulated chromatic dispersion at the operation wavelength is set to negative over a temperature range of 0° C. to 60° C., the optical transmission system further comprising a demultiplexer for demultiplexing a plurality of signal channels propagating through said optical fiber transmission line into one signal channel group in a first wavelength band including a zero-dispersion wavelength of said optical fiber transmission line and the other signal channel group in a second wavelength band, wherein said dispersion compensator compensates for the accumulated chromatic dispersion in the signal channel group of the second wavelength band, wherein, at the signal outputting end of said dispersion compensator, the accumulated chromatic dispersion in one of the signal channels of the second wavelength band passing through said dispersion compensator is negative over the temperature range of 0° C. to 60° C., and wherein a bit rate of at least one signal channel among the signal channels included in the second wavelength band is higher than any bit rate of all the signal channels in the first wavelength band.