| 摘要 |
PROBLEM TO BE SOLVED: To extend a permissible range of a dispersion compensation amount by providing a dispersion compensation device having a negative dispersion with respect to a wavelength of an optical signal to be sent and a chirp provision means providing a positive chirp to the optical signal at a transmitter side to the transmitter side. SOLUTION: In spite of a positive dispersion value of a single mode fiber(SMF) 14, a chirping parameter α of a transmitter is set to be a positive value, preferably a positive value of 2 or below, and more preferably +1. When a compensation value of a dispersion compensation device 22 is increased, the loss is also increased, the optical input power to a photodetector 24 is reduced resulting in deteriorating the reception sensitivity. Furthermore, when the amplification factor of a preamplifier 20 is increased to increase the input power of the photodetector 24 to increase the optical input power to the dispersion compensation device 22, the waveform is deteriorated because of self phase modulation(SPM) in the dispersion compensation device 22. Then a dispersion compensation device 26 is provided to a pre-stage of a post-amplifier 18 at the transmitter side so as to prevent the deterioration. |
