A 4 X 622 Mb/s 40 km WDM optical communication system with EDFA is described. Four DFB-LD modules with 1.55 micrometers wavelength range are used in the transmitters. An EDFA with 1480 nm pump LD is used as a boost power amplifier. It suppresses noises efficiently. A Fabry-Perot interferometer is used as a demultiplexer. Through 40 km transmission, the output waveform of the receiver is obviously improved. It makes the research on long haul and WDM/FDM optical communication systems great progress.
A balanced detector receiver using resonance optical front-end has been presented. The performance of five kinds of resonance optical front-ends has been analyzed and compared with each other. The receiver using mixed tuning resonance optical front-end has a bandwidth of 4.16 GHz and very low noise performance. A sensitivity of -34.2 dBm (for bit error ratio of 10 -9) has been achieved in a 1.1 Gbit/s FSK heterodyne optical communication system.
An electrical compensation network has been developed which preshapes the injection current modulation signal waveform to suppress both the low-frequency enhancement and relaxation oscillation of DFB-LD chip. The DFB-LD modules with electrical compensation network and optical isolators have been achieved with 4.7 GHz FM bandwidth.
Performance of wavelength division multiplexing (WDM) optical communication system using a F-P demodulator is analyzed. The power penalty expression resulting from LD linewidth, channel spacing, performance of F-P demodulator and crosstalk are proposed.