622 MBIT/S-16-CHANNEL FDM COHERENT OPTICAL-TRANSMISSION SYSTEM USING 2-SECTION MQW DFB-LDS

A light source and optical frequency control technique needed for realizing the optical frequency division multiplexing transmission (Optical FDM) is developed and experiments of a 622 Mbit/s-sixteen-channel FDM coherent optical transmission based on the heterodyne detection are conducted. The transmission is configured such that sixteen 1.55 mu m wavelength two-section MQW DFB-laser diode (LD) are multiplexed by a star coupler. The wavelength of each LD was spaced at 10 GHz intervals with the frequency fluctuation kept under +/- 100 MHz by the optical frequency control circuit that uses a scanning Fabry-Perot interferometer. The receiver configuration has a delay-line demodulator, polarization diversity, and a frequency discriminator with no dead bands. For the station light source, the two-section MQW DFB-LD was tuned, which is the same as the transmitter, using current and temperature control. Random channels could selectively be received with a receiver sensitivity of -39.3 dBm. It was verified that 16 channels of 622 Mbit/s high-vision (Japanese standard HDTV) signal could be transmitted through 110 km of 1.3 mu m zero dispersion fiber without signal degradation.