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A coherent optical frequency division multiplexing (FDM) experimental system for a n optical CATV distribution service has been developed. This system employed a channel frequency spacing locked optical FDM transmitter and a random access optical heterodyne receiver. In the transmitter, 10 1.54-pm wavelength tunable DBR LD modules were FSK modulated with a 400 Mbit/s PN pattern. A "reference pulse method'' for channel space control was proposed. Individual channel spacings for 10 LD's were stabilized to 8 GHz. The random access optical heterodyne receiver is realized with a wavelength tunable local DBR LD, polarization diversity reception technique and random access automatic frequency controller. A "current address method" realized the random access function. In order to evaluate these key techniques, a 10-channel FDM transmission experiment was carried out. A 114-GHz capture range, a n 80-GHz lock range, and less than 1-ms random channel selection time were realized with the random access optical heterodyne receiver. Receiver sensitivities were -45 dBm at 400 Mbits/s for all 10 channels. The power penalty dependency on signal polarization state was suppressed to 0.5-1 dB by a novel polarization diversity reception technique based on a n "active squarelaw combining method." It is estimated that over 80 channel high definition TV signals can be distributed to 2000 subscribers with 500-GHz frequency tunable DBR LD. The feasibility of expanding the subscriber number to over 10 000 was also confirmed by a n experiment with a traveling wave optical amplifier.