Upgrade of Passive Optical Subscriber Network

This paper describes an upgrade method for a two-way broad-band service transmission of a previously proposed passive optical subscriber network (PASS-NET). PASS-NET uses OFDM/TDM techniques for downstream transmission and TDMA for upstream. Fundamental experiments for downstream transmission to two subscribers are executed to demonstrate the possibility of the upgrade method. Two wavelengths emitted by a tunable laser (DBR-LD) with a 5-GHz (0.04 nm) space between them are directly intensity modulated at 32 Mb/s. Each wave transmits narrow-band service to each subscriber. The third wavelength emitted by another tunable laser (DBR-LD) with an 11-nm separation from the two wavelengths is directly intensity modulated at 100 Mb /s and overlaid. Three waves transmitted over a 10-km single-mode fiber are demultiplexed by a 1 x 2 wavelength selective star coupler. One subscriber receives two waves, one for a 32-Mb/s burst transmission and another for a 100-Mb/s continuous transmission. Both narrow-band and broad-band data are successfully transmitted and bit error rates are measured for both transmissions.