A 1 Mbit/s optical data bus employing micro-optic directional couplers, which can compatibly replace an electrical bus cable in an in-line work station computer system connecting a central processor and four work stations up to 1.5 km apart, has been developed, and the feasibility has been confirmed.

Photonic switching and coherent optical transmission would be key technologies for realizing future all optical broadband wide-area networks. This paper reports results of studies on integrating photonic switching systems and coherent optical transmission technologies. Introducing coherent optical transmission technologies to photonic space-division switching systems will lead to some excellent features, including line handling capacity expansion, transmission span increase and integration capability with coherent WDM/FDM broadcasting systems. Photonic wavelength-division (WD) switching systems with large number of WD channels would also be possible, with coherent optical transmission technologies. Space-division switching experiments in a 100 Mb/s optical FSK transmission system were carried out using LiNbO3 photonic switch matrices. Receiver sensitivity improvement of 7.5 dB was observed in the transmission experiments through a photonic switch matrix and long SMFs (22 km, 100 km). This allows more cascaded connection for photonic switch matrices in a photonic switching system. It was also shown that crosstalk component can be rejected at the receiver by introducing channel separation greater than 3 GHz, even when the crosstalk power is ten times larger than the desired signal. From these experimental results, a photonic SD switching system whose line capacity exceeding 500-lines and whose transmission line length was over 20 km, would be expected.

Receiver sensitivity improvements as much as 16.4 dB and 4.1 dB over direct detection and ASK heterodyne detection, respectively, have been realized in 32 Mb/s PSK heterodyne detection simulation experiments using a 1.3µm wavelength laser diode.