Planar-waveguide-type optical switching devices

This paper reviews our recent work on various planar-waveguide-type optical switching devices. Specifically we investigated N x N thermo-optic (TO) matrix switches. The matrix switch consists of N2 switching units and the switching unit has two cascaded Mach-Zehnder interferometers (MZIs). Switching is achieved by using a phase control technique based on the TO effect. The switching power of an MZI unit and the switching speed are typically 0.4 W and 2 ms, respectively. For N equals 16, we realized non-blocking connection with a very low-loss of 6.6 dB and a high-extinction ratio of 55 dB. We have also developed 1 x N configuration switches for use in optical path cross-connect systems. By integrating TO switches and arrayed-waveguide grating multi/demultiplexers, we fabricated single-chip optical add/drop multiplexers (OADM) for use in all-optical wavelength division multiplexing (WDM) routing systems. We have developed a power consumption reduction technique that is effective for all MZI TO switches as regards large scale integrated switch applications.