Silica-based 8 x 8 optical matrix switch integrating new switching units with large fabrication tolerance

An 8 x 8 optical matrix switch consisting of asymmetric Mach-Zehnder (MZ) i nterferometer switching units with a waveguide intersection was fabricated using silica-based planar lightwave circuits (PLC's) on a silicon substrate . This switching unit can realize a high extinction ratio and a wide operat ion wavelength range even if the coupling ratios of the directional coupler s (DC's) consisting the switching unit, deviate greatly from the ideal valu e of 50%. A matrix switch with a DC-coupling ratio of 30% was fabricated to test the validity of the proposed geometry. The average insertion loss was 7.3 dB in the transverse electric (TE) mode and 7.5 dB in the transverse m agnetic (TM) mode. The average extinction, ratio was 31.2 dB in the TE mode and 31.3 dB in the TM mode, The wavelength range with an extinction ratio greater than 20 dB was over 100 nm.