A tunable 1x4 silicon CMOS photonic wavelength multiplexer/demultiplexer for dense optical interconnects.

We report the first compact silicon CMOS 1x4 tunable multiplexer/ demultiplexer using cascaded silicon photonic ring-resonator based add/drop filters with a radius of 12 microm, and integrated doped-resistor thermal tuners. We measured an insertion loss of less than 1 dB, a channel isolation of better than 16 dB for a channel spacing of 200 GHz, and a uniform 3 dB pass band larger than 0.4 nm across all four channels. We demonstrated accurate channel alignment to WDM ITU grid wavelengths using integrated silicon heaters with a tuning efficiency of 90 pm/mW. Using this device in a 10 Gbps data link, we observed a low power penalty of 0.6 dB.