Eight-Channel SiO$_2$/Si$_3$ N$_4$/Si/Ge CWDM Receiver

We demonstrate a monolithic eight-channel coarse wavelength-division-multiplexing (CWDM) receiver. It has a spot-size converter in
$\hbox{SiO}_{2}$
and
$\hbox{Si}_{3}\hbox{N}_{4}$
, an arrayed-waveguide grating (AWG) in
$\hbox{Si}_{3}\hbox{N}_{4}$
, fan-out waveguides in Si, and photodetectors in Ge. By appropriately varying the waveguide widths in the AWG, polarization independence is achieved. The responsivity from fiber to photodiode for the best channel is higher than 0.34 A/W over all polarizations. We demonstrate
${-}$
20.3-dBm sensitivity at
$10^{-12}$
bit-error rate at 2.5 Gb/s for one of the channels using a commercial small-form-factor pluggable (SFP) transceiver as a transmitter.