Integrated Optical Delay Line Based on a Loopback Arrayed Waveguide Grating for Radio-frequency Filtering

Integrated silicon photonics provides an attractive platform for on-chip radio-frequency (RF) signal processing. We demonstrate an integrated silicon optical delay line based on a loopback arrayed waveguide grating (AWG). The optical delay varies discretely by changing the carrier wavelength of the input optical signal. The device can be used as a multi-tap finite-impulse-response (FIR) radio-frequency filter, where each delay channel provides a feedforward replica of the RF signal. By changing the number of delay channels and the time interval between the channels, the bandwidth and center frequency of the RF filter can be tuned, respectively. The loopback AWG performs spectrum slicing and wavelength-selective delay, which greatly simplifies the light source requirement in FIR filter.