High-speed, rate-scalable photonic-assisted digitizer equalization by frequency comb referencing.

A scalable analog-to-digital converter based on polychromatic sampling and optical-domain frequency referencing is described. The new architecture relies on low-distortion replication of an optical signal to spectrally distinct copies and subsequent polychromatic parametric sampling. Frequency comb referencing of parametric replication and sampling was used to convert processor distortions into quasi-stationary impairments and enable a practical equalization implementation. The operation of the new digitizer was demonstrated at 30 GS/s, achieving 6.5 effective number of bits in the first Nyquist zone. In contrast to conventional analog-to-digital converters, the new preprocessor sampling bandwidth is not restricted to the first Nyquist zone, and can operate in the second and third Nyquist zones beyond 40 GHz.