  Photonic integrated circuits that exploit nonlinear optics in order to
generate and process signals all-optically have achieved performance far
superior to that possible electronically - particularly with respect to speed.
We review the recent achievements based in new CMOS-compatible platforms that
are better suited than SOI for nonlinear optics, focusing on radio frequency
(RF) and microwave based applications that exploit micro-resonator based
frequency combs. We highlight their potential as well as the challenges to
achieving practical solutions for many key applications. These material systems
have opened up many new capabilities such as on-chip optical frequency comb
generation and ultrafast optical pulse generation and measurement. We review
recent work on a photonic RF Hilbert transformer for broadband microwave
in-phase and quadrature-phase generation based on an integrated frequency
optical comb. The comb is generated using a nonlinear microring resonator based
on a CMOS compatible, high-index contrast, doped-silica glass platform. The
high quality and large frequency spacing of the comb enables filters with up to
20 taps, allowing us to demonstrate a quadrature filter with more than a
5-octave (3 dB) bandwidth and an almost uniform phase response.
