Optically Controlled Low-Distortion Delay of GHz-Wide Radio-Frequency Signals Using Slow Light in Fibers

Continuously tunable delay of broadband analog signals for microwave photonics applications is described and demonstrated, based on stimulated Brillouin scattering (SBS) in optical fibers. The optical spectrum of the pump laser is synthesized using chirp control, in order to obtain a broadened SBS "slow light" process, with long delay and low amplitude and phase distortions. The resulting SBS process is applied to delay 1-GHz-wide linear frequency modulated radio-frequency signals of arbitrary carrier frequency. Delays up to 230 ps are observed, with a worst-case sidelobe suppression ratio of -26 dB