Stablized fiber-optic delay of arbitrary waveforms with application in distributed sensors

Arbitrary, broadband radio-frequency (RF) waveforms are distributed over long fibers with stabilized group delay. Thermal drifts in delay are compensated based on chromatic dispersion. The input waveform and a control RF sine wave modulate two separate tunable laser diode sources, coupled into a dispersive delay fiber. The output phase of the delayed control tone is used to provide feedback for setting the wavelengths of both lasers in a closed-loop operation. The two waveforms are separated in the optical domain, and no restrictions are imposed on their RF spectra. The method is employed in the distribution of broadband, linear frequency modulated radar waveforms, and in a high-resolution Brillouin analysis sensor experiment. In the latter, the stable interrogation of a 2 cm-wide local hot-spot is demonstrated, in the presence of thermal delay drifts that are several times larger.