Ultra-rapid dispersion measurement in optical fibers.

We present a novel method to measure the chromatic dispersion of fibers with lengths of several kilometers. The technique is based on a rapidly swept Fourier domain mode locked laser driven at 50kHz repetition rate. Amplitude modulation with 400MHz and phase analysis yield the dispersion values over a 130nm continuous wavelength tuning range covering C and L band. The high acquisition speed of 10micros for individual wavelength-resolved traces Deltat(lambda) can reduce effects caused by thermal drift and acoustic vibrations. It enables real-time monitoring with update rates >100Hz even when averaging several hundred acquisitions for improved accuracy.