Measurement of differential modal group delay of a few-mode fiber using a Fourier domain mode-locked laser.

We propose and experimentally demonstrate a method for measuring the differential modal group delay (DMGD) of a few-mode fiber using a Fourier domain mode-locked laser (FDML). We use the fast frequency-swept, wavelength-tunable output of the FDML in order to perform time domain measurements of interference of the modes, which is further postprocessed to extract the DMGD. We demonstrate the measurement of DMGD for a commercial two-mode fiber over the C-band. This method is not limited by the magnitude of DMGD or the number of modes and is minimally affected by time-dependent polarization and mode fluctuations, environmental noise, and spectral resolution of instruments.