High-frequency characterization of an optical phase modulator with phase modulation-to-intensity modulation conversion in dispersive fibers

We propose a new method for characterizing optical phase modulators based on phase modulation-to-intensity modulation (PM-to-IM) conversion in dispersive fibers. The fiber dispersion spectrally alters the relative phasing of the phase-modulated signal and leads to the PM-to-IM conversion, which is extended to measure the modulation efficiency of optical phase modulators. In the demonstration, the frequency-dependent modulation index and half-wave voltage are experimentally measured for a commercial phase modulator. Compared with conventional methods, the proposed method works without the restriction of small-signal operations, and allows swept-frequency measurement with high resolution and accuracy by using a vector network analyzer.