A new technique for measuring the dynamic response of optical phase modulators is presented. It is based on a photonic signal processor principle, in which the phase modulator is inserted in a Sagnac loop, and coherent summation of the counter-propagating phase modulated signals converts the off-loop-center phase modulation into intensity modulation, so that modulator response can be measured on a network analyzer from the envelope of the resulting microwave photonic filter response. Experimental results demonstrate that this technique is applicable for both polarizing and nonpolarizing waveguide optical phase modulators, and that it has wideband measurement capabilities with swept frequency response characterization features.
Chan, E. H. W., & Minasian, R. A. (2008). A new optical phase modulator dynamic response measurement technique. Journal of Lightwave Technology, 26(16), 2882-2888. https://doi.org/10.1109/JLT.2008.925704