Apparatus and method for measuring phase response of optical detectors using multiple-beatnote optical heterodyne

摘要

A heterodyne modulated optical signal that includes two or more beat notes is produced. A portion of the heterodyne modulated optical signal is coupled to a device under test (DUT). This portion includes modulation at least at two of the beat note frequencies. The output of the DUT includes signals corresponding to two of the beat notes. These signals are mixed to produce a mixed output signal having the same frequency as an additional beat note but a phase that depends on the phase response of the DUT at one or more of the two beat note frequencies. The phase of the mixed output signal is measured with respect to a reference signal having the same frequency and a known phase with respect to the additional beat note. The resulting phase measurement represents the dispersion of the DUT with respect to modulation frequency.