Ultrafast and Wideband Optical Vector Analyzer Based on Optical Dual Linear-Frequency Modulation

An ultrafast and wideband optical vector analyzer is proposed and demonstrated based on optical dual linear-frequency modulation. Optical dual linear-frequency-modulation waveforms (LFMWs) are generated through driving an electro-optic Mach-Zehnder modulator biased at its minimum transmission point via an electrical LFMW. Benefiting from the high frequency tuning speed of the electrical LFMW, the optical dual LFMWs can probe optical devices in a short time. Frequency-shifted dechirp processing is utilized to separate the dechirped photocurrents of the optical dual LFMWs, which leads to a doubled measurement bandwidth. In the experiment, an optical bandpass filter is measured with a measurement bandwidth of 36 GHz and a single-shot measurement time of
$20~\mu \text{s}$
. The frequency measurement resolution is demonstrated to be 10 MHz by measuring the reflection notch of an ultra-narrowband phase-shifted fiber Bragg grating.