Ultrahigh-Resolution Optoelectronic Vector Analysis Utilizing Photonics-Based Frequency Up- and Down-Conversions

An ultrahigh-resolution optoelectronic vector analyzer (OEVA) to characterize optoelectronic (O/E) frequency responses of photodetectors is proposed and experimentally demonstrated, which is characterized by potential sub-Hz frequency resolution, doubled frequency range and large dynamic range. A carrier-suppressed optical double-sideband (ODSB) signal generated by modulating two frequency-swept RF signals with a fixed frequency spacing is used as a probe signal, which is then converted into a photocurrent by the photodetector (PD) under test. Comparing the frequency up- and down-conversion components in the generated photocurrent, the O/E frequency responses can be achieved with no need to know the response of the electro-optic modulator and the modulation indices. As the desired components achieved by frequency up- and down-conversion are frequency distinguished from the two RF signals, the proposed OEVA is immune to electromagnetic interference during on-chip measurement. In the experiment, the O/E frequency responses of two high-speed PDs are characterized from 0.1 to 67 GHz using a 25-GHz Mach-Zehnder modulator (MZM). The frequency resolution is up to 200 kHz. Additionally, the measurement error analysis is analyzed, and the noise performance and the dynamic range are experimentally investigated and discussed.