Optical Test Set for Microwave Vector Network Analyzers based on Homodyne detection

We present an optical test set for a microwave vector network analyzer that transforms the instrument into a full vector optical analyzer (OVA), enabling measurements of the optical field transfer function of components and systems with Hz-level frequency resolution. The setup is simple, consisting of a laser source, a standard Mach-Zehnder electro-optic modulator, and a self-homodyne receiver based on a 90° optical hybrid and balanced detectors. Unlike other OVA methods that use RF-modulated optical signals, our technique avoids complex setups and multi-step procedures. It is also immune to errors caused by beating between unwanted modulation sidebands. We provide a detailed theoretical derivation of the mathematical framework underlying the method. In addition, we introduce a calibration technique that compensates for all optical and electrical non-idealities in the setup, including those introduced by the optical hybrid. We demonstrate the system's operation through proof-of-concept experiments, measuring both the magnitude and phase of the optical field transfer function of narrowband optical components.