Optical vector analyzers based on asymmetric two-band modulation

This article presents the principle of operation and the results of experimental prototyping of optical vector analyzers based on asymmetric double sideband modulation, created at the R&D Institute of Applied Electrodynamics, Photonics and Living Systems within the framework of the state task for KNRTU-KAI. Asymmetric double sideband modulation is used to solve the problems of modern optical vector analyzers. The advantages of its use are the ability to obtain a doubled measurement frequency range (80 GHz), and, in some cases, the absence of measurement errors caused by the presence of higher order side bands in the probe radiation. The latter removes restrictions on the magnitude of the modulation index of the optical carrier, and, therefore, on the dynamic range of measurements. Two variants of optical vector analyzers with asymmetric double sideband modulation are considered - with asymmetry in frequency and amplitude. A key element of the first option is a phase-shift fiber Bragg grating, which is used to form a biased carrier asymmetric double sideband modulation signal. To implement asymmetric double sideband modulation with amplitude asymmetry, the disadvantages of the scheme implementing single sideband modulation are used to form two components of different amplitudes. To verify the developed theoretical principles, a universal set-up, described in the article, was made.