An Optical Approach to Microwave Frequency Measurement With Adjustable Measurement Range and Resolution

TLDR

The study proposes an optical method to measure microwave frequency with adjustable range and resolution. The method employs two widely spaced optical wavelengths modulated by the microwave signal in a Mach‑Zehnder modulator, then sent through a dispersive fiber to generate distinct power penalties; the wavelengths are split and their microwave powers measured by photodetectors to infer frequency, with range and resolution tuned by adjusting the wavelength spacing. A fixed power‑ratio to frequency relationship was derived and experimentally validated, demonstrating adjustable measurement ranges and resolutions.

Abstract

We propose an approach for the measurement of microwave frequency in the optical domain with adjustable measurement range and resolution. In the proposed approach, two optical wavelengths with a large wavelength spacing are modulated by an unknown microwave signal in a Mach-Zehnder modulator (MZM). The optical output from the MZM is sent to a dispersive fiber to introduce different chromatic dispersions, leading to different microwave power penalties. The two wavelengths are then separated, with the microwave powers measured by two photodetectors. A fixed relationship between the microwave power ratio and the microwave frequency is established. The microwave frequency is estimated by measuring the two microwave powers. The frequency measurement range and resolution can be adjusted by tuning the wavelength spacing. Different frequency measurement ranges and resolutions are demonstrated experimentally.