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

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.