Measurement of Microwave Frequency Using a Monolithically Integrated Scannable Echelle Diffractive Grating

A novel approach to the measurement of microwave signal frequency is studied and demonstrated. The approach is based on a monolithically integrated echelle diffractive grating (EDG). The microwave signal is converted to an optical signal of two sidebands using an optical carrier and a Mach-Zehnder modulator. One of the sidebands is then filtered out by a fiber Bragg grating, while the other sideband is characterized by an EDG-based interrogator. Due to the better than 1-pm interrogation resolution of this interrogator, the center wavelength of the sideband tested is capable of being accurately measured. Combining this data with the wavelength of the optical carrier used, the frequency of the microwave signal can be calculated. The results obtained are found to be in good agreement with those of the microwave signals.