Accurate time-delay measurement of optical delay components based on frequency-shifted self-heterodyne spectrum

An electrical method is proposed for the absolute time-delay characterization of optical delay components based on the frequency-shifted self-heterodyning. The method utilizes the electrical spectrum of the heterodyne products between the delayed optical signal and the frequency-shifted optical carrier, and achieves the intrinsic absolute time-delay measurement from the notch frequencies of the spectrum at microwave region. Moreover, our method enables high-resolution and wide range measurement with low-frequency electrical spectrum analysis. The theoretical analysis is supported by experimental results.