Spurious-Free Dynamic Range of the Photonic Time-Stretch System

Analog-to-digital conversion based on photonic time-stretch (PTS) has been widely studied. The performance of PTS systems is limited by the inherent nonlinearity of external modulators. In this letter, for the first time, to the best of our knowledge, we analytically characterize the spurious-free dynamic range (SFDR) by obtaining the exact expressions for the power distribution of the third-order intermodulation products in the PTS system with either a single-arm Mach-Zehnder modulator (MZM) or a push-pull MZM. The relation between the SFDR and the time-stretch factor and several effective ways to improve the SFDR of the PTS system are also investigated. Both simulation and experimental results are given to verify the theoretical model. The presented results can largely simplify the design of PTS systems with desired performance.