Analytic Equations for Photonic Frequency Converter Design

Photonic frequency converters are optical systems used to translate data at RF or microwave frequencies to new carrier frequencies for processing or retransmission. The conventional architecture includes RF to optical conversion using Mach-Zehnder modulators, inherently nonlinear devices. The mixing process occurs in photodiodes acting as optical to electrical square law detectors. Therefore, the frequency converter performance metrics are governed by complex nonlinear functions that vary widely with power levels, bias points and specific configurations that require lengthy simulations to assess; this makes understanding the performance impacts of various architectures and components difficult. This work provides analytic expressions for the primary metrics of photonic frequency converters, validated thru comparison with simulations and experiment. The derived equations are useful for the design of photonic frequency converting links, whether integrated or non-integrated. The nominal architecture comprises two Mach-Zehnder modulators in parallel within a larger interferometer. Equations are presented that describe the performance of single drive, dual drive, single detection, and balanced detection implementations. Lastly, this work provides a means of assessing the component metrics necessary for high performance photonic frequency converters as well as the upper limits on system performance.