Published/Posted: September 1, 2018
Authors: Lipkowitz, S. T.; Horton, T. U.; Pagán, V. R.; Murphy, T. E.
Here we present a technique for realizing an image rejecting radio-over-fiber downconverting link. The system uses one arm of a dual-drive Mach-Zehnder modulator (DD-MZM) to modulate an optical carrier with an RF signal, and the other arm to modulate the carrier with a local oscillator (LO). The resulting output is then sent into an asymmetric Mach-Zehnder interferometer (AMZI) which separates the frequency components above and below the LO into separate output ports. By separately detecting these two outputs and applying the appropriate DC bias to the DD-MZM, we are able to obtain in-phase and quadrature photocurrents. By combining these I and Q photocurrents with a 90-degree electrical hybrid, we obtain over 40 dB of image rejection.
S. T. Lipkowitz, T. U. Horton, V. R. Pagán and T. E. Murphy, "Microwave image rejection mixing using a Mach-Zehnder electrooptic modulator", International Topical Meeting on Microwave Photonics (MWP), Toulouse (France) 1-4 (2018)