Simultaneous up- and down-frequency mixing based on a cascaded SOA-MZIs link.

Abstract

In this paper, a simultaneous frequency up- and down-conversion is performed using a cascaded semiconductor optical amplifier Mach-Zehnder interferometers (SOA-MZIs) link for radio-over-fiber (RoF) applications. The intermediate frequency (IF) signal carrying quadratic phase shift keying (QPSK) data at a frequency f1 is up-converted at the SOA-MZI1 output at nfs±f1, where n is the harmonic rank of the first sampling signal. In addition, this up-converted signal is concurrently up- and down-converted at the SOA-MZI2 output at mfs+nfs±f1 and |nfs±f1-mfs|, respectively, where m is the harmonic rank of the second sampling signal. Using the virtual photonics integrated (VPI) simulator, it has been shown that the optical transmission system based on a cascaded SOA-MZIs link has a better efficiency and more endurable quality of the frequency mixing of QPSK signals and the higher frequency range for up- and down-conversions. Positive conversion gains are obtained at the highest mixing frequency of 101.9 and 86.3 GHz for up- and down-conversions, respectively. The best error vector magnitude provided using a cascaded SOA-MZIs link is 15.5% at the mixing frequency of 101.9 GHz for up-conversion and 18% at 86.3 GHz for down-conversion at the bit rate of 40,500 Mbit/s. The maximum bit rates of 40.5, 81, and 121.5 Gbit/s for QPSK, 16-QAM, and 64-QAM modulations, respectively, that meet the forward error correction limit is fulfilled by using a cascaded SOA-MZIs link. Another advantage of using the cascaded SOA-MZIs link is the up- and down-conversion simultaneously achieved at the second stage.