Experimental topology of a femtosecond ring fiber cavity laser using SOA-MZI for coincident OFDM dispatch

Abstract

In this paper, we present an experimental design for the simultaneous transmission of 1024 subcarriers using a ring fiber cavity laser (RFCL) based on a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI). The SOA-MZI-RFCL system demonstrates exceptional passive power stability, with fluctuations under 0.27 % root mean square (RMS) over one hour and an average output power of up to 11.8 dBm with an optical bandwidth of 8.8 nm. Notably, the system achieves the output pulse width is compressed to 32 fs using a four-prism pulse compressor. We employ two configurations of orthogonal frequency-division multiplexing (OFDM): one with all 256 subcarriers transmitting 512-QAM-OFDM data and another with four carriers of 256 subcarriers each transmitting 1024-QAM or distinct M−QAM (quadrature amplitude modulation) data. A performance analysis based on Error Vector Magnitude (EVM) is conducted for both configurations, varying OFDM subcarrier frequencies and cyclic prefix (CP). By increasing the subcarriers to 1024 and using a 12-bit depth, we achieve significant improvement in transmission quality. For the 512-QAM-OFDM configuration, the EVM reaches 1.1 % at 100 GHz. In the second configuration, the EVM remains at 1.1 % for 1024-QAM at 103 GHz. Additionally, when varying M−QAM formats, the EVM decreases from 1.1 % for 512-QAM-OFDM at 100 GHz to 0.25 % for 4096-QAM-OFDM at 103 GHz with a 10 % CP. Ultimately, the SOA-MZI-RFCL system exhibits outstanding performance, making it a strong candidate for high-quality optical transmission applications.