Single longitudinal mode fiber laser with optimized compound ring cavity using genetic algorithm for optical fiber communication

As optical fiber communication continues evolving towards higher transmission rates and greater transmission capacity, a stable single longitudinal mode (SLM) narrow linewidth fiber laser is essential for optical fiber communication. This paper proposes a method to optimize the compound ring cavity (CRC) filter based on a genetic algorithm (GA) is proposed. Through the intelligent algorithm, a fiber laser with better performance can be obtained under the requirement of single longitudinal mode filtering. By using the optimized CRC structure in the experimentally-built fiber laser, the output center wavelength of the laser is obtained to be 1549.15 nm, the optical signal-to-noise ratio (OSNR) is more than 70 dB, and the fluctuation of wavelength and output power is below 0.01 nm and 0.25 dB within 60 min, respectively. In addition, the frequency noise characteristics of the output SLM laser of the proposed fiber laser are measured using a homemade linewidth test system based on an unbalanced Michelson interferometer, and the laser linewidth at different measurement times is estimated from the frequency noise spectrum by the β-line method. The minimum linewidth of the designed laser at an integration time of 0.002 s is 2.399 kHz. By building a coherent polarization-multiplexed optical communication system of 40 km, the designed laser achieves the transmission at a rate of 40 GBaud 16-quadrature amplitude modulation (16QAM), demonstrating that the designed laser can realize the requirement of communication transmission.