The radio frequency (RF) signal generation method using an external modulator is widely used in microwave photonics applications because it has the advantage of being able to generate coherent and stable RF signals with a higher resolution performance compared to the conventional method. A Mach–Zehnder modulator is widely used as an external modulator due to its high electro-optic coefficients and low attenuation characteristics but has a critical problem in that its electrical characteristics are changed by external environments such as temperature. In this paper, we considered the stabilization configuration to overcome this problem and propose an automatic bias control technique based on the simulated annealing algorithm of a dual-parallel Mach–Zehnder modulator (DPMZM) for quadruple signal generation. The proposed technique searches for the bias voltages of the modulator in real-time through the temperature test. In addition, the output of the quadrupled signal of the DPMZM is constantly controlled throughout the temperature range. Finally, it is confirmed that signals of a 10 GHz and 22 GHz frequency are generated using the intermediate frequency signals of a 2.5 GHz and 5.5 GHz frequency with the proposed automatic bias control technique, respectively.
Nonlinear intermodulation distortion suppression in coherent analog fiber optic link using electro-optic polymeric dual parallel Mach-Zehnder modulator