Progress on development of optical frequency combs at NTSC

In this paper, we demonstrate two techniques to improve performance of Er:fiber frequency combs at NTSC. the first technique is to obtain a robustness and low noise laser, we combine the nonlinear polarization rotation (NPR) and the nonlinear amplifying loop mirror (NALM) mechanisms to a single system. the laser has a large mode-locking range and can self-starting. It works normally after being unpowered six months, and the noise level is similar to the pure NPR. The second technique is proposed a broad bandwidth and large range frequency control method by tuning the polarization state. A special-designed electro-optic modulator (EOM) is used to rotate the polarization state in the NPR system. Compared with the traditional EOM, the sensitivity offr to the electric field intensity applied to the EOM is about 100 times larger.