Power compensation technique for precision frequency transmission via optical fiber

In order to suppress the influence of the power variation which caused by the polarization drift brought to the stability of the transmission, a frequency transmission system which could quickly compensate the change of polarization was designed. The system which used a mode-locked laser as the light source, combining with the principles of feedback regulation of the proportional-integral-derivative (PID) control, employed the erbium-doped fiber amplifier (EDFA), polarizer, variable power optical attenuator (VOA) and single ship microcomputer. Experimental results show that the system can effectively suppress the polarization drift which changes with the environment, to make the output optical power stability reach 110-5 that increases 200 times when comparing with the free float after a transmission of 10 km. The design applied in the optical frequency comb transmission system, can detect the phase more accuracy, and effectively eliminate ~ 50 fs phase jitter introduced by the polarization drift on the 5 GHz transmission frequency.