Common-Mode Suppression of Ambient Temperature-Induced Phase Drift in Phase-Stabilized RF Fiber Links Using Dual Optical Carriers

Ambient temperature fluctuations of system environments can significantly degrade the stability of fiber-based phase-stabilized RF transfer systems. In this work, the underlying mechanism of such degradation is systematically investigated. It is shown that, in conventional single-ended architectures, temperature-dependent phase variations originating from the laser source and local RF components are directly accumulated in the phase-locked loop, resulting in pronounced instability. To address this issue, a symmetric dual-carrier architecture is proposed by introducing independent optical carriers at both the central and remote sites. This configuration transforms the system into a differential reference scheme, where temperature-induced phase perturbations exhibit common-mode characteristics and can be effectively suppressed. Meanwhile, the reduced reliance on erbium-doped fiber amplifier (EDFA) in the return path mitigates amplified spontaneous emission noise and temperature-sensitive gain fluctuations. Experimental results demonstrate that, under ambient temperature variations of approximately 7 °C, the link delay fluctuation is reduced from over 15 ps to about 1.2 ps. The corresponding frequency stability reaches a modified Allan deviation of 6.70 × 10−19 at an averaging time of 10,000 s without strict temperature control. These results validate the effectiveness of the proposed approach for robust high-stability frequency transfer.