High Stability RF Transmission in Star Topology Fiber Networks via SOA-XGM Wavelength Conversion

We propose a star topology fiber-based radio frequency (RF) transmission system that integrates semiconductor optical amplifier cross-gain modulation (SOA-XGM) for wavelength conversion with optical delay line (ODL) compensation. This architecture effectively suppresses backscattering noise and phase jitter while maintaining scalability. Based on the carrier dynamics model of the SOA, we theoretically derive the RF-modulated carrier wavelength conversion from $\mathbf {\lambda _{1}}$ to $\mathbf {\lambda _{2}}$, and experimentally demonstrate that the module achieves efficient wavelength shifting while preserving the intrinsic stability of the RF signal. At the local end, the wavelength conversion module provides complete isolation between forward and backward signals. This design allows for the suppression of backwscattering noise at the remote end without requiring additional optoelectronic components. To dynamically compensate for phase jitter introduced during fiber transmission due to temperature fluctuations and mechanical vibrations, the system deploys optical delay lines (ODLs) with PID closed-loop control at each remote node. The compensation strategy is guided by the phase jitter expression $\mathbf {\Delta \varphi=2\pi f\,\Delta \tau }$, taking into account the round-trip accumulation effect. Deploying compensation modules at the remote end enhances the scalability of the system in star-topology fiber networks. Experimental results demonstrate that the system achieves frequency instabilities of $\mathbf {1.4 \times 10^{-14}}$ and $\mathbf {3.2 \times 10^{-14}}$ at 1 s over 40 km and 80 km fiber links, respectively, reaching the $\mathbf {10^{-17}}$ level at 1000 s. In addition, a phase noise suppression of approximately 10 dBc/Hz is observed across the entire frequency range. This approach enables high-precision RF signal distribution without complex hardware, offering a scalable solution for multi-node synchronization such as radio telescope arrays and distributed quantum communication systems.