Low‐Noise and Broadband Random Fiber Laser Enabled by Seed Injection for Advanced Distributed Raman Amplification

ABSTRACT High‐power, broadband, and low‐noise fiber lasers are ideal pump sources for distributed Raman amplification to suppress the pump‐to‐signal relative intensity noise (RIN) transfer. Random fiber lasers offer a modeless platform for low‐noise operation as promising pump sources for distributed Raman amplification systems. Nevertheless, conventional random fiber lasers exhibit narrow bandwidth and cascade noise transfer. Here, we demonstrate a method for RIN mitigation and spectral manipulation of a cascaded random Raman fiber laser via backward seed injection. The proposed backward seed‐injected cascaded random Raman fiber laser delivers a 1.64 W output power, a 12.35 nm 3‐dB bandwidth, and a low RIN baseline of −130 dB/Hz, which is >15 dB lower than the conventional narrowband cascaded random Raman fiber laser. The advantages of the low‐noise broadband CRRFL as a 2nd‐order distributed Raman amplification pump source are further validated, which can significantly reduce the integrated RIN of the amplified signal in the 1 MHz‐100 MHz span when compared with a noisy narrowband cascaded random Raman fiber laser as a 2nd‐order distributed Raman amplification pump source. This work provides a new methodology for achieving high‐power, broadband, and temporally low‐noise fiber lasers, offering technical support for long‐haul optical fiber communication and optical fiber sensing.