Experimental Observation of Anomalous RIN Transfer in Random Distributed Feedback Raman Fiber Lasers

Despite being demonstrated only in 2010 [1], ultralong random distributed feedback Raman fiber lasers (RDFLs) have been extensively investigated for their unique features and potentially excellent performance in a number of applications, including sensing and optical communications [2]. Although relatively simple in design, these devices display great complexity in operation, presenting multiple regimes and possible configurations, which make determining the optimal configuration for a particular application a daunting task. In particular, the relative intensity noise (RIN) transfer function (TF) of an RDFL [3] is highly dependent on multiple parameters and often imposes a limit on overall system performance. Recently [4], it was theoretically shown that in some particular configurations, maximum RIN transfer in RDFLs can be displaced towards high frequencies in spite of the filtering effect associated to the faster averaging of pump oscillations, which could help manage noise in sensing and communication schemes. In this paper we demonstrate this effect experimentally for the first time and show, with the help of precise numerical simulations, the physical mechanisms leading to such "anomalous RIN transfer function".