Raman cell optimisation for distributed amplification based transmission systems

Commercially available Raman fiber pumps display relatively high Relative Intensity Noise (RIN) that gets transferred to the output signal in systems relying on Raman distributed amplification. This has been shown to drastically hinder performance in Raman-based transmission systems [1], limiting the practically usable forward pump powers and setting constraints to the design of low signal power variation (SPV) bidirectional systems with optimised optical signal-to-noise ratios (OSNR) [2]. Recent works have highlighted a remarkable improvement in the resilience to RIN transfer of higher-order ultralong Raman fiber lasers (URFL) in a random Distributed Feedback (rDFB) laser amplifiers configurations with no fiber Bragg grating (FBG) at the front-end [3]. Moreover, we have shown [4] that a low-reflectivity front-end FBG can be more beneficial than no back-reflections at all, for enhancing pumping efficiency while still keeping RIN transfer under control. Here we extend previous analysis of the low-reflectivity URFL amplification scheme including experimental investigation of RIN transfer, OSNR and pump power requirements for different architectures. We perform a comparison with the rDFB approach and present a detailed optimisation of the main amplifier parameters for the effective design of Raman-based transmission systems.

[1]  M. A. Iqbal,et al.  Transmission performance improvement using random DFB laser based Raman amplification and bidirectional second-order pumping. , 2016, Optics express.

[2]  Sergei K. Turitsyn,et al.  Random distributed feedback fiber laser , 2011, 2011 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference.

[3]  J. Ania-Castañón.  Quasi-lossless transmission using second-order Raman amplification and fibre Bragg gratings. , 2004, Optics express.

[4]  M. Tan,et al.  Evaluation of 100G DP-QPSK long-haul transmission performance using second order co-pumped Raman laser based amplification. , 2015, Optics express.

[5]  H. Renner,et al.  Pump-to-Stokes RIN transfer in Raman fiber lasers and its impact on the performance of co-pumped Raman amplifiers , 2006 .

[6]  M. Tan,et al.  RIN Mitigation in Second-Order Pumped Raman Fibre Laser Based Amplification , 2015 .

[7]  J. Ania-Castañón,et al.  RIN transfer in 2nd-order distributed amplification with ultralong fiber lasers. , 2010, Optics express.

[8]  J D Ania-Castañón,et al.  RIN transfer in random distributed feedback fiber lasers. , 2012, Optics express.

[9]  M. Tan,et al.  Extended reach of 116 Gb/s DP-QPSK transmission using random DFB fiber laser based raman amplification and bidirectional second-order pumping , 2015, 2015 Optical Fiber Communications Conference and Exhibition (OFC).

[10]  M. A. Iqbal,et al.  Impact of input FBG reflectivity and forward pump power on RIN transfer in ultralong Raman laser amplifiers. , 2016, Optics express.

[11]  J. Ania-Castañón,et al.  Unrepeatered DPSK transmission over 360 km SMF-28 fibre using URFL based amplification. , 2014, Optics express.

[12]  C. Fludger,et al.  Pump to signal RIN transfer in Raman fiber amplifiers , 2001 .

[13]  S. Turitsyn,et al.  Ultralong Raman fiber lasers as virtually lossless optical media. , 2006, Physical review letters.