Transmission performance improvement using random DFB laser based Raman amplification and bidirectional second-order pumping

Abstract

Abstract:We demonstrate that a distributed Raman amplification scheme based on random distributed feedback (DFB) fiber laser enables bidirectional second-order Raman pumping without increasing relative intensity noise (RIN) of the signal. This extends the reach of 10×116 Gb/s DP-QPSK WDM transmission up to 7915 km, compared with conventional Raman amplification schemes. Moreover, this scheme gives the longest maximum transmission distance among all the Raman amplification schemes presented in this paper, whilst maintaining relatively uniform and symmetric signal power distribution, and is also adjustable in order to be highly compatible with different nonlinearity compensation techniques, including mid-link optical phase conjugation (OPC) and nonlinear Fourier transform (NFT). 2015 Optical Society of America

RIN Mitigation and Transmission Performance Enhancement With Forward Broadband Pump

“…The experiment and simulations show good agreement. As RIN is not included in the simulations, this indicates that there was no RIN-related penalty in the experiment and that the system performance was limited only by ASE noise and nonlinearity [7]. Using the broadband fibre laser as the FW pump, the optimum Q factor was improved to 12 dB at 100 mW FW pump power.…”

“…As a baseline, second order BW-pumping at 1366 nm with the FBG near the output end of the span was used. First order random fibre laser was generated due to the resonant mode reaching the lasing threshold in a distributed cavity formed by fibre Rayleigh scattering and an FBG [7][8][9]. When forward pumping was used, different FBGs with the same centre wavelength as the forward pump were used.…”

“…Different power levels were used for each pump type to evaluate the impact of FW-pumping. Backward pump powers were adjusted between 1.05 W and 1.25 W to compensate the fibre attenuation, depending on the pumping scheme [7]. The first FW-propagated pump was a 1452 nm commercially available broadband fibre laser with ~8 nm 3dB bandwidth (shown in Fig.…”

“…However, the major challenge of forward (FW) pumping is relative intensity noise (RIN) related penalty, particularly for long-haul transmissions [3][4][5][6]. We previously reported a Raman amplification technique based on random distributed feedback fibre laser with bidirectional second order pumping which suppressed the RIN-related penalty and extended the maximum reach by ~12% [7][8][9], compared with backward (BW) pumping only. However, the main drawback of that scheme was that the Raman gain efficiency near the span input was very low, requiring up to 1W FW pump power.…”

“…Using the proposed scheme gives a maximum reach of 7499 km, compared with 4999 km using Bidoped fibre laser or semiconductor laser diodes and 1500 km using narrowband fibre laser. Unlike other pump lasers, the RIN of the output signal using this broadband laser does not increase dramatically when the pump power increases, and therefore signal power profiles can be adjusted for different nonlinearity compensation techniques [7,11,12]. In addition, compared with BW-pumping only, FW broadband pumping reduces the noise figure (NF) tilt across the amplification band and leads to a flatter gain spectrum [13].…”