Low transmission penalty dual-stage broadband discrete Raman amplifier

Abstract

We present a broadband (>70nm), dual stage, discrete Raman amplifier designed with small and standard core fibres to maximize gain and minimize nonlinearity. The amplifier provides ~19.5dB net gain, 22.5dBm saturation output power and a noise figure of <7.2dB. 120Gb/s DP-QPSK transmission over 38x80km at a pre-FEC BER <3.8x10 is demonstrated.

Nonlinear Noise of Low Transmission Penalty Dual-Stage Discrete Raman Amplifier

“…The performance of every dual-stage DRA scheme was characterised through a WDM coherent transmission experiment inside a recirculating loop as shown in Fig. 5 [6]. Five 100GHz spaced ), 120Gb/s DP-QPSK signals were generated using an IQ modulator and a polarization multiplexer (PolMux).…”

“…Other types of Raman gain fibre: highly nonlinear fibre (HNLF), dispersion shifted fibre (DSF) and inverse dispersion fibre (IDF) have also been investigated [5]. Choosing the right fibre type is an important factor because while a smaller core area results in higher gain, their high nonlinear index can result in Kerrinduced nonlinear penalties due to self-phase modulation (SPM) induced nonlinear phase shift (NPS), cross-phase modulation (XPM) and four-wave mixing (FWM) [5][6][7].…”

“…In this paper, for the first time to our knowledge, we experimentally characterise the linear and nonlinear performance of >70nm, 19.5dB gain dual-stage amplifier designs built with different fibre types (IDF, DCF, SMF) in the second stage and identify an IDF10km-SMF10km configuration as the one with lowest nonlinear transmission penalty. The first stage is built with 10km of IDF, which was chosen because of its optimal trade-off between noise figure (NF), nonlinear impairments and gain efficiency compared with DCF and SMF [6]. We use 10km of SMF, 5km and 10km of DCF and 7.5km of IDF in the second stage, and compare the performance of all four architectures in terms of gain, noise figure and FWM product power, where we measure a 3.3dB power difference in integrated FWM product between the best (IDF10km-SMF10km) and worst (IDF10km-DCF10km) performing setup.…”

“…pumped so as to have a similar broadband average net gain (a) of 19.5dB across >70nm from 1530-1600nm. For this measurement, C and L band EDFA ASE was used, which was shaped with the help of wavelength selective switches (WSSs) to generate 24 channels (12 per band) from 192.5-195.8THz (15315-195.8THz ( .12-1557) in the C-band and 187.4-190.7THz (1572.06-1599.75nm) in the L-band, -20dBm power per channel and 300GHz spacing within each band[6].…”

Characterisation of Linear and Nonlinear Noise of a Dual-Stage Broadband Discrete Raman Amplifier

“…Here, we propose a dual-stage DRA design using 10km of IDF as the 1 st stage, which was chosen for this purpose because it gives the optimal trade-off between NF, nonlinear impairments and gain efficiency compared with DCF and SMF 3,4 . We compare performance, in terms of NF and FWM product power, for the same net gain using 10km of SMF, 5km of DCF, and 10km of DCF as the 2 nd stage.…”