Transmission comparison of ultra-long Raman fibre laser based amplification with first and dual order Raman amplification using 10×118 Gbit/s DP-QPSK

Abstract

Experimental investigations of 10×118 Gbit/s DP-QPSK WDM transmission using three types of distributed Raman amplification techniques are presented. Novel ultra-long Raman fibre laser based amplification with second order counter-propagated pumping is compared with conventional first order and dual order counterpumped Raman amplification. We demonstrate that URFL based amplification can extend the transmission reach up to a distance of 7520 km in comparison with 5010 km and 6180 km using first order and dual order Raman amplification respectively. Keywords: coherent fibre optic communications, Raman amplification, Raman fibre laser. INTRODUCTIONIn fibre optic communications, dual-polarisation quadrature-phase-shift keying (DP-QPSK) modulation with coherent detection is widely deployed due to its good balance between robustness against optical signal to noise ratio degradation (OSNR) and spectral efficiency [1,2]. In order to maximise the transmission distance, it is necessary to maintain an acceptable OSNR through the system. Distributed Raman amplification (DRA) reduces signal attenuation in the transmission span leading to a higher OSNR which can allow longer reach between the repeaters or longer total distance in unrepeatered systems [3]-[7]. Ultra-long Raman fibre laser (URFL) based amplification with fibre Bragg gratings (FBGs) can further reduce the signal power variation during transmission and has proved advantageous in comparison with EDFA based systems [8]- [10].In this paper, we experimentally investigate the performances of 10×118 Gbit/s DP-QPSK WDM transmissions with coherent detection in an 83.5 km SMF-28 recirculating loop using three types of DRA. These are first order counter-pumped, dual order (both first and second order) counter-pumped, and novel URFL based amplification with 2 nd order counter pumping. To the best of our knowledge, this is the first experimental transmission comparison between first order or dual order Raman amplification and URFL based amplification. In particular, we show an improved reach of 7520 km using URFL based amplification, compared with 5010 km and 6180 km using first order and dual order Raman amplification, respectively.

Unrepeatered DP-QPSK Transmission Over 352.8 km SMF Using Random DFB Fiber Laser Amplification

“…In particular, higherorder pumping can reduce variations of the effective gain-loss coefficient along the fibre by improving the distribution of gain within the span [2], [3] resulting in minimisation of the amplified spontaneous emission (ASE) noise [4] and better performance [5].…”

Digital back-propagation for unrepeatered transmission

“…In single span experiments to date, this has been approached, in part, by improving the transmission medium itself through low loss, large effective area/low nonlinearity optical fibers and/or hybrid fiber spans [1], [2]. However, the most significant strides in performance have been due to amplifier technology, including the development of rare earth doped fiber amplifiers (e.g., the erbium doped fiber amplifier (EDFA)), forward-and backward-pumped stimulated Raman amplification [3], higher order Raman amplification [4], ultralong Raman fiber lasers [5], and remotely pumped optical amplifiers (ROPA) [6], [7].…”

Performance improvement of broadband distributed Raman amplifier using bidirectional pumping with first and dual order forward pumps

“…In order to achieve a low intra-span signal power variation, higher or dual order pumping can be used to distribute the gain more evenly along the span, leading to better optical signal to noise ratio (OSNR) and noise figure (NF) performance [7][8][9]. The benefits of higher order pumping have also been demonstrated in [10,11] in terms of extended reach of data transmission where transmission bandwidth was limited in C-band.…”