Received: 17 November 2016 Revised: 14 April 2017 Accepted: 20 June 2017 DOI: 10.1002/dac.3383 RESEARCH ARTICLE Merit of hybrid EDFA/Raman amplification in fixed-grid all-optical network exploiting multirate transponders Arsalan Ahmad 2 Andrea Bianco 1 Hussein Chouman 4 Daniele DeTommas 1 Guido Marchetto 3 Sarosh Tahir 3 Vittorio Curri 1 1 Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, 10129 Torino, Italy 2 National University of Sciences and Technology, 44000 Islamabad, Pakistan 3 Dipartimento di Automatica e Informatica, Politecnico di Torino, 10129 Torino, Italy 4 TelecomParisTech, Universite Paris-Sud, Universite Paris Saclay, 75008 Paris, France Correspondence Sarosh Tahir, Dipartimento di Automatica e Informatica, Politecnico di Torino, 10129 Torino, Italy. Email: sarosh.tahir@polito.it Summary The constant need to improve network capacity and reduce power consumption in current fixed-grid WDM networks motivates researchers to find alternative solu- tions other than replacing the deployed equipment. One of the possible solutions is the use of hybrid EDFA/Raman amplifier, which improves signal-to-noise-ratio in a point-to-point link. This work aims at quantifying, by means of a detailed power model, the effect of these novel ideas on the power consumption of the network, which is key to build a future green Internet. In particular, we consider the use of a randomly generated topology of 20 nodes to study the effect of hybrid amplification, fiber type, fiber span length, and sensitivity to average link length and average traffic per node. Results show that hybrid amplification in moderate pumping regime min- imizes total network power consumption for networks made up of all 3 fiber types in particular for nonzero dispersion-shifted fiber. KEYWORDS GN-model, HFA, LTD, NyWDM, TDHMF, uncompensated transmission 1 INTRODUCTION In the near future worldwide IP traffic demand will undergo an average growth rate of 21% till 2018. 1 Hence, network operators are investigating solutions to enhance the capacity of currently installed dense wavelength division multiplexing (WDM) infrastructure. Ideally, it should be achieved avoid- ing the swap of installed fibers and components so that high costs involved in replacing installed equipment can be saved. 2 Formerly, in-line dispersion management was used to cope with this issue, but the introduction of multilevel modulation formats with digital signal processor (DSP)-based coherent receivers has opened a vast paradigm for researchers, where links are not designed for a specific transmission and net- work nodes can perform transparent wavelength routing. As a result, the whole network can be designed on the basis of a unique transmission layer quality parameter: the optical signal-to-noise ratio (OSNR), which includes both amplified spontaneous emission (ASE) noise accumulation and nonlin- ear impairments (NLI). 3 In particular, it has been shown that a control plane based on local OSNR maximization yields benefits to the network optimization. 4 Thus, to better exploit available network resources, we can take either or both of the following two directions: (1) development of improved transmission techniques using max- imum benefit of the available OSNR and (2) introduction of new solutions enhancing the OSNR values. In terms of transmission techniques, elastic transponders able to switch among different modulation formats are already available in the market. However, only discrete values of bit- per-symbol (BpS) are available, with a gap in OSNR requirement when switching from one format to another. To overcome such a limitation, the use of time-division hybrid modulation formats (TDHMF) was proposed. 5,6 The TDHMF permits to contin- uously tune the BpS value, thus maximizing the benefit of available lightpath OSNR. Besides experimental analyzes on Int J Commun Syst. 2017;e3383. wileyonlinelibrary.com/journal/dac Copyright © 2017 John Wiley & Sons, Ltd. 1 of 10 https://doi.org/10.1002/dac.3383