Economic and system impact of hybrid Raman–EDFA amplification in a 40 × 40 Gbps optical transmission network with DPSK modulation

Demands of modern high-bandwidth services drive the need to constantly improve existing optical amplification technology beyond its current bounds. In this paper, we demonstrate a hybrid broadband amplification scheme which is capable of improving the system performance of a wavelength-division-multiplexed (WDM) network. We present the study of optical signals with differential-phase-shift keying (DPSK) modulation at 40 Gbps and its transmission in a 50-GHz spaced, 40-channel WDM system over an 80-km link with hybrid optical amplification. A comparison of the system and cost impacts of a Raman-only amplification scheme with two hybrid Raman–erbium doped fiber amplifier schemes (Hybrids I and II) is performed. It is shown that one of the proposed hybrid schemes (Hybrid II) outperforms the other by (i) improving the tolerance to signal input power by 17 dB and (ii) increasing the system reach by 55 km for input signal power of 5 dBm, for a bit error rate (BER) performance of 10−12.

► An NRZ-DPSK-modulated WDM system amplified by Raman–EDFA hybrids is modeled.
► We compare system BER and amplification cost for three amplification schemes.
► A 40-channel network with 50-GHz channel spacing and 40-Gbps modulation is used.
► A Raman–EDFA hybrid that uses EDFA as power booster is shown to perform best.
► Better tolerance to signal input power, improved system reach and reasonable cost.