Abstract
Optical transmission technologies optimized for optical network segments sensitive to power consumption and cost, comprise modulation formats with direct detection technologies. Specifically, non-return to zero differential quaternary phase shift keying (NRZ-DQPSK) in deployed fiber plants, combined with high-performance, low-complexity electronic equalizers to compensate residual impairments at the receiver end, can be proved as a viable solution for high-performance, high-capacity optical links. Joint processing of the constructive and the destructive signals at the single-ended DQPSK receiver provides improved performance compared to the balanced configuration, however, at the expense of higher hardware requirements, a fact that may not be neglected especially in the case of high-speed optical links. To overcome this bottleneck, the use of partially joint constructive/destructive DQPSK equalization is investigated in this paper. Symbol-by-symbol equalization is performed by means of Volterra decision feedback-type equalizers, driven by a reduced subset of signals selected from the constructive and the destructive ports of the optical detectors. The proposed approach offers a low-complexity alternative for electronic equalization, without sacrificing much of the performance compared to the fully-deployed counterpart. The efficiency of the proposed equalizers is demonstrated by means of computer simulation in a typical optical transmission scenario.
Highlights
Due to the rapid evolution of cloud services, traffic demand is growing dramatically every year in every network segment
We investigate the performance of the conventional non-return to zero differential quaternary phase shift keying (NRZ-DQPSK) optical link that comprises an optical channel with standard single mode and dispersion compensating fiber and various receiver configurations that combine single-ended receivers and joint reduced complexity Volterra-type equalizers [2,10,11]
In this paper, starting from the requirements for low-complexity, high-performance equalizers, the effect of reducing the number of single-ended ports in the equalization process is investigated with exceptional results
Summary
Due to the rapid evolution of cloud services, traffic demand is growing dramatically every year in every network segment. Transporting traffic at high bit rates, such as 100 Gbit/s, may become challenging as various impairments manifest themselves [1] Combating those impairments is cumbersome and power consuming, the preferred solution choices are not obvious in network segments that are sensitive to cost and power consumption, like in metropolitan area networks [2] and inter-data center networks [3]. In high data rate systems, signal distortions caused by intersymbol interference increase proportionally to the square of the data rate, the performance of the transmission system is very sensitive to the possible residual dispersion at the receiver. As discussed in [2] optical transmission systems can benefit from a combination of rigid DCF with adaptive equalization at the receiver where residual dispersion is adjustably compensated after signal detection. A comparative study of the performance of the proposed equalization schemes is performed by means of computer simulations, using a typical 40 Gb/s optical transmission setup
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