Abstract
To improve the spectral efficiency and increase network capacity, wavelength signals must be multiplexed densely, i.e., ultra-dense wavelength-division-multiplexing (WDM) networks. However, the spectrum of each WDM signal is narrowed by the wavelength-selective switches placed in optical nodes, so the transmissible distance and node hop count of the signal are strictly limited. To counter this spectrum narrowing problem caused by optical node traversal in ultra-dense WDM networks, pre-filtering techniques have been proposed. This paper comprehensively investigates the performance of four pre-filtering techniques: conventional Nyquist filtering, pre-emphasis filtering, partial-response filtering, and the combination of pre-emphasis and partial-response filtering. We conduct extensive computer simulations and discuss the optimality of pre-filtering techniques. The simulation results show that the adaptive use of pre-filtering can substantially extend the maximum attainable transmission distance and hop counts of 4/16/64-QAM signals.
Highlights
In photonic networks, optical nodes based on wavelength-selective switches (WSSs) can transparently route wavelength-division-multiplexing (WDM) signals without costly optical-to-electrical and electrical-to-optical conversion
We evaluated pre-filtering techniques to counter the spectrum narrowing impairment caused by optical node traversal in ultra-dense WDM networks
Extensive computer simulations showed that adopting the suitable pre-filtering scheme could drastically increase the attainable node-hop count compared to the conventional Nyquist filtering scheme in both metro-scale networks and backbonescale networks
Summary
Optical nodes based on wavelength-selective switches (WSSs) can transparently route wavelength-division-multiplexing (WDM) signals without costly optical-to-electrical and electrical-to-optical conversion. To fulfil the demand for greater network capacity while retaining cost-effectiveness, we need to adopt ultra-dense WDM systems in which the bandwidth of guardbands placed between neighboring WDM signals is smaller than that of present dense WDM systems [1] In such systems, the impact of the spectrum-narrowing impairment caused by traversing WSSs in optical nodes is significant [2]–[11]. The SNR degradation due to ISI compensation can be alleviated by pre-emphasis filtering [15]–[17] In this scheme, frequency components that will be attenuated by node traversal are partly emphasized using transmitter-side digital signal processing (DSP) so that noise enhancement by post-compensation filtering is suppressed. Excess SNR degradation increases with the node-hop count Another possible solution, partial-response coding, alleviates noise enhancement at the receiver side.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
