Cross-Phase Modulation Induced by OOK Channels on Higher-Rate DQPSK and Coherent QPSK Channels

Abstract

Abstract-In this paper we show that, in hybrid wavelength division multiplexed systems, the performance of high datatrate QPSK channels impaired by cross-phase modulation (XPM) induced by the lower rate OOK channels can be simply estimated by an extension of a well-known linear model for XPM, and novel analytical expressions of the sensitivity penalty are provided. From such a model we prove that the reported QPSK penalty decrease with QPSK baudrate increase should be attributed to the action of the phase estimation process rather than to the walkoff effect. The model also simply shows how coherent QPSK is more affected by XPM than incoherent DQPSK, and allows to infer that even more impact is expected when the baudrate is further reduced through polarization multiplexing.Index Terms-Cross phase modulation (XPM), differential quadrature phase shift keying (DQPSK), phase estimation, phase shift keying.

Dependence of non-linear impairments on polarization state and baud rate in WDM systems with mixed DQPSK and OOK channels

“…Figure 5 also shows that the dependence of the overall non-linear impairments (intra-channel and crosscannel) on baud rate is low: indeed the non-linear tolerance (NLT, defined as the launch power for which the required OSNR is increased by 1 dB compared to back-to-back) varies only by 0.5 dB for LHP and only by 2.2 dB for 45°, suggesting at higher baud rates that the increase in penalty arising form self phase modulation (SPM) with increasing baud rate (for which dispersion causes pulses to broaden -and hence the power profile to deviate from constant -more quickly) is compensating the decrease in penalties arising from cross phase modulation (XPM) predicted in previous studies [10], [11]. The exact interplay of SPM and XPM is currently being studied.…”

Cross-Layer Approaches for Planning and Operating Impairment-Aware Optical Networks

“…A number of high-quality articles and books (e.g., [9] and [12]) addressed the evaluation of QoT of an optical signal in the past. Two techniques are usually adopted, namely, QoT estimator and probe signal.…”

“…Moreover, such higher transmission bitrate has to coexist with existing 10-and 40-Gb/s devices. The resulting mixed line-rate networks pose difficult technical challenges for the accurate evaluation of the QoT [12].…”

Influence of polarization state, baud rate and PMD on non-linear impairments in WDM systems with mixed PM (D)QPSK and OOK channels

“…However the performance of these PM (D)QPSK channels in pre-existing non-return-to-zero on-off keying (NRZ OOK) based dense wave division multiplexed (DWDM) systems is impacted by nonlinearities induced by cross phase modulation (XPM) and cross polarization modulation (XPolM) [1,2]. The impact of both XPM and XPolM depends on the baud rate of the PM (D)QPSK channel and relative state of polarization (SOP) to the neighbouring NRZ OOK channels [3,6].…”