Experimental Demonstration of Impairment-Aware PCE for Multi-Bit-Rate WSONs

Journal of Optical Communications and Networking (Impact Factor: 2.06). 09/2011; 3(8):610 - 619. DOI: 10.1364/JOCN.3.000610
Source: IEEE Xplore


In emerging multi-bit-rate wavelength switched optical networks (WSONs), the coexistence of lightpaths operating at different bit-rates and modulation formats (e.g., based on amplitude and phase modulation) induces relevant traffic dependent detrimental effects that need to be considered during impairment-aware routing and wavelength assignment (IA-RWA). The considerable complexity of IA-RWA computation has driven the Internet Engineering Task Force (IETF) to propose specific path computation element (PCE) architectures in support of IA-RWA for WSONs. In this paper, following the IETF indications, we expand two PCE architectures and experimentally evaluate five different PCE architectural solutions, performing either combined or separated impairment estimation and RWA, with on-line and off-line computation of impairment validated paths, and with the possible utilization of a novel PCE Protocol (PCEP) extension. Results in terms of traffic engineering performance, path computation delivery time and amount of exchanged PCEP messages are reported and discussed to highlight the benefits and application scenarios of the considered PCE architectures.

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    • "In the worst-case scenario, phase modulated (D-QPSK and DP-QPSK) lightpath has OOK neighbour lightpaths on both sides. Paolucci et al. (2011) have investigated various PCE architectures and have also experimentally evaluated these solutions. Different solutions employ either, combined or separated impairment estimation, and RWA with online and offline computation of impairment-validated paths. "
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    ABSTRACT: In transparent mixed-line-rate (MLR) optical networks, different line rates, on different wavelengths, can coexist on the same fiber. However, along the path, signal experiences various physical layer impairments (PLIs), and its quality also degrades. A major factor that affects transmission quality is launch power of the optical signal. On one hand, power must be high enough to ensure less noise at receiver; on the other hand, it must be lower than the limit where PLIs start to distort the signal. Further, high launch power is disruptive to both, the actual lightpath and its neighbors. In this study, we investigate the problem of determining appropriate launch power for provisioning dynamic connection requests in transparent MLR networks. We propose a heuristic that determines the appropriate launch power of a lightpath. The PLI-Average (PLI-A) approach is based on the optical reach of signals, is practical, and can adapt to the needs of network operators. Results show that performances of the proposed approach are better than the existing schemes.
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    • "This testbed exploited an IV tool integrated within the network management system (NMS) and accounting for impairment information provided by an optical performance monitor. More recently, in [21]–[23], two impairment-aware PCE architectures suitable for multi bit-rate WSONs were presented and evaluated on a fixed ITU-grid testbed including detrimental non-linear effects among 10 Gb/s OOK and 100 Gb/s dual polarization quadrature phase shift keying (DP-QPSK). Relevant effort has been spent within the Internet Engineering Task Force (IETF) to define the PCE architecture for WSONs. "
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