Abstract
In wavelength-switched optical networks (WSONs), quality of transmission
(QoT) has to be guaranteed during lightpath provisioning. In multibit-rate
WSONs, this task is complicated by the coexistence of optical connections
operating at different bit-rates and modulation formats. The major issue consists
in accounting for the severe impairments due to cross-phase modulation (XPM)
induced by 10 Gb/s lightpaths on neighbor 40 or 100 Gb/s lightpaths. In this
paper, QoT modeling is first reviewed for 10, 40, and 100 Gb/s transmission
according to the adopted modulation format and detection type. In addition,
a Gaussian approximation to compute the bit error rate of differential quadrature
phase-shift keying (DQPSK) and QPSK signals is proposed, as well as closed
formulas to compute the nonlinear phase noise variance due to XPM. Also, discussions
about the XPM cumulation over spans in a WSON and how XPM can be considered
in a dynamic network are provided. Then, four lightpath provisioning schemes
are proposed to effectively account for QoT and, in particular, for XPM. The
schemes differently exploit: 1) augmented spectral separation among lightpaths
at different bit rates; 2) XPM worst-case scenario; and 3) current and novel
generalized multiprotocol label switching extensions. The performance of the
proposed schemes is evaluated through simulations in several multibit-rate
scenarios. Results show that the proposed schemes provide effective network
resource utilization while guaranteeing the adequate QoT to lightpaths at
any bit rate.
© 2011 IEEE
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