Abstract
We present optical transmission systems employing minimum shift keying
modulation formats of single and dual-amplitude level under linear, weakly
nonlinear, strongly nonlinear variation of the lightwave carrier within a
bit-period depending on whether the phase variation within a symbol period
is linear or nonlinear. These formats are externally modulated, incoherently
and differentially detected based on the Mach–Zehnder delay interferometric
optical balanced receiver. Transmission performance of these optical transmission
systems is evaluated in terms of receiver sensitivity, amplification stimulated
emission noise loading, dispersion tolerances. These performance characteristics
are compared with return-to-zero (RZ) differential phase shift keying (DPSK)
and carrier-suppressed RZ on-off keying modulation formats. Accurate bit-error
ratios are obtained and confirmed by different statistical techniques: Monte
Carlo, single-Gaussian or multiple Gaussian distributions and generalized
Pareto distribution statistical methods, especially when the eye diagrams
are distorted.Among the three minimum shift keying (MSK) types, the weakly nonlinear
optical MSK is found to be the most promising because of its robust transmission
performance and more importantly, its reduced-complexity of the electrical
driving signals for transmitter in modulating the lightwave carrier as compared
to the linear MSK counterpart.Transmission performance of dual-level MSK optical transmission systems
depends on the intensity-splitting ratio of the two levels. The performance
of three ratios: 0.7/0.3, 0.8/0.2, and 0.9/0.1 are demonstrated. The spectral
attributes of 80 Gb/s dual-level MSK optical signals for these three ratios
are similar to each other and compatible with that of 40 Gb/s optical MSK,
but narrower than that of 40 Gb/s optical nonreturn-to-zero DPSK, hence high
spectral efficiency of the dual-level MSK.
© 2009 IEEE
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