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This paper evaluates and compares a range of optical pulse shapes for long-haul high-capacity dense wavelength division-multiplexed (DWDM) transmission links with return-to-zero (RZ) modulation format, in terms of their transmission performance and characteristics. Performance is compared at both 10 and 40 Gbit/s, using several different types of transmission fibre. Results show that different pulse shapes exhibit different optimal duty cycle and launch power level into the transmission fibre. In addition, the optimum values and the maximum achievable Q values also depend on transmission fibre type used due to the interplay between optical amplifier noise, fibre dispersion, nonlinear effects, and linear crosstalk from demultiplexers. For both 10 and 40 Gbit/s transmission, super Gaussian waveform gives the best transmission performance and largest optimal duty cycle, hyperbolic secant exhibits the worst Q value and smallest optimal duty cycle, and Gaussian is intermediate between for all the transmission fibre types considered. [Copyright &y& Elsevier]

Abstract: We have systematically studied the dispersion properties of a 40 channel×10 Gbit/s wavelength division multiplexed (WDM) transmission link using standard single mode fibre with all EDFA amplification, over 30×100 km spans. The dispersion map of the link was investigated by adding fibre sections with positive or negative dispersion at the transmitter, within each amplifier span, and at the receiver. Optimum combinations of these dispersive fibre lengths were found to significantly enhance the overall transmission performance. The dispersion slope mismatch between the transmission fibre and compensation fibre was investigated using the optimal dispersion map. The tolerable range of slope mismatches was found using a post-compensation method for individual channel compensation and overall channel compensation. [Copyright &y& Elsevier]

Abstract: We experimentally demonstrate an all-optical 10Gb/s format conversion from non-return-to-zero (NRZ) on-off-keying (OOK) to return-to-zero (RZ)-OOK with tunable duty cycle in the whole C-band using nonlinear polarization rotation (NPR) arising in an semiconductor optical amplifier (SOA). The experimental results show that, by tuning the polarizer at the SOA output, an RZ signal with tunable duty cycle from 33% to 66% could be obtained with an extinction ratio(ER) over 10dB. In addition, we show that the NRZ-to-RZ conversion with duty cycle of 33–66% can be obtained with less than 1dB power penalty at the bit error ratio (BER) of 10−9. The device can facilitate the cross-connection between optical transmission networks employing different modulation formats. [Copyright &y& Elsevier]