Shamil Appathurai

Extended Reach GPON Using High Gain Semiconductor Optical Amplifiers

A 1300 nm semiconductor optical amplifier has been developed for extended reach GPON applications. The high gain of 29 dB has and enabled a commercial GPON system to operate over 60 km and with 128-way split.

Investigation of the optimum alternate-phase RZ modulation format and its effectiveness in the suppression of intrachannel nonlinear distortion in 40-Gbit/s transmission over standard single-mode fiber

The results of a detailed study of the performance of 40-Gbit/s optical transmission over standard single-mode fiber with alternate-phase return-to-zero (AP-RZ) modulation formats are presented. While in the highly dispersed propagation regime, the use of RZ format signals with alternate phase between adjacent pulses can lead to a significant reduction in nonlinear interaction between pulses, allowing increased launch powers and, hence, increased transmission distances, this has not been systematically investigated. In this paper, we investigate the use of AP-RZ formats, both numerically and experimentally, to explain and quantify the effects of varying the peak-to-peak phase modulation, the amount of precompensation at the transmitter and the presence of multiplexer prefiltering for the case of wavelength-division multiplexing systems with high spectral efficiency. It is shown that, while the use of pulses with alternate /spl pi//2 rad phase shifts minimizes the build-up of shadow pulses in the zero bit slots due to intrachannel four-wave mixing, the best overall performance is obtained with /spl pi/ rad peak-to-peak phase modulation. We show experimentally, for the first time, that the optimum value of precompensation to minimize intrachannel nonlinear distortion is dependent on the signal format used.

Investigation of nonlinear distortion in 40-Gb/s transmission with higher order mode fiber dispersion compensators

The performance of 40-Gb/s transmission systems is limited by the nonlinearity of the transmission and dispersion compensating fibers, and hence, optimized dispersion map designs and signal formats are required to extend error-free transmission distances. In this paper, we describe systematic experiments and simulations of return-to-zero (RZ) and nonreturn-to-zero (NRZ) 40-Gb/s transmission over nonzero dispersion-shifted fiber using higher order mode fiber dispersion management devices. We compare the single channel transmission limits due to nonlinear distortion with dispersion compensators positioned at the start and end of each amplifier span (pre- and postcompensation) and show that the transmission distance of NRZ signals can be extended with the use of precompensation due to the reduced self-phase modulation in the transmission fiber. In contrast, the combination of precompensation and RZ format was found to give poor performance, and analysis shows that this is a result of intrachannel four-wave mixing. The best performance was obtained using an RZ signal format and postcompensated spans. The performance of wavelength-division multiplexing (WDM) signal transmission over the link was then investigated. The simultaneous transmission of multiple 40-Gb/s channels over long-distances was achieved, demonstrating broad-band compensation of the dispersion and dispersion-slope using higher order mode fiber. Results of experiments assessing cross-phase modulation between 40-Gb/s WDM channels spaced by 100 GHz are presented, and the penalties due to inter- and intrachannel nonlinear effects are compared.

Investigation of intra-channel nonlinear distortion in 40 Gbit/s transmission over standard fibre

We describe new distance-dependent experiments investigating infra-channel nonlinear distortion in 40 Gbit/s OTDM transmission over standard fibre. Simulations results predicting significant reduction in the distortion due to intra-channel four-wave mixing by using alternating pulse polarisation were experimentally confirmed.

Next generation extended reach PON

The author gives a slide presentation of next generation access passive optical networks.

Measurement of tolerance to non-uniform burst powers in SOA amplified GPON systems

We investigate the performance of an amplified GPON system under conditions of unequal burst powers from ONTs. Successful operation is shown for power differences up to 14 dB as might be expected in a deployed system.

Fiber nonlinearity and dispersion mitigation in 40-Gb/s NRZ WDM transmission using a multichannel optical equalizer

We investigate the mitigation of distortion due to self-phase modulation and dispersion in 40-Gb/s nonreturn-to-zero wavelength-division-multiplexed transmission using a multichannel optical equalizer. The ability of the equalizer to reduce the signal degradation due to fiber nonlinearities was demonstrated. We achieved 21-channel transmission at BER <10/sup -9/ without forward error correction over 750 km of true wave reduced slope fiber with 107-km amplifier span lengths.

Nonlinearity and in-line residual dispersion tolerance of /spl pi/-AP-RZ and CS-RZ modulation formats in 40-Gb/s transmission over standard single-mode fiber

We achieved a 40% increase in 40-Gb/s transmission distance in links with exact dispersion compensation through suppression of nonlinear distortion by using the alternate-phase return-to-zero (AP-RZ) modulation format. A novel experimental technique was used to compare in-line residual dispersion tolerances, and it was found that AP-RZ is less dispersion tolerant than conventional RZ and carrier-suppressed RZ (CS-RZ) when both linear and nonlinear transmission are considered. Maximum dispersion tolerance of /spl plusmn/50 ps/nm over 300 km was shown to be possible using CS-RZ.

Next generation fibre-to-the-home solutions

Fibre access networks capable of delivering high-speed broadband connectivity to the home is reviewed here. The paper also highlights the evolutionary steps in technology towards delivering symmetrical bandwidths in the Gbit/s range per customer.

Wideband 40 Gbit/s WDM transmission under higher-order-mode fibre dispersion management

We report on the transmission of 10/spl times/40 Gbit/s WDM channels with 100 GHz spacing, error-free over 450 km of nonzero dispersion shifted fibre (NZDSF) using HOM fibre dispersion management, without per-channel dispersion trimming.