Optical Transport Network

Different linear effects that occur in the physical medium are studied and analyzed in this chapter. Specifically, much attention is paid to fiber attenuation, Amplified Spontaneous Emission (ASE) noise due to optical amplifiers, and fiber dispersive effects that cause pulse broadening, which may represent a serious problem in high-speed optical transmission systems. In order to reduce fiber dispersive effects effectively, dispersion compensation fiber is employed. Other effects such as linear crosstalk, which causes distortion and interferes with the filtered channel, can be reduced by optimizing the optical filter bandwidth and shape to obtain a compromise between WDM linear crosstalk and filter induced intersymbol interference (ISI).

Modified DP-Q and MGF BER

The optical return-to-zero differential phase shift keying system is analyzed in this chapter to determine the accuracy of the recently proposed differential phase Q method in estimating the bit error rate. It is found that this method consistently underestimates the bit error rate though it successfully predicts the qualitative behavior of single channel and wavelength division multiplexed systems for back-to-back and point-to-point configurations. A simple modification reduced the underestimation and produced highly accurate estimation.

OTDM-WDM System Components Modeling

The purpose of this chapter is to discuss OTDM-WDM system components modeling.Any attempt to model the OTDM-WDM system components would need to take into account a number of key issues that have to be decided upon before a particular system setup can be implemented. Among the key issues are signal modulation format, OTDM channel bit rate, WDM channel bit rate, spectral density, length of transmission, amplification scheme, dispersion management scheme, and optical devices. Further, throughout the chapter, examples are used to demonstrate how OTDM-WDM devices, such as the transmitter, multiplexer, optical fiber, filter, amplifier, demultiplexer, and receiver, are modeled.

Optical Transport Network

The purpose of this chapter is to discuss two major categories of nonlinear effects related either to nonlinear refractive index or to nonlinear stimulated scattering effects. The effects related to nonlinear refractive index occur due to the dependence of the refractive index on the optical signal intensity. On the other hand, stimulated scattering effects are caused by interaction between light and material. As many wavelength signal channels travel through the optical fiber, they encounter many of those nonlinear effects impairments that affect the signal power level and hence degrade sharply the quality of the signal resulting in interference among signals carried by different wavelength channels. Therefore, before delving into the optical transmission performance issues, a physical picture of how optical signals behave in the presence of the most important nonlinear effect impairments is drawn.

Impact of a Post-OTDM-Demux Optical Filter

The impact of a post-OTDM-demultiplexing optical filter on the performance of dense On-Off Keying (OOK) Optical Time Division Multiplexing (OTDM)-Wavelength Division Multiplexing (WDM) systems is studied in this chapter. For Return-to-Zero (RZ) modulation, it was found that the additional filter working in a double-tier filter configuration did not offer any significant improvements to performance when the signal pulse width is optimized. Improvements generally increase only when the signal pulse width deviates from its optimal value and only for low spectral densities. For ideal Non-Return-to-Zero (NRZ) modulation, however, significant improvements of around 1 dB are obtained using the double-tier configuration over a large range of spectral densities.

Optical Soliton Transmission System

Performance analysis is carried out to evaluate the effect of XPM on a Dispersion Managed (DM) 40Gb/s optical soliton transmission using direct detection, in the presence of Group Velocity Dispersion (GVD), Self-Phase Modulation (SPM), and Amplified Spontaneous Emission (ASE) in this chapter. It is found that for a distance of 2000 km, a power penalty of 1.9 dB is required to achieve a BER of 10-9 when XPM is taken into consideration. This power penalty increases with increasing neighbouring channel power and decreases with increasing channel separation. The system performance is also shown to be dependant on the system dispersion whereby the optimum dispersion is linked to the channel input power.

Network Performance Analysis with Nonlinear Effects

The nonlinear Bit Error Rate (BER) performance of dense Wavelength Division Multiplexed (WDM) Manhattan Street Networks with deflection routing was obtained using a semi-analytical model. The chapter's results show that nonlinear effects impose significant performance penalties on dense WDM networks, both in terms of maximum hops attainable and average BER, and should be taken into account when modeling such networks. Simple techniques such as optimal amplifier positioning can mitigate some of the nonlinear penalties.

Performance Analysis Models

Modeling and performance analysis are crucial components in the understanding and design of high-speed optical communication systems. The purpose of this chapter is to discuss methods and techniques that can be used in modeling and performance analysis. It provides descriptions of various techniques that can be used to efficiently model and evaluate OTDM-WDM systems. Throughout the chapter, examples are used to demonstrate how the techniques can be applied to model and to evaluate the performance of high-speed optical communication systems.

OTDM-WDM

The purpose of this chapter is to discuss the operation principle of an OTDM-WDM transmission system. It provides a clear picture about all building blocks of the OTDM-WDM transmission system. It also contains descriptions of various techniques that can be used to generate ultra short optical pulses for OTDM system. The basic principles of multiplexing and demultiplexing and filtering processes are explained by a discussion of several practical scenarios related to OTDM-WDM transmission system.

Phase Encoded Optical Code Division Multiplexing Access System

Phase encoded optical code division multiple-access system is evaluated in a dispersive fiber medium in this chapter. An approximate analytical expression for the root mean square (rms) width of the phase encoded signal (pseudorandom optical signal with low intensity) propagating in linear dispersive fibers is derived. Bit-Error Rate (BER) analysis of the system is performed in the case of both ordinary Single-Mode Fiber (SMF) and Dispersion-Shifted Fiber (DSF). The numerical results demonstrate that even though system performance improves due to the smaller width of initial Gaussian optical pulse, the effect from dispersion is higher. Larger code length reduces the effect of dispersion and the use of DSF greatly increases the transmission distance.