Abstract
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.
TopOtdm-Wdm System Model
With reference to the block diagram of the OTDM-WDM system shown in Figure 1, optical signals with similar laser center frequencies modulated using different sets of pseudo-random bit sequences (PRBS) are referred to as OTDM channels and are multiplexed together using OTDM to form higher bit rate OTDM signals. These OTDM signals act as the WDM channels. The WDM channels are then multiplexed together using a WDM multiplexer to form the overall WDM signal that is to be transmitted. For system modeling using simulations, the signal can then be transmitted through one of two different configurations, back-to-back and point-to-point. In back-to-back transmission, the signal is sent straight to the receiver without passing through any fiber links. Optical noise is often added directly using an optical noise generator placed right before the receiver in order to specify the received optical signal to noise ratio (OSNR). In point-to-point transmission, the signal is propagated through a fiber link that consists of a variety of fiber types and amplifiers (EDFA) that are joined together end to end.
Figure 1. OTDM-WDM system block diagram