Optical CDMA Networks: Principles, Analysis and Applications

Chapter 3

Optical CDMA Review

3.1 Introduction

Interest in OCDMA has been steadily growing during recent decades and this trend is accelerating due to the optical fibre penetration in the first-mile and the establishment of passive optical network (PON) technology as a pragmatic solution for residential access. In OCDMA, an optical code represents a user address and it signs each transmitted data bit. We define optical coding as the process by which a code is inscribed into, and extracted from, an optical signal. Although a prerequisite for OCDMA is the optical coding as thoroughly introduced in Chapter 2, it has a wide range of novel and promising applications, such as access protocol and label switching. Most previous reviews of OCDMA have focused on physical layer (PHY) implementations. This chapter is an overview of OCDMA technologies and presents an overview of networking applications.

3.2 Optical Coding Principles

Optical code-division multiplexing (OCDM) is a process by which each communication channel is distinguished by a specific optical code rather than a wavelength, as in WDM, or a time-slot, as in TDM. An encoding operation optically transforms each data bit before transmission. The encoding and decoding operations alone constitute optical coding. OCDMA is the use of optical network technology to arbitrate channel access among multiple network nodes in a distributed fashion. Encoding involves multiplying the data bit by a code sequence either in the time domain or ...