Page 683 - Introduction to Information Optics

Chapter 12 Networking with Optics

Lintao Zhang, Guohua Xiao and Shudong Wu
AVANEX CORPORATION

Networking with optics includes optical networking based on time, on
optical frequency/wavelength, on space, and on optical coding. While research
has been ongoing in all these areas since fiber optics emerged as a dominant
communication technology in the 1970s, up until now, only optical networks
based on frequency/wavelength become a reality.

12.1. BACKGROUND

Wavelength division multiplexing (WDM) is the underlying technology for
optical networking based on the wavelength of optical signal [1, 2, 3]. Among
existing transmission media, optical fiber provides the most bandwidth, com-
pared to copper wire, coaxial cable, and microwave [4]. Today, All Wave™
fiber made by Lucent Technology has about 300 nm (~ 43 THz) of bandwidth
usable for optical transmission. The two most common ways of multiplexing
additional signals onto the huge bandwidth of fiber is by assigning different
optical frequencies to each signal (frequency-division multiplexing or FDM),
or by assigning different time slots to each signal (time-division multiplexing
or TDM). Because wavelength is the reciprocal of frequency, WDM is logically
equivalent to FDM. WDM is performed in the optical domain using a passive
optical wavelength division multiplexer (WDM mux or for short, mux) and
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