Page 216 - Introduction to Information Optics

Chapter 4 Switching with Optics

Yang Zhao
DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
WAYNE STATE UNIVERSITY
DETROIT, MI 48202

Switches are one of the most important devices employed for manipulating
optical signals, and are used in optical communication networks, optical
displays, and light modulations. In the past several decades, many types of
optical switches have been proposed and developed. A few books and mono-
graphs in this field have been published in the last several years [1,2,3]. This
chapter does not attempt to review the field of optical switches. Instead, several
switching devices are discussed as examples to introduce the concept and to
illustrate the principles and applications of the field. Since the main advantages
of using optical switches are ultrafast switching speed of more than 50 GHz
and massive parallelism, we will examine three kinds of optical switches with
these two advantages: ultrafast all-optical switches using nonlinear optics, fast
electro-optic modulators to convert electric data to optical ones, and massive
parallel switches using microelectromechanical systems.
Optical switches can be classified into two configurations, as shown in Fig.
4.1. One is an on-off switch in which the input is connected to one output port.
The other is a routing switch in which the input is connected to two or more
output ports. On-off switches are mainly used in modulation, light valves, and
displays, while routing switches are used in connecting many nodes in net-
works. There are several ways to control an optical switch, and the perform-
ance of the switch largely depends on the control mechanism. Traditional
control mechanisms include electro-optical effect, acousto-optic effect, mag-
neto-optic effect, thermo-optic effect, piezoelectric effect, and electro-
mechanical actuation. Switches based on these mechanisms have a speed well

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