With the increasing prevalence of the Internet and modern communications around the world, fiber optics, which signifying a significant information revolution in the telecommunication industry—are racing to keep up. The rapid growth of data transmission worldwide is driven by the existing demand for high quality Internet service. Meanwhile, software developers and users are constantly employing applications that take up more and more bandwidth in order to enhance the speed of information delivery, which, without doubt, placing heavy burdens on fiber networks. So carriers are looking for innovative ways to push more data through existing fiber.
To this end, there come various vital advancements in network communication that efficiently exploiting and extending the capacity of current fiber optic systems in significant ways, and optical switching captures an essential position among them.
What Is Optical Switching?
The backbone of telecommunications and networking today is the “all-optical network”, which means every communication would remain an optical transmission from start to finish. However, a certain amount of networking equipment today is still based on electronic signals, that is to say, the optical signals have to be converted to electrical ones, then to be amplified, regenerated or switched, and reconverted to optical signals. This process is referred to as an “optical-to-electronic-to-optical” (OEO) conversion. Which is considered to be a significant bottleneck in transmission. Therefore, huge amount of information traveling around an optical network needs to be switched through various points known as nodes.
Optical switching functions by replacing existing electronic network switched with optical ones, making no need for OEO conversions. It contributes to lower cost and physically smaller switches as well. However, optical switching technology currently is still immature, thus several ideas have been proposed as to how to implement light switching between optical fibers, among which the most common technique is that of the tiny movable mirrors known as micro-electro-mechanical systems (MEMS).
Introduction to MEMS
While the widely use of micro-electro-mechanical systems (EMES) in some other industries is nothing new, its adoption for telecom applications is relatively recent.
Conventional MEMS works by reflecting the beam of light from the surface of a tiny mirror. MEMS systems have moving parts, and the speed at which the mirror moves is limited. By applying more current, the mirror can move faster, but there's a limit to how much current can be sent into the array of mirrors. If this weren't bad enough, it seems that the speed and angular displacement terms in the calculation of the required current have integer powers of around 4 or 5, and so the bottom line is that we have to put a lot of current into the array for a small improvement in speed. By changing the mirror design so that the angle through which light is bent is smaller, it's possible to achieve faster switching speeds. This technique is known as "fast MEMS."
MEMS Switches Overview
MEMS optical switch is a micro-optical switch that made of the semiconductor material, which is generally used as movable micro-mirrors that can deflect optical signals from input to output fibers. It embraces the advantages as compact, lightweight and easy to expand. Besides, it shares the merits of both the mechanical optical switch and wave guide optical switch. Since EMES combines the electrical, mechanical and optical integration as a whole, it can apparently transmit different rates and different business services. MEMS switches feature good scalability. Two-dimensional arrays with size 32x32 are already available and can be used as basic building blocks, in single-stage architecture, to scale up to 256 ports.
Conclusion
Although MEMS still persists some drawbacks—too slow for optical burst switching or optical packet switching applications, the technique of it is under improving and progressing. Since it seems to have a monopoly on the high port-count optical switch market for the moment, a huge amount of investment is going into the implementations and into solving the basic problems.
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