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The Basics of Optical Switch

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Optical networking technology has grown rapidly and helped solve the problem of increasing demand for higher transfer data rates and bandwidths. In optical networks, optical fiber is the fundamental medium of transmission, but functions like switching, signaling and processing are accomplished electronically. To achieve conversions between optical signals and electrical signals, optical switches are naturally developed. What is an optical switch? This post will offer some basic information about optical switches.

Introduction

In telecommunication, an optical switch is a switch that enables signals in optical fibers or integrated optical circuits (IOCs) to be selectively switched from one circuit to another. An optical switch may operate by mechanical means, such as physically shifting an optical fiber to drive one or more alternative fibers, or by electro-optic effects, magneto-optic effects, or other methods.

Types of Optical Switches

An optical switch is simply a switch which accepts a photonic signal at one of its ports and send it out through another port based on the routing decision made. There are two kinds of optical switches, which are O-E-O (optical-electrical-optical) optical switch and O-O-O (optical-optical-optical) optical switch, also known as all optical switch. OEO switch requires the analogue light signal first to be converted to a digital form, then to be processed and routed before being converted back to an analogue light signal. OOO switching is done purely through photonic means.

Two Types of Optical Switches OEO-and-OOO

Applications of Optical Switches

Optical switches are widely used in high speed networks where high switching speeds and large switches are required to handle the large amount of traffic. Optical switches are likely used within optical cross-connects (OXCs). An OXC may contain a whole series of optical switches. OXCs are similar to electronic routers which forward data using switches. Optical switches can also be used for switching protection. If a fiber fails, the switch allows the signal to be rerouted to another fiber before the problem occurs. It takes an optical switch milliseconds to detect the failure and inform network and switch. Besides, optical switches can be utilized for external modulators, OADM (optical add-drop multiplexers), network monitors and fiber optic component testing. In early days, original optical transceivers were required to be plugged into these switches. Now third-party optical transceivers are produced to save the cost. As shown below, you can test the compatibility of a fiber optic transceiver, such as Avago AFBR-79EIPZ compatible QSFP+ transceiver, HP JD089B compatible 1000BASE-T SFP transceiver or HP J4859C compatible 1000BASE-LX SFP transceiver in an optical switch.

Switch for transceiver compatibility test

Advantages of Optical Switches

Optical switches have several advantages compared with electric switches. They can save room and power consumption significantly, about up to 92 percent space and 96 percent power. If power savings are translated into cost savings, it means 3 kw can be reduced for each rack, which can save carriers from expensive diesel power generators, rectifiers and batteries, and save monthly maintenance costs for these devices and the purchasing and maintenance of cooling equipment for these devices. Optical switches are more scalable and faster than electric switches. All-optical switches are protocol and bit rate independent, so transfer rates will not be affected by bit rate limitations of switching equipment.

Disadvantages of Optical Switches

Optical switches also have some disadvantages. Currently, optical switches can not realize the technology to store photonic signals as easily as electrical signals. But they can store signals using fiber delay lines, as light takes a certain time to travel through a certain length of fiber (200,000 km per second in silica), which means a 10000 bit frame traveling at 10Gb/s requires 200m fiber. That is both expensive and impractical. And once a signal is put through a delay line, it cannot be processed until it comes back out. A solution to this is adding switches within the lines, but that will increase the costs. Optical switches cannot process header information of packets, especially at high traveling speed. The maximum speed electronic routers currently can operate is 10Gb/s while optical signals can travel up to 40/100Gb/s or even higher. Thus, the routers will not be able to process the signals as fast as the transmission.

Conclusion

With the increasing demand for video and audio and challenges of data capabilities and high bandwidth of networks, optical networks have gradually become the most cost-effective solution. Optical switches can provide customers with significant power, space and cost savings. Today, the optical switch market is dominated by several companies, such as Cisco, HP, Arista, and Juniper. You can choose an optical switch based on your needs.

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