Are You Familiar With Optical Switch?

by www.fiber-mart.com

There are lots of fiber optical devices used for communication networks. And optical switch is the one transmitting light signals between different channels. If a light signal is propagated from one phone or computer to another, it may be required to move between different fiber paths. Under this condition, optical switch plays an important part as it can transfer the signal with a minimum loss of voice or data quality. With the growth of technologies, many new methods have been combined with optical switch to achieve higher speed performance. Today, let’s step into the world of optical switch and explore its secrets.

 

Types of Optical Switches

Basically, there are two types of optical switches – OEO (optical-electrical-optical) switch and OOO (optical-optical-optical) switch. Network management functions of operating a network are available today using an optical switch with an electronic-based switching matrix. OEO switch receives the optical signal and converts it into electrical signal. Then it switches the signal into a different port and converts it back to optical signal for the network. By using an electronic fabric, OEO switch accomplishes bandwidth grooming and overcomes the network impairments.

 

 

OOO switch or all-optical switch enables the managing and switching of optical signals without converting them into electronic signals. This is especially attractive to those carriers operating large offices where up to 80 percent of the traffic is expected to pass through the office on its way to locations around the globe. It receives the optical signal and switches it to a different port in the optical domain, then returns it back to the network as an optical signal.

 

Technologies Applied In Optical Switch

 

MEMS (micro electrical mechanical system) technology uses many moving mirrors to switch the signals by deflecting light waves from one port to another. There are two MEMS structures. One is called 2D MEMS mirror, and another is 3D MEMS mirror. 3D MEMS based optical switch is more widely used in the industry. Following figure shows the operation process of the MEMS switching.

 

 

Liquid Crystal Switching

Liquid crystal technology employs the polarization effects of light in liquid crystals for light switching. At first, the light is filtered through polarization beam splitter to be separated into two or more paths. Then the light is put through a liquid crystal where its polarization property may be changed. At last, the light comes into the polarization beam combiner to be steered into the output port. And the output port is decided by the new polarization property of light.

 

Bubble Based Switching

Bubble based switch can use air bubbles and micro trenches aligned vertically and horizontally to switch the light. When there is no need for switching, the light can pass through the trenches uninterrupted. This technology has the benefits of low cost and fast switching time.

 

Thermo-Optic Switching

Thermo-optic switch will send light down a wave guard. The light is then split into different wave guards. If a switching command is issued, one of the wave guard arms is heated and the light within the wave guard will change its optical path length. Then the light is recombined and the path lengths of the lights are measured. If the lengths are different then the beam will be switched into one output port. If they are the same, the beam will be switched into another port.

 

 

Applications

Optical switches can be applied to various applications. In high speed networks, switches for this function are usually used within optical cross-connects to handle large amount of traffic. Another application is for the protection switching. If a fiber fails, the switch allows the signal to be rerouted to another fiber before the problem occurs. Also, the OADM (optical add-drop multiplexer) will use some optical switches to convert signals from a DWDM stream allowing carriers to selectively remove some wavelengths from a signal.

 

Conclusion

Optical switch is an important device that transfers light signals into different channels. Based on the original OOO type and OEO type optical switches, many new technologies have been brought in, which ensures the high performance of optical switches. With growing demands for higher data bandwidth, the future of optical switch is bright.

The Basics of Optical Switch

by www.fiber-mart.com

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.

 

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.

 

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.