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.
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