Brief Introduction of Optical Switch

What is Optical Switch?

Optical switch is an optical path conversion device. In fiber optic transmission systems, optical switches are used for the conversion of multiple monitors, LANs, multiple light sources, detectors and protective Ethernet. In the fiber optic test system, it is used for fiber optic equipment testing and network testing, fiber optic sensing and multi-point monitoring system. 

Why is Optical Switch important?

When a light signal runs through from one computer to another in fiber optic networks, it may be required to move the signal between different fiber paths. To accomplish this, a switch is required to transfer the signal with a minimum loss. Optical switch is a technology needed. The optical switch we often see is operated by mechanical method which just moves fiber or other bulk optic components. But they can offer unprecedented high stability and unmatched low cost performance.

What are common types of Optical Switch?

Optical switch is an optical device with one or more optional transmission ports that physically switches or logically manipulates optical signals in an optical transmission line or integrated optical path. Optical switches are classified from the manufacturing process, which can be divided into mechanical, micro-opto-electromechanical MEMS system switches and other switches. The first two types of optical switches are currently the most mature and most widely used products in the market, and the last category can be subdivided into liquid crystal optical switches, electro-optical optical switches, thermo-optical optical switches, and acousto-optic optical switches.

• Traditional mechanical optical switch

  Traditional mechanical optical switches rely on the movement of optical fibers or optical elements (lenses or reflectors) to change the optical path and send or reflect light directly to the output end. Although mechanical optical switches are large in size and have long switching times, they are not suitable for large-scale switch matrices and applications, but they have low insertion loss, low crosstalk, good repeatability, are independent of the wavelength and polarization state of the light used, and are cheap.
  
  

• MEMS optical switch
  Mechanical optical switches are slow, usually in the order of milliseconds, and their large size and difficulty in large-scale integration limit their application in the future optical communication field. On this basis, the MicroElectro-Mechanical System (MEMS) optical switch has developed rapidly in recent years. It is a new type of microcomputer-electric-optical integrated switch produced by combining semiconductor microfabrication technology with micro-optics and micro-mechanical technology.
  
  It has the advantages of transparent data format of optical signals, no polarization, small loss, good reliability, high speed, and easy integration, and has become the mainstream direction of the development of large-capacity switching optical network switches.

• Magneto-optical switch
  The magneto-optical switch uses the Faraday rotation effect to change the effect of the magneto-optical crystal on the polarization plane of the incident polarized light by changing the external magnetic field, thereby achieving the effect of switching the optical path.
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  Compared with the traditional mechanical optical switch, it has the advantages of fast switching speed and high stability, and compared with other non-mechanical optical switches, it has the advantages of low driving voltage and small crosstalk. It can be foreseen that in the near future, the magneto-optical switch will be a very competitive optical switch.

What are applications of Optical Switch?

• Protection of optical networks

  
  As we all know, in the actual fiber optic cable transmission system,  spare optical fibers are commonly prepared to protect the optical network. When the transmission of the working channel is interrupted or the performance deteriorates to a certain extent, the optical switch will automatically transfer the main signal to the backup optical fiber  for transmission, so that receivers can receive the normal signal and do not feel that the network has failed. It will connect the network nodes into a ring to further improve the survivability of the network. 

• Monitoring of optical networks
  
  At the remote optical fiber test point, multiple optical fibers are connected to the optical time domain reflectometer(OTDR) through a 1×N multi-channel optical switch(OS) for real-time network monitoring.  Switching sequence and time of  optical switch are controlled by the computer to realize the detection of all optical fibers. Once issue is found in any a channel, test results are transmitted back to the network control center（NMU).

• Testing of optical components
   1×N optical switches can realize the production, inspection and testing of components. Each channel corresponds to a specific test parameter, so that multiple optical devices can be tested without having to connect each device to the instrument individually. As a result, testing is simplified and efficiency is increased.

• OADM system

  
  Optical add-drop multiplexing (OADM) is mainly used in ring metro networks to realize the free up/down of single wavelength and multiple wavelengths from the optical path. The optical switch matrix is a key part of 0ADM, and the optical switch OADM can control the dynamic up/down arbitrary wavelength through software. This will increase the flexibility of the network configuration.

Summary

Optical switches (OSW) are one of the most important basic components in optical communication networks. In recent years, with the construction of optical networks, the system's requirements for high speed, capacity expansion, and high integration have become increasingly higher. Customization,miniaturization, integration, and high port count will become the development trend of optical switches in the future.