Optical Switches

- Overview

Optical switches, also known as phototransistors or light valves, are devices used to open or close optical paths or switch and amplify optical signals. It is a multiport bridge that connects multiple fibers and regulates the routing of packets between input and output. Mechanical, optomechanical and electronic types are found. 

While the additional light source provides the output power, the light falling on the input of the optical transistor changes the intensity of the light emitted from the output of the transistor. Optical switches amplify optical signals because the input signal may be weaker than the source signal. 

Optical switches are used in optical computing and fiber optic communication networks, using only light to control light. This technology has the potential to outperform electronics in terms of speed while saving energy.

An all-fiber fiber optic switching device that keeps the signal as light from the input to the output. Traditional switches for connecting fiber optic lines are electro-optical. They internally convert photons from the input side to electrons for switching and then back to photons on the output side.

- How Do Optical Switches Work?

An optical switch is a fiber optic circuit-based device that functions like a standard electrical network switch. It directs light from the input to the desired output by moving a mirror (prism or directional coupler). Mechanical physical movement of an optical fiber or other bulk optical element. For example, optomechanical switches redirect optical signals by moving an optical fiber through a mechanical device, usually powered by a stepper motor. 

Optical switches are classified into optomechanical switches, MEMS (Micro-Electro Mechanical Systems) switches and other switches according to their manufacturing process and technology. The first two switch types are the most popular on the market today. In some cases, thermo-optical, electro-optical, and acousto-optical switches are used. 

- Optomechanical Switch

Optomechanical switch is the oldest type of optical switch. However, it was the most commonly used at the time. Because of how it works, it is much slower, with switching times in the 10-100 m range. 

Typically, opto-mechanical optoswitches collimate the beam optics from each input and output fiber and move them around within the device. Therefore, the distance between the input and output fibers can be increased without negative effects, thereby reducing optical losses. However, they can achieve high levels of reliability, insertion loss and crosstalk.

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- MEMS-based Optical Switch

MEMS mirrors reflect input signals to output ports regardless of line speed or protocol. The technique promises to be the primary method for building photonic switches.

Although some vendors refer to electro-optical switches as "optical switches," true optical switches support all transmission speeds. Unlike electronic switches, which are tied to a specific data rate and protocol, optical switches direct input bitstreams to output ports regardless of line speed or protocol (IP, ATM, SONET) and do not need to be upgraded for any such changes. Optical Switches can separate signals of different wavelengths and direct them to different ports. 

Using tiny mirrors that reflect an input signal to an output port, MEMS technology is expected to become the mainstream method for building optical switches (also known as "photonic switches"). There are several fabrication methods available for building MEMS mirrors.

- Applications of Optical Switches

Optical switches have the potential to be used in a variety of applications, such as improving the performance of fiber-optic communication networks. Although data is transmitted over fiber optic cables, functions such as signal routing are handled electronically. This often requires light-to-electron-to-light conversion, which creates a bottleneck. 

Optical switches automatically connect one fiber to another while keeping the signal in the optical domain. This eliminates the need to manually move the fibers and instead enables a fast, reliable connection as if the fibers were directly connected to each other.  

• Signal Routing 
• Network Monitoring 
• Quantum Photonics 
• Safe Exchange 
• Fiber Optic Sensing 
• Test and Measurement

Optical switches classified as photonic integrated circuits theoretically allow all-optical digital signal processing and routing. The same equipment can be used to develop new optical amplifiers to compensate for signal attenuation in transmission lines. The development of optical digital computers, in which components deal with photons rather than electrons, is a more advanced application of optical switches. Furthermore, single-photon optical switches can be used to selectively process individual units in quantum information processing.