Optical switches can be divided into mechanical and non-mechanical ones according to the driving methods.
Mechanical optical switch relies on the movement of optical fiber or optical elements to convert the optical path, such as a mobile optical fiber type, moving the sleeve to move the lens (including mirrors, prisms and self-focusing lens) types. The biggest advantage of this kind of optical switch is a low insertion loss and low crosstalk. Its disadvantage is slow and easy to wear, easy to vibration, impact shocks.
Non-mechanical optical switch relies electro-optic, magneto-optic, thermo-optic and other effects to change the refractive index of the optical waveguide, the optical path changes, such as electro-optic switch, magneto-optic switch, and thermo-optic switch. This kind of optical switch has good repeatability, fast switching speed, high reliability, long life and other advantages, and small size, can be monolithically integrated. The disadvantage is that the insertion loss and crosstalk performance is not ideal, which should be improved.
Here are three common optical switches.
Opto-Mechanical Switch
Opto-mechanical switch is the oldest type of optical switch and the most widely deployed at the time. These devices achieve switching by moving fiber or other bulk optic elements by means of stepper motors or relay arms. This causes them to be relatively slow with switching times in the 10-100 ms range. They can achieve excellent reliability, insertion loss, and crosstalk. Usually, opto-mechanical optical switches collimate the optical beam from each input and output fiber and move these collimated beams around inside the device. This allows for low optical loss, and allows distance between the input and output fiber without deleterious effects. These devices have more bulk compared to other alternatives, although new micro-mechanical devices overcome this.
Thermo-Optic
SwitchThermo-optic switches are normally based on waveguides made in polymers or silica. For operation, they rely on the change of refractive index with temperature created by a resistive heater placed above the waveguide. Their slowness does not limit them in current applications.
Electro-Optic Switch
These are typically semiconductor-based, and their operation depends on the change of refractive index with electric field. This characteristic makes them intrinsically high-speed devices with low power consumption. However, neither the electro-optic nor thermo-optic optical switches can yet match the insertion loss, backreflection, and long-term stability of opto-mechanical optical switches. The latest technology incorporates all-optical switches that can cross-connect fibers without translating the signal into the electrical domain. This greatly increases switching speed, allowing today’s telcos and networks to increase data rates. However, this technology is only now in development, and deployed systems cost much more than systems that use traditional opto-mechanical switches.
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