What Is an Optical Switch?
Optical switches, also known as optical line switching devices, are devices used in optical communications to branch or alter the destination of a specific signal without converting it from an optical signal to an electrical signal.
Since there is no need to convert optical signals into electrical signals, switching can occur while maintaining the high-speed characteristics of optical communications.
Optical switches can be broadly classified into three types based on the switching method:
1. The mechanical method involves switching the optical path by moving an input/output element or optical element mounted on an electrical actuator.
2. The MEMS method switches by controlling the position of a minute optical element using a weak force such as static electricity. It switches by reflecting light from two mirrors. MEMS switches can be integrated into a small size and operate at high speeds, making them suitable for multi-channel switching. Although the device must be constantly energized, it is possible to reduce power consumption because the power required to operate each element is also small.
3. The bending method switches by placing heaters on both sides of the optical waveguide on a substrate. This heats one side of the heater to create a temperature difference between the left and right sides of the waveguide. The optical waveguide method changes the refractive index in the waveguide by creating a temperature difference between the left and right sides, thereby altering the light propagation path.
Uses of Optical Switches
Optical switches are utilized in devices that control optical paths and manage light in optical communications, which are now essential for high-speed communications.
When optical communications are converted to electrical signals before switching, the time required from conversion to switching becomes a bottleneck. Optical switches were developed to address this issue by performing switching using light.
Optical switches continuously provide a stable optical access environment by switching to alternative paths when one optical path becomes unavailable due to device failure or other reasons.
Principles of Optical Switches
The mechanical method has a straightforward structure, and switching is achieved by sliding optical elements such as prisms. The control system is user-friendly, and losses are minimal.
The MEMS method is an optical switch that uses micro-mirrors, which can be fabricated with advancements in microfabrication technology. It switches by reflecting light from two mirrors. MEMS switches can be integrated into a small size and operate at high speeds, making them suitable for multi-channel switching. Although the device must be constantly energized, it is possible to reduce power consumption because the power required to operate each element is also small.
The optical waveguide type is realized using lightwave circuit technology, which creates an optical waveguide on a flat surface. It changes the optical path by altering the refractive index or using external inputs such as heat, light, or electricity. Although it incurs some loss, it can stack planar surfaces and is characterized by its compact size and ease of integration.