The working principle and application of MEMS optical switch

 What is optical switch?

Optical switch is a device that converts an optical signal from one optical channel to another optical channel within a certain range. It has one or more selectable transmission windows. Fiber optic switch is one of the core devices for optical cross-connection, optical add/drop multiplexing, network monitoring and automatic protection system.


Its implementation technologies are diverse, including: mechanical optical switches, thermo-optical switches, acousto-optic switches, electro-optical switches, magneto-optical switches, liquid crystal optical switches and MEMS optical switches. The traditional switch with electricity as the core is gradually unable to meet the demand for high-speed and large-capacity optical communication, which is why the all-optical switch appears in the market. Among them, MEMS optical fiber switches are widely used due to their small size, low power consumption, and good scalability.


Working principle of MEMS optical switch

What is MEMS? MEMS is shot for Micro-Electro-Mechanical System, which refers to a micro-device or system that can be mass-produced and integrate micro-machines, micro-actuators, signal processing and control circuits. The preparation process of micro-mechanical structures includes photolithography, ion beam Etching, chemical etching, wafer bonding, etc.

MEMS is driven by electronic technology, such as electrostatic attraction, electromagnetic force, electrostriction, and thermocouple. Among all the driving mechanisms of MEMS devices, the electrostatic attraction structure is the most widely used due to its simple preparation, easy control and low power consumption.


The MEMS optical switch is to engrave a number of tiny mirrors on the silicon crystal. The microarray is rotated by electrostatic force or electromagnetic force to change the propagation direction of the input light, thereby realizing the on and off function of the light path.


Structure of MEMS Fiber Optic Switch

Fiber optic switch is a multiport device. The port configurations include 2×2, 1×N, N×N. Optical switch with N×N ports is usually called OXC (optical cross connect). The structure of a MEMS-based 1×N optical switch is shown in Fig, which consists of a MEMS torsion mirror, a collimating lens and a multi-fiber pigtail. The MEMS mirror is usually assembled on a TO base, then the collimating lens is joint to the sub-assembly through the TO cap. Finally, the multi-fiber pigtail is actively aligned to the sub-assembly.


MEMS optical switch VS Mechanical optical

The working principle of mechanical optical switches is to redirect optical signals by physically moving optical fibers with the help of mechanical equipment. By moving the prism or directional coupler, the light at the input end will be directed to the desired output port. There are three main types of mechanical optical switches: one is to use a prism to switch the optical path technology, the other is to use mirror switching technology, and the third is to switch the optical path by moving an optical fiber.

MEMS optical switches are based on micro-electro-mechanical systems, which use optical micro-mirrors or optical micro-mirror arrays to change the direction of light beams to switch optical paths. The principle of MEMS optical switches is very simple. When the light is exchanged, the angle of the MEMS micro-mirror is moved or changed by the drive of the electrostatic force or the magnetic force, and the input light is switched to the different output terminals of the optical switch to realize the switching and on-off of the optical path.

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