How Do MEMS Optical Switches Work and Can a Raspberry Pi Drive Them? A Deep Dive into Hirundo's MEMS Switch Design
Optical networks, test instruments and data center links all need one fundamental function: changing an optical path quickly and reliably. An optical switch is the key component that makes this possible, and MEMS optical switches have become one of the most important technologies for compact, high-speed and low-loss light path routing. Hirundo Optics manufactures both mechanical and MEMS optical switch product lines, and this article explains how MEMS switches work, how they compare with mechanical switches, and how a Raspberry Pi can control Hirundo's MEMS switch driver board through SPI.
MEMS optical switch principle
MEMS stands for micro-electro-mechanical systems. A MEMS optical switch uses a tiny movable micromirror, or array of micromirrors, to change the direction of a light beam. When an electrical signal is applied, electrostatic or magnetic force changes the angle of the micromirror, steering light from one input fiber to a selected output fiber. Hirundo's MEMS switches combine semiconductor microfabrication, micro-optics and micromechanics. This integration makes the switch extremely compact and suitable for dense optical systems.
A useful example: 2x2 MEMS optical switch
A good way to understand the principle is a 2x2 port MEMS switch. When the micromirror is not in the optical path, light from waveguide 1 couples to waveguide 3, and light from waveguide 2 couples to waveguide 4. The connection states are 1 to 3 and 2 to 4, which is the straight-through state. When an electrostatic or magnetic force inserts the micromirror into the optical path, the beam from waveguide 1 is reflected to waveguide 4 and the beam from waveguide 2 is reflected to waveguide 3. The connection states become 1 to 4 and 2 to 3, which is the cross state.
For a 1xN MEMS switch, the concept extends naturally. The micromirror angle is controlled so that the input light can be directed to any one of N output ports. The same mechanism also enables high-density optical switch matrices for modern network and automation systems.
Performance advantages of MEMS optical switches
- Compact package: The MEMS chip and driver can be integrated on a small module board, saving space in optical test equipment and OXC systems.
- Low insertion loss: Hirundo's MEMS switches are designed with low insertion loss and low crosstalk to keep signal quality high during switching.
- High repeatability: Repeated switching produces very small parameter drift, which is critical for automated testing and reliable network monitoring.
- Fast response: The small mirror mass allows millisecond-level switching, sufficient for optical protection and dynamic path control.
- Long service life: after millions of switching cycles, parameter drift remains negligible, supporting long-term stable operation.
- Broad wavelength compatibility: MEMS switches from Hirundo can support O, C, L and other bands depending on the selected configuration.
Mechanical vs MEMS optical switches
Hirundo operates two complementary optical switch product lines. Mechanical optical switches use micro-motors or electromagnetic relays to physically move a reflector, prism or fiber. They are mature, cost-effective and available in models such as 1x1, 1x2, 1xN and 2x2B. These switches are well suited to low-frequency switching scenarios and applications where cost and low insertion loss are top priorities.
MEMS optical switches, by contrast, use micro-mirrors moved by electrostatic or magnetoelectric forces. Their miniature size, high integration, low power consumption and low crosstalk make them attractive for high-density optical switch matrices and miniaturized test equipment. The choice between mechanical and MEMS depends on switching speed, size, budget and lifetime requirements. Because Hirundo manufactures both types, engineers can select the best option for a specific application without changing supplier.
Can a Raspberry Pi drive Hirundo's MEMS switch driver board?
Yes. Hirundo's 1xN MEMS switch module includes an onboard driver board that provides the drive circuitry for the 2D MEMS chip. The user can control four analog voltages in the range from 0 to 60V to actuate the MEMS mirror. The board is powered from a 5V or 12V supply, and an internal high-voltage boost circuit generates the 60V rail for the high-voltage DAC, the AD5504.
The connector on the back side of the board is a 26-pin interface designed for a Raspberry Pi, but it also works with any SPI hardware. This makes it possible to build a low-cost laboratory test station using a Raspberry Pi to control the MEMS optical switch with standard SPI commands.
Step-by-step integration concept
- Select the required MEMS switch configuration, for example a 1xN MEMS optical switch with the integrated driver board from Hirundo.
- Connect the board to a stable 5V or 12V DC power supply. The internal high-voltage boost circuit will generate the 60V rail needed by the AD5504.
- Connect the 26-pin interface to the Raspberry Pi SPI pins. Common pins include SCLK, MOSI, MISO and CE0, but check the module documentation for the exact pin mapping.
- Write a small program in Python or C/C++ to send SPI commands to the AD5504. The DAC outputs can be programmed in the 0 to 60V range to control electrostatic actuation of the MEMS mirror.
- During calibration, measure optical power at each output port and create a lookup table that maps DAC voltage values to the correct output channel.
- Use the lookup table in the final automation script to switch optical paths quickly and repeatably.
Application scenarios and product strategy
MEMS optical switches from Hirundo are used in optical network monitoring, device testing, OXC equipment core switching, distributed fiber sensing and optical path protection. Multi-channel arrays can be customized, including channel count, packaging dimensions and electrical control interfaces. By combining standardized mass production with array customization, Hirundo can deliver complete optical path switching modules rather than only single components. This gives testing equipment manufacturers and system integrators a reliable path from prototype to production.
