Before we discuss a fused coupler, we must discuss light polarization. Light moves in different directions when no path is defined and nothing is defined. When the light goes in multiple directions, it isn’t polarized; whereas, when light is controlled and goes into a single desired direction, it’s polarized.

The movement of light into a single direction is crucial in many applications such as optical sensors and optical gyro. This is where a polarization-maintaining fused coupler is used. The coupler controls the direction of the light, leading it in a single direction. The ratio of polarization ratio varies depending on the application for which the fused coupler is used. If you are using fused couplers for optical sensors, a high polarization extinction ratio is required.

How does a polarization-maintaining fused coupler work?
A polarization-maintaining fused coupler splits high-power linearly polarized light into multiple paths without perturbing. This line is known as the state of polarization or SOP.

With a fused coupler, you can monitor signal power in a PM fiber system without interfering with the SOP of the light passing through the PM fiber.

What are the features of a fused coupler that make it a viable option for achieving light polarization?

  • Low insertion loss
  • High extinction ratio
  • Compact in-line package
  • High stability and reliability
  • Broad bandwidth
  • Variety of wavelengths
  • Low cost

More details about fused couplers
The polarization-maintaining fused couplers have two ports, namely N input ports and M output ports. N and M represent numbers, typically ranging from 1 to 64. In general, the fused couplers have four ports that work depending on the distributed coupling between two individual waveguides nearby, allowing power to gradually transfer between modes that are supported by these waveguides.

The working of 4 ports fused couplers: Light enters into port 1 that splits into port 3 and port 4 output ports. Similarly, port 2 functions. In a few conditions, port 1 or port 2 remains unused.

What should you know before buying a polarization-maintaining fused coupler?
As you know that a fused coupler couples the spilling light, it’s the right option to perfectly achieve light polarization. It’s an important element so you should choose wisely. The performance and productivity depend on the polarization-maintaining fused coupler you choose.

Before buying, you should know the need for a fused coupler and how it works. Just keep in mind that different versions or types of fused couplers are available in the market. You cannot just pick them randomly and expect good results.

To buy, you should connect with a reputable manufacturer or supplier. You will find manufacturers that offer customized products. If you have any specific requirements, you should connect with such a manufacturer. Make sure you check the online reviews and ratings of the manufacturer or supplier before buying a polarization-maintaining fused coupler.