Understanding the Basics of Polarization-Maintaining (PM) Components [A Beginner’s Guide]
The effects of polarization were already noticed during the first optical fiber transmission experiments. Even though the study of these effects was purely done out of curiosity in the beginning, they became the focus of many research groups later and result in the development of a variety of PM components available today.
In this guide, you will learn what polarization exactly means, how to achieve it, and PM components that use polarization.
What is Polarization?
We all know that light is an electromagnetic wave that consists of oscillating electric fields and magnetic fields. The properties of light can be accurately explained by studying the electrical field. Besides, you can also describe light and its effects by studying its magnetic field.
Light waves can propagate or vibrate in several directions. The ones that vibrate in one direction only (in a single plane) are called polarized light. The light waves that can vibrate in more than one direction are referred to as unpolarized light.
When a light wave vibrates in only one direction, this phenomenon is called polarization.
How to achieve single-polarization?
Using a polarization filter is a common method to attain single polarization. This filter is designed using specialized materials that can block one of the two planes of vibration of a signal or light wave. Meaning, a polarization filter is a device that is used to block half of the vibrations when a light wave passes through it. Hence, when unpolarized light passes through a polarization filter, it comes out with half the original intensity and with vibrations in a single plane. The light that comes out is called polarized light.
What Is Polarization-Maintaining Fiber?
Polarization-maintaining (PM) fiber is a specialty-single mode fiber that is designed to propagate only one polarization of the input light. In this type of fiber, the polarization of linearly-polarized light transmitted through the fiber is maintained during the entire propagation with negligible or no cross-coupling of optical power between polarization modes. The polarization-maintaining feature is very crucial for some optic fiber optic components that need polarized light input.
This characteristic (polarization-maintaining) is achieved in the fiber by inducing stresses in the material itself. In the market, you will find two types of PM fiber: linear PM fiber and circular PM fiber.
What are Polarization-Maintaining (PM) Components?
PM components are the components that maintain the polarization of the light or signal at their source and help minimize the polarization mode dispersion, eliminate the effects of polarization-dependent loss, and ultimately, increase the quality of the signal that is transmitted through the network.
There are different types of PM components available online that you can use in a variety of applications based on their use and features. Some of these are:
· In-line Polarizer
· PM Band Pass Filter
· PM Circulator
· PM Isolator
· Pump Combiner
· PM WDM
· PM Filter and Tap Coupler
· PM Splitter Module
· PM Fused Coupler and Fused WDM
· PM Hybrid Components
These PM components are generally categorized based on their central wavelengths as follows:
· 1.0μm PM Components
· 1.5μm PM Components
· 2.0μm PM Components
Good quality PM components are expected to have low insertion loss, high extinction ratio, and high stability. So, whether you use 1.5μm PM Components, 1.0μm PM Components, or 2.0μm PM Components, consider these features as well.
