It’s helpful to understand that manufacturers of optic fiber pay close attention to certain geometric parameters. It’s extremely important for them to maintain the stated tolerances – the exact physical dimensions – so the optic fiber will provide repeatable results.
Optic fiber has the following geometric parameters:
- Core-to-clad concentricity – In fiber optics, the core is the transparent section of the glass (or plastic) fiber. The core has a high refractive index through which the light travels by internal reflections. Core-to-clad concentricity is a measure of the relationship between the geometric center of the core of an optical fiber and the geometric center of the cladding. In other words, core-to-clad concentricity measures how centered the core is in the optic fiber.
- Clad diameter – Fiber optic cladding is a layer of glass (or other material) surrounding the core of the optic fiber. The cladding has a refractive index that is slightly lower than the core and forms a conduit that carries light through the fiber.
- Mode field diameter – This is the diameter of optical energy in a single mode fiber. Because the mode field diameter (MFD) is greater than the core diameter, MFD replaces core diameter as a practical geometric parameter.
These geometric parameters are expressed in microns. Plus, the individual specifications of various optic fibers are propriety to each manufacturer of optic fiber. Keep in mind, there are many different styles of optic fiber and physical sizes, which impact the geometric parameters.