Friday, April 22, 2011

Optical fibers: fiber parameter, diameter, types

Optical fibers: numerical aperture, fiber parameter, transversal modes, mode field diameter, fiber types

optical fiber

Light propagation: inner total reflection

optical reflection

How to change the refractive index?

refractive index

How much light we can couple into a fiber?

light in the fiber

Angle of acceptance: φA

"Opening" angle: 2φA

Numerical aperture: NA= n0 sin φA

Stepwise (SI) and gradient (GI) index fibers

SI GI fibers

Transversal modes:


transversal modes

Interference in fibers:

interference in fibers



Fiber parameter:

fiber parameters

Single mode operation at V ≤ 2.405

Materials for fibers:

Cladding materialCore materialFiber type
SiO2 (Glass)SiO2 (doped) (Glass)MMF, SMF (GOF)
PolymerSiO2 (Glass)MMF (GOF)
PolymerPolymerMMF (POF)

Mode field diameter:

mode field diameter

Mode field diameter for different fiber parameters
-> in SMF a big part of the field propagates in the cladding!