18-08-2012, 02:42 PM
LOSS MECHANISM IN OPTICAL FIBERS
[attachment=32061]
Extrinsic Absorption(OH ions)
Extrinsic absorption caused by dissolved water in the glass, as the hydroxyl or OH ion.
In this case absorption due to the same fundamental processes (between 2700 nm and 4200 nm) gives rise to so called absorption overtones at 1380,950 and 720 nm.
Typically a 1 part per million impurity level causes 1 dB/km of attenuation at 950 nm. Typical levels are a few parts per billion
Scattering Losses in Fibre
Scattering is a process whereby all or some of the optical power in a mode is transferred into another mode.
Frequently causes attenuation, since the transfer is often to a mode which does not propagate well. (also called a leaky or
radiation mode).
Microbending Loss:
microscopic bends of the fiber axis that can arise when the fibers are incorporated into cables. The power is dissipated through the microbended fiber, because of the repetitive coupling of energy between guided modes & the leaky or radiation modes in the fiber.
[attachment=32061]
Extrinsic Absorption(OH ions)
Extrinsic absorption caused by dissolved water in the glass, as the hydroxyl or OH ion.
In this case absorption due to the same fundamental processes (between 2700 nm and 4200 nm) gives rise to so called absorption overtones at 1380,950 and 720 nm.
Typically a 1 part per million impurity level causes 1 dB/km of attenuation at 950 nm. Typical levels are a few parts per billion
Scattering Losses in Fibre
Scattering is a process whereby all or some of the optical power in a mode is transferred into another mode.
Frequently causes attenuation, since the transfer is often to a mode which does not propagate well. (also called a leaky or
radiation mode).
Microbending Loss:
microscopic bends of the fiber axis that can arise when the fibers are incorporated into cables. The power is dissipated through the microbended fiber, because of the repetitive coupling of energy between guided modes & the leaky or radiation modes in the fiber.