Investigation of Damping Effects on Power Loss in an Optical Fiber Due to Higher Order Nonlinear Term
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Date
2009-07
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Addis Ababa Universty
Abstract
Many properties of optical fibers namely power loss, noise, distortion, attenuation,
absorption, damping etc are guided by nonlinearities. They must be checked and
calculated their effects before put into applications. We used a developed an-harmonic
oscillator model (by Sunita Sharma, S. K. Ghoshal and Devendra Mohan) in which
two oxygen atoms are connected to the silicon atom by springs which undergoes into
an-harmonic vibration. This formulation is targated for nanosecod pulses in long haul
optical communication. For such laser signal a nonlinearity is quite prominent. It is
this an-harmonic motion that leads to nonlinear effects. The equations for secondorder,
third-order, and fifth-order linear and nonlinear susceptibilities are derived
from this an-harmonic model. The equations for the dielectric constants and for the
index of refraction are also derived. The power loss due to imaginary part of the
higher-order nonlinear refractive index for Pure Silica Core Fiber, Dispersion Shifted
Fiber and Dispersion Compensating Fiber is explicitly calculated. The variation of
power loss with damping constant is also calculated at 2mW. The power loss by
the Kerr and the electrostrictive nonlinear refractive index and also the total power
radiated is theoretically calculated from the model. Our results demonstrate that the
electrostriction, the Kerr the damping effects are significant in optical fibers. These
results confirm some of the recent theoretical and experimental observations. The
model is quite general and is suitable for calculating many other nonlinear properties
of fiber materials.
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Optical Fiber