Some losses in optical fibres:-
The optical fibre does not experience the loss in terms of intensity of light. However, the presence of impurities, scattering at the edges, geometry of structure and dispersion of light causes some losses. Transmission loss/attenuation (α) If the intensity of light at the second end of the optical fibre be Iout and intensity at first end be Iin
The attenuation,
α=-log(Iout/Iin)
In decibel the attenuation,
α=-(10/L)log(Iout/Iin) dB
Other possible losses in optical fibre
The possible losses are absorption, scattering, radiation losses and geometric losses.
The absorption loss
The absorption losses appears as
a) Extrinsic losses
b) Intrinsic losses
c) Atomic defect losses
a) Extrinsic losses:- The extrinsic loss appears due to presence of impurities which absorbed the light. The impurities may be due to presence of Fe, Cr, Co and Cu in the core material. The impurities could absorb the energy that may reemit the absorbed energy during the de excitation in different wavelength which causes loss of intensity to original light of specific wavelength.
b) Intrinsic loss:-
Since, the fibre core itself absorbs some quantity of energy which is known as intrinsic loss.
c) Scattering and radiation losses:- Since, optic fibre contains glass as core, where impurities are present. The scattering of light at these impurities causes Rayleigh scattering where the energy of scattered wave directly proportional to 4th power
(E=1/λ4) of wavelength. Therefore, small change of energy causes 4th power of wavelength. The loss of energy at couplers and interfaces are known as radiative losses.
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