Attenuation in optical fibres

1. ATTENUATION IN OPTICAL
FIBERS
NAME YOGESHWAR DASH
BRANCH B.TECH (MECHANICAL) 3rd Sem
REGD. NO. 210301161091
SUBJECT OPTICS AND OPTICAL FIBRES

2. What is attenuation in optical fibers
Attenuation is the reduction in strength of the light signal as it is
transmitted in a fiber optic cable.
The amount of light lost between input and output of an optical fiber
is called attenuation.
Total attenuation is the sum of all losses in an optical fibers.

3. As fiber optics is a light based technology so there will always be
attenuation or light loss the further light travels down fiber.
Attenuation is caused in optical fibers due to scattering , dispersion
and bending of rays.
Attenuation is expressed in decibels (db).

4. Absorption losses in optical fibers
Absorption losses in optical fiber are the major cause of optical fiber
losses during the transmission.
When the photon interacts with the components of the glass, an
electron or metal ions, the light power is absorbed and transferred into
other forms of energy like heat, due to molecular resonance and
wavelength impurities.
Absorption loss is related to the material composition and fabrication
process of fiber.

5. Absorption loss results in dissipation of same optical power as hear in
the fiber cable.
Although glass fiber are extremely pure, some impurities still remain
as residues after purification.
The amount of absorption by these impurities depends on their
concentration and light wavelength.

6. Scattering looses in optical fibers
Scattering losses in optical fibers arise from microscopic variations in
the material density, from compositional fluctuations and from structural
inhomogeneities or defects occurring during fiber manufacture.

7. Linear Scattering
It causes the transfer of some or all of the optical power contained
within one propagating mode to be transferred linearly into a different
mode.
This process tends to a result in attenuation of the transmitted light as
the transfer may be to a leaky or radiation mode which does not
continue to propagate within the fiber core, but is radiated from the
fiber. With all linear process there is no change of frequency on
scattering.
Linear scattering may be categorized as:
Rayleigh scattering
Mie scattering

8. Non Linear Scattering
This scattering cause disproportionate attenuation, usually at high
optical power levels.
This non linear scattering causes the optical power from one mode to
be transferred in either the forward or backward direction to the same,
or other modes, at a different frequency.
Non Linear scattering may be categorized as:
Stimulated Brillouin scattering (SBS)
Stimulated Raman scattering (SRS)

9. Conclusion
• Hence optical fibers hold a very top level of position in our todays
digitalized world. As most of the communication data signals and
networks travels through the optical fibers. But also many
developments are taking place every day in optical fiber industry to
take the communication technology to next level.

10. THANK YOU