The optical fibers are the hair thin fibers made of ultra transparent glass or plastic material. The optical fiber flexible and it is used to transmit the light. The presentation here mainly focused on the brief explanation of principle, theory, characteristics, losses in fibers and applications.

1. TOPIC
LASER and OPTICAL FIBERS
BY
PRAVEEN VAIDYA
DEPARTMENT OF PHYSICS
S.D.M.COLLEGE OF ENGINEERING AND TECHNOLOGY
DHARWAD

2. OPTICAL FIBER
• Thin strand of ultra transparent dielectric material.
• Cylindrical shape with thickness about 125um.
• The light is transmitted through optical fiber.
• Optical fibers are maximum used in telecommunication to
transmit the information in effective. way

3. PRINCIPLE
• Optical fibers are working
on the principle of total
internal reflection (TIR)
• TIR takes place when light
travels from denser (high RI)
to rarer (low RI) medium.
• Light ray should incident of
surface separating two
media at least at the angle
of critical angle.

4. Total internal Reflection
Water, higher RI
Air , lower RI
Back
reflection/Refraction Refraction
Critical refraction
Total Internal
Reflection
Refraction
Critical refraction
Total Internal
Reflection

5. Geometrics of Total Internal Reflection
in optical fiber

6. Construction of optical fiber

7. Angle of acceptance And Numerical
Aperture
Snell’s law
n1Sin i = n2Sin r
90-C
C
θc
i>C
90-C
θc
i<C

8. Angle of acceptance And Numerical
Aperture
• Let, n0 = R.I of medium in which OF placed.
• If air n0 = 1, n1- R.I. core, n2 – R.I of cladding.
• Angle of incidence of light at OF face – θc, which hits core
cladding Interface at ‘Critical angle’ C.
• n0 xSin θc = n1x sin (90-C)
or n0 sin θC = n1 cos C
n0 sin θC = n1 [1 - sin2C]1/2 ---------1

9. When light travels from core to cladding at
critical angle….
Where n2 – R.I. of Cladding
--------- 2
Substituting eqn. 2 in eqn. 1,
Angle of acceptance And Numerical
Aperture
n1 sin C = n2 sin 90

10. Ratio of difference between R.I. of core and R.I. of cladding to to R.I. of
Core.
Relation between N.A. and Δ:
2
2
2
1 nn 
  2121 nnnn     121 nnn
  112 nn
N.A . =
=
=
21nN.A . =

11. Types of Optical Fibers
• Single mode optical fiber
• Multimode optical fiber
• Graded Index Multimode optical fiber

12. Types of Optical Fibers

13. Attenuation or Fiber loss

14. Applications of Optical Fiber

15. Applications of Optical Fiber
Fiber optic sensors are used commonly in the acquisition of real-time data on a variety of oil
well parameters such as temperature, strain, pressure, sand detection, vibration, and acoustic
signals, facilitating optimization of a reservoir through its lifecycle.
Optical Fiber Sensors
Physical sensors : Used to measure physical proparties like temperature, stress, etc.
Chemical sensors : Used for pH measurement, gas analysis, spectroscopic studies, etc.
Bio-medical sensors : Used in bio-medical applications like measurement of blood flow ,
glucose content etc.
OF experiences geometrical (size, shape) and optical
(refractive index, mode conversion) changes applied
external perturbations.
Fiber optic sensors can again be classified as
Extrinsic sensors: Sensing takes place in a region
outside of the fiber. The fiber essentially serves as a
conduit for the to-and-fro transmission of light to the
sensing region.
Intrinsic sensors: one or more of the physical
properties of the fiber undergo a change and this
change is measure of the external perturbation. See
the figure above.