6. Core is guided the light wave whose refractive index
is large
Out side of the core whose refractive index is lower
The outer layer of the fiber which protects core
and cladding from the surroundings
7. It works on the principle of total internal reflection
If the incident light makes angle with normal
at boundary of different media greater
than the critical angle,
the light will be internally reflected and cause
to the total internal reflection
15. Optical fiber designed in such a way
that refracive index of core is
greater than the refractive index of
cladding
16. Optical fiber designed in three ways
1.Glass core with glass cladding(100m)
2.Glass core with plastic cladding
3. Plastic core with plastic cladding
The majority of fibers made of glass
consisting either silica or silicate (1km)
17. The glass fibers are generally fabricated by fusing mixtures
of metal oxides and silica glasses.
Silica has a refractive index of 1.458 at 850 nm. To
produce two similar materials having slightly different
indices of refraction for the core and cladding, either
fluorine or various oxides such as B2O3, GeO2 or P2O3 are
added to silica.
Examples:
SiO2 core; P2O3 – SiO2 cladding
GeO2 – SiO2 core; SiO2 cladding
P2O5 – SiO2 core; SiO2 cladding
18. Types of fiber:
step index fiber
(A) single mode fiber
(B) multi mode fiber
graded index fiber
22. The light is launched at one end in too the optical fiber
at a particular angle,
is called Critical angle.
Acceptance angle is the maximum allowed angle that
the incident ray can make with the fiber axis for transmission
through the fiber.θ
Only rays of light which make angle less than
critical angle , are transmitted throug the fiber.
23. Numerical aperture:
Numerical aperture is light gathering capacity of
optical fiber.
or
Sine of the acceptance angle is called numerical aperture.
NA = sin θ = sqr root of n1
2 - n2
2
NA = sin θ = w/sqr root of 4L2 +W2
25. With the help of value of NA we can determine the
acceptance angle and launched the light rays easily
in to the fiber.
Acceptance angle increases when NA increases.
27. Applications:
1. It can be used as sensors
TEMPERATURE SENSORS
PRESSURE SENSORS
2. MORE INFORMATION can be carried by the optical fiber
3. It has high band width.
4. Transmission rate through the fiber is large ,
now a days Tbps possible
so fiber net communication is fast
5. It is help ful in communication system
28. 6. Low cost and safe(short circit not possible)
7. Immunity to inductive interference
8. Absence of cross talk
9. Long life span (20-30 years)
copper cables (12-15 years)
10 it is more reliable
29. Fiber optics used in medicine to see orgons
Video game surgery is possible with the fiber