20-07-2013, 02:57 PM
STUDY OF NUMERICAL APERTURE OF OPTICAL FIBER
AIM:
The objective of this experiment is to measure the numerical aperture of the plastic fiber provided with the
kit using 660nm wavelength LED
APPARATUS:
Fiber optic kit, CRO, Signal generator, 1m &3m plastic fiber.
THEORY:
Numerical aperture refers to the maximum angle at a light incident on the fiber end is totally internally
reflected and is transmitted properly along with the fiber. The cone found by the rotation of this angle
along with the axis of the fiber is the cone of acceptance of the fiber. The light ray should strike the fiber
end within its cone of acceptance; else it is reflected out of the fiber core.
CONSIDERATION IN A MEASUREMENT:-
1. It is a very important that the source should be properly aligned with the cable & the distance from
the launched point & the cable be properly selected to ensure that the maximum amount of optical
power is transferred to the cable.
2. This experiment is best performed in a less illuminated room.
PROCEDURE:
Slightly unscrew the cap of IR LED SFH 756V (660nm) Do not remove the cap from the
Once the cap Is loosened insert the fiber into the cap and tighten it.
Short the jumpers
Connect the power chord to the kit, switch on the power Supply.
Apply TTL high input to the LED from EXT- TTL Terminal.
Insert the other end of the fiber into numerical aperture Measurement jig.
Hold white sheet facing the fiber end. Adjust the fiber Such that its cut face is perpendicular to the
axis of the Fiber. Keep the distance of 5mm between fiber tip and Screen, and then gently tighten
screw.