20-07-2013, 02:55 PM
STUDY OF LOSSES IN OPTICAL FIBER
AIM:
The objective of this experiment is to measure the propagation loss for two different wave lengths‟ and
bending loss in plastic fiber provided in the kit.
APPARATUS:
Fiber optic kit, CRO, Signal generator, 1m &3m plastic fiber.
THEORY:
Optical fibers are available in different materials they are selected by considering the absorption
characteristics for different wavelengths of light.
Losses are introduced in the fiber due to a variety of reasons. As light propagates from one end of the fiber
to other end, part of it absorbed in the material exhibiting absorption loss. Part of the light is reflected back
or in some other direction from the impurity loss of the signal at the other end of the fiber. This
phenomenon is called propagation loss.
Whenever the condition for angle of incidence of the incident light is violated, the losses are
introduced due to refraction of light. This occurs when fiber is subjected for bending.
PROCEDURE:
1. Set up the analog link as shown in the block diagram.
2. Use an optical fiber link of length 1 meter and note down the output voltage V1 Volts.
3. Use an optical fiber link of length 3 meters and note down the output voltage say V2 Volts.
4. If is the attenuation of the fiber,
P1/P2 = V1/V2 = e [(L1+L2)]
Where = nepers/meter
L1=fiber length V1
L2=fiber length for V2