Aim

To Study the Propagation Loss Measurement in Fiber Optic System..

Apparatus Required

• Fiber Optics Analog Transmitter Module – 01
• Fiber Optics Analog Receiver Module – 01
• Plastic Fiber cable 1 meter – 01
• CRO – 01
• Adapter +15V/ DC – 02
• Patch Chords – 06

Theory

Propagation Loss

In Fiber Optic System. face some losses in communication, which losses accrued from material, cable length, couple the more no of fiber optic cable, splicing the fiber cable etc., in propagation loss, cable length act as a loss in Fiber Optic System.. In this loss identify from using long distance fiber optic cable in communication and it will be attenuate the signal gain and strength.

Optical fiber

The transmission medium in fiber-optic communications systems is an optical fiber. The optical fiber is the transparent flexible filament that guides light from a transmitter to a receiver. An optical information signal entered at the transmitter end of a fiber – optic communications system is delivered to the receiver end by the optical fiber.

Model Diagram for Plastic Fiber cable

This is multi mode plastic fiber cable, in this fiber cable core diameter 1000 micron and fiber cladding index 1.402.

Procedure

• Connect +15V adapter to both transmitter and receiver module
• Switch (sw1) ON the transmitter Module, CRO and receiver module (sw1).
• Set the sine wave output 1 Vpp/ 1 KHz at P1.
• Connect P1 and P8, P9 and P10 using patch chord.
• Connect the 1 m Plastic fiber cable between transmitter Module LED to receiver module Photo Diode.
• Connect P2 and P4, P5 and P6 using patch chord.
• Keep Amplifier pot meter in maximum position.
• Note down the analog output on test point P7.
• Now we get the output voltage (V1).
• Replace the Plastic fiber cable 1m into 3m.
• Now note down the analog output on test point P7 and will get output voltage (V3).
• Calculate the Propagation loss ‘α’ for 3m fiber in dB/m, α = -10 log10 (V3/V1)