20-07-2013, 02:53 PM
SETTING UP A FIBRE OPTIC ANALOG LINK.
AIM:
The objective of this experiment is to study a 950nm-fiber analog
Link and to study the frequency response of the phototransistor at
Various load conditions.
THEORY:
Fiber optic links can be used for transmission of digital as well as analog signals. Basically a fiber optic
link contains three main elements transmitter and optical fiber & a receiver. The transmitter module takes
the input signal in electrical form and then transforms it into optical (light) energy containing the same
information. The optical fiber is the medium, which carries this energy to the receiver. At the receiver,
Light is converted back into electrical form with the same pattern as originally fed to the transmitter.
PROCEDURE:
1. Slightly unscrew the cap of IR LED SFH 756V (950 nm). Do not remove the cap from the connector. Once
the cap is loosened, insert the fiber into the cap and tighten it.
2. Now short the jumpers JP15, JP17, JP18 & JP20 as shown in the block diagram.
3. Keep pr10 Optical power control pot at its maximum position( Anti clockwise direction)
4. Connect the power chord to the kit & switch on the power supply.
5. Feed about 2V(p-p) sinusoidal signal at 1KHz from the function generator to connector labeled as EXT-
ANALOG OUTPUT using connecting cables provided with the kit.
6. Connect the other end of the Fiber to detector SFH 350V (Analog detector) very carefully as per the
instructions in step 1.
7. The transistor photo detector output is available at the connector labeled as ANALOG OUT. Observe the
o/p signal on CRO. Adjust pr10 & pr9 (gain control pot) so that you receive signal of 2V (p-p) amplitude.