The transmitter and receiver circuit was built using LED and LDR due to unavailability and high cost of the available pre fabricated ones. Generally, LDR is not recommended for optical communication application’s but since here the operating frequency was not fixed one valued but could be chosen by the user which helped to use LDR (by setting somewhat low frequency).

Transmitter and Receiver

Mechanical aligner

Since the transmitter and receiver circuit was built manually using LED and LDR, so there was issue of alignment for optical fiber and the light source and detector (LED and LDR). While aligning the electrical insulation tape could have also been which had advantage of being easy but restricted experimental setup handler from repositioning the setup in case required, so to eliminate this shortcoming, a mechanical aligner was constructed. It’s made using thin metal sheet and has two sides:

1.      One holds the fiber in place

2.      Other side keeps the LED/LDR in place

The aligner provides various advantages over tape alignment:

a)     It gives more freedom for experiment setup handler to move the devices

b)     Output of experiment remains same under various changing conditions (of light , aging of setup)

Mechanical aligner

Plastic Optical Fiber (POF)

The Plastic optical fiber (POF) has been used instead of the Glass optical fiber (GOF) because POF has a larger core diameter compared to GOF and so launching light from source is easier in case of POF. Due to the same a satisfactory result was possible even on using normal LED with optical fiber. Moreover it’s difficult to launch the light into GOF and we need to use a laser light source for the same which would not be much recommended for experimental purpose due to damage it may cause to the eye if looked directly at.

Ni Elvis Board

To make the project data available on computer screen the function generator and oscilloscope of NI ELVIS board have been used, by connecting them to the existing circuit on breadboard. Also the select lines to be used for multiplexer/ Demultiplexer is taken from digital writer on ELVIS board which allows us to control the optical fiber that we need, from our computer screen.