Design and Development of Optical Communication System

Project Title

Design and Development of Optical Communication System

Project Area of Specialization Electrical/Electronic EngineeringProject Summary

With globalisation and the thirst for connectivity across society, the demand placed on wireless infrastructure and the associated resource is growing exponentially. Very soon this resource will reach saturation point, due to the finite bandwidth available in the Radio Frequency (RF) spectrum. A method of countering the impending saturation needs to be found. That method can be Optical Wireless Communication (OWC). Visible Light Communication is a research field within OWC that utilises the visible light band in the electromagnetic wave spectrum. This band is 10,000 times larger than the RF band and cannot be ‘leased’ or saturated with users. 
 

Project Objectives

The objective is establishment of a secure communication system as Visible Light Communication (VLC) based systems provide point to point communication. VLC based systems have a very high data rate and these systems can also be used for long range communication.

Project Implementation Method

Visible Light Communication takes place by modulating the intensity of light in such a way that it is undetectable to human eye. A photosensitive detector which demodulates light signals into electronic form is used as a receiver. 

The system comprises of a transmitter and receiver. Initially, the source information is encoded. Optionally channel coding can be done before modulation. The modulator performs the necessary modulation process. If required, an optical amplifier can be used to increase the power intensity of the optical source. The light beam is focused by beam forming optics such as lens before being transmitted. The receiver front end comprises of optical filters with a lens to focus the beam on photodiode. The low pass filter is used to eliminate the thermal and background noise level. Finally, demodulator performs the demodulation process to obtain original data.

The modulation technique being used is On Off Keying (OOK), which is the simplest form of Amplitude Shift Keying. In OOK, light source being on is interpreted as one and light source being off is interpreted as zero. We aim to introduce Orthogonal Frequency Division Multiplexing with Offset Quadrature Amplitude Modulation (OFDM/OQAM), which is an efficient technique and provides high data rates with reduced interferences. OFDM/OQAM encoder will encode the data signal accordingly and that signal will be transmitted by light source and at the receiving end, OFDM/OQAM decoder will decode the data signal.

Benefits of the Project

The communication done through Visible Light is secure, using lasers makes the system point to point and line of sight. The system is also cost effective, it does not require a license or antennas. It is easy to use and implement, the same LEDs which are being used to illuminate can also be used to communicate. Visible Light also provides a very high data rate.  

Technical Details of Final Deliverable

The transceiver consists of a mic, a speaker, a Raspberry Pi 3B, battery, MCP3008, laser and photodiode. When a user wants to communicate, the desired speech is stored as a .wav file in the raspberry pi 3B and then is converted into text.  The text is then converted into binary digits according to the Morse Code. A python code is used to control a laser, 1 bit is represented as the laser being on and 0 bit is represented as the laser being off. The laser is transmitted and refocused onto the photodiode at the receiver end using a lens. Raspberry Pi 3B is again used to decode the electronic signals received. Raspberry Pi 3B does not have an inbuild Analog to Digital Converter, hence a MCP3008 IC is used to convert the electronic signals of photodiode to be read easily by the Raspberry Pi 3B GPIO pin. The bits are mapped onto the Morse Code to decode the data. The text is again reconverted into speech and a speaker is used to demonstrate the received data.

Final Deliverable of the Project HW/SW integrated systemCore Industry TelecommunicationOther Industries Security Core Technology OthersOther TechnologiesSustainable Development Goals Clean Water and SanitationRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	79500
Raspberry Pi 3B	Equipment	7	7000	49000
MCP3008	Equipment	2	300	600
Casing	Equipment	2	5000	10000
Laser	Equipment	5	1000	5000
Photodiode	Equipment	5	1000	5000
Wires	Miscellaneous	50	10	500
Connectors	Miscellaneous	4	350	1400
LCDs	Miscellaneous	2	4000	8000