BRIGHAM YOUNG UNIVERSITY

Search BYU

Contact | Help

Navigation Menu

Overview
Info
Schedule

ECE 490 Free Space Optical Comunications

Instructors
Aaron Hawkins
Office: 437 CB
Phone: 422-8693
Email: hawkins@ee.byu.edu

Stephen M. Schultz
Office: 464 CB
Phone: 422-1693
Email: schultz@ee.byu.edu

	Tuesday	Thursday
9:00-10:00	Class (250 CTB)	Class (250 CTB)
10:00-11:00	Class (369CB)	Class (369CB)
11:00-12:00
12:00-1:00
1:00-2:00
2:00-3:00
3:00-4:00

Course Overview

Work in three- or four-person teams to construct a free space optical communication system capable of transmitting and receiving data from a DVD player. The system will consist of two parts – a laser transmitter and an optical receiver. The laser transmitter will take the digital bit stream out of a DVD player, and produce matching optical pulses. The receiver will translate these optical pulses back to an electrical bit stream that can be read by an audio receiver. The system should produce high fidelity audio transmission at DVD bit rates.

Each team will build the following.

Transmitter board (converts the digital signal from the DVD player into optical pulses)
Receiver board (converts the optical pulses into a voltage signal)
Battery charging for the two boards
An LED indicating that the battery is charged

Each team will integrate the various components into a complete professional looking system.

Each component will have audio cable connections to either the DVD player or the receiver.
The battery will be charge with a wall pull DC adapter.
Each group will have a single rechargeable 9V battery for the transmitter and a single 9V battery for the receiver

Provided components:

Two webcams
2 lasers
1 optical detector
2 rechargeable 9V batteries

The final system will be graded based on the completeness of the design, packaging, and documentation. The completed system will need to include a specification document and user’s manual.

There will be a competition for the team whose system has the lowest power consumption (which one can play for the longest time).

Grading criteria

Your base grade is based on the performance of your system. The base grade is adjusted up or down based on your milestone reports, your oral reports, your performance in the business portion of the class, and the professional look of your completed system. For example if you are in the A range but your report are of poor quality and the system does not look professional you would only get a B+.

A Range (Base Grade of A-):

High fidelity transmission over a range between 5 and 20 feet without any adjustment to the electronics (i.e. potentiometers)
The circuit boards must fit within the provided webcam package
The system operates for at least 5 hours

B Range (Base Grade of B):

High fidelity transmission over a range between 5 and 20 feet without any adjustment to the electronics (i.e. potentiometers)
The circuit boards must fit within the provided webcam package
The system operates less than 5 hours

C Range (Base Grade of C):

High fidelity music transmission but don't meet any other requirements

Weighting of the milestone reports and presentations:

20%	Project Plan
20%	1st Design
25%	2nd Design Review
35%	Final Demonstration

Project plan

This milestone will be the development of system specification document and a project plan.

This milestone will NOT include a presentation.
This report will include the Functional Specification Document (FSD).
The report should provide an overview of the system with a block diagram.
It should also include a test plan. The test plan will describe how the various sections of the project will be tested.
The report must also include measurement of the various components that were provided to you. The set of measurement should include at least the following.

Voltage level of digital DVD output

Bit rate of digital DVD output
Rise and fall times of the digital DVD output
Measured laser power as a function of supplied current (with a maximum current of 30 mA)
Minimum spot size vs. distance and corresponding beam divergence

Remember that you should adjust the lens for each distance

Be sure to explain what you designate as spot size

The output current of the photodetector as a function of optical input power. You will use your laser to make this measurement.
Estimate of the amount of optical power that will be received by the photodetector at 5 feet and 20 feet and the current that will be produced by the photodetector

It should also include a description of the different roles of the various members of the group.
It should state what measurements will be made for each of the additional reports. A list of the minimum measurements that need to be included in your reports is provided at the end of this document. All of these measurements need to be included plus any additional data that you think would be useful.

1st Design Review

This milestone demonstrates that you are on track to complete the project on time. The primary completion of this milestone is a functioning transmitter and the design and simulation of the receiver.

This design review will include a presentation.
The Concept Generation and Selection Document will have already been turned in to Doug Clifford, but it should also be incorporated into this report.
Demonstrate that the digital output of the DVD player can be plugged directly into your laser driver and produce an optical signal that matches the shape of the DVD’s digital output. The laser driver needs to be built using discrete components. (You cannot buy a laser driver board.)
The report needs to contain a project schedule.
The milestone should also include a design of the receiver. You need to estimate the required gain of the receiver.

2nd Design Review

This milestone is a design review of the complete system. The complete system must include the following

This design review will also include a presentation.
A system that takes the digital DVD output, converts it into a modulated optical beam, transmits it through space, and demodulates the signal to be heard on a speaker over a distance of 20 feet
Sufficient dynamic range to operate at either 5 feet or 20 feet
A plan to fit the systems into the webcam packages.
The complete system is due early in the semester to allow you enough time to transfer your receiver and transmitter onto circuit boards. If you desire you can have a commercial board fabricated. Details on this will be discussed later in the semester.

Final Demonstration

The final demonstration will include the following.

A system that takes the digital DVD output, converts it into a modulated optical beam, transmits it through space, and demodulates the signal to be heard on a speaker over a distance of 5 feet and 20 feet
A specification document
An operating manual
This design review will also include a presentation.
The presentation will be given after the demonstration.

The system will first be set up with a separation distance of 5 feet. Then the system will be set up at 20 feet. In addition to judging the system on operation, the operating time will be measure to determine power consumption of the system. The system will also be judge based on the look of the system and the easy of set up at the two distances.

Other Information

Here is a list of some of the data that should be included in the various reports. This list is not complete but is to give you any idea of the type of information that should be included in reports.

Simulated frequency response of the transmitter
Measure frequency response of the transmitter
Simulated frequency response of the receiver
Measured frequency response of the receiver
Measured power consumption of both the transmitter and receiver
Measured minimum detectable power of the receiver
Measured power density at 5 feet and 20 feet (W/cm2)
Measured alignment sensitivity
Voltage range of the commercial receiver box. This characterization should NOT include voltages above the level produced by the DVD player.
Find any standards related digital audio transmission protocols. (i.e. what is the DVD using)
Put eye safety class on your device
Document the eye safety requirements and specifications
Distance range over which the system will transmit music (This range should be at least 5 feet – 20 feet.)
Power consumption of the transmitter
Power consumption of the receiver

Honor Code

I expect you to live the honor code. Cheating of any kind will result in a failing grade in the course.

Preventing Sexual Harassment

Title IX of the Educational Amendment of 1972 prohibits sex discrimination against any participants in an educational program or activity that receives federal funds. The act is intended to eliminate sex discrimination in education. Title IX covers discrimination in programs, admissions, activities, and student-to-student sexual harassment. BYU's policy against sexual harassment extends not only to employees of the university but to students as well. If you encounter unlawful sexual harassment or gender based discrimination, please talk to your professor; contact the Equal Employment Office at 378-5895 or 367-5689 (24-hour); or contact the Honor Code Office at 378-2847.

Students with Disabilities

Brigham Young University is committed to providing a working and learning atmosphere which reasonably accommodates qualified persons with disabilities. If you have any disability which may impair your ability to complete this course successfully, please contact the Services for Students with Disabilities Office (378-2767). Reasonable academic accommodations are reviewed for all students who have qualified documented disabilities. Services are coordinated with the student and instructor by the SSD Office. If you need assistance or if you feel you have been unlawfully discriminated against on the basis of disability, you may seek resolution through established grievance policy and procedures. You should contact the Equal Employment Office at 378-5895, D-282 ASB.