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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

Monday Tuesday Wednesday Thursday Friday
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 digital audio data. The system will consist of two parts – a  transmitter and a receiver. The transmitter will take an analog audio signal, convert it into a digital signal, and then produce matching optical pulses. The receiver will translate these optical pulses back to an electrical bit stream and then convert the bit stream back into an analog signal that can be played on an audio speaker.

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 circuit for the two boards

Each team will integrate the various components into a complete professional looking system  
  • Each component will have audio cable connections to either a portable audio player or an audio speaker.
  • Each component will have a power plug that can be plug into an AC/DC adapter.  (You will need to provide an appropriate AC/DC apater.)
  • The battery will be charge with the AC/DC adapter.  
  • Each component will have ability to operate with the AC/DC adpter plugged in.
  • The batteries should charge when the component is plugged into the AC/DC adapter, even when is transmitting or receiving
  • A set of LEDs indicating the level of remaining battery charge
  • An on/off switch
  • The package will have an easy way to add or remove the analog-to-digital or digial-to-analog audio adapter

Provided components:

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)
  • Professional looking pacakage and has all of the 'bells and whistles' described above like battery indicator lights, on/off switch, etc.
  • The system operates for at least 2 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 system operates less than 2 hours, does not have a professional looking packaging, or is missing the 'bells and whistles'

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.
Deliverables: project report
  • This milestone will NOT include a presentation.
  • The 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 the digital-to-analog converter output
    • Bit rate of the digital-to-analog converter output
    • Rise and fall times of the digital-to-analog converter 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
    • Required input voltage levels for analog-to-digital converter
  • It should also include a description of the different roles of the various members of the group.

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.
Deliverables: project report and presentation
  • The report should be a self contained document.  It needs to include a brief overview of the system, specifications, and current status of the project.
  • 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.
Deliverables: project report and presentation
  • The report should be a self contained document.  It needs to include a brief overview of the system, specifications, and current status of the project.
  • There must be enough measurements in the report to verify that your complete system is working but the packaging does not need to be in teh final 'professional looking' form. 
  • At the completion of this milestone the system must take the analog signal out of a portable audio player, convert it into a modulated optical beam, transmits it through space, and demodulate 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.
Deliverables: demonstration of working system, final project report, specification document, users manual, and final presentation
  • At the completion of this milestone the system must take the analog signal out of a portable audio player, convert it into a modulated optical beam, transmits it through space, and demodulate the signal to be heard on a speaker over a distance of 20 feet 
  • The system will first be set up with a separation distance of 5 feet and then moved to a distance of 20 feet
  • The system will then be left to play until the music is no longer clear.
  • The system will be judged to ensure that it is professional looking and contins the required 'bells and whistles'

  • The specification document should be a one page document with any necesary specifications
  • The operating manual should be clear enough for someone unfamiliar with you rsystem to be able to connect it and get it to operate
  • This design review will also include a presentation.
  • The presentation, final report, and documents are not due the day of the demonstrations but can be completed the next week.


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
  • Put eye safety class on your device and in the specification document
  • 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.)

 

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.

   
Maintained by Stephen Schultz.
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