Friday, October 14, 2011
Lab 2 – Version 2
You must have a list of content.
List all the testing equipment.
Draw how everything is connected to each other in the lab.
Add the reference section to the end of your report.
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For each part write a short paragraph describing the basic idea and
objectives.
For each part draw the general setup.
Include all the questions in your report and make sure you reference the
number (e.g., A.2.a)
At the end of each section include a brief summary as to what you learned.
A- Go to http://cp.literature.agilent.com/litweb/pdf/N4901-91010.pdf and follow
the instructions.
1- Make sure you can sync and receive (generate) a single error. Show the
snapshot of the Error plot over one minute.
2- Check the Eye width and height for when you transmit OC12 and OC48
signals. Explain your answer and why they are different.
a. In each case how much the triggering point can move in amplitude
and time before any errors are generated?
3- Using OC12 data change the PG to use 10 MHz Ref. clock. You should first set
the external clock (RF functional generator) to 10MHz @ Negative 7 dBm (-7
dBm) [DO NOT EXCEED this power level. Excessive power level may damage
the test equipment].
a. Check the eye diagram using Eye Opening. Take a snap shop. How is it
compared to the case when Internal Clock was being used?
b. Change the frequency of the external clock. Find the frequency limits
(min. and max.) before the system start generating errors.
c. What does BERT stand for?
B- Connect the output of the Attenuator to the Power meter (through the switch - do
not change the setup configuration!)
1. Explain exactly what the Wavelength Adjust Enable knob does on the
Lightwave transmitter. Note that in all these cases the switch results in some
attenuation. Assume that the power, the Lightwave receiver, and the scope in
the setup all observe the same power level.
2. What happens to the optical output power when you change the WL?
3. Plot the generated power vs. wavelength as you adjust the knob.
4. What is the output power when the Adjustment is off?
C- Make sure the PG is set to OC 192. The ED clock must be set to External. Setup the
instruments as described in class. Make sure the Lightwave transmitted wavelength
adjustment light is OFF. Set the PG clock to Internal.
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Set the input range of the ED to the following: Input Range [-1 +1], Zero
Termination, Average 14mV.
Make sure the RED LED on the Lightwave transmitter is ON.
1- Using BERT take a snap shot of the eye diagram and elaborate on its width
and height.
2- Record ED and PG clocks as shown on the screen.
3- Can you run error free traffic? Add several errors and make sure the
interface is properly working.
4- What happens if you pinch the fiber? Can you ever get the signal back? What
type f error you get?
5- Under ANALYSIS click on Eye Opening. Take a snapshot of the diagram. Is the
Eye Opening symmetric? Is it good or bad?
6- When you press the Error Add button, how many errors do you inject? How
do you know?
7- Under PG generate 1.0E-3 BER. (you may have to press Auto Align after you
clicked on Apply).
a. What is the BER value displayed?
b. What happened to the Eye diagram when you inject error?
c. What type of error do you get (e.g., Sync Error, Bit Error)?
d. What is the difference between Sync Error and Clock Error – you may
have to refer to the HELP menu.
e. What does it mean to generate a pattern of 2^7-1?
f. What is one Error Second refer to?
8- Set the wavelength of the attenuator to the correct WL. Starting with 0 dB
attenuation, increase the attenuation such that we start getting error. For
each value of Attenuation, measure the Accumulated BER (under RESULTS –
BER RESULTS).
a. Plot your measured BER vs. the transmitted power.
9- Set attenuation to Zero. Make sure the system is working error free.
10- Redirect the signal from the Attenuator to the Optical Scope. Make sure there
is no Attenuation.
a. Measure the Eye diagram (height and width). Record these values.
b. Take a snapshot of the Eye on the scope.
11- Read reference [1] and briefly explain what an eye diagram represents.
12- Using the PG inject 1.0E-3 BER.
a. What happens to the Eye diagram on the Optical Scope.
b. Take a snapshot.
c. What happens if you increase the Error rate?
13- Change the attenuation of the signal. Using the Auto Scale on the scope find
the eye diagram. What is happening? Take a snapshot. Explain what you see.
14- Using the patter generator button change the PG pattern to 00….101101 and
show it on the scope. Make sure after changing the pattern you click on to
PG&ED on the screen.
a. Take a snapshot of the pattern.
b. Change the pattern to 00001 and then 11111111 (all-one). Compare
the output power. What happens?
c. What happens if you gently pinch the fiber?
D- Use Matlab to draw an eye diagram (later)
References:
[1] http://www.afcingenieros.com/uploads/Afc/InfoTecn/Osciloscopios/pdf/Anatomy%20of%20an%
20Eye%20Diagram%2065W26042-0%20-%20AFC.pdf
[2]
http://www.mathworks.com/products/communications/demos.html?file=/produc
ts/demos/shipping/comm/eyemeasuredemo.html