ENEE785 students,

Here is Hwk2. Remeber that Hwk1 can be found in Lecture8.tar.gz
on the course web page.

(1) Items (3) and (4) of Hwk1 should be handed in on Tuesday March 18th
    at the beginning of class. Please hand in print outs of both the 
    code you wrote as well as plots of the output data you generated.
    Produce enough output data to convince yourself and us that your code
    is correctly debugged. Make sure the output data plots are labeled.

(2) In addition here is one more homework problem, also due on Tuesday 
    March 18th. Please hand in plots and a written summary of your results.

    The purpose of this exercise is to find the optimal 
    bandwidth for a demuxing optical filter in our
    back-to-back noise-free system when we have a WDM signal.

    (i) Add the following two lines to the function

    void BackToBackNoiseFreeSystem(StartupExample * MyStartup)

    in the file MyApp.cc:

    Signal.WriteFileTimePower(Job + "tAfterDemuxOpt.dat");
    Signal.WriteFileFreqPower(Job + "fAfterDemuxOpt.dat",OmitDCFlag);

    They should be placed immediately after the line

    oOptFilter.FilterOptSignal();

    Note: In general the method OptFilter::FilterOptSignal() should NOT
    be used to demux a WDM signal!! When we discuss the receiver we will
    explain how to do it correctly. However, I checked that with the
    parameter settings I give in (iii) below this quick-and-dirty method
    works just fine. 

    (ii) Recompile the code using the linux command

    make upmyapp

    (iii) 

    First edit OptSignal.in so that

    $ChannSpacing           50e9  
    $NumChannels            5
    $EvenlySpacedFreqsFlag  1

    Also make sure that 

    $TypeBitString        5

    Next edit OptFilter.in choosing an appropriate value for 

    $FreqFWHM_OptFilter   

    Now run the code and look at the output. 

    Explain what the code did. In particular which channel was demuxed?

    The program will write the Back to Back Eye Opening for the 
    demuxed channel to the screen.

    Your task is to find out what value of FreqFWHM_OptFilter results
    in the largest value of the Back to Back Eye Opening.

    (iv) Repeat (iii) for an NRZ signal with a RiseTime of 30 ps
         and two channel spacings: 50 GHz and 25 GHz.

    (v) For the system in (iv) with the 25 GHz channel spacing and the
        optimal value of FreqFWHM_OptFilter 
        investigate how the Back to Back Eye Opening
        depends on the OptSignal parameters StringLength and qtPoints.

        In particular, if StringLength = 32, what is the smallest 
        value of qtPoints that you can safely use? 

        What are the reasons that qtPoints can't be smaller than this value?