M = 4;
numSymbs = 1000;

%% https://www.mathworks.com/help/comm/examples/passband-modulation-with-adjacent-channel-interference.html
Rsym = 2.5e10; % symbol rate (sym/sec)

span = 6; % Tx/Rx filter span
rolloff = 0.25; % Tx/Rx RRC rolloff
sps = 4; % samples per symbol


fs = Rsym * sps; % sampling freq (Hz)
Tsamp = 1 / fs;

t = (0 : 1 / fs : numSymbs / Rsym + (1.5 * span * sps - 1) / fs)';


data = randi([0 M - 1], numSymbs, 1);
modData = pskmod(data, M, 0, 'gray');
x = txFilter(modData, rolloff, span, sps);

%% Simulate chromatic dispersion
D = 20; % ps / (nm km)
lambda = 1550; % nm
z = 1000; % km

[xCD, xCDkstart] = chromaticDispersion(x, D, lambda, z, Tsamp);
xCD = normalizeEnergy(xCD, numSymbs, 1);


y = xCD;


yCDComp = CDCompensation(y, D, lambda, z, Tsamp);

%% Compare original signal and compensated signal
figure(1);
subplot(211);
plot(real(x(1:300)));
hold on
plot(real(yCDComp(1:300)));
hold off
title('Real part');
legend('original', 'dispersion compensated');
subplot(212);
plot(imag(x(1:300)));
hold on
plot(imag(yCDComp(1:300)));
hold off
title('Imag part');


r = rxFilter(yCDComp, rolloff, span, sps);
r = normalizeEnergy(r, numSymbs, 1); % Add noise energy if needed

rSampled = r(sps*span/2+1:sps:(numSymbs + span/2) * sps);

scatterplot(modData);
title('Constellation of original modulation');
scatterplot(rSampled);
title('Constellation of sampled received waveform');

demodData = pskdemod(rSampled, M, 0, 'gray');