4 Rsym = 2.5e10; % symbol rate (sym/sec)
5 Tsym = 1 / Rsym; % symbol period (sec)
8 span = 6; % filter span
9 sps = 8; % samples per symbol
11 fs = Rsym * sps; % sampling freq (Hz)
14 t = (0 : 1 / fs : numSymbs / Rsym + (1.5 * span * sps - 1) / fs).';
18 power = 10 .^ (power_dBm / 10) * 1e-3; % watts
20 Es = power * Tsym; % joules
21 Eb = Es / log2(M); % joules
23 N0ref_db = 10; % Eb/N0 at power = 1mW
24 %% Fix N0, such that Eb/N0 = N0ref_db at power = 1mW
25 N0 = 1e-3 * Tsym / (log2(M) * 10 ^ (N0ref_db / 10)); % joules
26 %% At current settings, N0 = 0.002 pJ
28 plotlen = length(power);
30 ber = zeros(1, plotlen);
32 data = randi([0 M - 1], numSymbs, 1);
33 modData = dpskmod(data, M, 0, 'gray');
34 %%modData = pskmod(data, M, pi/4, 'gray');
37 %% Chromatic dispersion
38 D = 17; % ps / (nm km)
49 snr = Es(i) / sps / N0;
50 snr_dB = 10 * log10(snr);
52 x = txFilter(modData, rolloff, span, sps);
53 %% Now, sum(abs(x) .^ 2) / length(x) should be 1.
54 %% We can set its power simply by multiplying.
55 x = sqrt(power(i)) * x;
57 %% We can now do split-step Fourier.
58 gamma = 1.2; % watt^-1 / km
61 xCDKerr = splitstepfourier(x, D, lambda, z, Tsamp, gamma);
63 y = awgn(xCDKerr, snr_dB, 'measured', 'db');
66 r = rxFilter(y, rolloff, span, sps);
70 rCDComp = CDCompensation(r, D, lambda, z, Tsamp);
71 rCDComp = normalizeEnergy(rCDComp, numSymbs * sps, 1);
73 rSampled = rCDComp(2:2:end);
76 [adaptFilterOut, convergeIdx] = adaptiveCMA(rSampled);
78 demod = dpskdemod(adaptFilterOut, M, 0, 'gray');
79 %%demod = pskdemod(adaptFilterOut, M, pi/4, 'gray');
82 [~, ber(i)] = biterr(data(convergeIdx:end), demod(convergeIdx:end));
84 [~, ber(i)] = biterr...
85 (data(ceil(0.8*numSymbs):end), ...
86 demod(ceil(0.8*numSymbs):end));
96 %% Plot simulated results
97 qp = 20 * log10(erfcinv(2*ber)*sqrt(2));
98 plot(power_dBm, qp, 'Color', [0, 0.6, 0], 'LineWidth', 2);
101 title({'CD + Kerr + CD compensation', ...
102 strcat(['$D = 17$ ps/(nm km), $z = ', num2str(z), '$ km'])});
104 xlabel('Optical power (dBm)');
105 ylabel('$20 \log_{10}\left(\sqrt{2}\mathrm{erfc}^{-1}(2 BER)\right)$');