Commit | Line | Data |
---|---|---|
5fae0077 | 1 | numSymbs = 2^16; |
f9a73e9e AIL |
2 | M = 4; |
3 | ||
4 | Rsym = 2.5e10; % symbol rate (sym/sec) | |
5 | Tsym = 1 / Rsym; % symbol period (sec) | |
6 | ||
7 | rolloff = 0.25; | |
8 | span = 6; % filter span | |
5fae0077 | 9 | sps = 8; % samples per symbol |
f9a73e9e AIL |
10 | |
11 | fs = Rsym * sps; % sampling freq (Hz) | |
12 | Tsamp = 1 / fs; | |
13 | ||
14 | t = (0 : 1 / fs : numSymbs / Rsym + (1.5 * span * sps - 1) / fs).'; | |
15 | ||
5fae0077 AIL |
16 | power_dBm = -6:1:4; |
17 | %%power_dBm = 0; | |
f9a73e9e AIL |
18 | power = 10 .^ (power_dBm / 10) * 1e-3; % watts |
19 | ||
20 | Es = power * Tsym; % joules | |
21 | Eb = Es / log2(M); % joules | |
22 | ||
5fae0077 AIL |
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 | |
f9a73e9e AIL |
27 | |
28 | plotlen = length(power); | |
29 | ||
30 | ber = zeros(1, plotlen); | |
31 | ||
32 | data = randi([0 M - 1], numSymbs, 1); | |
5fae0077 AIL |
33 | modData = dpskmod(data, M, 0, 'gray'); |
34 | %%modData = pskmod(data, M, pi/4, 'gray'); | |
f9a73e9e AIL |
35 | |
36 | ||
37 | %% Chromatic dispersion | |
38 | D = 17; % ps / (nm km) | |
39 | lambda = 1550; % nm | |
5fae0077 | 40 | z = 100; % km |
f9a73e9e AIL |
41 | |
42 | ||
5fae0077 AIL |
43 | TsampOrig = Tsamp; |
44 | ||
f9a73e9e | 45 | for i = 1:plotlen |
5fae0077 AIL |
46 | sps = 8; |
47 | Tsamp = TsampOrig; | |
48 | ||
f9a73e9e AIL |
49 | snr = Es(i) / sps / N0; |
50 | snr_dB = 10 * log10(snr); | |
51 | ||
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; | |
56 | ||
57 | %% We can now do split-step Fourier. | |
58 | gamma = 1.2; % watt^-1 / km | |
f9a73e9e | 59 | |
5fae0077 AIL |
60 | |
61 | xCDKerr = splitstepfourier(x, D, lambda, z, Tsamp, gamma); | |
62 | ||
63 | y = awgn(xCDKerr, snr_dB, 'measured', 'db'); | |
64 | %y = xCDKerr; | |
f9a73e9e AIL |
65 | |
66 | r = rxFilter(y, rolloff, span, sps); | |
5fae0077 AIL |
67 | sps = 2; |
68 | Tsamp = Tsamp * 4; | |
69 | ||
f9a73e9e | 70 | rCDComp = CDCompensation(r, D, lambda, z, Tsamp); |
5fae0077 | 71 | rCDComp = normalizeEnergy(rCDComp, numSymbs * sps, 1); |
f9a73e9e | 72 | |
5fae0077 | 73 | rSampled = rCDComp(2:2:end); |
f9a73e9e | 74 | |
5fae0077 AIL |
75 | %% adaptive filter |
76 | [adaptFilterOut, convergeIdx] = adaptiveCMA(rSampled); | |
f9a73e9e | 77 | |
5fae0077 AIL |
78 | demod = dpskdemod(adaptFilterOut, M, 0, 'gray'); |
79 | %%demod = pskdemod(adaptFilterOut, M, pi/4, 'gray'); | |
f9a73e9e | 80 | |
5fae0077 AIL |
81 | if convergeIdx < Inf |
82 | [~, ber(i)] = biterr(data(convergeIdx:end), demod(convergeIdx:end)); | |
83 | else | |
84 | [~, ber(i)] = biterr... | |
85 | (data(ceil(0.8*numSymbs):end), ... | |
86 | demod(ceil(0.8*numSymbs):end)); | |
f9a73e9e | 87 | end |
5fae0077 | 88 | end |
f9a73e9e | 89 | |
5fae0077 | 90 | ber |
f9a73e9e | 91 | |
f9a73e9e | 92 | |
5fae0077 | 93 | figure; |
f9a73e9e AIL |
94 | clf; |
95 | ||
96 | %% Plot simulated results | |
5fae0077 AIL |
97 | qp = 20 * log10(erfcinv(2*ber)*sqrt(2)); |
98 | plot(power_dBm, qp, 'Color', [0, 0.6, 0], 'LineWidth', 2); | |
f9a73e9e AIL |
99 | hold on; |
100 | ||
101 | title({'CD + Kerr + CD compensation', ... | |
5fae0077 | 102 | strcat(['$D = 17$ ps/(nm km), $z = ', num2str(z), '$ km'])}); |
f9a73e9e AIL |
103 | grid on; |
104 | xlabel('Optical power (dBm)'); | |
5fae0077 | 105 | ylabel('$20 \log_{10}\left(\sqrt{2}\mathrm{erfc}^{-1}(2 BER)\right)$'); |
f9a73e9e AIL |
106 | |
107 | formatFigure; |