O = 10; %order of prbs
N = 64; %length of prbs
[~,seed] = prbs(O,1); %initialize first seed of prbs

% Modulation
M = 4;
bitpattern = zeros(N,log2(M));

% Symbol Rate
fsym = 56e9;
% DAC Rate
fdac = 120e9;
% Simulation oversampling rate "k";
kover = 16;
% Simulation frequency in "analog domain"
fsimu = kover * fdac ;



%SIMULATE

for i = 1:log2(M)
    [bitpattern(:,i),seed] = prbs(O,N,seed);
end

pamData     = pam_mapping(bitpattern,M,0);

shapedData  = applyPulseShaping(pamData,fsym,fdac);



awg = AWG('preset','M8196A','fdac',fdac,'kover',kover,'lpf_active',1);
awgSignal   = awg.process_channel(shapedData);

fil = Filter('filtdegree',4,"f_cutoff",50e9,"fdac",fdac,"filterType",filtertypes.bessel_bilin);
filtered = fil.process(awgSignal);

u_pi = 3.5;
vbias = (0.5*u_pi)-u_pi;
eml = EML("mode",emlmodes.im_cosinus,"power",10,"fsimu",fsimu,"lambda",1550,"bias",vbias,"u_pi",u_pi,"linewidth",1000000);
laserfield = eml.process(filtered); 

att = Amplifier("amplification_db",10,"amp_mode","gain","type","ideal","saturation_mode",0,'saturation_power',10);
att_out = att.process(laserfield);

%fib = Fiber("fiber_length",2,"alpha",0.2,"D",17,"lambda0",1550);


figure;
plot(shapedData);
hold on
plot(awgSignal,'DisplayName','skew 0');
plot(filtered,'DisplayName','filtered');
plot(abs(laserfield),'DisplayName','laser');
plot(abs(att_out),'DisplayName','att_out');

hold off


function pam_sig = pam_mapping(bitpattern, M, unipolar)

switch log2(M)
    case 1
        % 2-ASK: BPSK / OOK
        pam_sig=bitpattern(:,1);

        if unipolar==0
            pam_sig=2*pam_sig-1;
        end

    case 2
        % 4-ASK:
        pam_sig=2*bitpattern(:,1)+(bitpattern(:,1)==bitpattern(:,2));

        if unipolar==0
            pam_sig=2*pam_sig-3;
        end


    case 3
        % 8-ASK:
        x1 = bitpattern(:,1);
        x2 = (bitpattern(:,1)==bitpattern(:,3));
        x3 = x2~=bitpattern(:,2);

        pam_sig = 4*x1 + 2*x2 + x3;

        if unipolar==0
            pam_sig=2*pam_sig-7;
        end


    case 4
        % 16-ASK:
        x1 = bitpattern(:,1);
        x2 = (bitpattern(:,1)==bitpattern(:,4));
        x3 = x2~=bitpattern(:,3);
        x4 = x3~=bitpattern(:,2);

        pam_sig = 8*x1 + 4*x2 + 2*x3 + x4;

        if unipolar==0
            pam_sig=2*pam_sig-15;
        end

end
end

function yout = applyPulseShaping(xin,fsym,fdac)

    if ~rem(fdac,fsym)
        %ist ein Vielfaches
        sps = fdac / fsym;
        up = sps;
        dn = 1;
    else
        %ist kein Vielfaches
        up = fdac / gcd(fdac, fsym);
        dn = fsym / gcd(fdac, fsym);
        sps= up;
    end

    %Bau das Filter (hier rrc)
    racos_len = 2048;
    alpha = 0.1;
    h = rcosdesign(alpha,racos_len,sps);
    
    %Apply Filter using Matlab build in fctn. 
    yout = upfirdn(xin,h,up,dn);
    
    %cut signal, which is longer due to fir filter 
    st = up/dn*racos_len/2; %we need to cut y_out 
    en = st + (length(xin)*up/dn) -1;

    yout = yout(st:en);

    %Check output integrity 
    if (up/dn * length(xin)) ~= length(yout)
        warning('Check signal length after pulse shaping');
    end

end

function yout = applyBandwidthLimitation(xin)
    data_out=ifft(repmat(state.H,1,size(data_in,1)).*fft(data_in.')).';
end