function [opt_out_x,opt_out_y,state] = CNLSE_plain(opt_in_x,opt_in_y,state)
    


    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % pre calculations
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    state.common_beta=struct('X',0,'Y',0);

    for n=1:2
        % get current polarization name and contrary one
        curPol   = state.polNames{n};

        % extend linear transfer function depending on beta values for the current polarization
        % Was ist der Sinn dieser komischen beta notation? zB. state.beta.X = [0.3142 0 -9.1105e-28 5.1068e-41]
        for n_beta = 1:length(state.beta.(curPol))
                state.common_beta.(curPol) = state.common_beta.(curPol) + state.beta.(curPol)(n_beta) * (state.omega).^(n_beta-1) / factorial(n_beta-1);
        end

        %opt_out_struct.(curPol)=opt_in_struct.(curPol).envelope;                   
    end

    beta_const = state.beta.('X')(1);
    beta_1 = state.beta.('X')(2);
    beta_2 = state.beta.('X')(3);
    beta_3 = state.beta.('X')(4);
    deltaomega = state.omega;
    beta_x = beta_const + beta_1 * deltaomega + 1/2 * beta_2 * deltaomega.^2 + 1/6 *beta_3 * deltaomega.^3; 
    
%     opt_in_x = gpuArray(opt_in_x);
%     opt_in_y = gpuArray(opt_in_y);

   
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % Split Step Method
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%     [opt_out_x,opt_out_y] = split_step_loop(state.L,opt_in_x,opt_in_y,state.gamma,state.SS_dzmin,state.SS_dzmax,state.SS_dphimax,state.alpha_lin,...
%     state.lin_z_test,state.corr_length,state.n_plates_done,state.missing_dz,state.brf,state.common_beta,....
%     state.chi,state.manakov,state.beat_len);

%     [opt_out_x,opt_out_y] = split_step_loop_mex(state.L,opt_in_x,opt_in_y,state.gamma,state.SS_dzmin,state.SS_dzmax,state.SS_dphimax,state.alpha_lin,...
%     state.lin_z_test,state.corr_length,state.n_plates_done,state.missing_dz,state.brf,state.common_beta,....
%     state.chi,state.manakov,state.beat_len);
    
    % get nonlinear step size
    [state.dz] = getNLstepsize(opt_in_x,opt_in_y,state.gamma,state.SS_dzmin,state.SS_dzmax,state.SS_dphimax,state.alpha_lin);
    %[state.dz] = getNLstepsize_original(state,opt_out_struct);
    
    state.n_step = 0;
    state.z_prop = 0;
    state.test_dz = [];
    state.powers = [];

    tic

    while state.z_prop < state.L  

        % reduce step length (dz) if we are to overshoot the fiber length
        % (L) in the next step
        if state.z_prop + state.dz > state.L
            state.dz = state.L - state.z_prop;
        end
        
        % update step number (n)
        state.n_step=state.n_step+1;

        % append current step length to logbook (dzs)
        state.dzs(state.n_step)=state.dz;

        
        % half linear step
        [opt_in_x,opt_in_y,state.z_prop,state.lin_z_test,...
        state.corr_length,state.n_plates_done,state.missing_dz,state.n_step,...
        state.test_plates,state.test_plate_numbers,state.brf,state.common_beta.X,...
        state.common_beta.Y,state.alpha_lin.X,state.alpha_lin.X]...
        = lin_step(...
        opt_in_x,opt_in_y,state.z_prop,state.lin_z_test,...
        state.dz/2,state.corr_length,state.n_plates_done,state.missing_dz,state.n_step,...
        state.test_plates,state.test_plate_numbers,state.brf,state.common_beta.X,...
        state.common_beta.Y,state.alpha_lin.X,state.alpha_lin.X);

        % complete nonlinear step
       
        [opt_in_x,opt_in_y] = nl_step(opt_in_x,opt_in_y, state.dz, state.gamma, state.chi, state.manakov, state.beat_len ,state.alpha_lin.X, state.alpha_lin.Y);
        
        % half linear step              
        [opt_in_x,opt_in_y,state.z_prop,state.lin_z_test,...
        state.corr_length,state.n_plates_done,state.missing_dz,state.n_step,...
        state.test_plates,state.test_plate_numbers,state.brf,state.common_beta.X,...
        state.common_beta.Y,state.alpha_lin.X,state.alpha_lin.X]...
        = lin_step...
        (opt_in_x,opt_in_y,state.z_prop,state.lin_z_test,...
        state.dz/2,state.corr_length,state.n_plates_done,state.missing_dz,state.n_step,...
        state.test_plates,state.test_plate_numbers,state.brf,state.common_beta.X,...
        state.common_beta.Y,state.alpha_lin.X,state.alpha_lin.X);

        % get nonlinear step size
        [state.dz] = getNLstepsize(opt_in_x,opt_in_y,state.gamma,state.SS_dzmin,state.SS_dzmax,state.SS_dphimax,state.alpha_lin);
        %[state.dz] = getNLstepsize_original(state,opt_out_struct);


               
    end
    
    toc

    



     opt_out_x   = (opt_in_x);
     opt_out_y   = (opt_in_y);

%     opt_out_x   = gather(opt_in_x);
%     opt_out_y   = gather(opt_in_y);
    
end