fix the mistake line 91 function

% This program simulates a single-channel fiber transmission link 
% using the symmetrized split-step Fourier algorithm. 
% 
% written by Jong-Hyung Lee 

clear all 
%============================================= 
% Define Time Window and Frequency Window 
%============================================= 

taum = 2000; 
dtau = 2*taum/2^11; 
tunit= 1e-12; % make time unit in psec 

tau = (-taum:dtau:(taum-dtau))*tunit; 

fs = 1/(dtau*tunit); 
tl = length(tau)/2; 
w = 2*pi*fs*(-tl:(tl-1))/length(tau); % w=angular freq. 
wst = w(2)-w(1); 

%============================================= 
% Define Physical Parameters 
%============================================= 

c = 3e5; %[km/sec] speed of light 
ram0 = 1.55e-9; %[km] center wavelength 
k0 = 2*pi/ram0; 
n2 = 6e-13 ; %[1/mW] 
gamm = k0*n2 ; %[1/(km*mW)] 
alphaDB = 0.2 ; % [dB/km] Power Loss 
alpha = alphaDB/(10*log10(exp(1))); %[1/km] Power Loss in linear scale 

% Dispersion parameters (beta3 term ignored) 

Dp = -2; % [ps/nm.km] 
beta2 = -(ram0)^2*Dp/(2*pi*c); % [sec^2/km] 

%============================================= 
% Define Input Signal 
%============================================= 
% A single Gaussian pulse is assumed. 

Po = 2; % [mW] initial peak power of signal source 

C = 0; % Chirping Parameter 
m = 1; % Super Gaussian parameter (m=1 ==> Gaussian) 
t0 = 50e-12; %[sec] initial pulse width 

at = sqrt(Po)*exp(-0.5*(1+1i*C)*(tau./t0).^(2*m)); % Input field in the 
time domain 
a0 = fft(at(1,:)); 
af = fftshift(a0); % Input field in the frequency domain 

%============================================= 
% Define Simulation Distance and Step Size 
%============================================= 

zfinal = 100; %[km] propagation distance 
pha_max = 0.01; %[rad] maximum allowable phase shift due to the 
nonlinear operator 
 % pha_max = h*gamma*Po (h = simulation step length) 
h = fix(pha_max/(gamm*Po)); % [km] simulation step length 
M = zfinal/h; % Partition Number 

% Define Dispersion Exp. operator 
% Dh = exp((h/2)*D^), D^=-(1/2)*i*sgnb2*P, P=>(-i*w)^2 

Dh = exp((h/2)*(-alpha/2+(1i/2)*beta2*w.^2)); % 

%================================================% 
% Propagation Through Fiber % 
%================================================% 

% Call the subroutine, sym_ssf.m for the symmetrized split-step Fourier 
method 

[bt,bf] = sym_ssf(M,h,gamm,Dh,af); 

% Preamplifier at the receiver 
% Optical amplifier is assumed ideal (flat frequency response and no noise) 

GdB = 20; % [dB] optical amplifier power gain 
gainA = sqrt(10^(GdB/10)); % field gain in linear scale 

rt = gainA*bt; 

% plot the received power signal 
figure(1) 
plot(tau,abs(rt).^2,'r') 
function [to,fo] =symssf(M,h,gamma,Dh,uf0)  
% Symmetrized Split-Step Fourier Algorithm 
% 
% ==Inputs== 
% M = Simulation step number ( M*h = simulation distance ) 
% h = Simulation step 
% gamma = Nonlinearity coefficient 
% Dh = Dispersion operator in frequency domain 
% uf0 = Input field in the frequency domain 
% 
% ==Outputs== 
% to = Output field in the time domain 
% fo = Output field in the frequency domain 
% 
% written by Jong-Hyung Lee 

for k = 1:M 

   %============================================================= 
   % Propagation in the first half dispersion region, z to z+h/2 
   %============================================================= 

   Hf = Dh.*uf0; 

   %========================================================== 
   % Initial estimate of the nonlinear phase shift at z+(h/2) 
   %========================================================== 

   % Initial estimate value 

   ht = ifft(Hf); % time signal after h/2 dispersion region 
   pq = ht.*conj(ht); % intensity in time 

   u2e = ht.*exp(h*1i*gamma*pq); %Time signal 

   %============================================================= 
   % Propagation in the second Dispersion Region, z+(h/2) to z+h 
   %============================================================= 

   u2ef = fft(u2e); 
   u3ef = u2ef.*Dh; 
   u3e = ifft(u3ef); 
   u3ei = u3e.*conj(u3e); 

   %======================================================== 
   % Iteration for the nonlinear phase shift(two iterations) 
   %======================================================== 

   u2 = ht.*exp((h/2)*1i*gamma*(pq+u3ei)); 
   u2f = fft(u2) ; 
   u3f = u2f.* Dh; 

   u4 = ifft(u3f); 
   u4i = u4.*conj(u4); 

   u5 = ht.*exp((h/2)*1i*gamma*(pq+u4i)); 
   u5f = fft(u5); 

   uf0 = u5f.*Dh; 

   u6 = ifft(uf0); u6i = u6.*conj(u6); 

   %============================================================= 
   % Maximum allowable tolerance after the two iterations 

   etol = 1e-5; 

   if abs(max(abs(u6i))-max(abs(u4i)))/max(abs(u6i)) > etol 
   disp('Peak value is not converging! Reduce Step Size'), break 
   end 
   %============================================================= 

end 

to = u6; fo = uf0;

[Jos (10584)]

You're more likely to receive an answer if you indicate what the mistake is. Note that we do not see any line numbers here ...

[Ghislaine Flore Kabadiang ngon]

Please what is sym_ssf and where did you define it? I got an error in Matlab because of that.

[Image Analyst]

Did you see my solution below? It seems you overlooked it.

Answer 1

[Image Analyst]

You're calling sym_ssf() but the function is actually called symssf() with no underline.

[Jos (10584)]

You're too helpful, Image Analyst :-)

[Image Analyst]

If I click edit, then I can get the "good" format code. Then I just copied and pasted and found out where it barfed. So, it wasn't too much work.

[abed]

I did what you told me and still it didn't work they told me about that I should put semicolon inside the function I don't know why and the interval bracket has an error which I couldn't solve ??????

[Image Analyst]

See attached. It runs fine with no errors.

[abed]

thank you