ssfm_for_cnlse_withpmd_linear_basis.m

是有分布傅立叶算法解薛定谔方程的一个程序（下面我就不乱说说了请认真阅读您的文件包然后写出其具体功能(至少要20个字)。尽量不要让站长把时间都花费在为您修正说明上。压缩包解压时不能有密码。系统会自动删除

function [u1x,u1y] = UPMPol(u0x,u0y,dt,dz,nz,alphax,alphay,betapx,betapy,gamma,correlationlength,angles,tetas,beta0s,beta1s);

nt = length(u0x); % nt is the number of point
w = 2*pi*[(0:nt/2-1),(-nt/2:-1)]'/(dt*nt); %constructing used frequencies

linearoperatorx = -alphax/2; % in the lines above are constructed the linear operator in X and Y.
for ii = 0:length(betapx)-1; 
  linearoperatorx = linearoperatorx - j*betapx(ii+1)*(w).^ii/factorial(ii);
end

linearoperatory = -alphay/2;
for ii = 0:length(betapy)-1;
  linearoperatory = linearoperatory - j*betapy(ii+1)*(w).^ii/factorial(ii);
end

u1x = u0x;
ufftx = fft(u0x); 

u1y = u0y;
uffty = fft(u0y);
  
fiberlength = nz*dz;
propagedlength =0;
auxlength = 0;
jj=1; % it will be used to choise the correct input angles, tetas, beta0s and beta1s

%  dz=0.1; % this is to set the longitudinal step-size

while propagedlength < fiberlength,
    

  %------the next "if" and the variable "auxlenght" are used to check if
  %the correlation length was riched
  if (auxlength >= correlationlength | auxlength ==0),
      auxlength = 0;
      
      angle = angles(jj);  
      teta = tetas(jj);
      ufftxaux = ufftx * cos(teta) - uffty * sin(teta)*exp(-i*angle);
      ufftyaux = ufftx * sin(teta)*exp(i*angle) + uffty * cos(teta);
      ufftx = ufftxaux;
      uffty = ufftyaux;
      
      betapx(1) = -beta0s(jj); % observe that b0x and b0y are defined such that b0x = -b0y = -beta0s(1)
      betapy(1) = beta0s(jj);
      betapx(2) = -beta1s(jj); % tha same as above for beta1x and beta1y
      betapy(2) = beta1s(jj);
      
      jj=jj+1; % I increase the value of jj so in the next time the correlation length is reached, different pseudo-random variables are taken
      
      linearoperatorx = -alphax/2; % in the lines bellow I define the linear operators again using the new beta0s and beta1s
      for ii = 0:length(betapx)-1;
        linearoperatorx = linearoperatorx - j*betapx(ii+1)*(w).^ii/factorial(ii);
      end
      linearoperatory = -alphay/2;
      for ii = 0:length(betapy)-1;
        linearoperatory = linearoperatory - j*betapy(ii+1)*(w).^ii/factorial(ii);
      end  
  end % here ends the "if" part that is done just at each correlation length.
  
  %Performing the SSFM with the given dz
  %------linear propagation until dz/2------------
  halfstepx = exp(linearoperatorx*dz/2);
  uhalfx = ifft(halfstepx.*ufftx); 
  
  halfstepy = exp(linearoperatory*dz/2);
  uhalfy = ifft(halfstepy.*uffty); 
  
  %---------non-Linear propagation----------------------
  
  deltateta = (-i*gamma*dz/3)*(uhalfx.*conj(uhalfy) - uhalfy.*conj(uhalfx));
  u1x = exp(-i*gamma*dz*(abs(uhalfx).^2 + abs(uhalfy).^2 )).*( uhalfx.*cos(deltateta) - uhalfy.*sin(deltateta) );
  u1y = exp(-i*gamma*dz*(abs(uhalfx).^2 + abs(uhalfy).^2 )).*( uhalfx.*sin(deltateta) + uhalfy.*cos(deltateta) );
  
  %------linear propagation from dz/2 to dz------------
  ufftx = halfstepx.*fft(u1x); % 
  uffty = halfstepy.*fft(u1y);
  %----------------------------------------------------
  auxlength = auxlength + dz;
  propagedlength = propagedlength + dz
end

u1x = ifft(ufftx);
u1y = ifft(uffty);