neff_co.m

光纤中纤芯基模的有效折射率计算程序,二分法求解！

Neffco=zeros(10);         % 初始化
for j=1:100
    lamda=(1450+j)*10^(-9);
x1=1.450001;
x2=1.460001;
xacc=1e-8;
f=func(lamda,x1);

%%%%%%%%%%%%%%%%以下调用二分法求解func函数的零点，即求解纤芯基模的有效折射率
fmid=func(lamda,x2);

if (f<0)
    rtb=x1;
    dx=x2-x1;
else
    rtb=x2;
    dx=x1-x2;
end
for i=1:40
    dx=dx*0.5;
   xmid=rtb+dx;
   fmid=func(lamda,xmid);
   if(fmid<=0.0) 
       rtb=xmid;
   end
   if (abs(dx)<xacc||fmid==0.0)
       break;
   end
   Neffco(j)=rtb;                       % matla 中的数组显示时是列优先的。即a[2]是第一列的第二个元素。
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

plot(lamda,Neffco(j));

hold on;
grid on;
end
hold off