singlelpg.m

长周期光纤光栅透射谱,用来描述长周期光纤光栅传输特性

clear
format long 

zhouqi=500e-6; 
dn=0.003;      
L=0.05;                           
dz=L/100;       

T=[1;0];
bolongb=1550e-9;   

for bolong=1520e-9:0.1e-9:1580e-9;
dneff=dn*cos(2*pi*100*dz/zhouqi);
dbeta=dneff*pi*(1/bolong-1/bolongb);         
k=pi/4/L;                                   
q=sqrt(k^2+dbeta^2);
F{100}=[cos(q*dz)+i*dbeta/q*sin(q*dz),i*k/q*sin(q*dz);i*k/q*sin(q*dz),cos(q*dz)-i*dbeta/q*sin(q*dz)]; 
    for n=99:-1:1;
        dneff=dn*cos(2*pi*n*dz/zhouqi);
        dbeta=dneff*pi*(1/bolong-1/bolongb);         
        F{n}=[cos(q*dz)+i*dbeta/q*sin(q*dz),i*k/q*sin(q*dz);i*k/q*sin(q*dz),cos(q*dz)-i*dbeta/q*sin(q*dz)];
        F{n}=F{n+1}*F{n};
     end
G=F{n}*T;
R=(abs(G(1)))^2;
hold on
plot(bolong*10^9,R,'--r')
end
grid on, xlabel('nm'), ylabel('|a01|^2'),title('LPG')