cfbg_gaussianvisibility_temperaturechange.m

利用传输矩阵法计算光纤啁啾brag光纤光栅滤波器的温度滤波特性

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%  [1]: The following program is used to calculate the Reflection 
%       spectrum of the CFBG, which has been calculated in the
%       program:'CFBG_GaussianVisibility.m'.
%  [2]: And the difference here is that environmental temperature 
%       has changed in this program.
%  [3]: For temperature changing, we only consider the two effects
%       that mainly influence our result -- thermal expand effect 
%       and thermal-optical effect.
%  [4]: In this simple program, we donot consider the origunal 
%       light source's chang when the environmental temperature
%       has been changed. 
% First  time:  2006-10-02
% Second time:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%  

% hold on
T0=300;          % initial temperature
delta_T=40;      % temperature variation
T=T0+delta_T    
alpha=1.0e-6;    % CFBG(Ge-doped,SiO2)temperature sensitivity coefficent
delta_L=alpha*L*delta_T;
L=L+delta_L;
l=L/M;
kesi=8.9e-6;     % CFBG(Ge-doped,SiO2)thermo-optic coefficient[(8.3-9.5)e-6]
Neff=Neff*(1+kesi*delta_T);
delta_N=delta_N*(1+kesi*delta_T);

count=0;
for i=1:M  % using transmit matrix method to obtain the reflecting spectrum                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
       F=[1,0;0,1];                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
   for k=1:M                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
	    Period(k)=Period(k)*(1+alpha*delta_T);
        Beita(i,k)=Beita(i,k)*(1+kesi*delta_T);
        if k<2
           sigma=(Beita(i,k)-pi/Period(k))+2*pi*delta_N(k)/lamda(i); %(formula 17 from Erdogan's 'Fiber Grating Spectra' )
        else
           sigma=(Beita(i,k)-pi/Period(k))+2*pi*delta_N(k)/lamda(i)+8*pi*Neff^2*(l/2)/lamda(k)^2*(Period(k)-Period(k-1))/l;   
        end
        K=pi*v(k)*delta_N(k)/lamda(i);
        sub=sqrt(K^2-sigma^2);       
        F=F*[cosh(sub*L/M)-j*(sigma/sub)*sinh(sub*L/M),-j*(K/sub)*sinh(sub*L/M);j*(K/sub)*sinh(sub*L/M),cosh(sub*L/M)+j*(sigma/sub)*sinh(sub*L/M)];  %传输矩阵
        count=count+1
    end                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
        r_design(i)=(abs(F(3)/F(1)))^2;                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
end                                                                                                                                                                                                                                                                                                                                                                                                                                           
       plot(lamda,r_design,'r');