# Calculate Relative intensity noise using Rate equations

by mido41854
Tags: equations, intensity, noise, rate, relative
 P: 2 Hello Everybody, I'm trying to plot the frequency spectrum of RIN using Matlab. I've the following code function p=rateblock tau_s = 3e-9; N0 = 1e24; A =1e-12; P0 = 1/(A*tau_s); TSPAN = 0:1e-2:10.23;; Y0 =[0 0]; [T,Y] = ODE45(@rate_equation,TSPAN,Y0); subplot(2,1,1) plot(T*tau_s ,Y(:,1)*N0) title('carriers density in high laser level') subplot(2,1,2) plot(T*tau_s ,Y(:,2)*P0) title('photons density in activer region') % dt=1e-2; s_avg=sum(Y(:,2))/1024;%average photon numbers ds=Y(:,2)-s_avg;%photon fluctuation with respect to average TT=1e-6; %total time of integration N=1024;%fft length F=[0:N-1]'; RIN=((dt^2)/((s_avg)^2*TT)).*(abs(fft(ds))).^2; RIN=10*log10(RIN); plot(F,RIN) title('RIN') And for the Rate equation i used this function function dy = rate_equation(t,y) dy = zeros(2,1); tau_s = 3e-9; % carriers lifetime tau_p = 1e-12; % photons lifetime A = 1e-12; % linear gain costant N0 = 1e24; % trasparency carries density V = 3.75e-14; % modal volume gamma = 1e-5; % gain compression factor q = 1.6e-19; % electron charge I0 = N0*q*V/tau_s; % trasparency current tau_norm = tau_s/tau_p; eta = A*tau_p*N0; % efficiency I = 2.5*I0; % pumping current dy(1)= I/I0 -y(2)*(y(1) - 1) -y(1); dy(2) = tau_norm*(y(2)*(eta*(y(1) - 1) -1) + gamma*eta*y(1)) Although I'm facing problems with caluclating the RIN and plot it with frequency ... Can anybody help me with this issue?

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