%signal FWHM fs=10^10

(1)

A^PPENDIXI

Matlab script used in Chapter 3 to simulate the Quasi-Asynchronous sampler behaviour.

clear all close all

Timp=0.5*10^(-12); %sampling pulse FWHM Tsign=1*10^(-12); %signal FWHM

fs=10^10; %signal frequency Delta_t=500*10^(-15);

fc=fs/(1+Delta_t*fs);

Ns=10;

dt=double(Timp/Ns);

flo=fs-fc;

%signal to be sampled

ts=[-50*10^(-12):dt:50*10^(-12)];

s=sech(ts*2.634/Tsign);

figure(1) plot(ts,s) grid on

%sampling pulse

tc=[-4*Timp:dt:4*Timp];

c=sech(tc*2.634/Timp);

tc=tc(1:length(tc)-1);

c=c(1:length(c)-1);

figure(2) plot(tc,c) grid on

%sampling

Nc=length(tc);

(2)

Analisi e realizzazione di un campionatore ottico quasi-asincrono basato su cross-phase modulation per segnali ultra-veloci

Tc=1/fc;

N_Ts=length(ts);

N_Delta_t=round(Delta_t/dt);

N_Tc=N_Delta_t+N_Ts;

N_zeros=N_Tc-Nc;

z=zeros(1,N_zeros-1);

sampling=s(1:Nc).*c;

sbis=[s,s(1:Nc)];

j=0;

for i=1:round(N_Ts/N_Delta_t)-1;

prod=sbis(i*N_Delta_t:i*N_Delta_t+Nc-1).*c;

sampling=[sampling,z,prod];

j=j+1;

end

cut=sampling(length(sampling)-(N_Tc/2)*round((Nc/N_Delta_t)- 2):length(sampling));

sampling=[cut,sampling(1:length(sampling)- (N_Tc/2)*round((Nc/N_Delta_t)-2)-1)];

t_sampling=[0:dt:dt*(length(sampling)-1)];

figure(3)

plot(t_sampling,sampling) grid on

tot=sampling;

t_tot=t_sampling;

for k=1:19

tot=[tot,sampling];

inc=t_sampling+k*t_sampling(length(t_sampling));

t_tot=[t_tot,inc];

end

figure(4)

plot(t_tot,tot) grid on

delta_f=(1/dt)/length(t_tot);

f=[-1/(2*dt):delta_f:1/(2*dt)];

f=f(1:length(f)-1);

OUT=(fft(tot));

OUT=abs(fftshift(OUT));

figure(5);

plot(f,OUT) grid on

f_taglio=3*10^9;

N_wind=2*round(f_taglio/delta_f);

H=[zeros(1,round(length(OUT)/2)- N_wind/2),ones(1,N_wind),zeros(1,round(length(OUT)/2)-N_wind/2)];

FINAL=OUT.*H;

final=abs(ifft(FINAL));

figure(6)

plot(t_tot,final) grid on

%polarization efficiency wt=[-2*pi:0.1:2*pi];

89

(3)

APPENDIX I

x=cos(wt);

y=zeros(2,length(wt));

i=0;

gamma=10;

alfa=10^0.079;

L=1; %Km

Ps=10*10^(-3);

Pp=10*10^(-3);

LV=0;

eff_tot=0;

for L=0.05:0.05:2

Leff=(1-exp(-alfa*L))/alfa;

fi_NL=gamma*Leff*(Ps+2*Pp);

i=0;

for fi=0:pi/4:pi/2;

i=i+1;

y(i,:)=cos(wt+fi);

teta=atan(cos(fi));

a=sqrt(1+2*cos(teta)*sin(teta)*cos(fi));

b=sqrt(1-2*cos(teta)*sin(teta)*cos(fi));

if fi<=(pi/2) eff(i)=(b/sqrt(2))^2;

else eff(i)=(a/sqrt(2))^2;

end

fiV(i)=fi;

end

grid on figure(2) plot(fiV,eff)

title(['efficienza al variare di fi, per L=', num2str(L)])

eff_tot=[eff_tot,eff(length(eff))];

LV=[LV,L];

end

figure(1) plot(x,y)

title(['stato della polarizzazione per L=', num2str(L)])

eff_tot=eff_tot*100;

figure(3)

plot(LV,eff_tot)

ylabel('efficiency (%)');

xlabel('L fiber (Km)');

90