Input Signal Power of the system

Hey hi, im sharing some part of the coding to let me know how can i find the input signal power of this system as this code was provided to me by someone so some parameters are hard to identify that is why im asking for help here. would be glad if someone identify that for me.

Thank u

num_bits = 1000;

SNR = [0 : 2 : 20];

[rows No_snr] = size(SNR);

tg = -7e-9 : 0.5e-9 : 7e-9;

t0 = 3.5e-9;

y0 = exp(-((tg/t0).^2));

y1 = [0 y0 0];

[rows num_samples_bit] = size(y1);

Carrier_freq = 1.94e14;

T = 1/Carrier_freq;

dt = 2.5*T/num_samples_bit;

num_Data_str = num_bits*num_samples_bit;

t = 0 : dt : (num_Data_str - 1)*dt;

Carrier_sig = exp(j*2*pi*Carrier_freq*t);

%% Filter Properties

P0 = 50;

deltaz = 0.5;

L =10;

lamda =1.55*10^-6;

r0 =4.1*10^-6;

n2 =10^-50;

D = 10;

speedlight = 3*10^8;

Aeff = pi*(r0)^2;

beta2 = -((D*10^-6)*(lamda^2))/(-2*pi*speedlight);

gamma = (2*pi*n2)/(lamda*Aeff);

Tp = 10*10^-12;

Ld = (Tp^2)/(abs(beta2));

Preq = (abs(beta2))/(gamma*(Tp^2));

P0 = P0*10^-3;

if P0<(Preq/10)

    N=1;

else

    N=(gamma*Ld*P0)^0.5;

end

b = [-0.500 -j*0.135 +0.400 ];

a = [1 +j*0.400 -0.135 ];

H1 = dfilt.df2t(b,a);

e =[0.125 -1];

m =[1 -0.125 ];

H2 =dfilt.df2t(e,m);

u =[-0.038 -j*1.100 +0.282 ];

k =[1.000 +j*1.000 -0.135 ];

H3 =dfilt.df2t(u,k);

g =[-0.038 -j*1.100 +0.282 ];

q =[1.000 +j*1.000 -0.135 ];

H5 =dfilt.df2t(g,q);

w =[-0.500 -j*0.135 0.400];

e = [1 +j*0.400 -0.135 ];

H7 = dfilt.df2t(w,e);

S1 = [0.125 -1 ];

S2 = [1 -0.125 ];

H6 = dfilt.df2t(S1,S2);

Hcas = cascade(H1,H2,H3,N,H5,H6,H7);