function ber = optical_BER(x,y,t)
env = WaveEnv();
INT_MIN = 10^(-10);
intensity = env.get_intensity([x y],[0,0,-1],t);

p_bg=5.8e-6;
delta_lambda = 30;
T_n = 0.95;
A = 1e-4;
n = 1;
Pn = p_bg*delta_lambda*T_n*A*n^2;

B = 2^30;
q = 1.6022e-19;
R = 0.6;
sigma_squre=2*q*R*Pn*B;

if intensity ==INT_MIN
    intensity = 0;
end

SNR = intensity^2/sigma_squre;
ber = log10(qfunc(log(sqrt(SNR))));