function opt_signal = channel_model_mpi(opt_signal,link_total_meter,oneway_interference_meter,sir)

%%%%% Local Parameter %%%%%%%%



%%%%% Ping Pong/ Interference Path %%%%%%
    interference_sig    = Fiber("fsimu",opt_signal.fs,"fiber_length",oneway_interference_meter*2/1000,"alpha",0.3,"D",0,"lambda0",1320,"gamma",0,"Dslope",0.07).process(opt_signal);
    
    interference_sig    = Amplifier("amp_mode","ideal_no_noise","gain_mode","gain","amplification_db",-sir).process(interference_sig);
    
%%%%% Delay the "main" signal as in reality the interference is "older" than the main signal %%%%%%
    [main_sig,dly] = opt_signal.delay("delay_meter",oneway_interference_meter*2);

    main_sig.power;
    interference_sig.power;
    
%%%%% ADD Interference and Main Signal  %%%%%%
    combined_sig = main_sig + interference_sig;

%%%%% Cut (due to the delays there is a jump in the signals) %%%%%%
    if dly == 0;dly = 1;end
    combined_sig.signal = combined_sig.signal(ceil(dly):end);
    
%%%%% Propagate through fiber %%%%%%
    opt_signal  = Fiber("fsimu",combined_sig.fs,"fiber_length",link_total_meter/1000,"alpha",0.3,"D",0,"lambda0",1320,"gamma",0,"Dslope",0.07).process(combined_sig);

end