How to calculate the detected intensity of an optical signal (in time) photodiode with MATLAB

I am trying to calculate the detected intensity of a photodiode (PD). The signal is supposed to be a pulse with a given shape which I determine through the simulation, defined over a time period, e.g.

    x(t)=J(1,t); %Bessel type 1

The photodiode impulse response is a kind of trapezoid which I define along the same time range and multiply it by intensity of the signal

    abs(x(t)).^2.

As far as I have understood, the value recorded by PD is the integral of the product over time, as I do

    trapz(t,abs(x(t)).^2*trapezoid).

I wanna compare this value (detected by PD) with the peak intensity. Could anyone help me please with this question?

Thanks