How do I calculate the minimum detectable optical power?
The minimum detectable optical power (Pmin) is a function of wavelength (l), measurement bandwidth (B), and noise-equivalent power (NEP). Pertinent parameters can be found in our specification tables and graphs, with the exception of measurement bandwidth. The measurement bandwidth is determined by your choice of output filtering. If you choose not to use any output filtering, the photoreceiver’s 3-dB frequency is a good approximation of measurement bandwidth. where Rmax is the maximum responsivity of the detector, R(l) is the responsivity of the detector at the wavelength of interest, and NEP is given in the characteristics tables. For an example, we can calculate the minimum detectable optical power of a Model 1611-AC receiver at 1.0 µm using an output filter with a 10-kHz bandwidth. From the specification table and responsivity graphs, Rmax is 1 A/W, and R at 1.0 µm is 0.7 A/W. Therefore, NEP at 1.0 µm is 28.6 pW•Hz-1/2 and Pmin is 3 nW.
