sensitivity of photodetector
The sensitivity depends on how you use the device.

Sensitivity is the minimum input power to obtain a specified bit error rate (typically between 10-15 and 10-9) in an optical communication system. 

The sensitivity depends on the receiver characteristics, but also on the modulation scheme and any data encoding used in the system.

You can tune the sensitivity by low-pass filtering the output of this device. But the bandwidth of the LPF that you can usefully apply depends on the bit rate of your communication system.  Once you determine the filter bandwidth you're going to use, you can estimate the sensitivity from the noise characteristics of the receiver, specified as an input-referred noise in the datasheet:



To roughly estimate the sensitivity, multiply the input-referred noise by the square root of your system noise bandwidth (hopefully mainly determined by the filter bandwidth). If you are using on-off keying (OOK) with no error-correcting codes, you'll need an input optical modulation amplitude of at least about 12x (IIRC) this value to achieve a 10-9 BER in your system.