Currently in the middle of a project and need help with some photodiode response time issues. I have two LEDs alternatingly lighting up with the following signal: {LED1 turns on for 250 us, both LEDs are off for 250 us, LED2 turns on for 250 us, both LEDs are off for 250 us}. I have the two LEDs set to this timing (1 kHz) as confirmed by an oscilloscope; however, the photdetector (s1337-33br datasheet --> http://www.alldatasheet.com/datasheet-pdf/pdf/212335/HAMAMATSU/S1337-33BR.html ) is unable to respond quickly enough to differentiate the two signals without overlap. Whenever a pulse is generated and an LED goes off the photodetector slowly falls back to baseline at the same rate it takes the next pulse to be generated no matter the frequency. I need the gap between the two LEDs for background subtraction and can't seem to figure out how to get my signal to the photodetector. Any suggestions would be helpful as I am completely out of ideas at the moment.