>Question. Rise and fall times are sub 40ps is that a typo in your email No, those are the times provided in the test report that was sent with the pulser. Modern laser diode drivers are very fast (a MAX 3930 has a spec'd risetime of  ~25 ps). -- Bill Ezell ---------- The day Microsoft makes something that doesn't suck will be the day they make vacuum cleaners. Or maybe Windows 10.