how to get a transfer function from a graph

greenspun.com : LUSENET : PID Controller Tuning : One Thread

I have a graph of voltage/time of a laser diode output.I need the transfer function (in the frequency domain). how can I get the function from the graph? (Vin was a step function). thanks.

-- david green (debili16@hotmail.com), October 26, 2004

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