Dear Adil,
There is a new example (VCSEL Laser Measured Impulse response.osd) in OptiSystem 17.0 that was released last week, which shows you how to measure the frequency response of a VCSEL. You can check the theory of the VCSEL laser component in the datasheet of the component that can be accessed through the “Help” button in the component properties popup window.
Regards,
Ahmad