(Noob) Want to detect string vibration. Preferably with light.

I want to detect the the vibration of a string and determine the wave characteristics being produced by this vibration. Light is preferable because I believe it reduces the power requirements if such a sensor exists. I am prototyping and proving concept so I do not need high precision but I like good quality instruments(sensors).

In several spy movies a laser beam has been used to listen to voices in a distant room. If this is not pure fiction, it should be possible to apply the same technique to a string.

Thanks for reply. After much research I found this website www.kortier.com . Mr Kortier sold me two of his sensors. Now I am off trying to figure out how to connect his u.fl connectors to my arduino uno.