Abstract: A system and a method for measuring deflection of a shaft in a wind turbine and adjusting a pitch angle of a rotor blade in the wind turbine based on the determined deflection are described. The system includes an emitter, a receiver, and a controller. The emitter is positioned adjacent a first portion of the shaft and is configured to emit photons. The receiver is positioned adjacent a second portion of the shaft and is configured to receive photons emitted from the emitter and determine a location on the receiver where the photons strike the receiver. The controller is communicatively coupled to the receiver and is configured to determine deflection of the shaft based on the location on the receiver where the photons strike the receiver. The controller is also configured to adjust the pitch angle of the rotor blade based on the determined deflection of the shaft to reduce deflection of the shaft.