When a frequency stabilized laser pulse transmits through an optical fiber, the phase noise generated by the optical fiber affects the stability of the laser frequency, resulting in a broadened laser spectrum. The measurement and feedback control of phase noise at the remote site of an optical fiber are introduced. Experimental setups are introduced for the measurement and active cancellation of the phase noise due to optical fiber. Using feedback control, the original 1 kHz spectral line broadening introduced by the optical fiber is reduced to less than 1 Hz. The methed to convert the demodulated voltage noise to phase noise in the process of phase detection is also discussed.