The suppression of laser excess noise using a cascaded imbalanced Mach-Zehnder interferometer with fiber optic components was proposed and demonstrated in the experiment.By developing an automatic phase control system,the phase of the fiber interferometer with a large path imbalance (127 m) can be stabilized in a long term,and the laser excess noise around 800 kHz and its integer multiples can be efficiently suppressed by more than 45 dB.The effective frequency bands of the noise filter can be controlled by adjusting the arm-length difference of the interferometer.The approach provides an effective solution for achieving compact and cost-effective laser noise reduction,and can be applied directly to the quantum optomechanical system where shot-noise-limited laser can be required.