A simple method enabling to generate a stable and controllable phase shift in a linearly chirped fiber Bragg grating (FBG) is theoretically and experimentally demonstrated, which is based on the utilization of the mini-size piezoelectric transducers (PZTs). The magnitude of the induced phase shift can easily be controlled by adjusting the voltage applied on the individual PZT. With this method, a narrow bandpass filter with 3-dB band width of 0.085 nm is obtained. Based on this kind of filter, an Erbium-doped fiber ring laser is also demonstrated, and both switchable and stable single-longitudinal-mode (SLM) laser emission is successfully realized.