Strain measurements on pipelines provide a nondestructive means to evaluate their in-service conditions. They have been proposed to detect abnormal operating pressures, pipe wall problems, or intrusive pipeline events. For such applications, optical fiber sensors are especially appealing because of their hazard and electromagnetic interference-free nature. In this work, two different types of optical fiber sensors are compared for use to monitor the hoop strain on a pressurized pipe, the well-developed fiber Bragg grating (FBG) sensor and a proposed simple fiber sensor based on multimode interference (MMI). The FBG sensor shows a better linearity of strain measurement, while the MMI sensor provides a larger wavelength shift with strain at relatively low pressures. An intensity-based detection of vibrations, simulating an intrusive pipe drilling event, was achieved using the proposed MMI sensor.