To overcome the accuracy limits of fringe counting method for a F-P interferometer and the complexity of a higher
resolution demodulation system such as phase generated carrier (PGC), where a residual amplitude modulation always
exists in frequency modulation, this paper presents a fiber F-P displacement sensor based on double-interferometer phase
demodulation, which eliminates the modulation of lightsource. Comparing to the reported double-fiber F-P structure, our
design has no strict requirement for a specific phase difference between the two optical paths. Experimental results
demonstrate a good linearity of 1.1% and a resolution of ±3 μm within a measuring range of 0-0.5 mm.