An apparatus (100) for measuring a thickness of a thin article according to an embodiment of the present apparatus is provided. The apparatus includes an optical fiber interferometer (101), a signal processor module (102) and a measuring module (103). The optical fiber interferometer is configured for obtaining an optical distance difference. This optical distance difference is a result of the thickness of the thin article between a first optical path in which the thin article is measured and a second optical path. The signal processor module is configured for converting an optical distance difference into a phase difference and processing the optical distance difference to obtain a linear signal. That linear signal is convertible into a thickness value of the thin article.