A novel acid-base titration based on fiber refractive index sensor principle is first proved and studied in this paper. It is a significant attempt for the optical fiber sensing technology application to chemical titration analysis. The experimental results show that this method is adapted to titration acids with bases and vice versa, and requires very small sample volumes. It is suitable that concentrated solution used to be the titrant when the sample is diluted solution. By adopting this method, the solution of 0.001 mol/L can be measured accurately. Compared to the traditional pH titration, end point indicator is unnecessary in this method, and real-time monitoring can be realized. In titration binary acid/base with base/acid, the end point is more explicit and higher accuracy can be obtained. The RSD of measurement of HNO₃, NaOH is 0.23% and 0.28% respectively, which show that text results of repeatability and accuracy is satisfactory.

Key words: fiber sensor, refractive index, acid-base titration, chemical analysis