Complex Refractive Index Profile Measurement for Special Fibers Using Total Variation Method

Refractive index profile (RIP) determines the property and effectiveness of optical fibers. Accurate measurement of the RIP is essential for fiber fabrication, test and calibration. At present, computer tomography (CT) method is widely used in RIP measurement. However, in the measurement of the optical fiber with a complex RIP, the CT method is much time-consuming due to its dependence on small rotation angle step usually with 2° (performing 90 steps of rotation for angle range from 0° to 180°). In this paper, the total variation (TV) method is proposed to fast reconstruct the complex RIP with both two-dimension and three-dimension in transverse as well as longitude direction. The RIP of a seven-core trench-assisted optical fiber and a twisted polarization maintaining optical fiber are measured experimentally as examples. Experimental results demonstrate that the proposed TV method has higher accuracy of 4 × 10 −4 and three times faster than that of traditional CT method.