Automatic refractive-index profiling of optical fibers

Area of Science:

• Optoelectronics and Photonics
• Materials Science
• Optical Metrology

Background:

• Accurate characterization of optical fiber refractive index profiles is essential for telecommunications and sensing applications.
• Traditional methods for measuring refractive index distribution can be complex and time-consuming.
• Interference microscopy offers a non-destructive approach to profile analysis.

Purpose of the Study:

• To develop and validate a novel video-based system for automated refractive index distribution measurement in optical fibers.
• To achieve high-accuracy measurements of refractive index differences (Deltan).
• To demonstrate the system's capability across different wavelengths and fiber orientations.

Main Methods:

• A video-based system directly analyzes the output of an interference microscope.
• A silicon-vidicon detector captures fringe field data, digitized to 8-bit accuracy.
• A programmable calculator controls digitization, performs fringe displacement measurements, corrects misalignments, and computes the refractive index profile.
• A best-fit power-law (alpha) curve is determined for the profile.

Main Results:

• The system automatically measures the refractive index distribution of optical fibers.
• Relative Deltan measurements are accurate to a few parts in 10^5.
• Profiles were successfully obtained and analyzed at different wavelengths.
• The influence of different fiber orientations on the measurements was investigated.

Conclusions:

• The developed video-based system provides an automated and accurate method for measuring optical fiber refractive index profiles.
• The system's precision in Deltan measurement is suitable for demanding optical fiber applications.
• The flexibility to analyze fibers at various wavelengths and orientations enhances its utility.