Improved techniques for the measurement of phase error in waveguide based optical devices

Phase-error measurement using an incoherent light source and information in the resulting interferograms is an effective technique for characterizing waveguide-based optical devices. We propose a new analysis scheme that utilizes Hilbert transformation along with an increased data sampling rate of the interferogram. The higher data sampling rate makes the measurement more noise tolerant and improves the accuracy of the resulting phase determination to 0.2/spl deg/. This technique enables a "windowing" analysis method that is capable of testing waveguides with very small path length differences. We also present a new analysis tool for device characterization by creating a "phase trend" plot that detects different optical modes propagating within the waveguide.