An accessory has been designed for FT-IR spectroscopy that can be used to measure the optical properties of fiber-optic cables or serve as an interface for remote sensing probes that use fiber optics. This accessory utilizes compound parabolic concentrators (CPCs) to focus the energy from the spectrometer into the optical fiber and to also refocus the energy returning to the spectrometer onto the detector. The design was optimized for the high acceptance angle of chalcogenide mid-IR fibers. However, the use of nonimaging concentrators yields an all-reflecting system that can be used to characterize fibers with different spectral transmission ranges. This accessory has been used to investigate the spectral response, cladding effects, and impurities in various optical fibers.
S. Lowry, T. May, A. Bornstein, Y. Weissman, R. Harman, and I. Tugenthaft, "New Accessory for Characterizing Optical Fibers with an FT-IR Spectrometer," Appl. Spectrosc. 48, 852-856 (1994)