Loss spectrum measurement for infrared hollow fiber based on the Fourier transform infrared spectrometer

Based on the Fourier transform infrared spectrometer, a system for measuring the loss spectrum of hollow fiber is established. Loss spectra can be measured for hollow fibers with length ranging from several centimeters to 3 m. Two kinds of light source coupler are designed and fabricated for achieving stable coupling and a repeatable spectrum. One is a short waveguide, and the other is a tapered tube. Both are inner-coated with a silver layer and they are of the same inner diameter at the output end as the measured hollow fiber. Characteristics of the measuring system are discussed theoretically and experimentally when using the two couplers. Several kinds of hollow fibers are measured, and the properties of the loss spectra are discussed. The measured loss value is shown to be dependent on the output divergence angle of the coupler. The tapered coupler has a larger output divergence and causes higher measured loss than that of the waveguide coupler. [c] 2010 Optical Society of America OCIS codes: 230.7370, 310.6860, 120.7000, 060.2270, 120.6200.