Based On Ftir Infrared Optical Fiber Loss Spectrum Characteristics Test System Research

Infrared (IR) optical fibers may be defined as fiber optics transmitting wave lengths greater than approximately2μm. Infrared fiber optics may logically be divided into three broad categories:glass, crystalline and hollow waveguides. Glass IR fibers may include heavy metal fluoride glass, germanate glass and chalcogenide glass etc. Crystalline IR fibers include single crystalline and polycrystalline. Performance of these fibers have improved much, but the shortage in fabrications and optic performances(especially transmitting high power laser) has limited its usage.Hollow waveguides have a hollow core for high-power laser delivery and their relatively simple structure and potential low cost. They have become the most important IR waveguides.Infrared hollow waveguides may be grouped into two categories:1) those whose inner core materials have refractive indices greater than one (leaky guides) and2) those whose inner wall material has a refractive index less than one (attenuated total reflectance guides). Leaky or n>1guides have metallic(especially silver) and dielectric films deposited on the inside of metallic, plastic, or glass tubing. Leaky guides are normally fabricated by using liquid-phase coating techniques and depositing metallic and dielectric coating inside capillary tubing. GeO2fibers are fabricated by depositing GeO2film inside glass tubing using chemistry liquid-phase coating techniques or chemistry vapor deposition, while hollow sapphire fibers are single-crystal fibers grown by the laser-heated pedestal growth method. By establishing a ray model, the transmission loss can be calculated in consider of the surface irregularities.To measure the loss property of infrared hollow fiber, the beam was guided out of the FT-IR spectrometer and a sample compartment was built outside along with the detector outside. 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. 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.Infrared hollow waveguides can be good probes for the Raman and infrared spectroscopy. as it has no end reflection and scattering, none toxicity and good flexibility. This help the infrared hollow waveguides useful for endoscopic measurements inside the body. Several probes made by infrared hollow waveguides are given, and the characteristics are discussed.