White Paper: Reliable Large Acceptance Optical Fibers For High Power Transmission

The UV and VIS spectral losses of high-OH Hard Plastic Clad Silica (HPCS) fiber were measured along with the NIR and VIS spectral losses of low-OH HPCS fiber with nominal core diameter for both types was 600 mm. High-OH fibers typically have >600 ppm of OH, while low-OH fibers typically have <2-4 ppm of OH.

A "cutback" method was employed using a Monolight Optical Spectrum Analyzer (OSA), manufactured by Macam Photometric Ltd of Livington, Scotland. The system includes a scanning monochromator, a 3-channel controller, a power supply, two light sources (deuterium and tungsten), and input and output blocks to handle fiber from 70 µm to 1000 µm in diameter.

The "cutback" method consisted of using two pieces of same-type fiber with a length ratio of about 1:4 or 1:5. Long lengths of over 25 m were measured via a Tektronix ODTR, and shorter lengths were manually calculated (i.e. the number of loops were counted and multiplied by P times the diameter of the spool.) The "cutback" length (in meters) was calculated by subtracting the shorter length from the longer length of fiber. More complete details on the spectral measurements were reported earlier.