Abstract: The silver halide was purified by melting at high vacuum, zone melting with reactive atmosphere and crystal growing in quartz ampoule with high vacuum.
The silver halide fibers were made by hot extrusion. The effects of the purification of silver halide and its fiber preparation method on transmission loss were studied. Experiment results show that the increase of the number
of times of the starting material purification will cause the decrease of absorption coefficient of silver halide preform. A high quality preform was
obtained by a reasonable technology. The absorption coefficient of the purified　silver halide preform measured by CO₂ laser calorimeter is less than 5×10^-4cm^-1. The transmission loss of the silver halide fiber is 0.3--0.5dB/m when measured by CO₂ laser beam at 10.6μm. Its output
power of transmitting CO₂ laser beam is more than 20W in the fiber of 1.0mm diameter and 1.64m length.

Key words: infrared optical fiber, silver halide, loss