Specialty optical fibers can be produced with a polyimide coating, which allows optical fibers to be used in environments up to 300°C. This type of fiber has been used extensively in the oil and gas industry to provide important communications and sensing functions for reservoir management.
For temperatures above 300°C, metal coatings would be attractive. Those produced to date have been deemed unsuitable for geothermal well deployment due to high attenuation values at low temperatures. Downstream oil processing can also benefit from high temperature measurements requiring low attenuation fibers that perform beyond 300°C.
In this paper, a metal-coated fiber capable of withstanding temperatures up to 500°C will be demonstrated. In addition, it will be shown that this fiber can be cycled between room temperature and 500°C, while maintaining low attenuation even at low temperatures.