A research program for development and field testing of fiber-optic sensors for monitoring geological environments : proposal to U.S. Department of Energy

"This proposal seeks to address major issues leading to improvement of fiber-optic geothermal probe and sensor designs for use in wells of 3 km (or more) depth. The main issue to be addressed is the increase in fiber-optic probe length. Current design limitations related to fiber-optic dispersion and attenuation at visible wavelengths have limited such probes to 300 meters (Sharma et al., 1990). We thus seek,' in this work, to develop fiber-optic sensors that operate at near-infrared (NIR) wavelengths where optical fibers have highest transmission. This is the same spectral range used by the communications industry for transmitting data at distance up to 200 km through optical fiber without the need for repeater amplifiers."