Fiber optics temperature and pressure probe

The feasibility of remote sensing of pressure in a hostile or inaccessible environment using a single fiber and a spectroscopic sensor is described. This type of system is immune to electromagnetic noise, low in cost, rugged, and has a sensing volume of less than 4 x 10 to the -6 power/cm cu. In particular, a ruby crystal was evaluated as an optical fiber-spectroscopic sensor for pressure, because ruby has been used as a hydrostatic pressure sensor in gasketted diamond anvil cells. It is anticipated that remote pressure measurements will be non-isothermal in contrast to the isothermal diamond anvil pressure measurements. Since the coefficients of linear compression are isotropic and the thermal coefficients are anisotropic, this suggests that a ruby sensor could measure both temperature and pressure. This article examines the practicality of using a ruby sensor as a non-isothermal pressure sensor. The design criteria for an optical-fiber/ruby-sensor fluorometer was critically characterized.