| A fiber-optic temperature sensor was developed that is rugged, compact, stable, and can be inexpensively fabricated. This thin-film interferometric temperature sensor was shown to be capable of providing a {dollar}pm{dollar}2{dollar}spcirc{dollar}C accuracy over the range of {dollar}-{dollar}55 to 275{dollar}spcirc{dollar}C, throughout a 5000 hr operating life.; A temperature-sensitive thin-film Fabry-Perot interferometer can be deposited directly onto the end of a multimode optical fiber. This batch-fabricatable sensor can be manufactured at a much lower cost than can a presently available sensor, which requires the mechanical attachment of a Fabry-Perot interferometer to a fiber. The principal disadvantage of the thin-film sensor is its inherent instability, due to the low processing temperatures that must be used to prevent degradation of the optical fiber's buffer coating.; The design of the stable thin-film temperature sensor considered the potential sources of both short and long term drifts. The temperature-sensitive Fabry-Perot interferometer was a silicon film with a thickness of {dollar}sim{dollar}2 {dollar}mu{dollar}m. A laser-annealing process was developed which crystallized the silicon film without damaging the optical fiber. The silicon film was encapsulated with a thin layer of Si{dollar}sb3{dollar}N{dollar}sb4{dollar} overcoated with aluminum. Crystallization of the silicon and its encapsulation with a highly stable, impermeable thin-film structure were essential steps in producing a sensor with the required long-term stability. |
