Cryogenic fiber optic temperature sensor

A temperature-referenced, chemical-monitoring transducer comprising:

• a chemical-monitor sensor, the chemical-monitor sensor for detecting changes in refractive index of a chemical, the chemical-monitor sensor having:
• a first optical fiber, the first optical fiber for carrying a first optical signal, the first optical fiber having:
• a thermal expansion coefficient and
• at least one core,
• the first optical fiber further comprising:
• a first grating associated with the core of the first optical fiber of the chemical-monitor sensor at a location along the first optical fiber, the first grating of the first optical fiber for selectively altering the first signal, and
• a total internal reflection reducer, the total internal reflection reducer for reducing the amount of first signal subject to total internal reflection within the core of the first optical fiber;
• and
• the temperature-referenced, chemical-monitoring transducer further comprising a temperature-reference sensor for providing signal regarding temperature changes associated with the chemical, the temperature-reference sensor having:
• a second optical fiber, the second optical fiber for carrying a second optical signal, the second optical fiber having:
• a length,
• a thermal expansion coefficient, and
• at least one core and
• at least one cladding,
• the second optical fiber further comprising:
• a second grating associated with the core of the second optical fiber at a location along the length of the second optical fiber, the second grating for selectively altering the second signal;
• and
• a coating integrated with the cladding at the location, the coating for increasing the sensitivity of the temperature-reference sensor to changes in temperature at the location, the coating having a thermal expansion coefficient that is larger than the thermal expansion coefficient of the second optical fiber,
• whereby, when the chemical-monitoring sensor and the temperature-reference sensor are in proximity to each other and when the chemical-monitoring sensor and the temperature-reference sensor are in the presence of the chemical, changes in refractive index of the chemical can cause a change in the first signal which is compensable by a change in the second signal.

A process for making an optical fiber temperature transducer, the optical fiber for carrying an optical signal, the optical fiber having:

• a length,
• a thermal expansion coefficient, and
• at least one core and
• at least one cladding,
• the process comprising the steps of:
• associating a grating with the core of the optical fiber at a location along the length of the optical fiber, the grating for selectively altering portions of the signal carried by the optical fiber;
• and
• integrating a coating with the cladding at the location, the coating for increasing the sensitivity of the transducer to changes in temperature at the location, the coating having a thermal expansion coefficient that is larger than the thermal expansion coefficient of the optical fiber.

A process of making a temperature-referenced, chemical-monitoring transducer comprising the steps of:

• fabricating a chemical-monitor sensor, the chemical-monitor sensor for detecting changes in refractive index of a chemical, the chemical-monitor sensor having:
• a first optical fiber, the first optical fiber for carrying a first optical signal, the first optical fiber having:
• a thermal expansion coefficient and
• at least one core,
• the chemical-monitor sensor made according to a process comprising the steps of:
• associating a first grating with the core of the first optical fiber of the chemical-monitor sensor at a location along the first optical fiber, the first grating of the first optical fiber for selectively altering the first signal, and
• reducing the amount of optical signal subject to total internal reflection within the core of the first optical fiber;
• and
• the process of making a temperature-referenced, chemical-monitoring transducer further comprising the steps of fabricating a temperature-reference sensor for providing signal regarding temperature changes associated with the chemical, the temperature-reference sensor having:
• a second optical fiber, the second optical fiber for carrying a second optical signal, the second optical fiber having:
• a length,
• a thermal expansion coefficient, and
• at least one core and
• at least one cladding,
• the temperature-reference sensor made according to a process comprising the steps of:
• associating a second grating with the core of the second optical fiber at a location along the length of the second optical fiber, the second grating for selectively altering the second signal carried by the second optical fiber;
• and
• integrating a coating with the cladding at the location, the coating for increasing the sensitivity of the temperature-reference sensor to changes in temperature at the location, the coating having a thermal expansion coefficient that is larger than the thermal expansion coefficient of the second optical fiber,
• whereby, when the chemical-monitor sensor and the temperature-reference sensor are in proximity to each other and when the chemical-monitor sensor and the temperature-reference sensor are in the presence of the chemical, changes in refractive index of the chemical can cause a change in the first signal which will be compensable by a change in the second signal.