Fiber Optic Displacement Probes in Liquid Oxygen

When the cryogenic medium is Liquid Oxygen (or Liquid Natural Gas), calibration in water is a better approximation than calibration in air:
Air Refractive Index = 1.000
Liquid Oxygen Refractive index = 1.221
LNG Refractive Index = 1.286
Water Refractive Index = 1.332

A sensor’s operating range is extended in proportion to the ratio of the refractive indices.

For example, to calculate a sensor’s response in LOX, first calibrate the sensor submerged in water. Then remap the displacement data by the ratio 1.221/1.332.

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