All optical fiber thermal vacuum gauge

A new concept of an all optical, dual-fiber-based Pirani thermal vacuum gauge is proposed and demonstrated. The configuration utilizes two fibers: one that produces heat, and one that responds to the resultant thermal exchange. The temperature of the latter fiber is a function of the heat transfer through the gas in which it resides. The active heat-generating fiber is a luminescence-quenched, heavily Yb³⁺-doped optical fiber that efficiently produces thermal energy when optically pumped. The temperature sensor is implemented with a conventional commercial fiber Bragg grating. Both fibers are inserted into a custom vacuum chamber whose internal pressure can be carefully controlled. Performance of the system is characterized with pressures ranging from 20 mTorr to Standard Pressure. The proposed system may also be used as a sensitive flow rate sensor.