In a preferred embodiment, the invention provides a
fiber optic
pressure sensor apparatus which includes a
light source, a reflective sensor diaphragm movable in accordance with pressure in a medium and an
optical fiber coupled to the
light source for delivering a first
wavefront of light to the reflective sensor diaphragm. The
optical fiber has an endface which is separated from the reflective sensor diaphragm by a gap, the endface receiving a second
wavefront of light reflected from the reflective sensor diaphragm. The first and second wavefronts constructively and destructively interfere to create a modulated optical
signal. A
spectrometer is coupled to the
optical fiber for converting the optical
signal into a series of digital values, and means for analyzing the digital values is provided for obtaining a measurement of the pressure in the medium. An
optical coupler is preferably provided for
coupling the
light source, the optical
fiber, and the
spectrometer. A power monitoring
optical detector means may be coupled to the light source by the
optical coupler. A graded-index lens may be coupled to the endface of the optical
fiber. The angle between the endface and a longitudinal axis of the optical fiber may be formed to be between zero and 11 degrees. A sealed or vented sensor body may be provided. In sealed embodiments, organic adhesives are preferably used to seal the sensor body. The means for analyzing the digital values preferably includes means for recovering phase information from the modulated optical
signal by taking a
Fourier transform of the modulated optical signal. Sensor gap measurements are then derived from this phase information.