An Optical Fibre Pressure Sensor

Fiber optical sensors for aircraft applications

“…Therefore, in practice a second light source of different wavelength λ 2 is added, resulting in a second fringe pattern that is shifted with respect to the fringe pattern at λ 1 . Undesirable intensity variations are largely common to both fringe patterns and can be eliminated by taking the ratio of both intensities 22 . Typically, the ratio is converted into an analog output voltage V PDC .…”

A frequency-modulated continuous wave birefringent fibre-optic strain sensor based on a Sagnac ring configuration

“…It is important that linearly polarized light be initially launched into only one of the two eigenmodes of the fibre. The optical fields for the modes shown in figures 1(a) and 1(b) are each described by a series of Mathieu functions [1]. Assuming that any eccentricity (e = [1 − (b/a) 2 ] 1/2 ) is minimal and that the system is operated at the single-mode threshold (normalized frequency ν = 2.4), the propagation number difference β can be written as…”

“…Although their measurement accuracy is generally limited by variations in environmental conditions, this apparent drawback can be turned to advantage if a Sagnac ring configuration is used to measure environmental parameters. In the past, sensor systems involving Sagnac ring and Mach-Zehnder interferometers were used to measure the rapid changes of temperature experienced by the fibre [1,2]. Later, several Sagnac distributed sensor schemes which allow the simultaneous determination of the position and amplitude of a time-varying environmental disturbance were reported [3].…”