Low-coherence Fiber-optic Sensors Research Articles

Integration of fiber-optic sensors in measuring machines

In last years, optical metrology due to its capability in miniaturization and sensitivity became the primary solution in measurement of complex geometries and fragile pieces. Here, we propose a promising approach to perform highly accurate distance measurements using low-coherence fiber-optic sensors for quality inspection of nozzle orifices in fuel injection systems. In this effort, we develop an adaptive image processing algorithm in MATLAB and install the necessary hardware on a form tester to accelerate and simplify the aligning process. As a result, the repeatability of measurements is one order of magnitude improved while the standard deviation is almost 60% reduced.

A Novel Common Path Interferometric Technique for Vibration Measurement Based on Two Fiber-Optic Couplers

A novel common path demodulation technique for low-coherence fiber-optic sensors for vibration measurement based on two serially connected fused silica fiber-optic directional couplers is presented. A 2 × 2 coupler is used in the sensor arm and a 3 × 3 coupler serves as a receiving interferometer, providing at the same time two quadrature signals for the interferometric demodulation. A very stable output signal is obtained after the differentiate-and-cross-multiply procedure with the minimal detectable amplitude of the vibration of about 70 pm/√Hz.

Low-coherence fiber-optic sensor ring network based on a Mach–Zehnder interrogator

A quasi-distributed fiber sensor system for smart-structure applications is proposed. The system is based on a fiber loop topology and interrogated by use of white-light interferometry. The results of preliminary experiments and a power budget analysis are presented.

Low-coherence fiber-optic sensor with a large numerical aperture for topographic measurements

We describe a compact fiber-optic setup for three-dimensional topometry. The measuring principle is based on low-coherence interferometry in combination with a confocal microscope. Integrating an optical arrangement based on compact disk optics together with fiber optics into one sensor yields a compact unit. The sensor has a numerical aperture of 0.45 and is suitable for measuring large surface slopes with high spatial resolution. Further, a depth measuring range of more than 1 mm can be achieved. The capabilities of our setup for three-dimensional measurements are demonstrated.