A miniature Fabry-Perot (FP) interferometric fiber-optic sensor suitable for high-temperature sensing is proposed and demonstrated. The sensor head consists of two FP cavities formed by fusion splicing a short hollow-core fiber and a piece of single-mode fiber at a photonic crystal fiber in series. The reflection spectra of an implemented sensor are measured at several temperatures and analyzed in the spatial frequency domain. The experiment shows that the thermal-optic effect of the cavity material is much more appreciable than its thermal expansion. The temperature measurements up to 1000 degrees C with a step of 50 degrees C confirm that it could be applicable as a high-temperature sensor.

Miniature fiber-optic high temperature sensor based on a hybrid structured Fabry-Perot interferometer

A simple refractive index sensor based on a Michelson interferometer in a single-mode fiber is constructed and demonstrated. The sensor consists of a single symmetrically abrupt taper region in a short piece of single-mode fiber that is terminated by ~500 nm thick gold coating. The sensitivity of the new sensor is similar to that of a long-period-grating-type sensor, and its ease of fabrication offers a low-cost alternative to current sensing applications.

/pdf/refractive-index-sensor-based-on-an-abrupt-taper-michelson-4anbvgiyho.pdf

Refractive index sensor based on an abrupt taper Michelson interferometer in a single-mode fiber

Mach-Zehnder and Michelson interferometers using core-offset attenuators were demonstrated. As the relative offset direction of the two attenuators in the Mach-Zehnder interferometer can significantly affect the extinction ratio of the interference pattern, single core-offset attenuator-based sensors appear more robust and repeatable. A novel fiber Michelson interferometer refractive index (RI) sensor was subsequently realized by a single core-offset attenuator and a layer of ~ 500-nm gold coating. The device had a minimum insertion loss of 0.01 dB and maximum extinction ratio over 9 dB. The sensitivity (0.333 nm) of the new sensor to its surrounding RI change (0.01) was found to be comparable to that (0.252 nm) of an identical long period gratings pair Mach-Zehnder interferometric sensor, and its ease of fabrication makes it a low-cost alternative to existing sensing applications.

/pdf/single-mode-fiber-refractive-index-sensor-based-on-core-v0szfh8sys.pdf

Single-Mode Fiber Refractive Index Sensor Based on Core-Offset Attenuators

We report a compact and stable all-microstructured-optical-fiber interferometer built with two fusion splices separated a few centimeters from each other. The air-holes of the fiber are intentionally collapsed in the vicinity of the splices. This broadens the propagating optical mode, allowing coupling of two modes in the section between the splices. A truly sinusoidal interference pattern was observed from 800 nm to 1600 nm with fringe visibility reaching 80%. The fringe spacing was inversely proportional to the distance between the splices. The potential of the device for sensing applications is demonstrated.

https://www.icfo.eu/images/publications/J07-013.pdf

Simple all-microstructured-optical-fiber interferometer built via fusion splicing.

A Mach-Zehnder interferometer with two abrupt single-mode fiber tapers is simulated, constructed, and demonstrated. The interferometer has an insertion loss of 5 dB and an extinction ratio over 15 dB. The interferometer is tested as a strain sensor based on the maximum attenuation wavelength shift with a comparable sensitivity (slope: 2000 nm/ epsiv, R 2 = 0.996) with long-period-grating-type sensor and promises low fabrication cost.

In-Line Abrupt Taper Optical Fiber Mach–Zehnder Interferometric Strain Sensor

A novel fiber-optic in-fiber integrated Michelson interferometer has been proposed and demonstrated. It consists of a segment of two-core fiber with a mirrored fiber end. The sensing characteristics based on the two-core fiber bending, corresponding to the shift of the phase of the two-core in-fiber integrated Michelson interferometer, are investigated.

In-fiber integrated Michelson interferometer.

A novel laser interferometer which adopts alternating modulation phase tracking homodyne technique is proposed. The
vibration of nanometer-accuracy is measured with the improved Michelson interferometer by adding cat's eye moving
mirror and PZT phase modulation tracking structure. The working principle and the structure of the interferometer are
analyzed and the demodulation scheme of alternating phase modulation and tracking is designed. The signal detection is
changed from direct current detecting to alternating current detecting. The signal's frequency spectrum transform is
achieved, the low-frequency noise jamming is abated, the Signal-to-Noise of the system is improved and the measured
resolution is enhanced. Phase tracking technique effectively suppresses the low-frequency noise which is caused by
outside environment factors such as temperature and vibration, and the stability of the system is enhanced. The
experimental results indicate that for the signal with the frequency of 100Hz and the amplitude of 25nm, the output
Signal-to-Noise is 30dB and the measured resolution is 1nm.

Laser interferometer used for nanometer vibration measurements

A method for measuring and calibrating the thickness of thin films based on infrared interference technology

http://www.cell.com/article/S2405844023037167/pdf

Jiaxing Sun

Papers

In-fiber integrated Michelson interferometer.

Laser interferometer used for nanometer vibration measurements

A method for measuring and calibrating the thickness of thin films based on infrared interference technology

A high accuracy measurement method based on vortex polar axis rotation phase-shifting interferometry (VPAR-PSI)