Optical fibers have been involved in the area of sensing applications for more than four decades. Moreover, interferometric optical fiber sensors have attracted broad interest for their prospective applications in sensing temperature, refractive index, strain measurement, pressure, acoustic wave, vibration, magnetic field, and voltage. During this time, numerous types of interferometers have been developed such as Fabry-Perot, Michelson, Mach-Zehnder, Sagnac Fiber, and Common-path interferometers. Fabry-Perot interferometer (FPI) fiber-optic sensors have been extensively investigated for their exceedingly effective, simple fabrication as well as low cost aspects. In this study, a wide variety of FPI sensors are reviewed in terms of fabrication methods, principle of operation and their sensing applications. The chronology of the development of FPI sensors and their implementation in various applications are discussed.

https://www.mdpi.com/1424-8220/14/4/7451/pdf-vor

Chronology of Fabry-Perot interferometer fiber-optic sensors and their applications: a review.

An apparatus and method for diagnosis or treatment of a vessel or organ. The apparatus includes a deformable body such as a catheter having a tissue ablation end effector and an irrigation channel in fluid communication therewith. At least two sensors are disposed within a distal extremity of the deformable body, the sensors being responsive to a wave in a specified range of frequency to detect deformations resulting from a contact force applied to the distal extremity. A microprocessor can be operatively coupled with the sensors to receive outputs therefrom, the microprocessor being configured to resolve a multi-dimensional force vector corresponding to the contact force. In one embodiment, the sensors are fiber Bragg grating sensors, and the wave is injected into the fiber Bragg grating strain sensors from a laser diode.

Medical apparatus system having optical fiber load sensing capability

A diaphragm-based interferometric fiber optic sensor that uses a low-coherence light source was designed and tested for on-line detection of the acoustic waves generated by partial discharges inside high-voltage power transformers The sensor uses a fused-silica diaphragm and a single-mode optical fiber encapsulated in a fused-silica glass tube to form an extrinsic Fabry-Perot interferometer, which is interrogated by low-coherence light Test results indicate that these fiber optic acoustic sensors are capable of faithfully detecting acoustic signals propagating inside transformer oil with high sensitivity and wide bandwidth

/pdf/fiber-fabry-perot-sensors-for-detection-of-partial-5giyjj5cok.pdf

Fiber Fabry-Perot Sensors For Detection Of Partial Discharges in Power Transformers

A catheter for diagnosis or treatment of a vessel or organ is provided in which a flexible elongated body includes a tri-axial force sensor formed of a housing and a plurality of optical fibers associated with the housing that measure changes in the intensity of light reflected from the lateral surfaces of the housing resulting from deformation caused by forces applied to a distal extremity of the housing. A controller receives an output of the optical fibers and computes a multi-dimensional force vector corresponding to the contact force.

Catheter having tri-axial force sensor

The fabrication and experimental investigation of a miniature optical fiber pressure sensor for biomedical and industrial applications are described. The sensor measures only 125 µm in diameter. The essential element is a thin polymer diaphragm that is positioned inside the hollow end of an optical fiber. The cavity at the fiber end is made by a simple and effective micromachining process based on wet etching in diluted HF acid. Thus a Fabry–Perot interferometer is formed between the inner fiber–cavity interface and the diaphragm. The fabrication technique is described in detail. Different sensor prototypes were fabricated upon 125 µm-diameter optical fiber that demonstrated pressure ranges from 0 to 40 and from 0 to 1200 kPa. A resolution of less than 10 Pa was demonstrated in practice. The fabrication technique presented facilitates production of simple and low-cost disposable pressure sensors by use of materials with that ensure the required biocompatibility.

Miniature fiber-optic pressure sensor with a polymer diaphragm

A three-wavelength-based passive quadrature digital phase-demodulation scheme has been developed for readout of fiber-optic extrinsic Fabry–Perot interferometer vibration, acoustic, and strain sensors. This scheme uses a superluminescent diode light source with interference filters in front of the photodiodes and real-time arctan calculation. Quasi-static strain and dynamic vibration sensing with up to an 80-kHz sampling rate is demonstrated. Periodic nonlinearities owing to dephasing with increasing fringe number are corrected for with a suitable algorithm, resulting in significant improvement of the linearity of the sensor characteristics.

Fiber-optic extrinsic Fabry–Perot interferometer sensors with three-wavelength digital phase demodulation

A fiber-optic extrinsic Fabry-Perot interferometer strain sensor (EFPI-S) of ls = 25 cm sensor length using three-wavelength digital phase demodulation is demonstrated to exhibit <50 pm displacement resolution (<2nm/m strain resolution) when measuring the cross expansion of a PZT-ceramic plate The sensing (single-mode downlead-) and reflecting fibers are fused into a 150/360 microm capillary fiber where the fusion points define the sensor length Readout is performed using an improved version of the previously described three-wavelength digital phase demodulation method employing an arctan-phase stepping algorithm In the resent experiments the strain sensitivity was varied via the mapping of the arctan - lookup table to the 16-Bit DA-converter range from 18825 k /V (6 Volt range 1130 k ) to 117 k /Volt (range 70 k )

Fiber-optic extrinsic Fabry-Perot interferometer strain sensor with <50 pm displacement resolution using three-wavelength digital phase demodulation

In this paper the development of a 180° high resolution video panorama system and results of initial field test at Braunschweig research airport are described. The system serves as main HMI for remote surface movement management of small airports or of movement areas not directly visible for the controller. It provides the framework for video-see-through augmented vision by integration of traffic and weather data and it allows for panorama replay. Preliminary evaluation of initial field tests quantify the visual resolution as compared to the real far view.

/pdf/development-of-an-augmented-vision-video-panorama-human-49wme6q3qz.pdf

Development of an augmented vision video panorama human-machine interface for remote airport tower operation

In this paper research is described which aims at the long term goal of a Virtual Airport Tower without the need of a real tower building, however with improved functionality. Specifically we address the intermediate step of a Remote Airport Tower Center (RTC) for remote surveillance and control of small airports. Because previous work and task analyses indicated the importance of the visual information for present days controller's work procedures, an experimental high resolution video panorama system was developed as main HMI. Field tests of the reconstructed far view yield the effective visual resolution of a 180°-video panorama in agreement with the theoretical predictions. The digital video panorama provides the framework for video-see-through augmented vision by integration of additional information like weather and transponder data, and it allows for panorama replay. An integrated zoom function provides a "foveal" component by means of a remotely controlled pan-tilt zoom camera, including object tracking options, with a high resolution exceeding the human eye within an observation angle smaller than 15°. Simulation environments are under development, based on a two-airport tower-simulator and a Petri-net based computer simulation using a simplified airport microworld. They support design of the new work environment and safety analysis.

https://www.enri.go.jp/eiwac/2009/pdf/StepsTowardstheVirtualTowerRemoteAirportTrafficControlCenterRAiCe.pdf

Steps towards the Virtual Tower: Remote Airport Traffic Control Center (RAiCe)

In this paper the initial results of the DLR project Remote Airport Tower Operation Research (RapTOr) are described. Within this project an augmented vision video panorama system and a corresponding HMI is developed for remote surface movement management of small airports or of movement areas not directly visible for the controller. Ground traffic management is performed from a remotely located control center, e.g. a tower at a different airport. The setup and functions of the high resolution video panorama system with integrated pan-tilt zoom camera (PTZ) at Braunschweig research airport is described. It provides the framework for integrating SMGCS traffic data, real time image processing and replay possibility of the complete 180° - panorama. Furthermore we describe how the results of a formal tower work analysis are transferred into a cognitive operator model for simulating the RTO controller work processes to be integrated into the conventional tower work environment.

/pdf/remote-airport-tower-operation-with-augmented-vision-video-1yv5qc69t2.pdf

Markus Schmidt

Papers

Fiber-optic extrinsic Fabry–Perot interferometer sensors with three-wavelength digital phase demodulation

Fiber-optic extrinsic Fabry-Perot interferometer strain sensor with <50 pm displacement resolution using three-wavelength digital phase demodulation

Development of an augmented vision video panorama human-machine interface for remote airport tower operation

Steps towards the Virtual Tower: Remote Airport Traffic Control Center (RAiCe)

Remote Airport Tower Operation with Augmented Vision Video Panorama HMI