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

Embedded optical fibre sensors are considered for structural health monitoring purposes in numerous applications. In fibre reinforced plastics, embedded fibre Bragg gratings are found to be one of the most popular and reliable solutions for strain monitoring. Despite of their growing popularity, users should keep in mind their shortcomings, many of which are associated with the embedding process. This review paper starts with an overview of some of the technical issues to be considered when embedding fibre optics in fibrous composite materials. Next, a monitoring scheme is introduced which shows the different steps necessary to relate the output of an embedded FBG to the strain of the structure in which it is embedded. Each step of the process has already been addressed separately in literature without considering the complete cycle, from embedding of the sensor to the internal strain measurement of the structure. This review paper summarizes the work reported in literature and tries to fit it into the big picture of internal strain measurements with embedded fibre Bragg gratings. The last part of the paper focuses on temperature compensation methods which should not be ignored in terms of in-situ measurement of strains with fibre Bragg gratings. Throughout the paper criticism is given where appropriate, which should be regarded as opportunities for future research.

https://biblio.ugent.be/publication/1152717/file/1265945.pdf

Strain measurements of composite laminates with embedded fibre Bragg gratings : criticism and opportunities for research

A fibre optic strain sensor based on Rayleigh backscatter using a time division multiplexing scheme with an optical pulse is presented. The sensor has a gauge length of <0.5 m and a strain sensitivity of <1 n/spl epsiv///spl radic/Hz at 2 kHz.

Strain sensing based on coherent Rayleigh scattering in an optical fibre

The distributed feedback (DFB) fiber laser strain sensor has demonstrated strain resolution comparable to that obtained from high-performance fiber-optic interferometry. This manuscript describes the characteristics and performance of this fiber laser strain sensor and discusses the technological developments necessary to obtain comparable performance from a multiplexed array of laser sensors. The design of the Bragg grating and doped fiber are discussed, where possible providing simplified equations to quantify the relevant design parameters. Techniques based on fiber-optic interferometry to decode the wavelength shifts of the laser are presented and potential noise sources are described. Measurements conducted on a test laser demonstrate the capability of the DFB fiber laser to resolve effective length changes to less than 0.76 fm/Hz1/2 at 2 kHz. The accuracy of the strain measurement, calculated by subtracting the output of two lasers subjected to the same strain, is found to be less than 1%. Issues relating to multiplexing lasers, such as pump power depletion and optical feedback, are described along with methods to maximize the number of lasers serially multiplexed on a single fiber. Finally, the strain transduction mechanism and methods to mount the laser sensor are described. It is shown that for certain applications, the DFB fiber laser sensor provides significant performance benefits when compared with remotely interrogated fiber-optic interferometric sensing techniques.

Distributed Feedback Fiber Laser Strain Sensors

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

A new optical sensing device containing fiber Bragg gratings (26), a scanning bandpass filter (28), an interferometer (40) and multiple photodetectors (44, 46, 48) is disclosed. The present invention also describes a new system and method for fibre Bragg grating sensor interrogation and multiplexing. The new system combines a scanning Fabry-Perot bandpass filter used to wavelength-multiplex multiple gratings in a single fiber, and an unbalanced Mach-Zehnder fibre interferometer made with a 3x3 coupler to detect strain-induced wavelength shifts.

Optical sensing device containing fiber bragg gratings

The authors describe a passive technique for sensing the strain-induced wavelength shift of a fibre Bragg grating (FBG) using a Mach-Zehnder interferometer that utilises a 3/spl times/3 coupler. Laboratory data show that a resolution of /spl sim/10 n/spl epsiv///spl radic/(Hz) RMS is achievable with inherent insensitivity to source intensity variations.

Passive, light intensity-independent interferometric method for fibre Bragg grating interrogation

We present a new technique for fiber Bragg grating (FBG) sensor interrogation and multiplexing. The technique combines a scanning bandpass filter used to multiplex by wavelength multiple gratings in a single fiber, and an unbalanced Mach-Zehnder fiber interferometer made with a 3/spl times/3 coupler to detect strain-induced wavelength shifts. A demonstration system interrogates four gratings in a single fiber at a sampling rate up to 20 kHz, with a noise floor measured at less than 10 n/spl epsiv///spl radic/(Hz) above 0.1 Hz.

Fiber Bragg grating interrogation and multiplexing with a 3/spl times/3 coupler and a scanning filter

An experimental investigation of strain gradient induced spectral broadening in fibre Bragg grating (FBG) based transducers is carried out. Closed form analytical results describing measurand induced strain gradients in circular geometry transducers are derived, which allow experimental demonstration of novel FBG bonding approaches which eliminate spectral broadening and should lead to the development of advanced FBG based transducers.

https://ieeexplore.ieee.org/iel4/2220/15492/00715385.pdf

Spectral broadening due to non-uniform strain fields in fibre Bragg grating based transducers

: Two tests, one involving a bent beam in the laboratory and one involving tensile testing of a ship hull substructure at Naval Surface Warfare Center/Carderock, were performed where strain readings were compared between conventional resistive strain gages (RSGs) and optical fiber Bragg gratings (FBGs) The closely matched results indicate the utility of FBG strain monitoring systems in the structural health field

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA370789&Location=U2&doc=GetTRDoc.pdf

Chia-Chen Chang

Papers

Optical sensing device containing fiber bragg gratings

Passive, light intensity-independent interferometric method for fibre Bragg grating interrogation

Fiber Bragg grating interrogation and multiplexing with a 3/spl times/3 coupler and a scanning filter

Spectral broadening due to non-uniform strain fields in fibre Bragg grating based transducers

The Use of Fiber Bragg Grating Strain Sensors in Laboratory and Field Load Tests: Comparison to Conventional Resistive Strain Gages