We demonstrate a 1km long optical fiber with continuous grating enhanced back scattering and attenuation close to standard single mode fiber. Scattering was observed to be more than 10dB above the Rayleigh back scattering of the optical fiber over a 10nm bandwidth between 1542 and 1552nm. The fiber attenuation was estimated to be 0.4dB/km. Our result was enabled through the fabrication of a standard single mode fiber with a UV transparent coating and reel to reel continuous UV grating inscription over more than 1km. We anticipate that enhanced scattering fiber will have impact in many sensor systems that rely on optical back scatter, including distributed acoustic sensing, security applications and structural health monitoring.
We describe the fabrication and performance of a continuously grated twisted multicore fiber sensor array. The grated fiber sensor comprises nearly continuous Bragg gratings along its entire length. The gratings are inscribed over lengths in excess of 10m in fibers with UV transparent coating using a flexible and scalable reel to reel processing system. The arrays are tested using optical frequency domain reflectometry (OFDR). We report on automated analysis routines applied to these OFDR measurements that allow for characterization of 100s of individual grating exposures that make up a continuously grated fiber length. We also report on the spectral loss of the continuously grated fiber, showing that it is suitable for applications with sensors in excess of 100m. Finally, we report on the fiber sensing characteristics by performing measurements of fiber bend using a fiber shape reconstruction algorithm on OFDR traces obtained from four of the fiber cores.
We report on the optical and sensor performance characteristics of meter long continuous twisted multicore optical fiber gratings. We describe a method to analyze the optical performance of all the cores in the multicore array. We also report on the sensitivity of our arrays to local changes such as bend and twist. Our analysis provides guidance for the proper operating range of multicore fiber sensing arrays.
We report on improved spatial uniformity of sensor grating arrays in offset and multicore fibers. We show improvement over conventional side writing in such fibers, in which cores offset from the center of the fiber exhibit grating strength variations due to lensing at the fiber surface. Such strength variations can degrade the performance of sensing systems that rely on continuous scattering from offset cores along a fiber. Our improved system uses multicore fibers whose coating is UV transparent and applies index matching materials to mitigate lensing aberrations. We show that it is capable of continuously inscribing gratings over any length of fiber.
In this work we report on a fiber grating fabrication platform suitable for parallel fabrication of Bragg grating arrays over arbitrary lengths of multicore optical fiber. Our system exploits UV transparent coatings and has precision fiber translation that allows for quasi-continuous grating fabrication. Our system is capable of both uniform and chirped fiber grating array spectra that can meet the demands of medical sensors including high speed, accuracy, robustness and small form factor.
A novel approach for stripping cladding light from double clad fibers is demonstrated. This is achieved by index matching the cladding of the fiber with a glass capillary collapsed onto the fiber, allowing the cladding modes to expand in a larger volume of the capillary before they are dissipated through a high-index heat sink material into a metal package. We minimize the signal quality degradation by using a lower melting point capillary glass. We demonstrate a device with 100W cladding power removed with 99% (20dB) extinction. Continuous operation for an hour without any power degradation is demonstrated.
In this paper we report on the development of a complete integrated optical fiber assembly suitable for shape sensing.
Our shape sensor module consists of a length (>1m) of twisted multicore optical fiber with fiber Bragg gratings inscribed
along its length. Our fiber has a compact 180 micron coated diameter, a twist of 50 turns per meter and grating
reflectivities greater than 0.01% per cm of array, suitable for high efficiency scatter measurements over many meters of
fiber. Single core to multicore fanouts and low reflectivity fiber termination are used to terminate the end of the array.