Dynamic curvature sensing using time expanded ΦOTDR.

Shape sensing can be accomplished using optical fiber sensors through different interrogation principles such as fiber Bragg gratings, optical frequency-domain reflectometry (OFDR), or optical time-domain reflectometry (OTDR). These techniques are either not entirely distributed, have poor performance in dynamic sensing, or are only valid for few-meter-long fibers. Here, we present a system able to perform distributed curvature sensing with a range of 125 m, 10-cm resolution, and a sampling rate of 50 Hz.

Time-expanded φOTDR using low-frequency electronics.

Time expanded phase-sensitive optical time-domain reflectometry (TE-φOTDR) is a recently reported technique for distributed optical fiber sensing based on the interference of two mutually coherent optical frequency combs. This approach enables distributed acoustic sensing with centimeter resolution while keeping the detection bandwidth in the megahertz range. In this paper, we demonstrate that TE-φOTDR can be realized with low-frequency electronics for both signal generation and detection.

Dual electro-optic comb spectroscopy using a single pseudo-randomly driven modulator.

We present a dual-comb scheme based on a single intensity modulator driven by inexpensive board-level pseudo-random bit sequence generators. The result is a simplified architecture that exhibits a long mutual coherence time (up to 50 s) with no need of stabilization feedback loops or self-correction algorithms. Unlike approaches that employ ultrafast arbitrary waveform generators, our scheme makes it possible to produce long interferograms in the time domain, reducing the difference in the line spacing of the combs even below the hertz level.

Monitoring of a Highly Flexible Aircraft Model Wing Using Time-Expanded Phase-Sensitive OTDR.

In recent years, the use of highly flexible wings in aerial vehicles (e.g., aircraft or drones) has been attracting increasing interest, as they are lightweight, which can improve fuel-efficiency and distinct flight performances.

Long-Range Distributed Solar Irradiance Sensing Using Optical Fibers.

Until recently, the amount of solar irradiance reaching the Earth surface was considered to be a steady value over the years. However, there is increasing observational evidence showing that this quantity undergoes substantial variations over time, which need to be addressed in different scenarios ranging from climate change to solar energy applications. With the growing interest in developing solar energy technology with enhanced efficiency and optimized management, the monitoring of solar irradiance at the ground level is now considered to be a fundamental input in the pursuit of that goal.

Distributed sensing of microseisms and teleseisms with submarine dark fibers.

Sparse seismic instrumentation in the oceans limits our understanding of deep Earth dynamics and submarine earthquakes. Distributed acoustic sensing (DAS), an emerging technology that converts optical fiber to seismic sensors, allows us to leverage pre-existing submarine telecommunication cables for seismic monitoring. Here we report observations of microseism, local surface gravity waves, and a teleseismic earthquake along a 4192-sensor ocean-bottom DAS array offshore Belgium.

Distributed Acoustic Sensing Using Chirped-Pulse Phase-Sensitive OTDR Technology.

In 2016, a novel interrogation technique for phase-sensitive (Φ)OTDR was mathematically formalized and experimentally demonstrated, based on the use of a chirped-pulse as a probe, in an otherwise direct-detection-based standard setup: chirped-pulse (CP-)ΦOTDR. Despite its short lifetime, this methodology has now become a reference for distributed acoustic sensing (DAS) due to its valuable advantages with respect to conventional (i.e.

Fiber-based distributed bolometry.

Optical fibers are inherently designed to allow no interaction between the guided light and the surrounding optical radiation. Thus, very few optical fiber-based technologies exist in the field of optical radiation sensing. Accomplishing fully-distributed optical radiation sensing appears then as even more challenging since, on top of the lack of sensitivity explained above, we should add the need of addressing thousands of measurement points in a single, continuous optical cable.

Long-range distributed optical fiber hot-wire anemometer based on chirped-pulse ΦOTDR.

We demonstrate a technique allowing to develop a fully distributed optical fiber hot-wire anemometer capable of reaching a wind speed uncertainty of ≈ ±0.15m/s (±0.54km/h) at only 60 mW/m of dissipated power in the sensing fiber, and within only four minutes of measurement time.

SNR enhancement in high-resolution phase-sensitive OTDR systems using chirped pulse amplification concepts.

Phase-sensitive optical time-domain reflectometry (φOTDR) is widely used for the distributed detection of mechanical or environmental variations with resolutions of typically a few meters. The spatial resolution of these distributed sensors is related to the temporal width of the input probe pulses. However, the input pulse width cannot be arbitrarily reduced (to improve the resolution), since a minimum pulse energy is required to achieve a good level of signal-to-noise ratio (SNR), and the pulse peak power is limited by the advent of nonlinear effects.

A Novel Fiber Optic Based Surveillance System for Prevention of Pipeline Integrity Threats.

This paper presents a novel surveillance system aimed at the detection and classification of threats in the vicinity of a long gas pipeline. The sensing system is based on phase-sensitive optical time domain reflectometry (-OTDR) technology for signal acquisition and pattern recognition strategies for threat identification. The proposal incorporates contextual information at the feature level and applies a system combination strategy for pattern classification.

Phase-sensitive OTDR probe pulse shapes robust against modulation-instability fading.

Typical phase-sensitive optical time-domain reflectometry (ϕOTDR) schemes rely on the use of coherent rectangular-shaped probe pulses. In these systems, there is a trade-off between the signal-to-noise ratio (SNR), spatial resolution, and operating range of the ϕOTDR system. To increase any of these parameters, an increase in the pulse peak power is usually indispensable.

Serratia marcescens osteomyelitis in Cushing's disease.

We report a case of a 46-year-old man with fever, hypotension and arthralgias of the ankles and knees after brain surgery for a pituitary tumour causing Cushing's disease. Blood and urine cultures isolated Serratia marcescens; antibiotic susceptibility testing showed sensitivity to piperacillin-tazobactan and ciprofloxacin. Articular MRI showed inflammation and necrosis of both knees and ankles, and left hip and right elbow (compatible with osteomyelitis).

Distributed phase birefringence measurements based on polarization correlation in phase-sensitive optical time-domain reflectometers.

In this paper a technique to measure the distributed birefringence profile along optical fibers is proposed and experimentally validated. The method is based on the spectral correlation between two sets of orthogonally-polarized measurements acquired using a phase-sensitive optical time-domain reflectometer (ϕOTDR). The correlation between the two measured spectra gives a resonance (correlation) peak at a frequency detuning that is proportional to the local refractive index difference between the two orthogonal polarization axes of the fiber.

PROUD-based method for simple real-time in-line characterization of propagation-induced distortions in NRZ data signals.

A simple, in-line method for real-time full characterization (amplitude and phase) of propagation distortions arising because of group velocity dispersion and self-phase modulation on 10-20 Gbps transmitted NRZ optical signals is reported. It is based on phase reconstruction using optical ultrafast differentiation (PROUD), a linear and self-referenced technique. The flexibility of the technique is demonstrated by characterizing different data stream scenarios.

High-sensitivity dispersive Mach-Zehnder interferometer based on a dissimilar-doping dual-core fiber for sensing applications.

A dual-core fiber in which one of the cores is doped with germanium and the other with phosphorus is used as an in-line Mach-Zehnder dispersive interferometer. By ensuring an equal length but with different dispersion dependencies in the interferometer arms (the two cores), high-sensitivity strain and temperature sensing are achieved. Opposite sensitivities for high and low wavelength peaks were also demonstrated when strain and temperature was applied.

Modulation instability-induced fading in phase-sensitive optical time-domain reflectometry.

Phase-sensitive optical time-domain reflectometry (φOTDR) is a simple and effective tool allowing the distributed monitoring of vibrations along single-mode fibers. We show in this Letter that modulation instability (MI) can induce a position-dependent signal fading in long-range φOTDR over conventional optical fibers. This fading leads to a complete masking of the interference signal recorded at certain positions and therefore to a sensitivity loss at these positions.

Diffractive micro bar codes for encoding of biomolecules in multiplexed assays.

Microparticles incorporating micrometer-sized diffractive bar codes have been modified with oligonucleotides and immunoglobulin Gs to enable DNA hybridization and immunoassays. The bar codes are manufactured using photolithography of a chemically functional commercial epoxy photoresist (SU-8). When attached by suitable linkers, immobilized probe molecules exhibit high affinity for analytes and fast reaction kinetics, allowing detection of single nucleotide differences in DNA sequences and multiplexed immunoassays in <45 min.

Covalent attachment of proteins to solid supports and surfaces via Sortase-mediated ligation.

Background: There is growing interest in the attachment of proteins to solid supports for the development of supported catalysts, affinity matrices, and micro devices as well as for the development of planar and bead based protein arrays for multiplexed assays of protein concentration, interactions, and activity. A critical requirement for these applications is the generation of a stable linkage between the solid support and the immobilized, but still functional, protein.

Methodology: Solid supports including crosslinked polymer beads, beaded agarose, and planar glass surfaces, were modified to present an oligoglycine motif to solution.

Multistep synthesis on SU-8: combining microfabrication and solid-phase chemistry on a single material.

SU-8 is an epoxy-novolac resin and a well-established negative photoresist for microfabrication and microengineering. The photopolymerized resist is an extremely highly crosslinked polymer showing outstanding chemical and physical robustness with residual surface epoxy groups amenable for chemical functionalization. In this paper we describe, for the first time, the preparation and surface modification of SU-8 particles shaped as microbars, the attachment of appropriate linkers, and the successful application of these particles to multistep solid-phase synthesis leading to oligonucleotides and peptides attached in an unambiguous manner to the support surface.