Showing papers on "Fiber Bragg grating published in 2003"
TL;DR: In this article, high quality retroreflecting fiber Bragg gratings were written in standard Ge-doped telecom fiber (Corning SMF-28) after a few minutes exposure with pulsed 800-nm, 120-fs laser radiation by use of a deep-etch silica zero-order nulled phase mask optimized for 800 nm.
Abstract: High-quality retroreflecting fiber Bragg gratings were written in standard Ge-doped telecom fiber (Corning SMF-28) after a few minutes exposure with pulsed 800-nm, 120-fs laser radiation by use of a deep-etch silica zero-order nulled phase mask optimized for 800 nm. Induced index modulations of 1.9×10-3 were achieved with peak power intensities of 1.2×1013 W/cm2 without any fiber sensitization. The fiber gratings are stable and did not erase after 2 weeks at 300 °C. The primary mechanism of induced index change results from a structural modification to the fiber core.
290 citations
TL;DR: In this paper, a fiber-optic system based on fiber Bragg grating sensors is proposed to detect ultrasonic Lamb waves in aircraft structures, in particular aircraft structural structures.
Abstract: This paper describes a fiber-optic system which is able to detect ultrasound in structures. The aim of the sensing system is to monitor structures, in particular aircraft structures, by detecting ultrasonic Lamb waves. This type of monitoring technique has recently become a key topic in structural health monitoring. Most common approaches use piezoceramic devices to launch and receive the ultrasound. A new way of fiber-optic detection of Lamb waves is based on fiber Bragg grating sensors. In addition to the well known advantages of fiber-optic sensors, this new interrogation scheme allows the use of Bragg gratings for both high-resolution strain and high-speed ultrasound detection. The focus of the paper is on the ultrasonic part of the system. The theoretical approach and the implementation into a laboratory set-up are elaborated. Experiments have been carried out to calibrate the system and first results on simple structures show the feasibility of the system for sensing ultrasonic Lamb waves.
280 citations
TL;DR: This work describes what is to their knowledge the first use of fiber Bragg gratings written into three separate cores of a multicore fiber for two-axis curvature measurement.
Abstract: We describe what is to our knowledge the first use of fiber Bragg gratings written into three separate cores of a multicore fiber for two-axis curvature measurement. The gratings act as independent, but isothermal, fiber strain gauges for which local curvature determines the difference in strain between cores, permitting temperature-independent bend measurement.
266 citations
TL;DR: In this article, a new type of interrogator for distributed fiber Bragg grating (FBG) sensors that employs an arrayed waveguide grating is proposed and its operating features are in detail investigated both theoretically and experimentally.
Abstract: A new type of interrogator for distributed fiber Bragg grating (FBG) sensors that employs an arrayed waveguide grating (AWG) is proposed and its operating features are in detail investigated both theoretically and experimentally. The remedy for achieving the linear characteristics of wavelength detection as well as for insuring the reliable and environmentally stable operation of interrogation is proposed and its usefulness is demonstrated in good agreement with the experimental results. The developed interrogator consists of a fully passive, small, all-solid, rugged optical IC and can detect wavelengths of a great number of FBG sensors with high precision better than 0.5 pm and high speed.
214 citations
Patent•
01 Oct 2003
TL;DR: In this paper, the authors used a high compliance material, resonating the ultrasound sensing transducer, using an attenuation-reducing coating and/or thickness, and using optical wavelength discrimination.
Abstract: An imaging guidewire can include one or more optical fibers communicating light along the guidewire. At or near its distal end, one or more blazed or other fiber Bragg gratings (FBGs) directs light to a photoacoustic transducer material that provides ultrasonic imaging energy. Returned ultrasound is sensed by an FBG sensor. A responsive signal is optically communicated to the proximal end of the guidewire, and processed to develop a 2D or 3D image. In one example, the guidewire outer diameter is small enough such that an intravascular catheter can be passed over the guidewire. Techniques for improving ultrasound reception include using a high compliance material, resonating the ultrasound sensing transducer, using an attenuation-reducing coating and/or thickness, and/or using optical wavelength discrimination. Techniques for improving the ultrasound generating transducer include using a blazed FBG, designing the photoacoustic material thickness to enhance optical absorption. Techniques for distinguishing plaque or vulnerable plaque may be used to enhance the displayed image.
198 citations
TL;DR: This work experimentally demonstrated coherent combining of 2 and then 4 fiber lasers, and theoretically confirmed that the combining method can be scaled to a large number of lasers without decreasing the combining efficiency.
Abstract: We have experimentally demonstrated coherent combining of 2 and then 4 fiber lasers, with respectively 99% and 95% combining efficiency. The combining method investigated here is based on a multi-arm resonator of interferometric configuration. In spite of its interferometric nature, the multi-arm laser operates without significant power fluctuations, even in an unprotected environment. This occurs when the arm length difference is large enough to introduce spectral modulations of period smaller than the laser bandwidth. We have also experimentally shown that the combining method is compatible with wavelength tuning. A Mach-Zehnder Fiber Laser was tuned over a wide spectral range of 60nm Theoretically then, we confirm that the combining method can be scaled to a large number of lasers without decreasing the combining efficiency.
176 citations
TL;DR: In this paper, the anomalous dispersion provided by the photonic-crystal fiber permits construction of a femtosecond fiber laser at 1 μm wavelength without prisms or diffraction gratings.
Abstract: A photonic-crystal fiber provides dispersion compensation in a soliton fiber laser. The anomalous dispersion provided by the photonic-crystal fiber permits construction of a femtosecond fiber laser at 1 μm wavelength without prisms or diffraction gratings. The laser produces ˜100-fs pulses with 1 nJ energy, and is a major step toward environmentally-stable all-fiber devices at 1 μm.
163 citations
01 Jan 2003
TL;DR: In this article, Raman Gap Solitons Experiments within the bandgap of a nonlinear fiber Bragg Grating were conducted in order to investigate the effect of pulse propagation in fiber Gratings with quadratic nonlinearity.
Abstract: 1 Introduction- 2 Theory of Nonlinear Pulse Propagation in Periodic Structures- 3 Polarization Effects in Birefringent, Nonlinear, Periodic Media- 4 Raman Gap Solitons in Nonlinear Photonic Crystals- 5 Self-transparency and Localization in Gratings with Quadratic Nonlinearity- 6 Photonic Band Edge Effects in Finite Structures and Applications to x(2) Interactions- 7 Theory of Parametric Photonic Crystals- 8 Nonlinear Propagation in Fiber Gratings- 9 Gap Solitons Experiments within the Bandgap of a Nonlinear Bragg Grating- 10 Pulsed Interactions in Nonlinear Fiber Bragg Gratings- 11 Chalcogenide Glasses- 12 Optical Properties of Microstructure Optical Fibers- 13 Semiconductor Optical Amplifiers with Bragg Gratings- 14 Atomic Solitons in Optical Lattices- 15 Discrete Solitons- 16 Nonlinear Localized Modes in 2D Photonic Crystals and Waveguides
158 citations
TL;DR: In this article, a sensor scheme consisting of a combination of a polymer fibre Bragg grating and a silica fibre grating was proposed for temperature and strain discrimination. But it was not shown to provide a large sensitivity and dynamic range.
156 citations
TL;DR: This work reported on grating writing in air-silica structured optical fibers with pure silica cores by use of two-photon absorption at 193 nm with a decrease in propagation loss with irradiation.
Abstract: We report on grating writing in air-silica structured optical fibers with pure silica cores by use of two-photon absorption at 193 nm. A decrease in propagation loss with irradiation was observed. The characteristic growth curves were obtained.
152 citations
TL;DR: An effective method for achieving a room-temperature multiwavelength erbium-doped fiber ring laser by addition of sinusoidal phase modulation in the ring cavity to prevent single-wavelength oscillation is presented.
Abstract: An effective method for achieving a room-temperature multiwavelength erbium-doped fiber ring laser is presented. Simultaneous multiwavelength lasing with 0.5-nm intervals is achieved both experimentally and theoretically by addition of sinusoidal phase modulation in the ring cavity to prevent single-wavelength oscillation.
TL;DR: Unambiguous simultaneous measurement of strain and temperature based on dual long-period fiber gratings by controlling their thermal and strain sensitivities is proposed and experimentally demonstrated.
Abstract: Unambiguous simultaneous measurement of strain and temperature based on dual long-period fiber gratings by controlling their thermal and strain sensitivities is proposed and experimentally demonstrated. The difference in the wavelength peak shift and the separation with the variation of strain and temperature allows discrimination between the strain and temperature effects, respectively.
TL;DR: A mode-locked ytterbium fiber laser that generates femtosecond pulses with energies as large as 2.2 nJ is reported, which represents a 20-fold improvement in pulse energy compared with that of previously reported femTosecond Yb fiber lasers.
Abstract: We report a mode-locked ytterbium fiber laser that generates femtosecond pulses with energies as large as 2.2 nJ. This represents a 20-fold improvement in pulse energy compared with that of previously reported femtosecond Yb fiber lasers. The laser produces pulses as short as 52 fs, which are to our knowledge the shortest pulses to date from a Yb fiber laser. The laser is diode pumped by a wavelength-division multiplexing coupler, which leads to excellent stability.
TL;DR: In this article, a fiber Bragg grating (FBG) sensor for detection of ultrasonic waves in liquids and solid structures is investigated, which contains a fiber probe with a FBG, a tunable narrowband laser source, and a photodetector.
Abstract: A fiber Bragg grating (FBG) sensor for detection of ultrasonic waves in liquids and solid structures is investigated. The sensor contains a fiber probe with a FBG, a tunable narrowband laser source, and a photodetector. When ultrasonic waves impinge on the fiber probe, the pitch of the grating is modulated through the elasto-optic effect. The corresponding changes in reflectivity of the grating are detected by a photodetector. The sensitivity of the sensor and its frequency and directional response in the 0.5 to 3.0 MHz range are measured. Some anomalous features of the FBG ultrasound sensor response are noted. It is shown that these features result from a combination of the sensor's response to the direct ultrasonic waves propagating through the medium and the signal generated by axially guided ultrasonic waves propagating through the fiber probe.
TL;DR: In this article, a numerical method is presented for determining the transmittance of long-period (LP) fibergratings having arbitrary azimuthal/radial refractive index variations.
Abstract: A numerical method is presented for determining the transmittance of long-period (LP) fiber-gratings having arbitrary azimuthal/radial refractive index variations. The method uses coupled-mode theory and includes both the sine and cosine character of the LP modes. The model treats interactions between the fundamental LP/sub 01/ mode and high-azimuthal-order cladding modes. The method utilizes the transfer matrix method to model cylindrical layers both in the core and the cladding regions.
TL;DR: The discovery of a quantization of the separation between phase-locked soliton pairs that is related to the radiation waves known as Kelly sidebands, in a passively mode-locked fiber ring laser is reported.
Abstract: We report the discovery of a quantization of the separation between phase-locked soliton pairs that is related to the radiation waves known as Kelly sidebands, in a passively mode-locked fiber ring laser. Our numerical simulations that predict this phenomenon have been confirmed by our experimental results.
TL;DR: In this paper, a sensor for accurate and long-term fluid pressure monitoring in oil bore-holes based on optical fiber Bragg gratings (FBGs) is presented, which converts fluid pressure into optical fiber strain by means of a mechanical transducer designed to withstand downhole conditions.
Abstract: A sensor for accurate and long-term fluid pressure monitoring in oil bore-holes based on optical fiber Bragg gratings (FBGs) is presented The sensor converts fluid pressure into optical fiber strain by means of a mechanical transducer designed to withstand downhole conditions The sensor response is investigated as a function of pressure and temperature Effects of shock and vibration are also considered The expected stability and lifetime of the polyimide-coated gratings in a downhole environment are estimated by modeling and extended accelerated mechanical and thermal aging tests
TL;DR: In this article, the Bragg grating technology offers an innovative platform for emerging optical devices in applications ranging from highly reflective flat panel displays to photonic crystals, and it has been used in a wide range of applications.
Abstract: Electrically switchable Bragg grating technology offers an innovative platform for emerging optical devices in applications ranging from highly reflective flat panel displays to photonic crystals.
TL;DR: In this paper, a multilevel phase-only sampling function was proposed for the sampled fiber Bragg gratings with high channel count, which require significantly less refractive-index modulation than that does the sampled grating with amplitude sampling.
Abstract: Binary and multilevel phase-only sampling functions are proposed for the sampled fiber Bragg gratings (FBGs) with high channel count, which require significantly less refractive-index modulation than that does the sampled grating with amplitude sampling. The design using the new simulated quenching optimization with temperature rescaling results in high channel uniformity and minimum energy in the out-of-band channels. The technique can be applied to the sampled FBGs with very high channel count. A five-channel nonlinearly chirped multilevel phase-only sampled FBG for tunable chromatic dispersion compensation is demonstrated.
TL;DR: In this paper, a correlation-based continuous-wave technique for high spatial resolution and distributed dynamic strain measurements using stimulated Brillouin scattering is presented, which has successfully measured dynamic strain from a 5-cm vibrating section, at a sampling rate of 8.8 Hz with a strain accuracy of about
Abstract: Conventional fiber Brillouin-based strain sensors are capable of distributed sensing, making them advantageous over fiber Bragg grating-based sensors for structural monitoring applications. However, Brillouin sensors have low spatial resolution and are inappropriate for dynamic strain measurements as they have large measurement times of several minutes. We present a correlation-based continuous-wave technique for high spatial resolution and distributed dynamic strain measurements using stimulated Brillouin scattering. Using our technique, we have successfully measured dynamic strain from a 5-cm vibrating section, at a sampling rate of 8.8 Hz with a strain accuracy of about /spl plusmn/38 /spl mu//spl epsiv/.
TL;DR: By optimizing the cavity dispersion map, 1.5-nJ pulses as short as 36 fs were obtained from a Yb-doped fiber laser as mentioned in this paper, where residual higher-order dispersion currently limits the pulse duration.
Abstract: By optimizing the cavity dispersion map, 1.5-nJ pulses as short as 36 fs are obtained from a Yb-doped fiber laser. Residual higher-order dispersion currently limits the pulse duration, and it should be possible to generate pulses as short as 25–30 fs with Yb-doped fiber.
TL;DR: In this article, a comprehensive analysis of multichannel grating optimization strategies is presented, where the central idea is in dephasing of partial gratings with respect to each other, allowing the utilization of ultraviolet-induced refractive index changes with maximum efficiency.
Abstract: A comprehensive analysis of multichannel grating optimization strategies is presented. The central idea is in dephasing of partial gratings with respect to each other. This dephasing allows the utilization of ultraviolet-induced refractive index changes with maximum efficiency. The dependence of group delay ripple on optimization strategy, number of channels, and other grating characteristics is also briefly discussed. Finally, we discuss further generalization of the dephasing approach to the case of multichannel gratings with nonidentical spectral characteristics.
TL;DR: A new multiplexing method demonstrating the separation of two series of geometrically arranged fiber-optic distributed sensors in a Michelson interferometer (MI) configuration has been developed.
Abstract: A new multiplexing method demonstrating the separation of two series of geometrically arranged fiber-optic distributed sensors in a Michelson interferometer (MI) configuration has been developed. This method can acquire data from two sensors, then propagate the data into one channel, and finally separate the data by determining their working point, which is essential for some remote measurements. The working point of one sensor was deflected from the normal MI by introduction of two reference arms. The deflection was extracted electrically and employed to label the sensor. Verification with commercial piezoelectric transducers proves the efficiency of the method.
Patent•
24 Feb 2003
TL;DR: An optical thermal device and methods for monitoring temperature and detection of a vulnerable plaque of a patient comprising an elongate tubular element comprising at least one optical fiber, the fiber having at least 1 optical grating along an axis of the fiber; and a light source having a light beam that is coupled into the optical fiber as mentioned in this paper.
Abstract: An optical thermal device and methods for monitoring temperature and detection of a vulnerable plaque of a patient comprising an elongate tubular element comprising at least one optical fiber; the fiber having at least one optical grating along an axis of the fiber; and a light source having a light beam that is coupled into the at least one optical fiber; wherein the optical grating reflects a certain wavelength or intensity of the light beam, the certain wavelength or intensity of the reflected light beam being correlated to the temperature of the tissue regions.
TL;DR: In this article, a novel hydrogel-coated singlemode fiber Bragg grating (FBG) sensor is investigated, which uses a swellable polymer material as the active sensing component.
Abstract: A novel hydrogel-coated single-mode fiber Bragg grating (FBG) sensor is investigated The sensor uses a swellable polymer material, hydrogel, as the active sensing component The sensing mechanism is based on the stress that is induced in the chemically sensitive swellable hydrogel coating The stress shifts the Bragg wavelength of the FBG By reducing the cladding diameter of FBG through etching with hydrofluoric acid, the tension tuning force of FBG can be lowered Therefore, the stress induced in hydrogel can shift the wavelength of FBG more and the sensitivity of the sensor is improved When the grating fiber is etched 375 μm in diameter, the sensitivity of sensor is approximately 10-fold larger than that without fiber etching
TL;DR: In this paper, a silica-based tunable fiber Bragg grating filter with a wavelength tuning range over 90 nm is presented. But the performance of this filter is limited by the polarization-mode dispersion and polarization-dependent loss.
Abstract: We demonstrate a silica-based tunable fiber Bragg grating filter with a wavelength tuning range over 90 nm. A bend-tuning technique in a simple tuning package is employed to obtain a wide wavelength tuning range from 1634 to 1544 nm, covering the entire L-band and a half of the C-band. The polarization-mode dispersion and polarization-dependent loss of the device show little variations over the whole operating region.
TL;DR: In this paper, two devices using fiber Bragg grating (FBG) sensors have been developed for temperature-compensated strain measurement, which are named hybrid sensor and laminate sensor, respectively.
Abstract: For accurate strain measurement by fiber Bragg grating (FBG) sensors, it is necessary to compensate the influence of temperature change. In this study two devices using FBG sensors have been developed for temperature-compensated strain measurement. They are named 'hybrid sensor' and 'laminate sensor', respectively. The former consists of two different materials connected in series: carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic. Each material contains an FBG sensor with a different Bragg wavelength, and both ends of the device are glued to a structure. Using the difference of their Young's moduli and coefficients of thermal expansion, both strain and temperature can be measured. The latter sensor is a laminate of two 90° plies of CFRP and an epoxy plate, and an FBG sensor is embedded in the epoxy plate. When the temperature changes, the cross section of the optical fiber is deformed by the thermal residual stress. The deformation of the fiber causes the birefringence and widens the reflection spectrum. Since the temperature can be calculated from the spectrum width, which changes in proportion to the temperature, the accuracy of the strain measurement is improved. The usefulness of these sensors was experimentally confirmed.
TL;DR: The dependence of the refractive-index modulation on intensity at equal fluences points to a two-photon absorption mechanism for grating inscription.
Abstract: We report on what is to our knowledge the first fabrication of fiber Bragg gratings by UV femtosecond radiation. The Bragg gratings, with photoinduced refractive-index modulation up to 1.92 x 10(-3) in H2-loaded SMF-28 and up to 1.05 x 10(-3) in Nufern GF1 fibers, were written by high-intensity (31-77-GW/cm2) femtosecond pulses at 264 nm. The dependence of the refractive-index modulation on intensity at equal fluences points to a two-photon absorption mechanism for grating inscription.
TL;DR: In this paper, the authors proposed possible configurations of multiplexing and demultiplexing (DEMUX) schemes using an arrayed-waveguide grating with two input and N output waveguides (N: total channel number).
Abstract: The frequency-interleaved dense- wavelength-division-multiplexing (DWDM) millimeter-wave (mm-wave) radio-on-fiber is an indispensable technique to improve the optical spectrum efficiency. We propose possible configurations of multiplexing and demultiplexing (DEMUX) schemes using an arrayed-waveguide grating (AWG) with two input and N output waveguides (N: total channel number). In this paper, we focus on the DEMUX scheme and experimentally demonstrate the DEMUX scheme using a commercially available AWG. In the experiment, 25-GHz-separated two-channel optical double sideband signals modulated by a 60-GHz millimeter-wave carrying a 156-Mb/s data are optically multiplexed by the frequency interleaving. The power penalty after DEMUX, which was due to interchannel interference, was less than 0.5 dB. We also made a transmission experiment over 25-km standard single-mode fiber (SMF). No noticeable power penalty in the received data due to chromatic dispersion of the transmission fiber was observed. This is because only the carrier and a sideband are detected in the proposed DEMUX scheme.