A5020521075- Advanced Fiber Optic Sensors
- Advanced Fiber Laser Technologies
- Optical Network Technologies
- Advanced Photonic Communication Systems
- Photonic and Optical Devices
- Semiconductor Lasers and Optical Devices
- Laser-Matter Interactions and Applications
- Seismic Waves and Analysis
- Advanced Optical Sensing Technologies
- Advanced Measurement and Metrology Techniques
- Geophysics and Sensor Technology
- Laser-Plasma Interactions and Diagnostics
- Optical Polarization and Ellipsometry
- Analytical Chemistry and Sensors
- Near-Field Optical Microscopy
- Insect-Plant Interactions and Control
- Advanced Chemical Physics Studies
- Laser-induced spectroscopy and plasma
- Optical Coherence Tomography Applications
- Surface Roughness and Optical Measurements
- Structural Health Monitoring Techniques
- Advanced Frequency and Time Standards
- Abdominal Trauma and Injuries
- Radioactive Decay and Measurement Techniques
- Legume Nitrogen Fixing Symbiosis
Nagasaki Rousai Hospital
2024
NTT (Japan)
2013-2023
Information Systems Laboratories (United States)
2020-2021
Hokkaido University
2000-2010
Tohoku University
1997-2000
We review recent advances in distributed fiber optic sensing (DFOS) and their applications. The scattering mechanisms glass, which are exploited for reflectometry-based DFOS, Rayleigh, Brillouin, Raman scatterings. These sensitive to either strain and/or temperature, allowing optical cables monitor ambient environment addition conventional role as a medium telecommunications. Recently, DFOS leveraged technologies developed telecommunications, such coherent detection, digital signal...
Extreme ultraviolet (XUV) single-order high harmonic pulses with 10 6 photons/pulse were separated from multiple orders by a time-compensated toroidal-grating monochromator consisting of pair toroidal gratings.The first grating separates the order and second one compensates for pulse-front tilt.The center photon energies tunable between 42 23 eV.The single spatially temporally characterized as having spot size 58 ± 3 µm at focus, shortest pulse duration 47 2 fs.The developed XUV light source...
Scanning near-field optical microscopy using a slit-type probe is discussed. The has width of much less than wavelength, λ, and length on the order thus high transmission efficiency. Two dimensional images objects have been constructed an image reconstruction algorithm based computerized tomographic imaging. Experiments performed at 60 GHz (λ=5 mm) show that this type can achieve spatial resolution better λ/45 for two A method fabricating submicron slit end fiber presented extending to waves.
We experimentally demonstrate a two-color two-photon resonant excitation of the doubly excited 2p 2 1 S state in helium atoms by combination 19th and 21st harmonic photons Ti:sapphire laser.Production is confirmed experimental observation that electron emission from this does not depend on direction polarization.Our ab-initio theoretical results through solution time-dependent Schrödinger equation are consistent with confirm first successful production high-harmonic pulses.
We investigate the impact of frequency modulation induced by vibration occurring at a preceding distance in distributed acoustic sensing (DAS) based on optical domain reflectometry (OFDR), which analyzes waveform calculating spectrum shift Rayleigh backscattered light same manner as fiber Bragg grating. When measurement time beat signal is shorter than period distance, vibration-induced can be treated offset for light. The becomes through - allocation OFDR, and forces us to interrogate...
Distributed vibration sensing (DVS) utilizes an optical fiber as array of virtual strain sensors. It can reveal dynamic distributions such seismic events and car traffic, thus giving a new function to existing communication fibers. In this work, we use frequency domain reflectometry (OFDR) investigate the distribution along implemented in deployed aerial cable that vibrates with wind. The OFDR setup is customized for distant location interrogation high repetition rate probe light overcomes...
We describe a novel optical correlation domain reflectometry technique based on coherence synchronization between probe and local lights. Coherence is realized by using artificially generated low lights, which are controlled arbitrary waveform generators. Thanks to the flexibility of electronics, we can easily design characteristics lights yield gating that filters an autocorrelation original laser at delay. The effective as long measurement length less than laser. demonstrate Fresnel...
We developed a laser phase noise characterization technique by using linear optical sampling. Thanks to the broad bandwidth nature of sampling technology, proposed provides FM spectrum and error variance characterizing beat note between under test reference laser, even when wavelengths signal beams differ considerably. Requirement two lasers is overlap pulse. This eliminates need choose with similar observe their note. characterized characteristics different confirmed validity this comparing...
Distributed acoustic sensing (DAS) measures local strains along a fiber using as an array of dense virtual strain sensors. One related application DAS is seismic wave sensing. Due to the densely deployed sensors, can detect propagation fiber, which useful for underground structure imaging. Thus, has been used alternative conventional sparsely seismometers investigating geophysical phenomena. uses optical time domain reflectometry (OTDR), differential phase caused by elongation between two...
We measure vibration waveforms along an installed aerial optical fiber cable and identify a sagging section. This is the first demonstration of telecom maintenance by distributed sensing.
We present a robust interferometer-based laser phase noise reduction technique that can easily be tuned to apply corrections at frequencies which the interferometer is less affected by environmental disturbances. The operates measuring in-phase and quadrature components of interference pattern along circular Lissajous figure compute short-term error reject long-term drift, then uses correct noise. successfully demonstrate for an external cavity semiconductor without need stabilization...
This paper describes a signal quality monitoring technique for wavelength division multiplexing (WDM) signals that uses an ultrafast field sampling approach, where the observed is parallelly sampled with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> channel coherent mixers include delay of xmlns:xlink="http://www.w3.org/1999/xlink">nT</i> , xmlns:xlink="http://www.w3.org/1999/xlink">n</i> number and...
We investigate the statistical property of Rayleigh backscattered light to confirm tolerance vibration-induced beat frequency offset, which forces us interrogate an unintentionally-positioned sensor. A long sensor is capable measuring vibrations correctly.
We show that pulse waveform analysis based on ultrafast xy-field sampling can correctly estimate the complete polarization-mode dispersion (PMD) vector over signal bandwidth. The sampling, implemented as polarization-diversity coherent detection with short local pulses, observe time-resolved complex amplitude for x- and y-polarizations at time scales. By fully characterizing temporal response of xy polarized fields after transmission, their Fourier transforms directly yield output Jones...
A metal microslit has been used as an interaction circuit between a CO2 laser beam and nonrelativistic free electrons. Evanescent waves which are induced on the slit by illumination of light modulate energy electrons passing close to surface slit. The electron-energy change more than ±5 eV for 80 keV electron observed using 7 kW at wavelength 10.6 μm.
Phase error variance is an important figure in many laser applications such as coherent optical communication and interferometric diagnosis directly related to system performance. In this letter, we show that the phase of a single-mode with narrow linewidth can be measured function relative delay without using any reference (local) beam. addition, results are good agreement those beat note two identical lasers, one which acts local The new method, uniquely believe, enables us evaluate lasers...
The complex impulse responses of two types coupled 2-core fibers, with homogeneous and heterogeneous cores, were measured by using a measurement system based on linear optical sampling. measurements performed over bandwidth 20 nm (∼2.5 THz), the spatial-mode dispersion (SMD) was analyzed. Several lengths both core fibers prepared to investigate length dependence SMD. SMDs for divided frequency bands examined numerically analyzing broadband response. Consequently, power response at each...
We propose a novel technique for characterizing laser phase noise using parallel linear optical sampling. The high bandwidth of the sampling relaxes limitation, which is critical problem in characterization digital coherent receiver.
We investigate the impact of frequency modulation induced by vibration in distributed sensing based on OFDR and show that causes spurious vibration. demonstrate compensation to measure simultaneous events.
A novel optical correlation domain reflectometry technique utilizing artificially-generated low-coherence light is proposed for long-range measurement with high resolution. We successfully demonstrate the selection of one peak a laser at an arbitrary delay fibre under test.
We introduce a dual-channel sampling technique for WDM signal observation that uses sequential ultrafast field to observe DPSK signals. An 8 channel × 25 Gbit/s is successfully observed the first time.
We measured a seismic event with OFDR. OFDR together the unique feature of adjusting measurement performance was used to analyse from different perspectives, and it could also be useful for revealing features infrequent events.
We demonstrate a rapid Mueller matrix and PMD measurement based on ultrafast xy-field sampling, by analyzing temporal complex amplitudes of polarization-multiplexed signals. The time 1 ms was successfully accomplished for the probe bandwidth 300 GHz.
We demonstrate the two-photon resonant excitation of doubly excited 2p2 1S state in helium atoms by combination 29.5- and 32.6-eV harmonic photons. Our ab-initio calculation confirms nonlinear high harmonics.