Toyota Technological Institute, Japan
Kazuo Hotate received Dr. Eng. degree from the University of Tokyo in 1979, and joined the university as Lecturer. He became Professor in 1993, served as Dean of Graduate School of Engineering, and as Executive Vice President. On March 31, 2017, he retired from the university, and now is Professor Emeritus. He joined Toyota Technological Institute as a Vice President and Professor, and became the President on September 1st, 2019. He has been engaged in measurement and analysis of optical fibers and optical fiber sensors. He was a pioneer in Fiber Optic Gyros, and has contributed to fiber distributed sensing with proposing his own sensing mechanisms, Brillouin optical correlation-domain analysis/reflectometry. He has authored and coauthored several books on optical fibers, and more than 450 journal papers and international conference presentations. He is the IEEE Life Fellow, and is the Fellow of IEICE, SICE, and JSAP. He received numerous awards, including OFS Life-time Achievement Award. He was IEEE PS BoG member, and served as Associate Editor of IEEE/OSA JLT. He was President of JSAP and also President of IEICE Electronics Society. He served as Co-chairs for SPIE Fiber Optic Gyros: Twentieth Anniversary Conference, Technical Program Chair for OFS-13, and General Chair for OFS-16.
Abstract of Tutorial Speech
Fiber Optic Gyroscope (FOG) is a rotation sensor with respect to an inertial frame. Historically, spinning mass gyroscopes had been used, but these need a long worming-up time. By the way, two lightwaves, propagating in opposite directions in a closed optical path, shows a phase difference in proportion to the path rotation rate. This phenomenon, “Sagnac effect,” was demonstrated in 1913. However, the sensitivity was quite tiny, because the light speed is quite high. A ring laser, having a triangle shaped loop cavity with two laser lightwaves propagating in opposite directions, realized a gyroscope function in 1963. This Ring Laser Gyroscope (RLG) has reached an aircraft navigation grade, but a mechanical angular vibration is inherently required. Then, FOG using interferometer for the phase difference detection (I-FOG) was proposed in 1973, as a gyroscope without any moving parts. However, various phenomena in a fiber, such as back scattering, optical nonlinearity, Faraday effect, cause huge noises. Fortunately, effective countermeasures have been invented, then a navigation grade has been realized. In this tutorial talk, principle of I-FOG, system configurations, countermeasures for noises, and applications are discussed. Additionally, other types of FOG, such as Resonator FOG (R-FOG) and Brillouin FOG (B-FOG), are also discussed.
Chung-Ang University, Korea
Kwang Yong Song received the Ph. D degree in Physics from Korea Advanced Institute of Science and Technology (KAIST) in 2003, where his research topic was fiber taper devices for spatial mode coupling such as mode selective couplers for LP11 and LP02 modes in few-mode fibers. He moved to Nanophotonics and Metrology Laboratory in Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, where he conducted researches on Brillouin optical time domain analysis (BOTDA) and performed pioneering works on Brillouin slow light in optical fibers. In 2005, he joined in the Dept. of Electronic Engineering in the University of Tokyo as a research fellow, where he contributed to the performance enhancement of Brillouin optical correlation-domain analysis (BOCDA). In 2007, he moved to Chung-Ang University in South Korea where he has been working as a professor in Dept. of Physics. His main research area is the applications of Brillouin scattering in optical fibers such as distributed Brillouin sensors, Brillouin dynamic grating, and Brillouin slow light in single-mode and few-mode optical fibers. He is a senior member of Optical Society of America (OSA) and a fellow of Optical Society of Korea (OSK).
Abstract of Tutorial Speech
Brillouin scattering is an inelastic scattering that occurs due to the interaction of a light wave with an ultrasound wave. It can be easily observed with low optical power in an optical fiber. The Brillouin frequency shift of the scattered wave due to the Doppler effect shows a linear dependence on ambient temperature and strain variations, and this has been the main operation principle of Brillouin sensors. Distributed Brillouin sensors have proven to be useful for real-time structural health monitoring of civil structures and natural object, and various schemes have been developed with unique advantages and target applications according to the operation domain and scattering mechanism. Significant advances have been achieved in their performances through decades of active research, and current state-of-the-art Brillouin sensors can provide the distribution map of Brillouin gain spectrum with a distance over 100 km, a spatial resolution below 1 cm or a sampling rate exceeding 1 MHz. In this tutorial an introductory lecture on the fundamentals and advanced techniques will be provided on Brillouin scattering-based sensors and Brillouin dynamic grating-based sensors with optical time-domain and correlation-domain approaches.
University of New South Wales, Australia
Gang-Ding Peng eceived the B.Sc. from Fudan University, China, in 1982, M.Sc and PhD from Shanghai Jiao Tong University, China, in 1984 and 1987, respectively. From 1987 through 1988 he was a lecturer of the Jiao Tong University. He was a postdoctoral research fellow in the Optical Sciences Centre of the Australian National University, Canberra from 1988-1991. He has been working with University of NSW in Sydney, Australia since 1991, being a Queen Elizabeth II Fellow from 1992-1996 and currently a Professor in Photonics and Optical Communications. He is a fellow and life member of both OSA and SPIE. His research interests include optical fibres and devices, fibre sensors and nonlinear optics.
Abstract of Tutorial Speech
Since the first observation of photosensitivity and the first demonstration of Bragg grating in a Ge‐doped silica optical fibre reported by Hill et al in 1978, fibre Bragg grating technology has attracted enormous research interest and gained tremendous advances. Nowadays a great variety of fibre gratings have been developed and applied for a broad range of scientific and industrial applications. In this tutorial, the fundamentals of fibre Bragg gratings: principles and analysis, designs and fabrications, tests and characteristics, as well as current and future applications will be introduced, while highlighting specialty fibre Bragg gratings extended to other types, e.g. tilt gratings, chirped gratings, phase-shifted gratings, and other material systems, e.g. polymers and glasses for various niche scientific and commercial applications, and highlighting specialty fibre Bragg grating arrays based on WDM, TDM and SDM techniques for quasi-distributed optical fibre sensing requiring great multiplexing capacity and high sensitivity.
Shanghai Jiao Tong University, China
Zuyuan He received BS and MS degrees in Electronic Engineering from Shanghai Jiao Tong University, China, in 1984 and 1987, respectively, and PhD degree from University of Tokyo, Japan, in 1999. He joined Nanjing University of Science and Technology, China as a Research Associate in 1987, and became a Lecturer in 1990. In 1999, he became a Research Associate in the University of Tokyo. In 2001, he joined CIENA Corporation, Maryland, USA, as a Lead Engineer heading the optical testing and optical process development group. He returned to the University of Tokyo as a Lecturer in 2003, then became an Associate Professor in 2005 and a full Professor in 2010. He is now a Chair Professor in Electronic Engineering, Shanghai Jiao Tong University. His research interests include optical sensing, optical interconnects, and optical computing. He co-authored about 500 papers in peer-refereed journals and international conferences. Dr. He is an OPTICA fellow and a senior member of IEEE. He worked as an associate editor of Journal of Lightwave Technology 2013-2019 and served as TPC members in a variety of international conferences, such as CLEO, OFC, and OFS, and as the General Chair of ACP 2014 and APOS 2016, respectively.
Abstract of Tutorial Speech
DAS, the distributed acoustic sensor, is a fiber-optic device for distributed sensing of dynamic strain with high fidelity. The DAS interrogator launches an optical probe down to the fiber, then analyzes the Rayleigh backscattering from the fiber to acquire acoustic wave or vibration information around the fiber. In this way, an optical fiber becomes a continuous sensor that can collect vibrations at all positions along tens of even hundreds of km-long optical fiber. It is an amazing technology suitable for long-range and large-area application in various areas, such as geoscience and geoengineering, oil and gas industry, structural health monitoring, and perimeter security. In this tutorial, sensing principles and positioning mechanisms involved in DAS systems are reviewed, and different DAS schemes compared. Two major challenges with conventional phase sensitive OTDR DAS systems, i.e., the trade-off between spatial resolution and sensing length and the dead-zone due to interference fading, are analyzed. High performance DAS technology based on pulse-compression and rotated-vector-summation algorithms is explained, which are newly developed to answer the above challenges. Then several application demonstrations in geophysical exploration, seismic measurement, and perimeter security are introduced. Finally, possible research and development trends are discussed.