Dual-layer orthogonal fiber Bragg grating mesh based soft sensor


Recent technological advances have triggered the need to utilize electronics-based 3D-shape sensors to accomplish 3D geometry reconstruction, body shape change measurement and surface shape measurement. Conversely, most of these electronics based approaches are not suitable for extreme environment – high temperature, chemically unstable, and electromagnetic sensitive environments. Fortunately, the recently developed fiber optics technique has emerged as a promising candidate and highly efficient method for shape sensing. Several fiber optics techniques are viable, however, most focus chiefly on 3D curve sensing along an optical fiber or line instead of shape sensing of an object surface. Luckily, the fiber Bragg grating possessing various structures has displayed auspicious shape sensing capabilities, despite the limitations of: uni-directional curve sensing or limited resolution. To this end, there is need to develop a novel simple 3D shape sensor with higher resolution for application in biomedical works and soft robotics.

University of Georgia researchers: Li Xu, Jia Ge, Jay Patel and Mable Fok developed a compact soft 3D shape sensor utilizing a dual-layer orthogonal fiber Bragg grating mesh that could measure the complete 3D shape of an object surface. They achieved visualized 3D shape sensing which would come in handy in many potential application fields. Their work is currently published in the research journal, Optics Express.

Their experimental setup entailed the embedment of a sensor comprising of 18 standard fiber Bragg gratings inside a thin and flexible silicone film. Additionally, the 18 fiber Bragg gratings were orthogonally aligned in a dual-layer mesh structure with 9 fiber Bragg gratings in the x-direction at the top layer and 9 fiber Bragg gratings in the y-direction at the bottom layer.

The authors observed that the off-center embedding of optical fiber in the silicone film enabled the measurement of both positive and negative bending curvatures, while the orthogonal structure decomposed a curve into x- and y- axis. Moreover, the bending direction and bending curvature at each sensing point were obtained by measuring the direction and amount of Bragg wavelength shift of each fiber Bragg grating in the mesh, and the information of all the 9 sensing points could be obtained through one single spectral scan. In addition, the surface profiles of the test objects were successfully reconstructed with visual 3D plotting.

Professor Mable Fok and her colleagues has shown successful design of a soft silicone shape sensor comprising of 18 fiber Bragg gratings embedded in a flexible silicone film for 3D shape measurement. It has been seen that the proposed scheme can measure the complete 3D shape of an object surface simply by placing the sensor on top of the object. Even better, the compact and soft silicone rubber is highly compatible with human body, therefore making the demonstrated sensor a promising design for wearable monitoring devices and medical robotics.

Dual-layer orthogonal fiber Bragg grating mesh based soft sensor for 3-dimensional shape sensing. Advances in Engineering

About the author

Li Xu received her Bachelor’s degree in electronic information science and technology from Shandong University, Shandong, China in 2010. After that, she has 5 years working experience as a Technical Support Engineer. In 2017, she received her Master’s degree in Electrical and Computer engineering from the College of Engineering of at the University of Georgia. During her Master study, she worked with the Lightwave and Microwave Photonics Lab and focused on the design of novel optical fiber sensor and their applications in biomedical and soft-robotics. She also assisted projects on microwave photonic RF systems and biomimetic photonic systems.

About the author

Jia Ge received the B. Eng. degree in electrical engineering from Shandong University, Shandong, China in 2010, and M. Eng. degree in optical engineering from Jinan University, Guangzhou, China in 2013. He received his Ph. D. degree in engineering in 2017, with the Lightwave and Microwave Photonics Lab at the University of Georgia, Athens, GA, USA. His research areas include microwave photonics, fiber optics, optical signal processing, optical communications and optical fiber sensors, for developing photonics based high-speed and dynamic signal processing techniques for broadband RF systems, as well as coherent technologies for high capacity optical communication systems. He is currently a Senior Optical Engineer at Infinera Corporation in Sunnyvale, CA.

Dr. Ge has published over 30 journal and conference papers, and received multiple awards for his research efforts. He is the recipient of 2017 Chinese Government Award for Outstanding Self-Financed Students Abroad, and Brahm P. Verma Award for Academic and Leadership Excellence. Dr. Ge has also received the Dissertation Completion Award and Innovative and Interdisciplinary Research Grant from the University of Georgia.


About the author

Jay Patel was born in Anand, India, in 1995. He received his bachelor’s in Computer Systems Engineering from the University of Georgia in 2017. In 2016, he utilized the CURO program that offers University of Georgia undergraduates the opportunity to engage in faculty-mentored research to join Dr. Mable Fok’s Lightwave and Microwave Photonics Lab research team. He enjoyed learning about fiber optics and photonics techniques used to conduct experiments in the research lab.

His main areas of interest are computer programming and working with microcontrollers. He is currently works full time for AT&T at their headquarters in Dallas, Texas as a developer.

About the author

Mable Fok is an Associate Professor and a Distinguished Faculty Fellow in the College of Engineering at the University of Georgia. She received the B.Eng., M.Phil., and Ph.D. degrees in electronic engineering from the Chinese University of Hong Kong (CUHK), Hong Kong. After graduation, Dr. Fok joined the Department of Electrical Engineering at Princeton University, Princeton, NJ, USA, as an Associate Research Scholar in 2007, where she was focusing on hybrid analog/digital processing of optical signals based on neuromorphic algorithm and developing new techniques to enhance physical layer information security in optical communications network.

Currently, Dr. Fok is the Director of the Lightwave and Microwave Photonics Laboratory at the University of Georgia. She has published over 170 journal and conference papers. Her recent research interest is on development of novel photonic techniques for dynamic and flexible RF communication systems, implementing neuromorphic algorithm using photonics, and the development of novel biomedical and soft robotic sensors.

Dr. Fok is the recipient of the 2017 NSF CAREER award, 2016 University of Georgia CURO Research Mentoring Award, 2015 University of Georgia College of Engineering Excellence in Research Faculty Award, 2014 Ralph E. Powe Junior Faculty Enhancement Award from ORAU, and 2010 IEEE Photonics Society Graduate Student Fellowship.


Li Xu, Jia Ge, Jay H. Patel, and Mable P. Fok. Dual-layer orthogonal fiber Bragg grating mesh based soft sensor for 3-dimensional shape sensing. Volume. 25, No. 20 | 2 Oct 2017 | Optics Express 24727


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