1 Abstract—In an era of unprecedented progress in sensing technology and communications, health services are able to evolve towards a close monitoring of patients and elderly citizens, without jeopardizing their daily routines, through health applications on their mobile devices, in what is known as e-Health. Within this field, we propose an optical fiber sensor (OFS) based system for simultaneous monitoring of shear and plantar pressure during gait movement. These parameters are considered to be two key factors in gait analysis which can help in early diagnosis of multiple anomalies, such as diabetic foot ulcerations or in physical rehabilitation scenarios. The proposed solution is a biaxial OFS based on two in-line fiber Bragg gratings (FBGs), which were inscribed in the same optical fiber and placed individually in two adjacent cavities, forming a small sensing cell. Such design presents a more compact and resilient solution with higher accuracy, when compared to the existing electronic systems. The implementation of the proposed elements into an insole is also described, showing the compactness of the sensing cells, which can be easily integrated into a non-invasive mobile e-Health solution for a continuous remote gait analysis of patients and elder citizens. The reported results show that the proposed system outperforms existing solutions, in the sense that it is able to dynamically discriminate shear and plantar pressure during gait. This work is funded by FCT/MEC through national funds and when applicable co-funded by FEDER – PT2020 partnership agreement under the project UID/EEA/50008/2013. Cátia Tavares, Nélia Alberto and Ayman Radwan, are with Instituto de Telecomunicações, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal (e-mails: catia.tavares @ua.pt; nelia @av.it.pt, aradwan @av.it.pt). M. Fátima Domingues is with the Instituto de Telecomunicações, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal; Department of Physics & I3N, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal and Centro de Automática y Robótica, CSIC-UPM ctra. Campo Real, 28500 Arganda del Rey, Madrid, Spain (e-mail: fatima.domingues @ua.pt). Anselmo Frizera Neto is with the Telecommunications Laboratory LABTEL,Electrical Engineering Department, Federal University of Espírito Santo, 29075-910, ES, Brazil (e-mail: frizera @ieee.org). Tiago Leite, Cátia Leitão, Carlos Marques and Paulo Antunes are with Department of Physics & I3N, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, and Instituto de Telecomunicações, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal (e-mails: tmpl @ua.pt; catia.leitao @ua.pt; carlos.marques @ua.pt; pantunes @ua.pt). Eduardo Rocon de Lima is with Centro de Automática y Robótica, CSIC- UPM, ctra. Campo Real, 28500 Arganda del Rey, Madrid, Spain (e-mail: erocon @iai.csic.es). Paulo André is with Department of Electrical and Computer Engineering and Instituto de Telecomunicações, Instituto Superior Técnico, University of Lisbon, 1049-001 Lisbon, Portugal (e-mail: paulo.andre @lx.it.pt). Index Terms—Gait analysis; e-Health application; physical rehabilitation; shear and plantar pressure sensor; biaxial optical fiber sensor; multiplexed fiber Bragg gratings; I. INTRODUCTION ately, we have witness great progress in electronics and networking, leading to a shift in innovation direction. It could easily be noticed that mobile networks have moved from offering applications mainly for entertainment and human communications (i.e. phone calls, messaging, social networking, etc.) towards more vital applications, such as smart cities, e-Health or intelligent transportation systems, collectively known as Internet of Things (IoT). IoT has been receiving much attention from the research and industry communities, due to the foreseen gains that it can bring in enhancing the life quality of citizens and increasing the safety of our environment and society. One of the very hot fields of IoT is e-Health, which has been on the rise due to the change of the population demographics (increase of population over 65 years old). Between 2000 and 2050, the world's population aged over 60 years is expected to double from about 11% (605 million) up to 22% (2 billion), with the group aged 80 years and over growing most rapidly (predictably will quadruple from approximately 100 million to 395 million people). Many elderly and patient groups experience vary degrees of mobility impairments, which requires a closer monitoring. Assistive devices play a pivotal role in their lives and have a great impact on their ability to live independently and perform basic daily tasks. The assistive products market is set to expand significantly in response to the ageing population and disability trends, with a global market for home medical equipment expected to grow from $27.8 billion in 2015 to nearly $44.3 billion by 2020 [1]. This growing demand for e-Health solutions aims to improve both the quality of healthcare services, as well as the life quality of people, by providing them the autonomy and mobility during their daily activities. The use of electronic and mobile networking in health services (i.e. e-Health) increases the quality given to patients and helps medical staff in early diagnosis of anomalies, when premature display of patients’ irregular health conditions is reported. Non-invasive continuous monitoring of individuals’ health conditions, rehabilitation status, or assistance appears as a natural evolution of current healthcare services, providing Cátia Tavares, M. Fátima Domingues, Anselmo Frizera-Neto, Member, IEEE, Tiago Leite, Cátia Leitão, Nélia Alberto, Carlos Marques, Ayman Radwan, Senior Member, IEEE, Eduardo Rocon, Paulo André, Senior Member, IEEE, Paulo Antunes Gait’ shear and plantar pressure monitoring: A non-invasive OFS based e-Health solution L