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In this work, a simple design and cost-effective displacement-curvature sensor based on macro-bend single-mode fiber (SMF) is planned and demonstrated. The optical fiber sensor encompasses a bending configuration and the macro-bending losses were exploited as the sensing process for the capturing of angular displacement motion in an angle span between 0° and 90° (that corresponds to curvature displacement between 0 and 49.5 cm). A straight SMF shape and other four bent sensor structures (U-like, drop-like, Knot-like, and eight-like) have been fabricated from sections of 90 cm length SMF. These five sensor configurations will provide high maneuvering for versatile applications. In these adjustable sensing schemes, the fiber sensors were described by monitoring the power loss corresponding to the diverse angular displacement at various bending structures in terms of the shape of the bend, the bending diameter, and the number of wrapping turns. Then, these measurement schemes based on the macro-bending losses were employed to detect the human motion elbow joint, and a proper sensing scheme was adopted to examine the flexion/extension joint motion in detail. The proposed sensors showed enhanced sensitivity to flexion/extension joint motion range between −0.25 and −0.477 dB/° and good sensitivity to curvature ranging between −0.552 and −1.052 dB/cm. The demonstrated and planned sensing techniques are adjustable and accessible for different types of human and mechanical movements. [Display omitted] • Wearable Optical Fiber Sensor based macro-bending loss for Biomechanical Motion Evaluation. • A simple design and cost-effective displacement-curvature sensor based on macro-bend single-mode fiber (SMF) has been integrated into elbow joint phantoms and measuring its response to various elbow joint movements in the range of 0°-90°. • A straight SMF shape and other four bent sensor structures (U-like, drop-like, Knot-like, and eight-like) have been exploited as the sensing process for the capturing of angular displacement motion in a span between 0 and 49.5 cm. • Adjustable sensing measurement schemes based on the macro-bending losses have been employed to detect the human motion elbow joint, and a proper sensing scheme has been adopted to examine the flexion/extension joint motion in detail. [ABSTRACT FROM AUTHOR]

• Wearable Optical Fiber Sensor based macro-bending loss for Biomechanical Motion Evaluation. • A U-shaped fiber sensor has been integrated into elbow and knee joint phantoms and measuring its response to various elbow and knee joint movements in the range of 0°-90°. • The recorded sensing data revealed an extra sensitivity of −0.457 nm/° with linear regression coefficients of more than 98.7 % for elbow flexion angle and a 0.506 nm/° sensitivity with a high linear regression coefficient of ∼ 99.6 % for knee flexion angle. • The proposed sensor exhibits a high sensitivity which it significantly improves the optical sensing signal to more than 5.5 times in correspondence with many previous published works. The biocompatibility and other unique physical properties of optical fibers reflect their potential for use in biomechanical motion sensing. In this paper, a wearable macro-bending structure fiber sensor has been fabricated and its potential is demonstrated for observing key motions during physical therapy for patients with joint stiffness. The sensor's performance has been evaluated by integrating it into elbow and knee joint phantoms and measuring its response to various elbow and knee joint movements in the range of 0°-90°. The recorded sensing data revealed the extra sensitivity of −0.457 nm/° with linear regression coefficients (R2) of more than 98.7 % for elbow flexion angle and a 0.506 nm/° sensitivity with a high linear regression coefficient (R2) of ∼ 99.6 % for knee flexion angle. Additionally, good reproducibility and swift response facility were demonstrated during the experiment, indicating that the designed sensor possesses enormous potential in terms of different body motion monitoring applications, even subtle ones. The results show that the sensor's high sensitivity leads to a very good correlation between the sensor's output and the actual elbow joint movement. [ABSTRACT FROM AUTHOR]