## 5 Conclusions  
This study presented the development and validation of a wearable photonic and wireless sensor system designed for high-resolution monitoring of knee-referenced gait cycles. The integrated system demonstrates clear advantages in terms of sensitivity, accuracy, portability, and usability, positioning it as a promising tool for both clinical and sports-related applications. By combining a single Fiber Bragg Grating (FBG) optical sensor with wireless \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Reference System** & **Sensor Type** & \begin{tabular}{c} **Angular/Spectral** \\ **Resolution** \\ \end{tabular} & \
\begin{tabular}{c} **Required** \\ **Infrastructure** \\ \end{tabular} & **Portability** &
\begin{tabular}{c} **Estimated** \\ **Cost** \\ \end{tabular} \\ \hline Proposed System & FBG (10 p.m.) + IMUs (\(\pm 1^{\circ}\)) & \(\pm 1^{\circ}\) (IMU), 10 p.m. (FBG) & None (wearable and autonomous) & High & Low \\ Vicon/Qualisys & Optical with active/ passive markers & \(<\)1\({}^{\circ}\) & High (multi-camera lab setup) & Low & Very high \\ IMU-only Systems & Accelerometers, gyroscopes, magnetometers & 1–3\({}^{\circ}\) & Medium (requires calibration) & High & Medium \\ FBG with POF & Plastic Optical Fiber (POF) sensors & Low resolution, bend-sensitive & Medium (requires calibration and reference) & Medium & Medium \\ ([PERSON] et al., 2020) [25] & FBG + IMU & \(\sim\)1\({}^{\circ}\) & Medium (semi-wearable) & Medium & Medium \\ ([PERSON] et al., 2022) [30] & FBG + IMU & Not specified & Medium & High & Medium \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparative summary of the proposed system and existing gait monitoring technologies. inertial measurement modules, the proposed system offers a practical, real-time solution for characterizing knee joint motion without relying on bulky, laboratory-based motion capture systems. The photonic component, featuring a single FBG sensor with a 10 p.m. resolution embedded in a flexible polyvinyl chloride (PVC) structure, successfully captured strain patterns associated with knee flexion and extension. The sensor was secured with an elastic band, enabling consistent signal quality and reliable differentiation of gait phases such as stance and swing. These measurements were correlated with angular displacement between the tibia and femur, producing repeatable waveforms across varied walking conditions and subject profiles. The wireless module comprised a microcontroller operating in the 2.4 GHz band, integrated with a 3-axis accelerometer and magnetometer capable of 12-bit and 24-bit resolution, respectively. With data transmitted via the eLPRT protocol, the system accurately calculated the roll, pitch, and yaw using onboard fusion algorithms, minimizing the error from external acceleration. Its compact, battery-powered design allowed for easy attachment to the leg without restricting movement, enhancing both user comfort and system flexibility. This work contributes to the field of wearable biomechanics by demonstrating that a hybrid photonic-inertial system can achieve high-fidelity gait monitoring with minimal setup. Specifically, the key contributions are (i) high sensitivity and resolution, with the FBG sensor detecting small angular changes in the knee joint with 10 p.m. precision; (ii) a modular and adaptable design suitable for various body types and potentially extensible to other joints; (iii) clear applicability in clinical and sports domains, supporting diagnostics, rehabilitation tracking, and performance analysis; and (iv) validation across subjects with different physical characteristics and gait speeds, confirming robustness and repeatability. Looking forward, several enhancements are proposed to extend the system's capabilities. Embedding the FBG sensor directly into textile substrates could reduce mechanical displacement during rapid movements, while refining the inertial sensor alignment may further improve angular accuracy.