This paper presents the development, characterization and analysis of an intensity variation-based polymer optical fiber (POF) force sensor using cyclic transparent optical polymer (CYTOP) fiber through side-coupling light source embedded in different materials. Tests with application of vertical force on the sensor with different supports were performed to analyze the sensor responses when embedded in different materials. In addition, vertical force tests along the fiber were performed to analyze the sensor feasibility of detecting the location of applied force. Results of the force characterization on different materials show that the POF-CYTOP force sensor response is related to elastic modulus of the materials. Using the support I, more flexible (elastic modulus of $18.6\mathit{MPa}$), the sensor responses presented a high influence of the light coupling, resulting in an increase of the optical power. In contrast, the responses using the support II (elastic modulus of $1.6\mathit{GPa}$), presented a decrease of optical power variation with only a minor increase in the optical power when small forces are applied. This is due to the higher strain in the POF, resulting in optical power decrease due to radiation losses and stress-optical effect. Tests with application of the force along the fiber show that the sensor had different sensitivities for impacts located at different distances of the lateral section, leading to the possibility of estimating the impact location using a multiplexed sensor array. The differences in the sensor’s responses over the different supports show the feasibility of using the proposed sensor system for the stiffness assessment in users, where wearable optical fiber sensors can be employed on the real-time estimation of soft tissues, which finds important applications in rehabilitation as well as wearable robotics control and design.

本文介绍了基于强度变化的聚合物光纤 (POF) 力传感器的开发、表征和分析，该传感器使用环状透明光学聚合物 (CYTOP) 光纤，通过嵌入不同材料的侧耦合光源。对具有不同支撑物的传感器施加垂直力进行测试，以分析嵌入不同材料时的传感器响应。此外，还进行了沿纤维的垂直力测试，以分析传感器检测施加力位置的可行性。不同材料的力表征结果表明 POF-CYTOP 力传感器响应与材料的弹性模量有关。使用支撑 I，更灵活（弹性模量为$18.6\mathit{兆帕}$)，传感器响应对光耦合的影响很大，导致光功率增加。相比之下，使用支撑 II 的响应（弹性模量为$1.6\mathit{GPa}$)，当施加较小的力时，光功率变化减少，光功率仅略有增加。这是由于 POF 中的应变较高，由于辐射损失和应力光学效应导致光功率下降。沿纤维施加力的测试表明，传感器对位于横向截面不同距离处的冲击具有不同的灵敏度，从而可以使用多路复用传感器阵列估计冲击位置。传感器在不同支撑上的响应差异表明使用所提出的传感器系统进行用户刚度评估的可行性，其中可穿戴光纤传感器可用于软组织的实时估计，