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Development of various health monitoring devices for health monitoring applications such as spine monitoring, respiration rate, heart rate, as well as upper and lower limb motion detections are at increasing rate. The use of optical fiber-based devices provides significant contribution in this area due to their advantages such as immunity to electromagnetic interference, lightweight and possibly small sensor setup. However, the application of intensity-based optical fiber sensor for human joint motion detections resulted in limited detection angle, where most sensor are not able to detect more than 90 deg. angle. To improve this limitation, we propose an optical sensor approach with mechanical-assisted components assembly that translates angular movement to linear movement. The light detection on the photodiode array at different pixels is analyzed to represent the angle movement of the knee. Based on our study, the proposed device can be applied to detect angle between 0−160° with an accuracy of 0.08°. The obtained results make it possible to apply this technique as knee monitoring device.

Knee monitoring is one of the common injuries suffered by people who are active in extreme sports. Traditional ways to identify these problems are based on background study of the patient, physical examination, and sometimes with the use of x-rays and MRIs. The use of x-rays and MRIs for repetitive use is not preferably suggested by physicians due to the high cost and other associated side-effect related to exposure to radiation. Due to these factors, an alternative device based on optical fibre sensor is proposed in this study. The proposed knee monitoring sensor is based on the use on step index type plastic optical fibre and linear array photodiode sensor. Based on the mathematical estimation and initial sensor measurement, this sensor is able to perform full range of motion between 0 to 155 degrees. The accuracy and resolution of this sensor is 1.0 degree and 0.5 degree, respectively. The aim of this study is to determine the current performance of the device before further improvement could be proposed.

Health monitoring devices are highly demanded in order to determine patients’ health condition, to monitor the health recovery progress, and to help the physiotherapist during rehabilitation period of a patient. This paper is focused on knee joint assessment devices and technology implementation. Knee joint angle measurement devices includes many devices such as accelerometer, electro-goniometer, torsiometer, acoustic, visual sensory, and optic fibre. There are several limitations to these technologies which require improvements. Many of the existing techniques and technologies are becoming conventional and there is a need to identify and to explore better methods to enhance the limitations of existing devices. The need of technologies with higher accuracy, reliability, and lower cost have always been a crucial factor. In this paper, a study of conventional and latest technologies are reviewed, and suggested to further explore the implementation of optical fibre based technology for the above-mentioned application. Optical fibre device has faster response, better accuracy, lighter in weight, lower cost, and is not effected by external physical variable such as electromagnetic waves as compared to conventional sensors.

Human joint angle measurement involves various applications, for example monitoring of spine movement in sagittal and frontal planes, upper limb motion such as shoulder, neck and elbow, as well as lower limb motion such as hip, knee, and ankle. As the range of motions of different human joints are not similar, the output estimation of the designed sensor for these applications need to be carried out prior to sensor development. In this paper, the conceptual design of low-cost plastic optical fibre based on single step index fibre is illustrated, the mathematical modelling is explained, and the sensor’s hardware assemble is designed using CATIA software, before the estimated sensor output is presented. These results will be used as a reference values for actual optical fibre sensor design in the near future.

This paper presents the theoretical investigation and experimental validation of an extrinsic optical fiber bending sensor based on intensity modulation with automatic compensation. The proposed optical fiber bending sensor can measure continuous bending movement in flexion, extension, and lateral directions, simultaneously. The theoretical study is significant in choosing the most suitable parameter values for the sensor so that its sensitivity and working range are applicable for spine monitoring application. The fabricated bending sensor also shows a minimum signal fluctuation due to temperature effect.

An extrinsic optical fibre bending sensor based on intensity modulation technique aimed for physiological application is presented. This sensing technique is capable of measuring the bending angle continuously in flexion, extension and lateral movements. The sensor working range is between −22° and 22° with 0.4° accuracy and 0.1° resolution. From the theoretical estimation, the bending sensor automatically compensates for variation in the source intensity and various losses in the input and output fibres. The experimental results obtained in this investigation verified the theoretical finding. Among the advantages of the this optical bending sensor are being noninvasive, suitable for continuous measurement and immune from electromagnetic effects.

This paper presents the investigation of an extrinsic optical fibre bending sensor for dynamic spine bending measurement in 2D planes. The sensor consists of one input fibre and three output fibres, confined in two modified holders. The spine bending causes the tilting angle between these two fibres to change, thus modulating the light intensity propagating in each output fibre. The output ratio between the output fibres is applied to represent the bending angle as well as to provide signal referencing for the optical fibre sensor. The study shows that the fabricated sensor is capable of measuring the spine movement in flexion, extension and lateral directions continuously.

This paper presents the implementation of an extrinsic optical fibre sensor based on intensity modulation technique aimed for continuous bending assessment of human spine movement. The sensor under investigation is non-invasive and capable of providing a continuous measurement of the bending angle in both flexion and extension directions of the human spine. The bending assessment is determined based on the measurement of the tilt angle loss between an input fibre and dual output fibres. Additionally, a reference fibre is also integrated into the sensor configuration by means of the divided beam system to compensate for any output variation resulting from temperature changes.

peer-reviewed The light attenuation measurement of a plastic optical fibre sensor based on a referenced intensity modulation technique with respect to different input voltage level and room temperature has been investigated. The results show that light attenuation at the sensor output and reference output are dependent on the source (LED) drive current and temperature, but the output ratio is small and tolerable for this application. This is significant for bending monitoring applications using optical fibre sensor based on intensity modulation, providing a more reliable technique based on power and temperature compensation. PUBLISHED peer-reviewed

This paper presents the investigation of sensing range limit for intensity modulated optical fibre bending sensor using single input and dual input fibres. Plastic optical fibre is used to measure the bending angle by measuring the changes of light intensity using tilt angle loss measurement approach. To define the bending range of the sensor configurations under investigation, the fibre was bended at several bending angle for a 30 second period purposely to reduce the effect of light source fluctuation and drift in measurement. It was found that, with the use of dual input source fibres, the bending angle range can be extended at almost twice angle range than the single input fibre but with a lower output resolution.

This paper presents the development of bending sensor using plastic optical fibre. The bending angle is measured with respect to the changes in light intensity at the receiving fibre. To study the relationship between the sensor's output intensity power and the bending angle, three mediums with different refractive index were used at the gap in between of the emitting and receiving fibres. It was found that, a higher refractive index medium could be used to improve the resolution of the sensor but with a reduced sensor working range.

peer-reviewed This paper presents a study on the application of plastic optical fibre for spine bending monitoring based on an intensity modulation. The bending angle is measured as the angle between the emitting and receiving fibres is changed. The measured light attenuation is compared with a theoretical evaluation and the differences between these values are discussed. It was found that the light attenuation for the light intensity agreed well (margin of error < 15%) with the theoretical value for the range between 180o (representing no bend) and 200o and it was significantly increased for the bending angle beyond that value due to the effect of fibre gap increment which resulted in a less reliable experimental estimation. PUBLISHED peer-reviewed

This paper presents the development of an extrinsic optical fibre sensor for continuous measurement of the human spine bending movement based on intensity modulation technique. Using the investigated sensor configuration, the bending angle was measurable in both flexion and extension direction with a maximum range of motion of 18° and -10°, respectively. From the output drift assessment of the sensor, bending accuracy of up to 0.5° was achievable, thus making it suitable for clinical environment application. A divided-beam referencing technique was also implemented in the sensor configuration to compensate for the input power fluctuation and temperature variation.

peer-reviewed This paper presents the implementation of power fluctuation compensation for an intensity-based optical fibre bending sensor aimed at monitoring human spine bending in a clinical environment. To compensate for the light intensity changes from the sensor light source, a reference signal was provided via the light reflection from an aluminum foil surface fixed at a certain distance from the source fibre end tips. From the results, it was found that the investigated sensor compensation technique was capable of achieving a 2° resolution for a bending angle working range between 0° and 20°. The study also suggested that the output voltage ratio has a 0.55% diversion due to input voltage variation between 2.9 V and 3.4 V and a 0.25% output drift for a 2 h measurement. With the achieved sensor properties, human spine monitoring in a clinical environment can potentially be implemented using this approach with power fluctuation compensation. PUBLISHED peer-reviewed