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Plastic optical fiber testing as a sensor can be applied in pH measurement using loop configuration. It was made of a plastic optical fiber material with two types of peel, namely with cladding and without cladding. Sensor testing was done by dipping the sensor into buffer solutions with varying pH values. The light intensity from the LED will experience power losses due to the effect of adding the solution refractive index around the sensor, so the phototransistor will receive smaller the light intensity. Changes of light intensity in the optical fiber causes the output voltage read on the microcontroller and the computer decreases. The best measurement was obtained at sensor type of without cladding 4 loops with sensitivity 0.035 V/pH and resolution 0.029 pH. Aplication of plastic optical fiber as sensor for pH measurement has advantages such as low cost, real time, high sensitivity, accurate and simple measurement.

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This research discusses the polymer optical fiber sensor for respiratory measurements. The infrared LED that produces light will propagate along the polymer optical fiber which will be received by the phototransistor and the differential amplifier. The output voltage in the form of an analog signal will be converted to a digital signal by the Arduino Uno microcontroller and displayed on the computer. The polymer optical fiber sensor is installed on the corset using a variety of configuration (straight, sinusoidal, and spiral), placed in the abdomen, and a variety of positions (abdomen, chest, and back) using only a spiral configuration. While doing the inspiration, the stomach will be enlarged so that the optical fiber sensor will have strain. The strain will cause loss of power, the resulting light intensities received by the phototransistor are reduced, and the output voltage on the computer decreases. The result shows that the highest voltage amplitudes were in the spiral configuration placed in the abdominal position for slow respiration measurements with the highest range, sensitivity, and resolution which are 0.119 V, 0.238 V/s, and 0.004 s, respectively. The advantages of our work are emphasized on measurement system simplicity, low cost, easy fabrication, and handy operation and can be connected with the Arduino Uno microcontroller and computer.

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