摘要： The research about milk fat content based on plastic optical fiber sensor using gamma and spiral spring without cladding configurations has been reported. LED light transmitted through the plastic optical fiber to be received by the phototransistor. Changes in milk fat content affect the light intensity received by the phototransistor. Sensor output voltage amplified by a differential amplifier and then the analog signal converted into the digital signal by the Arduino Uno microcontroller furthermore, the output voltage read on a computer. The milk fat content sample with a percentage of 0.773 % to 4.473 % affect the propagation of light in the core of plastic optical fiber results in power losses that occur so that the light intensity decreases and the output voltage measured becomes smaller. The results showed that the higher the milk fat content, the sensor output voltage decreases. The best measurements obtained on the spiral spring configuration with 4 windings produce value range 0.044 V, sensitivity 11.887 mV/%, and a resolution of 0.084 %. This method is effective as well as efficiently used as milk fat sensor because it has good sensitivity and resolution.