Abstract: A fluid detector includes a coupler. The coupler includes a hollow tube, an optical fiber, and a jacket. A fluid delivery device includes a fluid output end and a fluid recovery end. The fluid output end is connected to a first input end of the hollow tube. The fluid recovery end is connected to a first output end of the hollow tube. An optical signal generator inputs an optical signal to a second input end of the optical fiber. A detection module includes an optical sensor, a database, and a processor. The optical sensor detects the optical signal outputted by the second output end and generates a sensing datum. The processor is electrically connected to the optical sensor and the database. The processor compares a characteristic value of the sensing datum with characteristic values of sample data stored in the database and generates a detection data.