A compact fibre-based fluorescence sensor

A compact sensor consisting of two positive guiding fibres and one negative non-guiding fibre has been developed with large sensitivity for detection of fluorescence emitted from a laser dye. The positive fibre is used to deliver laser light to the negative fibre. The negative fibre acts as a sensing element, the pump light leaks into its surrounding which excites the laser dye molecules embedded in an index matched liquid coated onto the core of the negative fibre. The fluorescence is guided by another positive fibre attached to the distal end of the negative fibre and detected by a CCD camera. The response of the sensor with various fibre diameters and sensing lengths as a function of laser dye concentration has been determined. The sensor is capable of measuring 50 pg/ml of laser dye (rhodamine 6G).