Systems and methods for measuring a target radiation substance using a fiber-optic sensor. An ample method includes activating the sensor at a first power level, measuring light at a photo sensor, increasing power to a second power level, if the measured light indicates possible presence of the target radiation substance, measuring light at the photo sensor after the increase in power, and outputting an error signal, if the target radiation type was not detected based on the measured light signatures. The first power level is typically between 1-1000 .mu.Watts and the second power level is typically between 100-10000 .mu.Watts. In a further confirmation, the power is decreased to approximately the first power level, if the error signal is not outputted.