We describe experimental results demonstrating the performance of an erbium-doped silica fiber as a remote temperature sensor in the temperature interval 21 to 96°C. We present the measured fluorescence spectrum corresponding to the energy levels 2H11/2 and 4S3/2. This sensor features simple signal detection in a band and its data analysis system, incorporating a power ratio to reduce noise effects. The channel responsivity, power ratio, and sensitivity for a number of possible filters are presented. By using filters transmitting the 527- to 537-nm and 545- to 555-nm spectral bands, the following figures of merit are achieved: the responsivity is greater than 0.2 μW/K, and the sensitivity is 0.0065 K–1. With a custom-made filter centered on 545 nm, even higher sensitivity is predicted.