An infrared fiber-optic device is able to monitor esophageal temperature during an ablation/cryoablation procedure over a volume of interest to sense whether the temperature is too high or too low. The device may include a plurality of optical fibers each with a wide angle lens collectively disposed circumferentially and longitudinally to cover the volume of interest, as the particular region over which undesirable temperature may not be known beforehand. In other examples, the device may include an embedded array of infrared sensors extending sufficiently to encompass a volume of interest. The device may be used as part of a feedback control to regulate and stop operation of the ablation/cryoablation procedure to prevent vessel damage.
