The depth of an ablation lesion is assessed using a differential opticalresponse of a catheter with multiple fiberoptic transmitters and receiversat the tip. To detect tissue optical response at shallow depths,closely-spaced transmitter/receiver pairs of optical fibers are used. Todetect deeper tissue response, the same or a different transmitter canbe used with another receiver that is relatively farther away. The distancebetween the transmitter and receiver is chosen depending on thedesired depth of sensing. Plateauing or peaking of the optical signalduring the course of ablation indicates an end point at a selected tissuedepth.
