A catheter is adapted to ablate tissue and provide optically-based lesion qualitative and quantitative monitoring, comprising a catheter body and a tip electrode distal the catheter body adapted for ablating tissue, the tip electrode having a shell and an alignment member defining a hollow distal portion therebetween. In accordance with the invention, the catheter further includes a plurality of optical waveguides adapted to transmit optical energy to and from the tip electrode. A distal portion of each waveguide extends through the hollow distal portion and terminates in openings formed in the shell. Advantageously, the alignment member fixedly secures the distal portion of each waveguide against movement relative to the alignment member and the shell.