Abstract: A catheter based optical system for generating data as to the condition of a tissue sample of a mammalian vessel. The system includes an elongated catheter shaft having a tissue engaging distal end and a coupled proximal end and an elongated optical delivery fiber arrangement disposed through a lumen of said catheter, said optical delivery fiber arrangement having a distal end and a proximal end. The distal end of the delivery fiber arrangement has a re-director light emitter thereon for directing light against mammalian tissues. An elongated optical collection fiber arrangement is disposed through a lumen of the catheter, the optical collection fiber arrangement having a distal end and a proximal most end. The distal end of the collection fiber arrangement has a re-director light receiver thereon for receiving light reflected from the mammalian tissue by the light emitter. The light emitter and the light receiver are longitudinally spaced apart from one another in the distal end of the catheter.