A surgical system for penetrating and determining a characteristic of tissue. An instrument generates rotational torque, and a drill bit tool body extends along an axis between a distal end to engage tissue and a proximal end to couple to the instrument. An emitter operatively coupled to the instrument emits light. A detector operatively coupled to the instrument detects light. An emission lightguide within the tool body transmits light emitted by the emitter toward the tissue as the instrument rotates the tool body. A detection lightguide within the tool body is spaced from the emission lightguide and transmit light reflected by the tissue toward the detector as the instrument rotates the tool body. The emitter emits light into the emission lightguide along the axis, and the detector detects light reflected from the tissue exiting the detection lightguide transverse to the axis when the tool body is coupled to the instrument.