Disclosed herein are medical systems, devices, and methods for identifying a blood vessel as a vein or as an artery. The system includes an optical fiber configured for insertion into a blood vessel coupled with a console having a light source, an optical receiver, processors, and logic stored in memory. The optical fiber includes sensors disposed along its length configured to determine a state or condition of the optical fiber, where the state or condition includes a strain, movement, pressure, or temperature. The logic analyzes reflected optical signals emanating from the sensors to determine that the optical fiber is inserted within an artery or within a vein. Logic may also determine a red-blue shift of a projected light to determine a blood flow direction with respect to the optical fiber.