A medical device used in a medical robotic system has a conduit and an orientable tip. An optical fiber coupled to a laser source and/or a catheter coupled to one or more biomaterial sources extends through the conduit and tip so that the tip of the medical device may be robotically directed towards a target tissue for laser and/or biomaterial application as part of a medical procedure performed at a surgical site within a patient. A protective sheath covers the fiber as it extends through the conduit and tip. A first coupler adjustably secures at least the sheath to the medical device and a second coupler adjustably secures the fiber to at least the sheath. A similar dual coupler mechanism may be used to secure the sheathed catheter to the medical device.