Embodiments of endo-illuminators and related methods are disclosed. One embodiment of an illuminator can comprise a cannula defining a passage, an optical element disposed at an end of the cannula, and an optical fiber running through the passage with the distal end of the optical fiber in contact with the optical element. The optical fiber includes at least a heat preconditioned distal portion that terminates in the distal end that is in contact with the optical element. One embodiment of a method can comprise inserting an optical fiber through a proximal portion of a cannula and optical element assembly until the distal end of the optical fiber contacts the optical element, heating a distal portion of the optical fiber to between a softening temperature and a melting temperature for a period of time to cause the distal portion to axially shrink and moving the optical element so that the optical element is in contact with the distal end of the optical fiber when the distal portion of the optical fiber has axially shrunk. Moving the optical element so that the optical element is in contact with the distal end of the optical fiber when the distal portion of the optical fiber has axially shrunk can comprise applying a force to the cannula and optical element assembly to maintain the optical element in continuous contact with the distal end of the optical fiber while the optical fiber axially shrinks.