The present invention provides improved collimating lens assemblies (32), improved methods of reducing the
optical power density in collimating lens assemblies, and to improved
fiber optic rotary joints (31) incorporating such improved collimating lens assemblies. The improved collimating lens
assembly broadly includes: a singlemode
fiber (38) terminating in a distal end; a step-index multimode
fiber (44) having a proximal end abutting to the singlemode fiber distal end, and having a distal end; a graded-index multimode fiber (45) having a proximal end abutting the step-index multimode fiber distal end, and having a distal end; and a collimating lens (34) longitudinally spaced from the graded-index multimode fiber distal end by an intermediate air gap (43), and operatively arranged to collimate light rays emanating from the graded-index multimode fiber distal end. The improved collimating lens
assembly is characterized by the fact that there is no
epoxy,
silicone gel or index-matching material between the graded-index multimode fiber distal end and the collimating lens. Rather, these various elements are fusion-spliced together. The improved collimating lens
assembly is capable of handling energy levels that are typically used in various
wavelength division
multiplexing techniques.