Three-dimensional space-division Y-splitter for multicore optical fibers

A three-dimensional space-division Y-splitter for multicore optical fibers, comprising:

• an input leg adapted for connection to an input multicore optical fiber;
• two output legs adapted for connection to two output multicore optical fibers, the input multicore optical fiber and the two output multicore optical fibers each having the same number of independent cores, wherein the multicore optical fibers include a longitudinal axis and are disposed in a manner that is rotated by 19° around their longitudinal axis thereby providing a line-of-sight view between cores in the waveguide of each Y-splitter;
• and
• a plurality of Y-sub-splitters equal to the number of cores in the input multicore optical fiber, each of the Y-sub-splitters being connected between a unique one of the cores of the input multicore optical fiber and a corresponding core of each of the two output multicore optical fibers, each of the Y-sub-splitters having a space division splitter splitting an input optical beam in the corresponding input core into two identical output optical beams of one-half the power of the input optical beam, wherein each of the Y-sub-splitters are configured so as to allow line-of-sight view among the respective cores without any crossings thereby reducing the cross-talk between each Y-splitter's two output legs, wherein each said Y-sub-splitter comprises:
• i) an expander for expanding the input optical beam to produce an output wherein the expander comprises a graded-index (GRIN) rectangular waveguide lens, the rectangular waveguide lens having a constant refractive index profile, wherein the index profile defines a parabolic index optimized to have a small slope;
• ii) the space division splitter being a double-hump graded refractive index splitter defining a rectangular waveguide having a central input core and two lateral output cores on opposite sides of the central input core, the output of the expander optically feeding the space division splitter, the splitter producing two output beams, wherein the rectangular waveguide lens has a refractive index profile distributed along a waveguide width of 60 μm;
• and
• iii) a separator defining two laterally separated waveguides receiving the two output beams of the splitter and separating the two output beams for transmission to the corresponding cores of the two output multicore optical fibers.