Patent ID: 7876986

Claim:
A planar lightwave circuit comprising: an MMI (multi-mode interference) slab comprising a first set of input ports comprising at least two ports and a second set of input ports comprising at least two ports; the MMI slab further comprising a first set of output ports comprising at least two ports and a second set of output ports comprising at least two ports; the first set of input ports positioned to photonically couple each of the first set of input ports to each of the first set of output ports without substantial photonic coupling between each of the first set of input ports and each of the second set of output ports; the second set of input ports positioned to photonically couple each of the second set of input ports to each of the second set of output ports without substantial photonic coupling between each of the second set of input ports and each of the first set of output ports; and a plurality of grating waveguides configured to photonically connect the first set of output ports to the second set of input ports.