Design difficulties of 3D lightwave circuits for switching

For recently proposed 2-D lightwave circuits (LWCs) the architectural implications of introducing several wavelengths are discussed. Three types of 3-D architectures are considered (1) reconfigurable router (2) straight-forward extension of the 2-D LWCs of any geometry N 3 to 3-D by introducing several wavelengths at every waveguide (WG) and (3) mapping a generated network topology (which starts with the 2-D LWC) onto the 3-D LWC in (2). The architectures in (2) require the generation of the total number of permutations at every switch for non-blocking networks whereas the architectures in (3) allow (amongst others) for some switches the reduction of the number of permutations. The computation of the total number of permutations requires (i) a photonic feedback (FB) controller matrix at several wavelengths which provide rn! x k! permutations and additionally (ii) several frequency conversions (FCs) which complete the total number (m x k)! permutations where k is the size of switches and rn is the number of wavelengths.