High-tolerance broadband-optical switch in planar lightwave circuits

A 2×0.2 optical switch having a main propagation axis, comprising:

• a) a first 3 dB adiabatic coupler having
• i) a first pair of constant width, asymmetric waveguide branches, each said branch extending between a proximal end and a distal end, each said branch having a curved section with a variable curvature, said branches separated over a coupling length by a changing spacing therebetween and blending in a symmetric intersection area at said distal end, and
• ii) two symmetric branches connected to said intersection area at said distal end,
• b) a second 3 dB adiabatic coupler having
• iii) a first pair of constant width, asymmetric waveguide branches, each said branch extending between a proximal end and a distal end, each said branch having a curved section with a variable curvature, said branches separated over a coupling length by a changing spacing therebetween and blending in a symmetric intersection area at said distal end, and
• iv) two symmetric branches connected to said intersection area at said distal end, wherein said first and second adiabatic couplers facing each other along the main optical propagation axis in a mirror image,
• c) two identical arms connecting said first and second pairs of symmetric branches optically to each other along the main propagation axis, and
• d) at least one active element coupled to at least one of said identical arms for dynamically changing an optical property of said at least one arm, whereby the implementation of the switch in a planar lightwave circuit provides a switch that is practically polarization independent, and has a low loss and a very high extinction ratio over an exceptionally broad band range.