High-tolerance broadband-optical switch in planar lightwave circuits

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

• a) a first 3 dB adiabatic coupler having a first pair of symmetric branches, said first coupler further characterized by having two straight branches with different widths, said first coupler straight branches separated over a coupling length by a changing spacing therebetween;
• b) a second 3 dB adiabatic coupler having a second pair of symmetric branches, said second coupler further characterized by having two straight branches with different widths, said second coupler straight branches separated over a coupling length by a changing spacing therebetween, said first and second adiabatic couplers facing each other with their respective symmetric branches along the main 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 which is practically polarization independent, and has a low loss and a very high extinction ratio over an exceptionally broad band range.