Hybrid optical isolator, circulator or switch, and systems utilizing same
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Citation (published version)Greg Blonder, Charles Henry, Rudolf Kazarinov, Raymond Wolfe. "Hybrid optical isolator, circulator or switch, and systems utilizing same." U.S. Patent 4,978,189-A.
An optical circulator/isolator is implemented in a semiconductor package formed by a semiconductor substrate, which supports integral thin film waveguide polarization splitters and combiners, and a semiconductor lid, which supports four spherical lenses and a polarization rotator. The latter is a composite of at least two adjacent slabs of optically active material, one slab serving as a nonreciprocal 45° rotator (e.g., a Faraday rotator) and the other as a reciprocal 45° rotator (e.g., half-wave device). The lenses, serving both as beam expanders/condensers and as collimators, are positioned between the waveguide ends and major surfaces of the composite slab. When used with means for reversing the direction of the magnetic field in the nonreciprocal rotator, the device functions also as a switch. Also described are system architectures made possible by these devices; e.g., a single-fiber LAN having a ring architecture for non-interfering counter flow of information and a single fiber, bidirectional FTTH system for handling CATV and POTS.