Patent ID: 6088491
Filing Date: 2000-07-11
Classification: G02B,G02F

Abstract:
An optical circulator comprising:a first port comprising a first optical fiber;a second port;a third port comprising a second optical fiber;a beam splitter connected to said first and third ports for separating a first light signal entering said first port into first and second outgoing light signals and for separating a second light signal entering said third port into third and fourth outgoing light signals, said first and third outgoing light signals being spaced-apart from said second and fourth outgoing light signals, said first and second outgoing light signals comprising, respectively, orthogonal polarization components from said first light signal, and said third and fourth outgoing light signals comprising, respectively, orthogonal polarization components from said second light signal, said beam splitter comprising a first pair of beam splitting walk-off crystals comprising a first splitting walk-off crystal having a first walk-off direction and a second beam splitting walk-off crystal having a second walk-off direction, said first walk-off direction being opposite to that of said second walk-off direction, said first optical fiber of said first port being connected to said first walk-off crystal and said second optical fiber of said third port being connected to said second walk-off crystal, said beam splitter further comprising a second pair of beam splitting walk-off crystals comprising a third splitting walk-off crystal having a third walk-off direction and a fourth beam splitting walk-off crystal having a fourth walk-off direction, said third walk-off direction being opposite to that of said fourth walk-off direction, and said first and second walk-off directions being orthogonal to said third and fourth walk-off directions;a plurality of Faraday stages including a first Faraday stage and a last Faraday stage, said Faraday stages being arranged in series, said first Faraday stage receiving light from said beam splitter and said last Faraday stage being positioned so as to provide light to said second port,wherein each Faraday stage comprises a Faraday rotator and a walk-off crystal, each Faraday rotator being characterized by a direction of rotation and each walk-off crystal being characterized by a walk-off direction, and wherein said second port and said walk-off directions and directions of rotation of said Faraday stages are chosen such that light entering said first port exits said second port, light entering said second port exits said third port, and light entering said third port is prevented from exiting said first and second ports.