摘要：

An optical circulator type device comprising: first, second, third and fourth input/output waveguides; a series of optical elements including polarisation rotation elements; wherein input light omitted from the first input/output waveguide traverses the series of optical elements which spatially separate the light into orthogonal polarisation states, projecting them towards the second and third input/output waveguides respectively; and polarised input light emitted from the second and third input/output waveguides traverse the series of optical elements and is combined at the fourth input/output waveguide.

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