Reflection suppression by orthogonal modes

A method is proposed where isolation of a single-frequency laser from reflections of an optical network is obtained using reciprocal elements throughout. The principle is based on the isolation obtained by a double transit quarter-wave plate, which can be generalized. Only linearity and time invariance are required. Thus the network elements can even be nonreciprocal. An application is the isolation of the local-oscillator laser in an integrated optical heterodyne/homodyne receiver.<
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