A 90° optical hybrid is a four-port optical device with two inputs and two outputs. The two output signals are proportional to E1 + E2 and E1 + E2 exp(j90°), respectively, where E1 and E2 are the complex amplitudes the two input signals. The 90° hybrids are needed in many applications, including homodyne optical receivers in both phase-locked and phase-diversity configurations. In this paper, the principle of operation of an all-fiber 90° hybrid is described, and an experimental unit using connectorized in-line single-mode fiber components is reported.
© 1987 Optical Society of America
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