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 of 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
Leonid G. Kazovsky, Lyn Curtis, William C. Young, and Nim K. Cheung, "All-fiber 90° optical hybrid for coherent communications," Appl. Opt. 26, 437-439 (1987)