A polarization-insensitive N-port optical circulator is proposed. A four-port and a six-port circulator are assembled and their characteristics are measured. Experiments demonstrate that the circulators have a low insertion loss (≤1.3 dB), a high isolation level (≥65.0 dB), and a high return loss (≥61.3 dB) for any polarization state of input light. # 1997 Optical Society of America
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