We propose a novel optical 45° hybrid employing a 2 × 8 paired interference based multimode interference (MMI) coupler, three phase shifters and three 2 × 2 optical couplers. Since the proposed 45° hybrid can demodulate an 8-ary differential phase shift keyed (8-DPSK) signal with only one delayed Mach-Zehnder interferometer (DMZI), the demodulator has simpler configuration and much smaller device dimensions than conventional 8-DPSK demodulators consisting of four pairs of DMZIs and 2 × 2 optical couplers. We calculate and experimentally demonstrate octagonal phase response of the proposed 45° hybrid with a relative phase deviation of < ± 5° over 32-nm-wide spectral range.
©2010 Optical Society of America
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