title: Optical 45 degrees hybrid for demodulating 8-ary DPSK signal.
abstract: We propose a novel optical 45 degrees hybrid employing a 2 x 8 paired interference based multimode interference (MMI) coupler, three phase shifters and three 2 x 2 optical couplers. Since the proposed 45 degrees 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 x 2 optical couplers. We calculate and experimentally demonstrate octagonal phase response of the proposed 45 degrees hybrid with a relative phase deviation of < +/- 5 degrees over 32-nm-wide spectral range.
authors.affiliation: Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, 243-0197, Japan. jeong.sh@jp.fujitsu.com
authors.forename: Seok-Hwan
authors.initials: SH
authors.lastname: Jeong
authors.forename: Ken
authors.initials: K
authors.lastname: Morito