title: Polarization insensitive 25-Gbaud direct D(Q)PSK receiver based on polymer planar lightwave hybrid integration platform.
abstract: We report a direct DPSK receiver based on polymer planar lightwave circuit technology, which incorporates a 2x25 GHz photodiode (PD) array hybridly integrated via 45° mirrors. In this direct DPSK receiver, a half-wave plate and heating electrodes are implemented to eliminate the polarization-dependent frequency-shift (PDFS) of the delay-line interferometer (DLI). By applying a proper heating current, a residual PDFS of practically zero at 1550 nm and within ±125 MHz was achieved over the full C-band. Integrated with the PD array, the peak responsivity is ~0.14 A/W for orthogonal polarizations over the C-band. To characterize this direct receiver, we introduce an adapted common-mode rejection ratio (CMRR), which takes into account the unequal responsivities of the PDs, the uneven split of the input power by the DLI, the phase error and the extinction ratio of the DLI. The measured CMRR under DC condition is below -20 dB over the C-band.
authors.affiliation: Fraunhofer Institute for Telecommunications, Heinrich-Hertz-Institut, Einsteinufer 37, D-10587 Berlin, Germany. jin.wang@hhi.fraunhofer.de
authors.forename: Jin
authors.initials: J
authors.lastname: Wang
authors.forename: Crispin
authors.initials: C
authors.lastname: Zawadzki
authors.forename: Nelson
authors.initials: N
authors.lastname: Mettbach
authors.forename: Walter
authors.initials: W
authors.lastname: Brinker
authors.forename: Ziyang
authors.initials: Z
authors.lastname: Zhang
authors.forename: Detlef
authors.initials: D
authors.lastname: Schmidt
authors.forename: Norbert
authors.initials: N
authors.lastname: Keil
authors.forename: Norbert
authors.initials: N
authors.lastname: Grote
authors.forename: Martin
authors.initials: M
authors.lastname: Schell
mesh_terms: D001718:Birefringence; D017097:Electric Impedance; D007368:Interferometry / Q000295:instrumentation*; D008027:Light; D008163:Luminescent Measurements / Q000295:instrumentation*; D008962:Models, Theoretical; D011108:Polymers / Q000737:chemistry*; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*
chemical_list: D011108:Polymers