Keying

About: Keying is a research topic. Over the lifetime, 6598 publications have been published within this topic receiving 82943 citations.

Eight-state trellis-coded optical modulation with signal constellations of four-dimensional M-ary quadrature-amplitude modulation.

Abstract: We apply the eight-state trellis-coded modulation (TCM) using signal constellations of four-dimensional M-ary quadrature-amplitude modulation (4D-MQAM) to optical communication systems for the first time to our knowledge. In the TCM scheme, the free distance of the trellis diagram is equal to the minimum distance between constellation points in partitioned subsets, which enlarges the coding gain effectively. In fact, its asymptotic power efficiency is 3-dB larger than that of the set-partitioned 4D-MQAM (SP-4D-MQAM) format, while their spectral efficiencies are the same. Such theoretical predictions are confirmed through computer simulations on eight-state TCM with constellations of 4D-4QAM (i.e., 4D quadrature phase-shift keying: 4D-QPSK) and 4D-16QAM. In particular, eight-state TCM with 4D-QPSK constellations is practically important because of its simple encoder structure, relatively low computational cost, and high coding gain against dual-polarization QPSK (DP-QPSK) and SP-4D-QPSK. Through measurements of its bit-error rate (BER) performance, we confirm that the coding gain against DP-QPSK is about 3 dB at BER=10−3.

Simultaneous All-Optical and and nor Gates for NRZ Differential Phase-Shift-Keying Signals

Abstract: A scheme for realizing all-optical logic AND and NOR gates simultaneously for nonreturn-to-zero differential phase-shift-keying signals is proposed and demonstrated based on a delayed interferometer and two semiconductor optical amplifiers. Experimental demonstration at 20 Gb/s verifies the logic integrity of this scheme. The final results are derived in the ON-OFF keying format with clear open eyes and extinction ratios over 10 dB. The proposed scheme can be expanded to realize arbitrary logic gate.

Performance of an Integrated Coherent Receiver Module for up to 160G DP-QPSK Transmission Systems

Abstract: A coherent receiver module is presented, comprising two optical 90° hybrids monolithically integrated with eight waveguide p-i-n photodiodes in balanced configuration and two dual-channel linear transimpedance amplifiers. Its performance is demonstrated by transmitting up to 160 Gb/s dual-polarization quadrature phase-shift keying signals over 610 km standard single-mode fiber.

Keyed connector assembly for flat flexible circuitry

Abstract: A keying system is provided in a connector assembly for electrically interconnecting the conductors of a flat flexible circuit to the conductors of a complementary connecting device. The assembly includes a first connector having a body member for positioning the flat flexible circuit thereon. A second connector mates with the first connector and includes a pattern of keying projections isertable into a corresponding pattern of keying holes in the flat flexible circuit on the first connector.

Coherent UDWDM PON with joint subcarrier reception at OLT

Abstract: In this contribution, we report on the experimental investigation of an ultra-dense wavelength-division multiplexing (UDWDM) upstream link with up to 700 × 2.488 Gb/s polarization-division multiplexing differential quadrature phase-shift keying parallel upstream user channels transmitted over 80 km of standard single-mode fiber. We discuss challenges of the digital signal processing in the optical line terminal arising from the joint reception of several upstream user channels. We present solutions for resource and cost-efficient realization of the required channel separation, matched filtering, down-conversion and decimation as well as realization of the clock recovery and polarization demultiplexing for each individual channel.