Topic
Keying
About: Keying is a research topic. Over the lifetime, 6598 publications have been published within this topic receiving 82943 citations.
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TL;DR: A maximum-likelihood estimate of the amplitude of a binary phase-shift keying modulated signal is derived and an iterative SNR search algorithm is developed that achieves low bias for low SNR.
Abstract: Signal-to-noise ratio (SNR) is an important parameter in many receivers. In this letter, we derive a maximum-likelihood estimate of the amplitude of a binary phase-shift keying modulated signal and develop an iterative SNR search algorithm. Low bias is achieved for low SNR.
67 citations
TL;DR: In this paper, the input power tolerance of a single-pump fiber-optic parametric amplifier (FOPA) is experimentally shown to be enhanced for return-to-zero differential phase-shift keying (RZ-DPSK) modulation compared to RZ on-off keying modulation at 40 Gb/s.
Abstract: The input power tolerance of a single-pump fiber-optic parametric amplifier (FOPA) is experimentally shown to be enhanced for return-to-zero differential phase-shift keying (RZ-DPSK) modulation compared to RZ on-off keying modulation at 40 Gb/s. The improved nonlinear tolerance is exploited to demonstrate amplitude regeneration of a distorted RZ-DPSK signal in a gain-saturated FOPA. An optical signal-to-noise ratio penalty of 3.5 dB after amplitude distortion is shown to be reduced to 0.2 dB after the FOPA, thus clearly demonstrating the regenerative nature of saturated FOPAs for RZ-DPSK modulation.
67 citations
TL;DR: A new calibration method that uses the training sequence received at each received burst of data to calibrate the five-port system and results on quaternary phase-shift keying demodulation are presented.
Abstract: Many experiments have been proposed in order to demonstrate that the "five-port" system performs a homodyne demodulation . The large bandwith of a five-port circuit is its main advantage. However, this kind of system must be calibrated for each frequency in order to carry out the inphase and quadrature demodulation. The subject of this paper is to show a new calibration method. This technique uses the training sequence received at each received burst of data to calibrate the five-port system. A method to synchronize the receiver with the training sequence of each burst is presented. We also study the effect of adjacent channels and cochannel interferer on the calibration. Results on quaternary phase-shift keying demodulation are presented.
67 citations
TL;DR: This paper surveys the literature on communication theory from 1968 to 1973 and describes the literature from this period on nonlinear and non-Gaussian problems, analog communication, and feedback communication.
Abstract: This paper surveys the literature on communication theory from 1968 to 1973. A large part of this literature, and of this paper, deals with digital communication through linear dispersive channels. Error rate bounds for pulse-amplitude modulation systems, the optimization of linear transmitters and receivers, and adaptive equalization are topics discussed initially. Important results from the literature on non-linear receivers are described next, including decision feedback, maximum-likelihood, and Viterbi algorithm approaches. New results on the conventional digital modulation formats of amplitude, phase, and frequency-shift keying are summarized. The paper concludes with sections describing the literature from this period on nonlinear and non-Gaussian problems, analog communication, and feedback communication.
67 citations
TL;DR: In this article, a new class of optical modulation formats based on the combination of m-ary pulse-position modulation (m-PPM) or mary frequency-shift keying (FSK) with additional polarization and/or phase modulation is presented.
Abstract: We present a new class of optical modulation formats based on the combination of m-ary pulse-position modulation (m-PPM) or m-ary frequency-shift keying (FSK) with additional polarization and/or phase modulation, which is applied on the information carrying pulses in the case of m-PPM or on the information carrying frequency carriers in the case of m-FSK. We describe the principle and implementation of this class of optical modulation formats, and formulate their theoretical receiver sensitivities in optically pre-amplified receivers. Pilot-assisted frequency-domain equalization, similar to that used in coherent optical orthogonal frequency-division multiplexing (CO-OFDM), is used for reliable channel estimation and compensation. CO-OFDM also allows m-FSK to be implemented with high spectral efficiency. As a particular format in this class, m-PPM in combination with polarization-division-multiplexed quadrature phase-shift keying (PDM-QPSK), termed as PQ-mPPM, offers superior receiver sensitivity in optically pre-amplified receivers at bit error ratios (BERs) around the thresholds of common forward-error correction codes. Record receiver sensitivities of 3.5 photons per bit (ppb) at BER = 10−3 and 2.7 ppb at BER = 1.5 × 10−2 are experimentally demonstrated at 2.5 Gb/s and 6.23 Gb/s using PQ-16PPM and PQ-4PPM, respectively. We further demonstrate the transmission of a 6.23-Gb/s PQ-4PPM signal over a 370-km unrepeatered ultra-large-area-fiber span with 71.7-dB total loss budget.
67 citations