Phase Shift Keying Transmission Research Articles

The reconfigurable dispersion compensator based on LNOI waveguide grating

In this paper, we propose a novel reconfigurable optical dispersion compensator achieved by waveguide grating and electro-optic effect of lithium niobate on insulator. Reconfigurable compensation is attained by controlling the voltage of the electrodes on waveguide grating. The measured bit error rate in the system is below 10−10 in a 40 Gbit/s quadrature phase shift keying transmission system.

Enhanced frequency-domain fractionally spaced equalization for coherent optical transmission system with colored noise

An enhanced minimum mean-square-error (MMSE) frequency-domain (FD) fractionally spaced equalizer (FSE) for polarization demultiplexing is proposed in the presence of colored noise. The 2-norm of the estimated channel matrix and polynomial fitting of equalization coefficients are introduced to mitigate the colored noise without requiring knowledge of the optical and electrical filtering. Simulation results show that ∼3-dB improvement of equalization performance is achieved compared to conventional MMSE FD-FSE in an 8×112-Gbit/s wavelength-division multiplexing polarization-division multiplexing-quadrature phase shift keying transmission system over a 1200-km single mode fiber link.

Implementation of Health Monitoring System using Mixed Environment

Background: Research shows that the health care cost per capita have grown 2.4 percent faster than the gross domestic product (GDP) since 1970. The aim of this paper is to present a useful model of wireless system that can combine both hardware and software environments and it can also integrate with other technologies or infrastructure at a low cost, which can be used for the patient monitoring system. Methods: The biomedical sensor which is attached to the patient, will read analog data. The recorded data will be converted digitally by using Analog to Digital Converter (ADC) and a FPGA transmitter will be used to send this data to Phase Shift Keying (PSK) transmitter. The modulated data will be received by PSK receiver and another FPGA receiver will be used to get the data back on the system. For behavioural modelling Verilog hardware descriptive language is used to provide a high level abstraction and language constructions. And the Simulink software is used to provide a high-level mathematical modelling condition for digital communication system which can be used for the verification and algorithm development.The important modules implemented for the transmitter and receiver FPGA are bus interfacing, compression and the data framing. Findings: A short range wireless health monitoring wireless system is modelled by using a mixed software and hardware simulation environment.At all the stages of the hardware and software designs, different types of languages like Verilog HDL codes and MATLAB used to verify the operation of the modules. The behavioural HDL designed of the FPGA transmitter and receiver will be interfaced with the RF Simulink models of PSK transmitter and receiver by using System Generator (Sysgen) tool that acts as the converter simulator. A realistic design model of health monitoring system is implemented which can be used for future hardware design. Compression and framing are the two main operations used in the transmitter side. Data compression is implemented by Run-Length Encoding method and for data framing high data link control protocol has been used. The unique features of this models simulation are low cost, less complexity, low power dissipation and efficient data transmission. Finally the FPGA based healthcare system allows us to change the design configurations or up gradation of the system based on the requirements. Conclusion: In this paper distributed simulation approach is used for designing the health monitoring system which allows checking the specification of design at all the stages. Simulation by HDL and Simulink mixed models in not the objective of this work, but to prove that realistic design is possible for future health care system design.

Tunable Optical Parametric Regenerator Assessment in a 43 Gb/s RZ-DPSK Signal Transmission Link

We study a wavelength-tunable optical parametric regenerator (OPR) demonstrated experimentally by assessing numerically its performance as an inline component of a 43-Gb/s return-to-zero differential phase-shift keying transmission system. The device features wide input wavelength range operation and regenerative wavelength conversion. The improvement in the transmission reach that it provides is predicted by simulations benchmarked against the experimental data. An up to fourfold improvement at a bit error ratio of ~ 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> is estimated for a 360-km long regeneration span. We show that the improvement is achieved by a combination of the amplitude regeneration capabilities with the phase noise blocking character of the OPR, despite of the small amount of phase fluctuations induced by the regenerator itself.

Simple Estimation of the XPM-Induced Phase Error Variance in Hybrid OOK-PSK Systems

The variance of cross-phase modulation-phase error induced by low bit rate on-off keying (OOK) channels is analytically estimated based on the stochastic properties of random binary sequences. These results may be applied to coherent quadrature phase-shift keying transmission systems with neighboring 10-Gb/s OOK channels.

All-Optical 2R Regeneration With a Vertical Microcavity-Based Saturable Absorber

This paper gives an overview of recent demonstrations of optical 2R regeneration achieved by vertical microcavity mirror-based multiple-quantum-well saturable absorber (SA). The potential of the device to perform wavelength division multiplexing regeneration is first demonstrated through the first pigtailed SA chip implemented with eight independent fibers using a cost effective coupling technique. The cascadability and wavelength tunability assessment of this module associated with a power limiter fiber-based function has been experimentally demonstrated at 42.6 Gbit/s. Because this method of power limiting is not a suitable solution for all-optical multichannel 2R regeneration, a new SA structure allowing a power limiting function was proposed. We describe and characterize such a structure in this paper. This new SA opens the door to a complete passive all-optical 2R regeneration relying upon a single technology, as shown in this paper through the use of two SA: SA.0 for extinction ratio enhancement and SA.1 for high-power level equalization allowing receiver sensitivity (up to 3.5 dB) and Q-factor (up to 1.4 dB) improvement for a RZ signal at 42.6 Gbit/s. The limitation of SA.1 when the regenerator must be cascaded a large number of times is also described, leading to the observation that SA.1 should be more suitable for phase encoded formats that are more spectrally efficient than ON-OFF keying formats. A SA.1 used as a phase-preserving amplitude regenerator in a 42.6 Gbit/s RZ differential quadrature phase-shift keying transmission system is, therefore, assessed . A fiber launched power margin of 2 dB and a receiver sensitivity improvement of 5.5 dB are obtained. Finally, we use, for the first time an SA.1 as a phase-preserving amplitude regenerator of RZ differential quadrature phase-shift keying signals. The regenerator is assessed in a recirculating loop at 28 Gbaud. The system tolerance to nonlinear phase noise is enhanced by 3 dB and the distance improvement factor was 1.3 for a bit error rate = 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> .

Chromatic dispersion compensation in coherent transmission system using digital filters

We present a comparative analysis of three popular digital filters for chromatic dispersion compensation: a time-domain least mean square adaptive filter, a time-domain fiber dispersion finite impulse response filter, and a frequency-domain blind look-up filter. The filters are applied to equalize the chromatic dispersion in a 112-Gbit/s non-return-to-zero polarization division multiplexed quadrature phase shift keying transmission system. The characteristics of these filters are compared by evaluating their applicability for different fiber lengths, their usability for dispersion perturbations, and their computational complexity. In addition, the phase noise tolerance of these filters is also analyzed.

Comparative Studies on the Performance of Low Power Transmitters for Wireless Sensor Nodes

Problem statement: Power consumption was one of the most challenging aspects to design low power wireless sensor nodes. The objectives of the study were to (i) Design low voltage, low power transmitters for wireless sensor nodes and (ii) Compare and analyze the performance of the transmitters. Approach: The transmitters employed direct digital modulation scheme to reduce the power consumption of the sensor nodes. Emphasis was placed on observing device reliability constraints at low power to maximize the life time of the wireless sensor nodes. Results: The Amplitude Shift Keying (ASK) transmitter consumed a power of 400.104 μw from the 1.2 V supply. The Frequency Shift Keying (FSK) and Phase Shift Keying (PSK) transmitters consumed 520 μw and 5.2 mw respectively at 2.4 GHz. The transmitters suitable for low voltage, low power wireless sensor nodes were designed and implemented in 120 nm CMOS technology Conclusion: The performances of the ASK, FSK and PSK transmitters were analyzed and were compared with the previously reported low power approaches operated in similar frequency ranges.

Multiplier-Free Real-Time Phase Tracking for Coherent QPSK Receivers

This letter presents a hardware-efficient phase estimation algorithm that can replace the common complex estimators for a coherent quadrature phase-shift keying transmission system.

Optically Amplified Direct Detection With Pre- and Postfiltering: A Volterra Series Approach

We present yet another quasi-analytic model for an optically amplified receiver, comprising an optical preamplifier, an optical prefilter, a photodetector, and an electrical postfilter. Due to the square-law nonlinearity and its interaction with the linear pre- and postfilters, the understanding of this seemingly simple structure has been elusive, gradually evolving over a succession of studies, culminating in the models by Lee and Shim and Forestieri. Here we adopt a new approach to this old problem, applying Volterra nonlinear theory to obtain fresh insight deriving a simplified model streamlining the pseudoanalytic simulations. Volterra series is a powerful mathematical tool for simulating nonlinear systems, applied here to quadratic optical detection in an unconventional way, by deriving a mixed frequency-time representation, leading to a simple and compact quadratic form in the combined signal-plus-noise signal spectra, albeit not computationally efficient. Next, Forestieri's results, which used distinct bases for the signal and noise, are rederived using the insightful Volterra formalism. Finally, we reformulate the model using an expansion of both signal and noise in a common harmonic basis over a sliding window of duration equal to the ISI system memory. This final version of the optically amplified receiver model is most computationally efficient, provides the most compact description, and lends itself to intuitive interpretation. Applications of the new method include accurate determination of the bit error ratio of amplitude-shift keying, frequency-shift keying, and differential phase-shift keying transmission systems in the linear optical link propagation regime, including the effects of dispersion and fully accounting for intersymbol interference. The theory developed here is naturally extensible to advanced optical equalization techniques, involving Volterra nonlinear optoelectronic equalizers.

Optical transmission of variable-pulse-width alternating-phase duobinary modulation: MATLAB Simulink simulation and comparison with carrier-suppressed return-to-zero amplitude-shift-keying experimental transmission

Abstract. Transmission in a 40-Gbit/s alternating-phase 0 and duo-binary modulation format with 67%, 50%, and 33% pulse width modu-lation duobinary carrier suppression CS and carrier maximum pulsecarving is demonstrated. A minimum 136-ps/nm dispersion tolerancecan be achieved at this transmission rate.At least 5- and 1.2-dB receiversensitivity improvements are achieved for CS return-to-zero RZ 67%and 50% duobinary modulation, respectively, as compared with the ex-perimental measurement under CS RZ differential phase-shift keyingtransmission over a 320-km three-span optically amplified dispersion-compensated standard single-mode fiber system. A MATLAB Simulinkplatform is described for simulation of the transmission performance. © 2008 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.2957965 Subject terms: optical communications; modulation formats; duobinary;modulation . Paper 080186 received Mar. 8, 2008; accepted for publication Apr. 28, 2008;published online Jul. 22, 2008.

Electronic Post-compensation for Nonlinear Phase Fluctuations in a 1000-km 20-Gbit/s Optical Quadrature Phase-shift Keying Transmission System Using the Digital Coherent Receiver

We demonstrate electronic post-compensation for nonlinear phase fluctuation in a 1000-km 20-Gbit/s optical quadrature phase-shift keying (QPSK) transmission system, where group-velocity dispersion is well managed. The inter-symbol interference (ISI) at the transmitter induces the nonlinear phase fluctuation through self-phase modulation (SPM) of the signal transmitted through a fiber. However, when the optimized phase shift proportional to the intensity fluctuation is given to the complex amplitude of the signal electric field by using a digital coherent receiver, the nonlinear phase fluctuation can be reduced effectively.

Convergence of phase fluctuation induced by intrachannel four-wave mixing in differential phase-shift keying transmission systems via phase fluctuation averaging

This work investigates the effect of phase fluctuation averaging on phase fluctuation induced by intrachannel four-wave mixing (IFWM) in highly dispersed differential phase-shift keying transmission systems. Through repeatedly averaging the phase fluctuations of adjacent pulses, a simple analytical model and numerical simulation revealed that the IFWM-induced differential phase fluctuation is suppressed and convergent, even after an ultralong transmission. The influence of averaging the phase fluctuations on the bit error rate is also evaluated by the semianalytical method.

Analysis of nonlinear phase noise in single-channel return-to-zero differential phase-shift keying transmission systems

Self-phase modulation and intrachannel cross-phase-modulation- (IXPM) induced nonlinear phase noise is investigated by the variational method. IXPM can cause a considerable increase of phase noise. We show, however, that IXPM leads to a partial correlation between the phase noises of adjacent pulses, which tends to reduce the influence of nonlinear phase noise in return-to-zero differential phase-shift keying transmission. In highly dispersive transmission systems, intrachannel four-wave mixing-induced differential phase fluctuations are typically larger than differential nonlinear phase noise. The analysis is validated by Monte Carlo simulation.

Optimum dispersion mapping of single-channel 40 Gbit/s return-to-zero differential phase-shift keying transmission systems

We present a numerical study of the performance of 40 Gbit/s return-to-zero differential phase-shift keying (RZ-DPSK) transmission with different dispersion maps. The optimum dispersion mapping for RZ-DPSK format are discussed and compared with those for on-off keying (OOK). Two pseudo-linear transmission systems, one using standard single-mode fiber and the other nonzero dispersion-shifted fiber, are investigated, respectively. In principle, the optimum dispersion mapping for RZ-DPSK format is different from that for OOK and depends on intra-channel four-wave mixing and nonlinear phase noise.

Analysis of intrachannel impairments in differential phase-shift keying transmission systems

The evolution of the phase in a return-to-zero differential phase-shift keying system is studied by the generalized momentum method. The results show that phase fluctuation in the case of dispersion-managed solitons is much smaller than that in quasi-linear systems for a given launch power.

Interchannel nonlinear transmission penalties in polarization-multiplexed 2×10Gbit?s differential phase-shift keying transmission

We discuss the performance of a multichannel 2 x 10 Gbit/s polarization-multiplexed differential phase-shift keying transmission system. Through simulations and transmission experiments we find that, despite the constant power envelope of non-return-to-zero phase-shift keying modulation formats, polarization multiplexing strongly reduces the nonlinear tolerance and transmission performance at a 2 x 10 Gbit/s line rate with multichannel transmission. This results in a 10 dB power penalty when comparing single- and nine-channel transmission. Additionally, multichannel impairments in differential phase-shift keying and on-off keying are compared for 2 x 10 Gbit/s polarization-multiplexed transmission.

Performance comparison of optical 8-ary differential phase-shift keying systems with different electrical decision schemes

We examine the performance of optical 8-ary differential phase-shift keying transmission systems according to the type of receiver structure and modulation format. Compared with the approach based on a multilevel decision, we found that a bilevel receiver provides 3-dB gain in optical signal-to-noise ratio sensitivity and is more robust against chromatic dispersion for either nonreturn-to-zero or return-to-zero modulation.

A PSK transmission system employing transmitting and receiving butterworth filters with optimized noise performance

AbstractA band‐limited phase‐shift keyed (PSK) transmission system satisfying Nyquist's first criterion by an equalizer using Butterworth filters for transmitting and receiving filters is discussed. Minimum noise equalization that minimizes the receiver equivalent noise band width is proposed and the characteristics of such a system are calculated. In addition, minimum noise equalization is compared with reference equalization and roll‐off equalization and it is clarified that minimum noise equalization is better than these equalization method in frequency and power efficiency. It is shown also that the frequency efficiency and the efficiency of transmitting power have a trade‐off relationship in a bandwidth‐limiting and then power‐amplifying scheme and the frequency efficiency is increased without decreasing the transmission power by decreasing the heat loss of a high‐order transmitting filter in a power‐amplifying and then band‐width‐limiting scheme.

Polar quantizing for coded PSK transmission

The issue of demodulator quantization prior to decoding in error control systems employing M-ary phase-shift keying (PSK) as a modulation technique is considered. The use of angle-only, or polar, quantization with J>or=M levels, which is an easily implemented alternative to rectangular quantization, is described. The R/sub 0/ parameter is presented as an effective indicator of coding potential for quantized M-ary PSK channels, and different designs in the R/sub 0/ context are discussed. The principal results are that for J=2M, a polar quantizer satisfies the necessary condition for optimality, and it is conjectured that the design is in fact optimal. The corresponding performance closes about half the gap (in decibels) between the hard-decision demodulator and the unquantized demodulator. Angle-only quantization, in the limit of fine precision, costs only a fraction of a decibel in performance for typically operated coded 8-PSK and 16-PSK. Numerical results for quantizers with J=2M and J=4M are presented, and the case of an added erasure zone is considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>