Phase Modulation System Research Articles

Multiuser cpm transmission for mimo systems

Abstract Frequency-Division Multiplexed Continuous Phase Modulation (FDM-CPM) systems with Multiple Input Multiple Output (MIMO) transmission are investigated. In this paper, a multiuser reception scheme for CPM MIMO transmission is presented. The analyzed system is designed to achieve high spectral efficiency by exploiting the multiplexing gain of MIMO techniques. To take advantage of the multiplexing gain of MIMO systems, a Zero Forcing (ZF) MIMO detector and a low-complexity iterative algorithm for Inter- Carrier Interference (ICI) cancellation are considered. Numerical simulations have been performed to assess the performance improvement achieved with the proposed frequency-division multiplexed CPM multiuser MIMO system

Anti-Jamming Performance Simulation of PN-LFM Combined Ranging System

The pseudo-random binary-phase code phase modulation and linear frequency modulation (PN-LFM) combined ranging system is a new detection system, which has proven to be powerful capacity in range resolution, velocity resolution and maximum range measurable without ambiguity. In this paper, we study the anti-jamming performance of the new ranging system, especially in the fractal stochastic noise environments. We analyze the impact mechanism of fractal noise on the PN-LFM detection system, and simulate the output of correlating detection. The cross correlation function, power spectrum function and average power of pseudo random signal and fractal noise are deduced, compared with the impact of white noise on the pseudo code detection system. Simulation shows that PN-LFM combined ranging system possess powerful anti-jamming capacity, and performs better in the fractal noise environment than Pseudo random code phase modulation system.

The Gordon—Mollenauer Effect in 112 Gbit/s DP-QPSK Systems

Gordon and Mollenauer (G-M) proposed in 1990 that the interplay between the nonlinear Kerr effect and amplified spontaneous emission noise can generate an enhanced level of noise and degrade the performance of optical phase-modulated systems. We systematically investigate the G-M effect in 112 Gbit/s coherent dual polarization quaternary phase shift keying (DP-QPSK) systems through comprehensive simulation. The results show that in the presence or absence of inline dispersion compensation, the G-M effect will seriously damage the system performance. Some of our important conclusions are listed as follows: with the increase in the input power into each span, the G-M effect is enhanced simultaneously; the smaller the span length, the stronger the G-M effect caused by more inter-span interaction; for non-zero dispersion-shifted fibers, different coefficient values will cause a similar amount of G-M effect penalty; by comparing the system performance with different dispersion compensation ratios, one can conclude that different residual dispersions of the same magnitude, no matter whether they are under-compensated or over-compensated, can derogate the overall system performance to a similar degree. In brief, the G-M effect cannot be ignored. We also have a short discussion on how to reduce and compensate for the G-M effect in DP-QPSK systems.

Fiber-optic project-fringe interferometry with sinusoidal phase modulating system

A fiber-optic sinusoidal phase-modulating (SPM) interferometer for fringe projection is presented. The system is based on the SPM technique and makes use of the Mach–Zehnder interferometer structure and Young’s double pinhole interference principle to achieve interference fringe projection. A Michelson interferometer, which contains the detection of Fresnel reflection on its fiber end face and interference at one input port of a 3 dB coupler, is utilized to achieve feedback precise control of the fringe phase, which is sensitive to phase drifting produced by the nature of the fiber. The phase diversity for the closed-loop SPM system can be real-time measured with a precision of 3 mrad. External disturbances mainly caused by temperature fluctuations can be reduced to 57 mrad for the fringe map. The experimental results have shown the usefulness of the system.

Encoding Performance of Orthogonal Space-Time Coded Continuous Phase Modulation System

The orthogonal space-time coded continuous phase modulation (OST-CPM) system shows attractive performance over fading MIMO channels. In this paper, the Chernoff bound on pair-wise error probability (PWEP) is studied for two transmit antennas over spatially correlated quasi-static Rayleigh-fading channel. The maximum likelihood sequence detection (MLSD) algorithm is applied to the OST-CPM system. Approximate bound for high signal-to-noise ratio (SNR) is derived to evaluate the encoding performance in correlated channel. The effects of correlation coefficient matrices on the coding performance are simulated. Both analytical and simulation results show that the coding performance of this system decreases as the fading coefficients between the antennas increases. And the penalty on the coding performance increases a lot in fully correlated channel. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2469

Variable-Rate Ring Convolutional Coded Continuous Phase Modulation Using Puncturing

AbstractIn this paper, puncturing technique is used to establish variable-rate ring convolutional coded continuous phase modulation (CPM) systems. Maximum likelihood sequence detectors over both AWGN channels and Rayleigh flat-fading channels are considered. The suggested system provides us with different rates and performance when simple adjustment is taken to the puncturing matrix. Since the performance of the first error event of this system is represented by normalized minimum squared Euclidean distance (NMSED), some typical codes with maximum NMSED are searched and given. The performance of symbol error rate for the suggested system is simulated using computer software, and the results show that this system provides good performance of symbol error rate with variable-rate capabilities in time varying channels. Furthermore, simulation results also prove that the transmission efficiency increases when code rate is decreasing.

All-optical phase modulation for integrated interferometric biosensors

We present the theoretical and the experimental implementation of an all-optical phase modulation system in integrated Mach-Zehnder Interferometers to solve the drawbacks related to the periodic nature of the interferometric signal. Sensor phase is tuned by modulating the emission wavelength of low-cost commercial laser diodes by changing their output power. FFT deconvolution of the signal allows for direct phase readout, immune to sensitivity variations and to light intensity fluctuations. This simple phase modulation scheme increases the signal-to-noise ratio of the measurements in one order of magnitude, rendering in a sensor with a detection limit of 1.9·10⁻⁷ RIU. The viability of the all-optical modulation approach is demonstrated with an immunoassay detection as a biosensing proof of concept.

Intrachannel nonlinearity enhancement in polarization multiplexed phase modulated systems with differential detection

We compare nonlinear impairments in phase-modulated transmission with and without polarization multiplexing. Using an analytic approach that enabled us to accurately predict the Q factor at the receiver, we show that, without polarization multiplexing, the differential receiver is insensitive to two-pulse cross phase modulation, whereas with polarization multiplexing two-pulse interaction between cross-polarized components causes significant performance degradation.

A special type of codimension two bifurcation and unusual dynamics in a phase-modulated system with switched strategy

We investigate a new type of codimension two bifurcation and related dynamics in a phase-modulated system with switched strategy. Two curves intersect at a point and are called the crisis–Hopf bifurcation. At the critical crisis–Hopf vertex, a boundary crisis and Hopf bifurcation coincide. Metamorphosis of coexisting attractors can be observed in the vicinity of the vertex. Another novelty is that we discover some sets of measure zero with riddled holes in the neighborhood of the bifurcation point. These sets display some qualitative and quantitative features of riddled basins but they are essentially different from the riddled basin. It may provide a more comprehensive picture for unusual dynamical features.

Analysis of signed chromatic dispersion monitoring by waveform asymmetry for differentially-coherent phase-modulated systems

We analytically study received waveform asymmetries induced by chromatic dispersion (CD) for signed CD monitoring in differential quadrature phase-shift keying (DQPSK) systems and show that the asymmetries are results of differential detection and the ±π/4 phase shifters used in conventional DQPSK receivers. The theoretical insights developed help explain various published results on signed CD monitoring based on waveform asymmetries and allow us to further propose signed CD monitoring for differential eight phase-shift keying (D8PSK) systems without any modification to the receiver. Simulation results also show that the CD-induced waveform asymmetric features are preserved in presence of self-phase modulation (SPM) and polarization-mode dispersion (PMD).

Intra-channel nonlinearity in differentially phase-modulated transmission

The mechanisms responsible for nonlinear impairments in single-channel phase modulated system employing differential detection are investigated. The role of dispersion precompensation is discussed. It is shown that precompensation may be designed as to minimize the in-phase components of the fluctuations thus reducing nonlinear impairments. In differential-phase-shift-keying the effect of precompensation is stronger than in differential-quadrature-phase-shift-keying. The results of an analytic theory are compared with split-step based computer simulations using realistic system parameters.

Phase Noise Monitor and Reduction by Parametric Saturation Approach in Phase Modulation Systems

Nonlinear phase noise (NLPN) is investigated theoretically and numerically to be mitigated by parametric saturation approach in DPSK systems. The nonlinear propagation equation that incorporates the phase of linear and nonlinear is analyzed with parametric saturation processing (PSP). The NLPN is picked and monitored with the power change factors in the DPSK system. This process can be realized by an optical PSP limiter and a novel apparatus with feedback MZI. The monitor range of phase noise is 0°–90°, which may be reduced to 0°–45° if the monitor factor is about the Stockes wave but not an anti-Stockes wave. It is shown that DPSK signal performance can be improved based on the parametric saturation approach.

Chromatic dispersion monitoring for multiple modulation formats and data rates using sideband optical filtering and asynchronous amplitude sampling technique

We propose and experimentally demonstrate a low-cost technique for chromatic dispersion (CD) monitoring in various return-to-zero (RZ) amplitude and phase-modulated systems at different data rates by analyzing the asynchronously sampled amplitudes of two vestigial sideband (VSB) signals. The proposed technique graphically represents the CD induced-effects in a scatter plot of which a parameter is extracted to monitor CD and is resilient to OSNR variations. Simulations and experimental results demonstrate good monitoring ranges and sensitivities for various modulation formats at different data rates without any modification of the monitoring hardware. The influence of first-order polarization-mode dispersion (PMD) on the accuracy of proposed monitoring technique is also investigated.

Study of the Gordon–Mollenauer Effect and of the Optical-Phase-Conjugation Compensation Method in Phase-Modulated Optical Communication Systems

Optical phase-modulated systems are promising candidates for the development of ultrahigh-bit-rate transmission links, thanks to their high spectral efficiency and increased tolerance to fiber-optic nonlinearities. However, their implementation was considerably slowed down by theoretical studies, suggesting that the transmission performance can be severely hindered by nonlinear phase noise (the so-called Gordon-Mollenauer effect). The simulations presented here show that, in realistic systems (including nonlinearity, dispersion, and attenuation), Gordon-Mollenauer noise does not represent the main source of signal distortions. We demonstrate that all nonlinear impairments can be efficiently compensated by optical phase conjugation, independent of system characteristics. The combination of optical-phase-conjugation with phase-modulation formats could enable ultrahigh-transmission-capacity and easy embedded-link upgrading.

Decision-Aided Carrier Phase Estimation for Coherent Optical Communications

We analytically studied the block length effect (BLE) of decision-aided maximum likelihood (DA ML) carrier phase estimation in coherent optical phase-modulated systems. The results agree well with the trends found using extensive Monte Carlo simulations. In order to eliminate the BLE and accurately recover the carrier phase, an adaptive decision-aided (DA) receiver is proposed that does not require knowledge of the statistical characteristics of the carrier phase, or any parameter to be preset. The simulation results show that using the adaptive DA receiver, the maximum tolerance ratio of the linewidth per laser to symbol rate (?vT) at a bit error rate (BER) = 10-4 has been increased to 2.5 × 10-4, 4.1 × 10-5, and 9.5 × 10-6, respectively, for quadrature-, 8- and 16-phase-shift keying formats. The ratio (?vT) of the adaptive DA receiver in 16 quadrature amplitude modulation (QAM) is decreased to 2 × 10-5 due to the constellation penalty from 2.5 × 10-5 by using DA ML with optimum memory length, though it consistently performs well without optimizing any parameters as in DA ML. The phase error variance of the adaptive DA receiver is also analytically investigated. In addition, an analog-to-digital converter with bit resolution higher than 4 bits is shown to be sufficient to implement our adaptive DA receiver.

Random phase modulation and sparse sampling-based optical imaging system

We describe an optical imaging system based on random phase modulation and sparse sampling. The system is also an application of compressive sensing in the field of imaging. Different from the Rice compressing imaging system, the imaging system needs only a signal exposure. Meanwhile, the space-bandwidth product of the system is extended, which means the pixels of imaging sensor can be reduced without a loss of image's resolution. A random phase modulation is employed to make the energy of optical field spread out across the entire modulated image, which can facilitate the sampling process. A random sparse sampling scheme is designed to effectively reduce the pixels of imaging sensor, and the sensing matrix is uncorrelated with arbitrary sparse representation matrix. The feasibility of the proposed system is validated by numerical experiments.

光相位调制传输系统中相位噪声的概率分布特性

光相位调制传输系统中相位噪声的概率分布特性

Effect of phase noise on optical minimum-shift keying transmission systems

Phase-modulated (PM) signals have recently been used in long-haul lightwave communication systems to reach record distances. Added directly to the signal phase, linear and nonlinear phase noise cause performance degradation in PM systems. Minimum-shift keying (MSK), as a special format of PM signals, presents some different features of phase noise tolerance. This paper investigates the effect of phase noise on the performance degradation in the 10 Gb/s optical MSK systems and analyzes the contribution of phase noise to the bit error rate (BER), compared with the conventional PM format, 50% duty cycle optical return-to-zero differential phase-shift keying (RZ-DPSK) signals, in several typical local fiber dispersion transmission systems. The effect of intensity noise on the performance degradation in the corresponding transmission systems is also investigated.

Tolerance of laser frequency offset in optical minimum-shift keying transmission systems

A mismatch between laser frequency and delay interferometer (DI) phase is found to be the most critical impairment for the receiver performance in a practical phase-modulated (PM) system. This paper investigates the receiver performance degradation caused by frequency offset between optical signal and DI in a 10 Gb/s minimum-shift keying (MSK) system, and compares it with the conventional PM formats, optical differential-phase-shift keying (DPSK) and differential-quadrature-phase-shift keying (DQPSK), which are nonreturn-to-zero (NRZ) and 50% duty cycle return-to-zero (RZ). Results show that the MSK system is about double times and six times more robust to frequency offset than the DPSK and DQPSK systems operating at the same bit rate, respectively.

Modeling nonlinear phase noise in differentially phase-modulated optical communication systems

Using an alternative approach for evaluating the Bit-Error Rate (BER), we present a numerical and experimental investigation of the performance of phase-modulated optical communication systems in the presence of nonlinear phase noise and dispersion. The numerical method is based on the well known Karhunen-Lo;eve expansion combined with a linearization technique of the Nonlinear Schr odinger Equation (NLSE) to account for the nonlinear interaction between signal and noise. Our numerical results show a good agreement with experiments.