Nonlinear Phase Reconstruction and Compensation Method Based on Orthonormal Complete Basis Functions in Synthetic Aperture Ladar Imaging Technology

Due to the short laser wavelength, almost all practical targets are rough. Surface elevations in rough targets will result in layovers in synthetic aperture ladar (SAL). High resolution SAL image with layovers will be different from the target picture taken by incoherent tools as digital camera. To investigate the layovers in SAL image, a simplified mathematical model is built by optics diffraction theory and a laboratory SAL is setup using 1550 nm tunable laser source. Layovers in SAL images, in both theoretical simulation and experimental demonstra- tion, are carefully observed. Detailed results on various targets are illustrated.

To simplify the analysis, the performance of differential phase-shift-keying signals with nonlinear phase noise is usually calculated for receiver with an optical matched filter. With a special single-span experimental setup to isolate the contribution from nonlinear phase noise, the measured signal-to-noise ratio (SNR) penalty is within /spl plusmn/0.15 dB of the theoretical results in the range of SNR penalty less than 1.5 dB.

Neural network based synthetic aperture ladar imaging through marine atmosphere

The error probability is derived analytically for differential phase-shift keying (DPSK) signals contaminated by both self- and cross-phase modulation (SPM and XPM)-induced nonlinear phase noise. XPM-induced nonlinear phase noise is modeled as Gaussian distributed phase noise. When fiber dispersion is compensated perfectly in each fiber span, XPM-induced nonlinear phase is summed coherently span after span and is the dominant nonlinear phase noise for typical wavelength-division-multiplexed (WDM) DPSK systems. For systems without or with XPM-suppressed dispersion compensation, SPM-induced nonlinear phase noise is usually the dominant nonlinear phase noise. With longer walkoff length, for the same mean nonlinear phase shift, 10-Gb/s systems are more sensitive to XPM-induced nonlinear phase noise than 40-Gb/s systems.

We numerically study and isolate the impact of nonlinear phase noise and intrachannel nonlinearities in 42.7-Gbit RZ-DPSK transmission over 32×100-km non-zero dispersion-shifted fiber (NZDSF) for different scenarios of optical noise loading. (2 pages)

In this paper, we discuss the application of the spatial correlation algorithm (SCA) (Attia and Steinberg, 1989; Attia, 1993; Attia, 1994), and some of its variants, to synthetic aperture LADAR (SAL) imaging. These algorithms (which derive the required phase corrections from range-resolved LADAR clutter received by the SAL sensor) are very robust, computationally efficient, perform very well in the presence of large uncorrelated phase errors, and do not require dominant scatterers of opportunity. Performance and limitations of the basic SCA are discussed. Dependence of the accuracy of the resulting phase corrections on the SNR per pulse and number of range cells available for estimating the corrections is presented in considerable detail. The impact of residual uncorrected phase errors on image SNR and dynamic range is statistically evaluated taking into account the total number of pulses coherently combined along the imaging baseline. Also, a method for exploiting special features of 3D interferometric SAL imaging for the purpose of improving phase correction accuracy is introduced.

Synthetic aperture ladar motion compensation method based on symmetrical triangular linear frequency modulation continuous wave

We develop a simple analytic gaussian model, predicting BER performance of optical DPSK receivers with high accuracy in the wake of all three phase noise sources impairing differential phase detection: linear phase noise (ASE-induced), nonlinear phase noise (the Gordon-Mollenauer effect), and laser phase noise Brownian fluctuations. We validate our analytical Q-factor based formulas using known analytical cases and importance-sampling based Monte-Carlo simulations.

We show that nonlinear interference noise (NLIN) produced by faraway WDM channels is dominated by nonlinear phase-noise and polarization-rotations, whereas NLIN produced by nearest channels tends to be more circular. We discuss the impact of these results on nonlinear mitigation.

Partial mitigation of nonlinear phase noise by standard carrier phase recovery has been reported both, experimentally and through simulations. In this paper we quantify the achievable mitigation by using different implementations of the carrier phase recovery. All the approaches are based on the widespread blind phase search algorithm but follow different optimization strategies for handling simultaneously both, linear and nonlinear impairments of the channel. We apply the algorithms on probabilistically shaped signals transmitted over standard single mode fiber and non-zero dispersion shifted fiber in order to consider conditions in which the system performance is evidently affected by nonlinear phase noise. The results obtained are finally compared to the statistically estimated achievable phase noise removal. This allows to evaluate in different system scenarios an upper bound to the potential gain obtainable by algorithms developed to mitigate the detrimental impact of short-correlated nonlinear phase noise.

The probability density of nonlinear phase noise, often called the Gordon–Mollenauer effect, is derived analytically. The nonlinear phase noise can be accurately modeled as the summation of a Gaussian random variable and a noncentral chi-square random variable with two degrees of freedom. Using the received intensity to correct for the phase noise, the residual nonlinear phase noise can be modeled as the summation of a Gaussian random variable and the difference of two noncentral chi-square random variables with two degrees of freedom. The residual nonlinear phase noise can be approximated by Gaussian distribution better than the nonlinear phase noise without correction.

In this paper, the effect of coherent acoustic wave excitation system on the echo signal detection of Synthetic Aperture Ladar (SAL) is studied. The local atmospheric refractive index fluctuation model of the disturbed troposphere is established by the coherent acoustic wave theory, and the detection process of target echo signal is simulated. The influence of the phase fluctuation of the disturbance echo signal on the intermediate frequency signal of the coherent acoustic wave excited system is studied. By employing the coherent acoustic wave excitation system interfering with the Michelson laser interferometer imaging, the effect of the coherent acoustic wave on the phase fluctuation of the echo signal is explained theoretically. The results of this study lay a theoretical foundation for using coherent acoustic excitation system against SAL imaging.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text A. Mafi, S. Lobanov, and S. Raghavan, "Nonlinear Phase Noise in DPSK Systems: BER Calculation," in Frontiers in Optics 2008/Laser Science XXIV/Plasmonics and Metamaterials/Optical Fabrication and Testing, OSA Technical Digest (CD) (Optica Publishing Group, 2008), paper FTuH2. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Nonlinear phase noise, often called the Gordon-Mollenauer effect, can be compensated electronically by subtracting from the received phase a correction proportional to the received intensity. The optimal scaling factor is derived analytically and found to be approximately equal to half of the ratio of mean nonlinear phase noise and the mean received intensity. Using optimal compensation, the standard deviation of residual phase noise is halved, doubling the transmission distance in systems limited by nonlinear phase noise.

This paper analyzes the error of data transition tracking loop (DTTL) in 60 GHz millimeter wave pseudo-noise (PN) regenerative ranging systems caused by nonlinear power amplifier and phase noise. We propose mathematical analysis based on the models of nonlinear power amplifier (PA) and phase noise of 60 GHz given by IEEE 802.11ad task group. Theoretical and simulation results indicate that the tracking error of DTTL in 60 GHz ranging systems is serious, therefore the performance of DTTL has a decisive effect on the precision of ranging.