Impact Of Phase Noise Research Articles

Impact of Sampling Clock Phase Noise on $\Sigma \Delta$ Frequency Discriminators

SigmaDelta frequency discriminators (SigmaDeltaFDs) convert instantaneous frequency deviations of a carrier signal to digital. They are used for decoding narrowband phase or frequency modulated signals in communication receivers, self calibration of RF frequency synthesizers and in digital phase locked loops. In this paper, the impact of reference (sampling) clock phase noise on a SigmaDeltaFD's spurious-free dynamic range (SFDR) is derived. It is shown that for SigmaDeltaFDs with jittered sampling clock, in addition to FM sidebands, a high baseband tonal content is generated degrading overall SFDR. The reference clock phase noise impact is derived mathematically, and two commonly used SigmaDeltaFDs circuits are designed and implemented to verify the results experimentally. Experimental results are shown to match the theoretical prediction of SFDR within 3 dB.

Smoothing GPS carrier phase double differences using inertial measurements for high performance applications

This paper will describe an enhancement to the GPS double difference carrier phase measurements on a single airborne platform by smoothing them with inertial measurements while preserving the dynamic bandwidth. This enhancement will reduce the impact of carrier phase multipath and carrier phase noise on baseline determination between multiple antennas on an aircraft when in flight. This type of measurement system has numerous applications where platform pointing and relative body motion must be determined at the mm-level for applications such as sensor stabilization, Synthetic Aperture Radar, long range RADAR (i.e. angle-of-arrival measurements). Lower noise levels (mm-level and below) enable more performance to the stabilized system such as increased aperture for longer range, operation at higher frequencies, and more image resolution. The focus of this paper will be on a technique to provide this enhanced performance for these various applications using the available navigation systems. Additionally, this type of smoothing can effectively remove the additional noise induced by carrier phase measurement differencing. The noise level of a double or triple difference can be reduced below that of the raw measurement. A complimentary synthesized double difference quantity with ultra-low-noise characteristics will be used to smooth the GPS carrier phase double difference measurements without losing dynamic bandwidth since it follows the airborne dynamics. Flight test data will be presented to demonstrate the performance improvement in the midst of aircraft dynamics. Results will show that the noise reduction follows the theoretical prediction.

Analysis and minimization of cross phase modulation in semiconductor optical amplifiers for multichannel WDM optical communication systems

A theoretical model for crosstalk in multichannel wavelength division multiplexing communication systems due to cross phase saturation in semiconductor optical amplifier structure is developed. This theoretical model is used to analyze the impact of the cross phase noise on the performance of semiconductor optical amplifiers in saturation region for WDM communication system by using differential phase shift modulation format. It is shown that by increasing the carrier life time, width and thickness while reducing the confinement factor, differential gain and bias current in the SOA structure mitigates the cross talk due to cross phase saturation. The impact of penalty and cross phase noise imposed on multichannel WDM links have been investigated for different parameters of the SOA with the variation in transmission distance. With the slight increase in differential gain of 200.2 × 10 −18 cm 2 and confinement factor 0.41, the maximum transmission distance observed is 5220 km with good quality and nil power penalty for 10 × 40 Gb/s soliton RZ-DPSK WDM signals for the first time.

Impact of channel sounder phase noise on directional channel estimation by space-alternating generalised expectation maximisation

Multi-input multi-output (MIMO) radio channel sounders commonly employ time-division multiplexing (TDM) technique to switch between transmit and receive antennas. The TDM method offers single-input single-output sounders the MIMO capability in a cost-effective manner. However, the TDM approach leads to errors in MIMO channel measurements because of phase noise in local oscillators. Phase noise varies in the short term during the switching sequence for a MIMO channel sample. The high-resolution space-alternating generalised expectation maximisation (SAGE) algorithm has been efficiently applied for the estimation of the channel parameters. The impact of phase noise on the directional channel parameters, which are estimated by the SAGE algorithm, has been studied. Although the previous studies have investigated long-term random walk noise, we concentrate on the short-term noise which affects consecutive MIMO channel matrix measurements. It has been shown that errors in direction of arrival and direction of departure estimation because of the short-term phase noise can be effectively decreased by time domain filtering of the impulse responses prior to the SAGE processing.

Reducing Impact of Phase Noise on Accuracy of Measured MIMO Channel Capacity

Despite the fact that time-division multiplexed switching (TDMS)-based multiple-input-multiple-output (MIMO) wireless channel sounders are cost effective implementation techniques, they may result in significant measurement errors due to phase noise (PN) in the local oscillators. In this letter, the impact of PN on the accuracy of measured MIMO channel capacity is studied by considering its effect on both the spatial multiplexing gain and on the power gain. We show that in case of a low rank physical channel matrix the impact of PN is more pronounced on the spatial multiplexing gain than on the power gain. Based on that, we propose an eigenvalue filtering (EVF) technique to improve the accuracy of measured channel capacity.

Parametric-gain approach to the analysis of single-channel DPSK/DQPSK systems with nonlinear phase noise

This paper presents a novel method based on a parametric gain (PG) approach to study the impact of nonlinear phase noise in single-channel dispersion-managed differentially phase-modulated systems. This paper first shows through Monte Carlo simulations that the received amplified spontaneous emission (ASE) noise statistics, before photodetection, can be reasonably assumed to be Gaussian, provided a sufficiently large chromatic dispersion is present in the transmission fiber. This paper then evaluates in a closed form the ASE power spectral density by linearizing the interaction between a signal and a noise in the limit of a distributed system. Even if the received ASE is nonstationary in time due to pulse shape and modulation, this paper shows that it can be approximated by an equivalent stationary process, as if the signal were continuous wave (CW). This paper then applies the CW-equivalent ASE model to bit-error-rate evaluation by using an extension of a known Karhunen-Loe/spl acute/ve method for quadratic detectors in colored Gaussian noise. Such a method avoids calculation of the nonlinear phase statistics and accounts for intersymbol interference due to a nonlinear waveform distortion and optical and electrical postdetection filtering. This paper compares binary and quaternary schemes with both nonreturn- and return-to-zero (RZ) pulses for various values of nonlinear phases and bit rates. The results confirm that PG deeply affects the system performance, especially with RZ pulses and with quaternary schemes. This paper also compares ON-OFF keying (OOK) differential phase-shifted keying (DPSK) systems, showing that the initial 3-dB advantage of DPSK is lost for increasing nonlinear phases because DPSK is less robust to PG than OOK.

Impact of nonlinear phase noise to DPSK signals: experimental verification of a simplified theoretical model

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.

Probability density function of noise statistics for optically pre-amplified DPSK receivers with optical Mach–Zehnder interferometer demodulation

We present explicitly semi-analytical probability density functions (pdf’s) of noise statistics in DPSK receivers with Mach–Zehnder interferometer (MZI) demodulation with considering the phase noise for the first time. Error performance of DPSK receivers with MZI demodulation is evaluated by using the calculated pdf’s. It is found that DPSK receivers with MZI demodulation and balanced detection are less sensitive to phase noise impact than those with the single-port detection to some extent. Moreover, it is found that ASE–ASE beat noise induced pdf difference in balanced detection compared to single-port detection may result in ∼3dB improvement in receiver sensitivity mainly depending on optical filtering, ASE-amplified spontaneous emission. Therefore, the measured receiver sensitivity improvement by using balanced detection consist of the improvements due to signal energy difference and ASE–ASE beat noise induced pdf difference compared to single-port detection.

Coherent optical MIMO (COMIMO)

We present a multiple-input multiple-output (MIMO) optical link based on coherent optics and its ability to exploit the inherent information capacity of multimode fiber. A coherent implementation differs from previous work in optical MIMO by allowing the system to tolerate smaller modal delay spreads, because of a much larger carrier frequency, and yet maintain the necessary diversity needed for MIMO operation. Furthermore, we demonstrate the use of MIMO adaptive equalization to mitigate intersymbol interference when exceeding the bandwidth-length product of the link. The impact of phase noise is studied with numerical simulation.

Analysis of the phase noise in saturated SOAs for DPSK applications

A theoretical model is used to analyze the impact of phase noise on the performance of semiconductor optical amplifiers (SOAs) in the saturation regime for differential phase-shift keying (DPSK) applications. It is found that the variance of the differential phase error scales as T/sup 2///spl tau//sub c//sup 2/ for /spl tau//sub c//spl Gt/T, where T is the bit period and /spl tau//sub c/ is the carrier lifetime of the SOA. This suggests that the adverse effect of saturation-induced phase noise can be significantly reduced by increasing the bit rate or the carrier lifetime.

Impact of Nonlinear Phase Noise to DPSK Signals: A Comparison of Different Models

When a differential phase-shift keying signal is contaminated by nonlinear phase noise, various models to evaluate the error probability are compared. The simplest method is based on the Q factor. The exact method takes into account the dependence between amplifier noise and nonlinear phase noise. All approximated models underestimate both the error probability and the required signal-to-noise ratio.

Investigation of 10-Gb/s optical DQPSK systems in presence of chromatic dispersion, fiber nonlinearities, and phase noise

The impact of phase noise, chromatic dispersion, and nonlinear effects on a 10-Gb/s optical differential quadrature phase-shift keying (oDQPSK) system has been evaluated by computer simulations. Both single channel and multiple wavelength-division-multiplexing channels have been considered. The results show that the low spectral width of this format allows a reduced channel spacing as low as 25-12.5 GHz. Furthermore, the use of this format leads to an increase in dispersion tolerance together with a robustness to nonlinear effects due to the signal near constant envelope characteristics. Finally, simulations show that phase noise can be the limiting factor of oDQPSK systems.

Numerical simulation of the SPM penalty in a 10-Gb/s RZ-DPSK system

The impact of self-phase modulation-induced nonlinear phase noise in a 10-Gb/s return-to-zero differential phase-shift keying system is studied by numerical simulation. We show that the simple differential phase Q method based on the Gaussian approximation for the phase noise provides a relatively good estimate of the nonlinear penalty.

A method to eliminate effect of phase noise in OFDM synchronization system

OFDM (the orthogonal frequency division multiplexing) and its variety DMT (the discrete multitone) as delegates of the multicarrier modulation technology have given a big impact on the conventional data communication applications. Based on the theoretic a analysis of the OFDM technology, the impact of phase noise that introduced by the bit and symbol timing mechanism is discussed. Then a pilot correction and the cyclic prefix protection method are put forwarded to deal with the problem. These methods have been used in our experimental OFDM cable modem system to cope with the impulse noise and narrow band interference in the HFC (hybrid fiber and coax) upstream channel.

Impact of laser phase noise on binary- andM-ary-PSK coherent optical systems using multiple optical amplifiers

This study evaluates the performance of binary- and M-ary-PSK coherent optical systems using cascaded optical amplifiers in the presence of noise originating from the detector, receiver, optical amplifiers, and the laser phase fluctuations. Our results on the analysis of these systems indicate that at an amplifier input power of −20 dBm and a system length of 10,000 km, the power penalties incurred due to the laser phase noise at a bit error rate of 10−9 correspond to 0.57, 0.99, and 3.38 dB at linewidths of 770.31, 101.86, and 6.37 kHz for binary-PSK, four-PSK, and eight-PSK systems, respectively. ©1996 John Wiley & Sons, Inc.

Impact of laser phase noise on binary‐ and M‐ary‐PSK coherent optical systems using multiple optical amplifiers

This study evaluates the performance of binary- and M-ary-PSK coherent optical systems using cascaded optical amplifiers in the presence of noise originating from the detector, receiver, optical amplifiers, and the laser phase fluctuations. Our results on the analysis of these systems indicate that at an amplifier input power of −20 dBm and a system length of 10,000 km, the power penalties incurred due to the laser phase noise at a bit error rate of 10−9 correspond to 0.57, 0.99, and 3.38 dB at linewidths of 770.31, 101.86, and 6.37 kHz for binary-PSK, four-PSK, and eight-PSK systems, respectively. ©1996 John Wiley & Sons, Inc.

On Envelope Detection of Noisy Phase Signals with Asymptotically Small Linewidths

The impact of laser's phase noise on heterodyne and homodyne linewidth communications, as well as on direct detection systems with optical amplification is governed by intractable statistics induced by the phase sample path. Here we derive analytic asymptotic bounds on the underlying distribution inherited by the squared envelope of noisy phase signals. The approach taken invokes standard results from the theory of Large-Deviations and yields straightforward, closed-form expressions. This fundamental problem has many applications in linewidth communications, such as the determination of the BER floor in heterodyne ASK systems, which is hereby illustrated. The asymptotic theory predicts an IF bandwidth increase with the square root of the linewidth-to-bit ratio for a specified floor level. A comparison with the numerical solution of the underlying Fokker-Planck equation reveals a good agreement even at significant (non-asymptotic) laser's linewidths.

Influence of laser phase noise on dispersive optical fiber communication systems

Noise from semiconductor lasers in dispersive optical communication systems can give rise to a BER floor. Due to frequency-to-intensity noise conversion, the impact of laser phase noise increases with the fiber length. It is shown that the maximum transmission distance for dispersion-supported transmission obtained in laboratory experiments is mainly determined by the laser phase noise.

Analytical upper bounds for noisy phase optical communication invoking Gaussian quadratic functionals

The impact of laser phase noise on lightwave communication systems is governed by certain exponential functionals (EFs) of the phase trajectory, which apparently prohibit the exact derivation of the decision statistics. In contrast, phase noise quadratic functionals (QFs) feature tractable statistics. The fundamental limitations imposed by simple replacement of the exponential nonlinearity by a quadratic one are explored in the presence of additive noise, and it is shown analytically that this may yield bit-error-rate (BER) approximations only. A novel class of upper bounds on the BER with envelope detection is presented. The bounds and the approximations are both given by easily computable closed-form algebraic expressions and are based on the moment generating function inherited by the QF. >

The impact of laser phase noise on the coherent subcarrier multiplexing system

In coherent optical subcarrier multiplexing (CSCM) systems, the laser phase noise may cause signal spectrum broadening and hence, causes significant deterioration in the system performance. The impact of phase noise on the CSCM system is analyzed in terms of carrier-to-noise ratio, intermodulation distortion, and adjacent channel crosstalk. The optimal modulation index and carrier to noise ratio are also presented. Some numerical results are outlined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>