System Penalty Research Articles

Impact of PMD induced Timing Misalignment Jitter in a Dispersion Managed IM-DD Optical Transmission Link

The Bit Error Rate (BER) performance of a dispersion managed optical transmission link in the presence of timing misalignment jitter induced by Polarization Mode Dispersion (PMD) has been investigated. The present work focuses on analytical evaluation of the timing jitter variance of the recovered signal, which is impaired by the pulse distortion induced by PMD. The system penalty is obtained as a function of system parameters and the signal jitter characteristics. Our investigation shows that the random signal perturbations can seriously degrade clock recovery performance and have a considerable degradation in the optical receiver performance. The robustness of different modulation format against the PMD induced random perturbation has also been studied.

Stabilizing PMD Compensators by Means of Polarization Dithering

Feedback-based single-stage polarization-mode dispersion compensators can suffer from dynamical limitations. These can be prevented by modulating the polarization of the transmitted signal. A high-depth modulation can result in high jitter and partial eye closure. A low-depth modulation (dithering) effectively stabilizes the compensator while it does not introduce significant system penalty.

Analysis of PMD-Induced System Penalty Using Pulse Spreading

This paper presents a technique that predicts the polarization-mode-dispersion (PMD)-induced system penalty based on rms pulse spreading. Amplifled-spontaneous-emission noise limited and thermal noise limited cases are investigated for the nonreturn to zero (NRZ) and return to zero modulation formats. A comparison is made with similar approaches that use three alternative metrics: the string length up to first order, the conventional string length, and the weighted string length. It is shown that the technique based on pulse spreading extends the applicable range of the system-penalty prediction in terms of both the mean link PMD and the modulated-signal bandwidth.

Optimal Placement of Multi-Type FACTS Devices for Total Transfer Capability Enhancement Using Hybrid Evolutionary Algorithm

In this article, a new hybrid evolutionary algorithm (HEA) is proposed to determine the optimal placement of multi-type FACTS devices for simultaneously maximizing the total transfer capability (TTC) and minimizing system real power losses of power transfers between different control areas. Multi-objective optimal power flow (OPF) with FACTS devices including TTC, system real power loss and penalty functions is used to evaluate the feasible TTC value without violating system constraints. Test results on the modified IEEE 30- and 118-bus systems indicate that optimally placed OPF with FACTS devices by the HEA could enhance the TTC value far more than other metaheuristic methods, leading to an efficient utilization of the existing transmission system.

MLSE receiver tolerance to all-order polarization mode dispersion

We experimentally characterize a maximum likelihood sequence estimation (MSLE) based receiver's tolerance to first- and all-order polarization mode dispersion (PMD). We show that the response of the MLSE receiver to first-order PMD can be characterized in two ways depending on the differential group delay (DGD). In addition we show that first-order PMD-induced system penalties dominate those from high-order PMD. High-order PMD induces a large system penalty only when the first-order penalty is small, or the DGD exceeds a bit period.

System Penalty From Second-Order PMD Approximation: Reference Frame Implication

In this paper, we show that second-order PMD approximations, when derived using the input frame and output frame of an optical link, result in two different PMD systems represented by two distinct Jones matrices. In contrast to an all-order representation of a system, which is independent of reference frame, it is found that a finite second-order approximation cannot be obtained simultaneously in both input and output reference frames, except in some limited special cases. The consequences of this are illustrated by analyzing the difference between these two approximations in pulsewidth distortion. It is shown that the second-order PMD approximation in the input frame corresponds to a truncated second-order expansion of the pulse distortion, whereas the second-order PMD approximation in the output frame leads to an infinite-order pulse distortion

Cascadability study for optical label swapping using synchronous phase modulation

We experimentally investigate the cascadability of optical label swapping using a synchronous phase modulation technique without wavelength conversion in a recirculating loop to emulate multihop networks. We find that the power penalties for both label and payload are below 1 dB at 10-7 bit-error rate after five hops. We also show that a system penalty can be maintained below 1 dB for an accumulated timing mismatch of 20% of bit period using synchronous phase modulation-based optical label swapping. The results show the potential to save up to 80% of wavelength converters in optical packet switched networks applications

Experimental comparison of PMD-induced system penalty models

We present experimental investigations of polarization-mode dispersion (PMD)-induced system penalties arising from an all-order PMD source, for amplified spontaneous emission and thermally limited systems. Further, we compare the experimental first-order PMD-induced penalties with predictions from both the string length model and the modified quadratic model. We show that the both models are in good agreement with the experimental data. The major difference between the two models is in the measurement requirements, which are less stringent for the string length method

Fast analytical assessment of the signal quality in transparent optical networks

Constraint-based routing (CBR) requires a fast and accurate assessment of the different physical degradation effects in optical communications systems. This paper deals with fast analytical approximation formulas describing the induced system penalty due to the dominant nonlinear effects in 10-Gb/s nonreturn to zero (NRZ) transmission systems. This paper concentrates on the multichannel effects of cross-phase modulation (XPM) and four-wave mixing (FWM).

Error free all optical wavelength conversion in highly nonlinear As-Se chalcogenide glass fiber

We present the first demonstration of all optical wavelength conversion in chalcogenide glass fiber including system penalty measurements at 10 Gb/s. Our device is based on As2Se3 chalcogenide glass fiber which has the highest Kerr nonlinearity (n(2)) of any fiber to date for which either advanced all optical signal processing functions or system penalty measurements have been demonstrated. We achieve wavelength conversion via cross phase modulation over a 10 nm wavelength range near 1550 nm with 7 ps pulses at 2.1 W peak pump power in 1 meter of fiber, achieving only 1.4 dB excess system penalty. Analysis and comparison of the fundamental fiber parameters, including nonlinear coefficient, two-photon absorption coefficient and dispersion parameter with other nonlinear glasses shows that As(2)Se(3) based devices show considerable promise for radically integrated nonlinear signal processing devices.

System penalty owing to polarisation-mode-dispersion in presence of fast polarisation scrambling

Polarisation-mode-dispersion (PMD) induced penalty is investigated for an optical signal in a PMD medium under fast polarisation scrambling. A phenomenological model for the timing jitter penalty is proposed and is verified by computer modelling. The Q penalty from pulse distortion is complementary to the Q penalty from timing jitter.

Effective suppression of transient-induced impairments in transparent optical networks

In transparent networks, fiber cuts can generate severe penalties: Sudden disappearing of channels in one lightpath may affect channels on joint lightpaths and even channels in disjoint lightpaths. We propose a simple and cost-effective scheme that is able to fully suppress these power transients in a realistic network environment. Using the symmetric counter-propagating wavelength-division-multiplexing (WDM) signals, the missing channels can be effectively replaced. In the experiments, we obtained a very short replacement time, complete suppression of any power transient, and full recovery of system penalty in joint and disjoint lightpaths. The scheme was found to be also robust to power unbalance and spectral difference between the missing and replacement WDM signals.

Comparison of system penalties from first- and multiorder polarization-mode dispersion

We experimentally investigate the polarization-mode dispersion (PMD)-induced system penalty arising from first-order and all-order PMD. We use a measurable quantity, "string" length, to parameterize the penalty, find a deterministic correction to the accepted first-order PMD-induced system penalty approximation, and discuss the implications for system outages. Further, we show that higher orders of PMD introduce an additional penalty scatter that is nearly independent of "string" length, and correlated to the magnitude of the second-order PMD vector.

PMD-induced penalty statistics in fiber links

We study the statistics of polarization-mode dispersion (PMD)-induced system penalty in optical telecommunication systems. First, we extend the analysis from Maxwellian fiber-to-fiber routes with a finite number of degrees of freedom, or "hinges". Second, we take into account higher order terms in the optical signal-to-noise ratio penalty beyond the standard approximation. Our results show that in systems with few hinges, a smaller margin to PMD will result in the same outage probability.

Small-signal analysis of amplitude-, phase-, and polarization-to-intensity conversion in general optical linear systems with application to PMD compensation

A general small-signal model for amplitude-, phase-, and polarization-to-intensity conversion in optical systems affected by chromatic dispersion, polarization-mode dispersion (PMD), and polarization-dependent loss (PDL) is presented, which extends a previous scalar model by Wang and Petermann . The model leads to simple intensity filters, which can be expressed as a linear combination of the components of the Stokes' vector of the signal input state of polarization (ISOP), and facilitates the prediction of the ISOPs, which minimize/maximize the intensity modulation on the output signal. The model is first used to study the output intensity in a first-order PMD-compensated single-channel system with either input amplitude, or phase, or polarization modulation. The small-signal model provides a good prediction of the received intensity up to modulation indexes of about 20%-30%, according to the modulation type. The model is then successfully used in a semianalytical bit-error rate (BER) evaluation method to estimate the system penalty induced by cross-phase modulation (XPM) in a two-channel wavelength-division-multiplexed (WDM) dispersion-managed system with PMD compensation.

Impact of pump phase modulation on system performance of fibre-optical parametric amplifiers

Bit error rate induced in a parametric amplifier has been measured with a 10 Gbit/s line rate. It is shown experimentally that the phase modulation of the pump distorts the mark level of the channel and may cause system penalty. Different phase modulation schemes have been compared.

Determination of SRMC with Non-Smooth Fuel Cost Functions Using Evolutionary Programming

In this article, a new algorithm for determination of short run marginal cost (SRMC) for feasible bilateral transactions using optimal power flow (OPF) solution has been presented. Determination of SRMC using conventional methods suffer due to the presence of non-smooth fuel cost generators in the modern deregulated utilities. Hence in this article, evolutionary programming (EP) based OPF solution has been developed for obtaining optimal generator settings with four non-smooth fuel functions. System transmission loss and penalty factor at each and every bus are computed using the OPF solution. Further bus incremental cost at all the buses is computed using penalty factors. Generalized loss coefficients are also obtained from OPF solution and they are the functions of the system operating state with non-smooth fuel functions. The performance of the proposed algorithm has been validated with IEEE 30 bus and Indian utility 62-bus practical test systems.

Analytic Estimation of Penalty Due to Filter Transfer Function Variation on WDM Systems

Analytic estimates of pulse broadening and system penalty caused by wavelength-division-multiplexing (WDM) filter amplitude variation is derived. We show that root mean square pulsewidth is not a reliable measure of system penalty and noise equivalent bandwidth plays a key role in determining system penalty.

Group delay dispersion performance requirement for optical cross connects and add-drop multiplexers in ultralong-haul DWDM transport systems

The system penalty of undesirable chromatic group delay dispersion in wavelength-selective optical cross connects (OXCs) and add-drop multiplexers (OADMs) is the critical design constraint for 10- and 40-Gb/s transparent ultralong-haul dense wavelength-division-multiplexing network systems. Although narrow-featured dispersion within the passband of OXCs and OADMs causes a relatively small penalty, its system penalty is often overestimated when a wavelength-independent uniform dispersion model is applied. Considering a model that represents an arbitrary dispersion function, we assess generalized requirements for the narrow-featured dispersion impairment, and propose the sliding-window group delay ripple as the measure of system penalty estimation.

Group-delay ripple correction in chirped fiber Bragg gratings.

Group-delay ripple (GDR) introduced by systematic and random errors in chirped fiber Bragg grating fabrication is the most significant impediment to application of these devices in optical communication systems. We suggest and demonstrate a novel iterative procedure for GDR correction by subsequent UV exposure by use of a simple solution of the inverse problem for the coupled-wave equation. Our method is partly based but does not fully rely on the accuracy of this solution. In the experiment we achieved substantial reduction of the low-frequency group-delay ripple, from +/- 15 to +/- 2 ps, which resulted in dramatic improvement of the optical signal-to-noise-ratio system penalty, from 7 to less than 1 dB, for a chirped fiber Bragg grating used as a dispersion compensator in a 40-Gbit/s carrier-suppressed return-to-zero system.