Order Polarization Mode Dispersion Research Articles

Technical specifications and spectral performance characteristics of dispersion flattened fiber (DFF) in optical fiber systems

Abstract This work has clarified the technical specifications and spectral performance characteristics of dispersion flattened fiber (DFF) in optical fiber systems. Effective nonlinear refractive index and first, second order polarization mode dispersion against spectral wavelength with fiber length of 1000 m and coupling length of 20 m are simulated and demonstrated. Total DFF fiber losses/dispersion performance parameters are investigated and simulated by using OptiFiber simulation. Zero DFF fiber dispersion and its dispersion slope are demonstrated clearly in details. The dominant modes and the cutoff data theoretical values based these modes for the proposed DFF fiber is determined and simulated in a clear manner.

Joint CD and PMD monitoring based on a pair of low-bandwidth coherent receivers.

A joint chromatic dispersion (CD) and 1st order polarization mode dispersion (PMD) monitoring technique for both a coherent and a non-coherent single carrier system based on a pair of cost effective low-bandwidth coherent receivers is proposed and experimentally demonstrated. By jointly detecting the narrow band around ± 1/2 baud rate, the CD and PMD can be estimated simultaneously by time domain correlation and Stokes space rotational angle recovery, respectively. The CD estimation range is theoretically infinite and the PMD estimation range is limited to the maximum of 1/2 symbol period. Simulation results show that for a 28 G baud dual-polarization (DP)-16QAM transmission system, with dual 1 GHz coherent receivers, the monitoring error for CD and differential group delay (DGD) is 30 ps/nm and 0.5 ps, respectively. We also experimentally verified it for a 12 GBit/s NRZ-OOK transmission system with a full-bandwidth coherent receiver and two 1 GHz digital filters to simulate dual 1 GHz coherent receivers. The monitoring error for CD and DGD is 60 ps/nm and 1.5 ps, respectively.

PMD Emulator based on PZTs attached to pieces of an Hi-Bi fiber

In this paper we demonstrate the development of an adjustable and compact polarization mode dispersion (PMD) emulator device, based on piezoelectric actuators that squeezes a defined pieces of an Hi-Bi fiber. Using this device, the first and second order PMD (SOPMD) can be reproduced in a controlled and compact way, allowing its use as a reliable metrological reference for PMD compensators and for the study of several polarizations phenomena that can represent impairments to the high data transmission networks. This emulator was used to perform an analysis of the correlation between the PMD and SOPMD under different climate chamber temperature.

Investigation of OSNR monitoring technique based on the beat noise detection

We propose an optical signal-to-noise ratio (OSNR) monitoring technique based on the beat noise detection. The signal under test (SUT) is filtered by a band pass filter (BPF) at the signal center frequency. The incident power of the monitor module is adjusted to keep constant. Through measuring the noise power at low radio frequencies (RF), OSNR can be monitored. The monitoring performance for 80Gb/s non-return-to-zero differential quadrature phase shift keying (NRZ-DQPSK) signal is experimentally demonstrated. OSNR of 8~33.5dB can be monitored with a 25.4dB dynamic range (DR) at 100MHz RF. The impacts of the BPF bandwidth, received power, RF position, chromatic dispersion (CD), and first order polarization mode dispersion (PMD) on the monitoring performance are experimentally investigated. The bandwidths of the receivers can be reduced to tens of MHz.

A deeper analysis of the second order polarization mode dispersion in optical communications systems

This article presents a new approach to the combined analysis of the first and second-order polarization mode dispersion (SOPMD) and shows their importance in optical communication systems performance. How it affects the relation between second-order polarization mode dispersion (PMD) and the differential group delay (DGD) in a single mode fiber is discussed. The analysis is based on time or wavelength and temperature variations changing/impacting PMD and DGD measured values. We present long term statistical characteristics of second-order PMD over a PMD emulator, and investigate the correlation between SOPMD, depolarization (DEP) and polarization dependent chromatic dispersion (PCD). Some authors calculate these modes from measurements obtained from the first order polarization mode dispersion, assuming a positive correlation between these effects, but this not the real relationship between them. A new interpretation of SOPMD was used to analyze the problem of the spectral stability in terms of the temperature. Actual techniques for determination SOPMD, consequently DEP and PCD, use the variation in time and/or wavelength. In some studies the results obtained for SOPMD are correlated to first-order PMD (FOPMD). This paper shows, based on measurements, that the correlation between first and second order Polarization Mode Dispersion (PMD) in the case where the last one is a function of the temperature can assume positive or negative values.

Polarization dependent loss complications on polarization mode dispersion emulation

Polarization dependent loss (PDL) and polarization mode dispersion (PMD) coexist in an optical network system. So, PMD emulation is normally complicated by PDL. In this paper, an analysis of the implications of PDL on PMD statistics is done using a 35-PMF section emulator. The first order PMD (FO-PMD) and second order PMD (SO-PMD) statistics of the emulator with a PDL value of 0.06dB approached the theoretical Maxwellian and Foschini et al. distributions respectively. On increasing the PDL value to 4.59dB, both FO-PMD and SO-PMD statistics were distorted away from the above theoretical distributions even with presence of high number of random mode coupling sites.

Essence of re-calibrating optical instruments: analysis of the digital delay line

In this work a digital delay line (DDL) from Oz Optics was used. The DDL introduces a delay in optical paths between the fast and slow orthogonal polarizations by adjusting the relative travel distance of the two orthogonal modes. The insertion loss of the DDL is 1.5 dB. A Labview programme was used to write and read from the DDL. The DDL was adjusted from 0 to 60 ps and the observed first order polarization mode dispersion (FO-PMD) was measured. With 1018 random values between 0 and 60 ps, written to the DDL to adjust it, the resulting FO-PMD values give a histogram approaching the Maxwellian distribution, although not well populated on the tail. This therefore means the DDL alone can be controlled to generate a distribution approximating the Maxwellian distribution over a large sample size as would be expected theoretically.

A DOP feedback controlling multi-stage electrical PMD compensator in digital coherent receiver

We proposed a degree of polarization (DOP) controlling multi-stage electrical polarization mode dispersion (PMD) compensator in digital coherent receiver. The compensator is modulation format independent and can mitigate both first order and higher order PMD. We evaluated this PMD compensator in both 100-Gb/s 16-QAM and QPSK signal transmission systems with 15ps and 20ps average differential group delay (DGD) respectively. The results show that, for both two cases, less than 0.2dB optical signal to noise ratio (OSNR) penalty at 1e−3 symbol error rate (SER) can be achieved after 4-stage PMD compensation.

Effects of fiber impairments on constellation diagrams of optical phase modulated signals

The effects of chromatic dispersion (CD) and first order polarization mode dispersion (PMD) on constellation diagrams of phase modulated signals are investigated via simulation and different methods to visualize these effects are presented. It is shown that constellation diagrams of (D)QPSK signals sampled by an asynchronous receiver can be used to simultaneously monitor CD and first order PMD. The amount of accumulated impairments can be estimated by quantifying certain deformations in patterns of constellation diagrams.

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Effect of Polarization Mode Dispersion on the BER Performance of Optical CDMA

In this paper, impact of polarization mode dispersion (PMD) on the bit error rate (BER) performance of direct sequence optical code division multiple access with in-line optical amplifiers is analytically investigated. Intensity modulation direct detection technique is employed in optical correlator receiver. Optical orthogonal codes are used as address sequence. The system BER performance is determined in presence of PMD and different noises induced from receiver, optical amplifiers, and multiple access interference. The power penalty suffered by the system is evaluated at BER of 10 -9 . It is found that the BER performance of the proposed system degraded more at high chip rate, chirp parameter and long fiber length due to the effect of PMD. Further, the BER performance of the proposed system is studied in presence of PMD compensation with frequency advanced higher order PMD vectors. The results demonstrate that the system BER performance is improved significantly for a particular fiber length and third-order PMD compensation technique shows better performance compared to first-, and second-order compensations.

Distribution of Double-Sideband OFDM-UWB Radio Signals in Dispersion Compensated Long-Reach PONs

The performance of orthogonal frequency division multiplexing ultra wideband radio signals distribution in dispersion compensated (DC) long-reach passive optical networks (LR-PONs) is assessed numerically for conventional chirpless Mach-Zehnder (MZ) and chirped linearized (L) electro-optic modulators (EOMs). The optimum modulation index and the minimum required optical signal-to-noise ratio are evaluated for optical network units (ONUs) at different distances from the optical line termination (OLT). The degradation due to first-order polarization mode dispersion (PMD), fiber nonlinearity, phase noise due to the Kerr effect, and the phase noise due to finite laser linewidth is assessed as well. It is shown that the use of dispersion compensation in LR-PONs employing the MZ-EOM is a powerful solution to mitigate the dispersion-induced power fading. It is also shown that, contrarily to the L-EOM case, the same optimum voltage level at the EOM input is required by DC LR-PONs employing the MZ modulator, independently of the ONUs distances. In addition, an optical signal-to-noise ratio penalty not exceeding 0.5 dB due to first order PMD effect is obtained for a PMD parameter below 0.5 ps·km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1/2</sup> and for a fiber nonlinearity corresponding to a nonlinear phase shift not exceeding 11 mrad. This conclusion holds for pre (at the OLT) and post (at the remote node) compensation schemes. The performance degradation induced by the laser phase noise is also negligible in DC LR-PONs for typical laser linewidths due to the reduced phase-to-intensity noise conversion.

Fabrication and Characteristics of Elliptical-Holes and near Elliptical Core Hexangular Lattice Photonic Crystal Fibers Based on Polymer

The polarization properties of a new structure of high birefringence polarization maintaining photonic crystal fibers were explored, which were consisted of elliptical-holes and near elliptical core triangle lattice of hexangular structure based on polymer. The optical birefringence and the first order polarization mode dispersion were studied based on a full-vector localized basis function method. The numerical results show that the polarization properties are strongly dependent on structural parameters of the PCF. Furthermore, the proposed fiber was fabricated based on MMA monomer polymerization method in situ. So the proposed PCFs may be useful in the field of high birefringence polarization-maintaining optical communication.

First-Order PMD Outage Prediction Based on Outage Maps

We compare the applicability of different methods for the calculation of first order polarization-mode dispersion (PMD) outage probabilities under the Maxwellian probability density assumption for the differential group delay. Results based on measured outage maps are contrasted with outage predictions using various simplifying approximations. We present a comprehensive data set of measured PMD outage maps at 10.7 Gb/s using non return-to-zero and return-to-zero on-off keying in combination with both standard threshold detection and maximum likelihood sequence estimation, with and without residual chromatic dispersion.

PMD compensation via real-time phase retrieval from spectral interference

We present a technique for pulse recovery based on real-time measurement of the differential optical phase spectrum from spectral interference patterns. Using a phase retrieval algorithm we can obtain accurate all order polarization mode dispersion (PMD) information for the optical signal and correspondingly compensate the impairment in optical transmission lines. Linear PMD is accurately extracted from measurements, and analytical simulations show recovery of pulses distorted by higher order PMD.

Performance of a 46-Gbps Dual-Polarization QPSK Transceiver With Real-Time Coherent Equalization Over High PMD Fiber

We report experimental results on the transmission performance of a coherent dual-polarization quadrature phase-shift-keyed (DP-QPSK) transceiver with real-time electronic equalization over fiber having 50-ps mean polarization mode dispersion (PMD). Both single-channel, single-span and multi-channel, multi-span measurements were performed over the high PMD fiber, which has near Maxwellian statistics for the differential group delay (DGD) as well as higher order PMD as expected for a long, mode-coupled fiber. Transmission of eighty channels was achieved over 8 times100 km of TrueWave Reduced Slope fiber plus distributed high PMD fiber, where individual channels had instantaneous DGD as high as 127 ps. The dependence of the OSNR penalty on the launch state of polarization was evaluated and found to be minimal, and the contribution of fiber nonlinearities to the transmission penalty was evaluated for two different per-channel launch powers. Finally, using a transceiver equipped with forward-error-correction, error-free transmission over the 800-km link was demonstrated over a 10-day period; during this time the DGD of the measured channel varied from 13 to 116 ps.

PMD Effects in Fiber Optic Transmission Systems

Polarization mode dispersion (PMD) remains the most important limiting impairment for high bit rate transmission over optical fibers. In this article, after a brief description of PMD model and the associated statistic, we study the pulse distortion due to PMD using a powerful time-frequency diagram. This approach allows a very simple illustration of the second and high order PMD effects through effective pulse broadening. Finally, the PMD emulation issue and both electronic and optical compensation techniques are presented, that is a current field of cooperation between ENST-Bretagne and France Telecom R&D.

A Change of Perspective on Single- and Double-Stage Optical PMD Compensation

We present a rigorous investigation on how to optimize the degrees of freedom of optical polarization mode dispersion (PMD) compensators composed of differential group delay sections and polarization controllers, up to two stages. The analytical treatment relies on the extracted Jones matrices of the transmission and compensation fibers. The analysis of a single-stage compensator with two degrees of freedom (fixed DGD) is based on the maximization of the eye opening, as provided by the generalized Chen formula. The outage probability is quantified through a fast semi-analytical technique. It is shown how the benefits of single-stage compensation are strongly reduced and can lead to outage events, when certain critical input states of polarization are launched into transmission fibers with strong eigenmodes depolarization (i.e., strong higher order PMD). Focusing on such transmission fibers and input configurations, a novel algorithm is introduced for controlling a double-stage compensator with five degrees of freedom. The algorithm is based on an ideal equalization of the transmission fiber at half the bit-rate, realized resorting to spherical geometry. To this aim, we show that the first compensator stage must be a PMF fiber with very large DGD, equal to the bit period, in order to compensate the most critical configurations associated with outage events.

On the Decision-Feedback Equalizer in Optically Amplified Direct-Detection Systems

This paper investigates the combined feed-forward and decision-feedback equalizer (DFE) in a lightwave system with optical amplifiers and a direct-detection receiver. Based on a nonlinear channel model, the paper provides a modification of the classical minimum mean square error theory of the DFE. Furthermore, an analytical method that is capable of accurate bit error rate (BER) evaluation is used to optimize the DFE for minimum BER. The paper evaluates the DFE performance for both optical ON-OFF keying and duobinary modulation formats in the presence of chromatic dispersion as well as the DFE performance for the mitigation of higher order polarization mode dispersion in first-order compensated systems. The paper shows that the DFE can compensate for the BER degradation due to narrow-band receiver-side optical filtering and can significantly improve the spectral efficiency of dense wavelength-division multiplexed systems.

Synthesis of optical PMD compensating filter using FIR lattice structure

We investigate the potential of n-stage optical finite impulse response (FIR) lattice filter for compensating first order polarization mode dispersion (PMD). This compensation is based on minimizing the differential group delay (DGD) between the two principal state of polarization (PSP) within a given frequency range. The filter is realized by concatenating optical delay lines, directional couplers, and phase shifters in a lattice architecture. A numerical simulation is performed for an 8th and 12th order filters to demonstrate the impact of using higher order filters. The results show that DGD can be reduced significantly as we increase the order of the filter.