Polarization Mode Dispersion Mitigation Research Articles

Open-loop polarization mode dispersion mitigation for fibre-optic time and frequency transfer.

The non-reciprocal and dynamic nature of polarization mode dispersion (PMD) in optical fibers can be a problem for accurate time and frequency transfer. Here, a simple, passive solution is put forward that is based on transmitting optical pulses with alternating orthogonal polarization. The fast and deterministic polarization modulation means that the PMD noise is pushed far away from the frequencies of interest. Furthermore, upon reflection from a Faraday mirror at the receiver, the pulses have a well-defined polarization when they return to the transmitter, which facilitates stable optical phase detection and fibre phase compensation. In an open-loop test setup that uses a mode-locked laser and a simple pulse interleaver, the polarization mode dispersion is shown to be reduced by more than two orders of magnitude.

PMD mitigation through interleaving LDPC codes with polarization scramblers

The combination of forward error correction (FEC) and distributed fast polarization scramblers (D-FPSs) is approved an effective method to mitigate polarization mode dispersion (PMD) in high-speed optical fiber communication system. The low-density parity-check (LDPC) codes are newly introduced into the PMD mitigation scheme with D-FPSs in this article as one of the promising FEC codes to achieve better performance. The scrambling speed of FPS for LDPC (2040, 1903) codes system is discussed, and the reasonable speed 10MHz is obtained from the simulation results. For easy application in practical large scale integrated (LSI) circuit, the number of iterations in decoding LDPC codes is also investigated. The PMD tolerance and cut-off optical signal-to-noise ratio (OSNR) of LDPC codes are compared with Reed–Solomon (RS) codes in different conditions. In the simulation, the interleaving LDPC codes bring incremental performance of error correction, and the PMD tolerance is 10ps at OSNR=11.4dB. The results show the meaning of the work is that LDPC codes are a substitute for traditional RS codes with D-FPSs and all of the executable code files are open for researchers who have practical LSI platform for PMD mitigation.

PMD mitigation through interleaving LDPC codes with polarization scramblers

The combination of forward error correction (FEC) and distributed fast polarization scramblers (D-FPSs) is approved as an effective method to mitigate polarization mode dispersion (PMD) in high-speed optical fiber communication system. The low-density parity-check (LDPC) codes are newly introduced into the PMD mitigation scheme with D-FPSs in this paper as one of the promising FEC codes to achieve better performance. The scrambling speed of FPS for LDPC (2040, 1903) codes system is discussed, and the reasonable speed 10MHz is obtained from the simulation results. For easy application in practical large scale integrated (LSI) circuit, the number of iterations in decoding LDPC codes is also investigated. The PMD tolerance and cut-off optical signal-to-noise ratio (OSNR) of LDPC codes are compared with Reed–Solomon (RS) codes in different conditions. In the simulation, the interleaving LDPC codes brings incremental performance of error correction, and the PMD tolerance is 10ps at OSNR=11.4dB. The results show that the meaning of the work is that LDPC codes are a substitute for traditional RS codes with D-FPSs and all of the executable code files are open for researchers who have practical LSI platform for PMD mitigation.

PMD Mitigation by Various Distribution Patterns of Fast Polarization Scramblers with Forward Error Correction

The joint distributed fast polarization scramblers (D-FPSs) and forward error correction (FEC) is one of methods used to mitigate polarization mode dispersion (PMD). The distribution pattern of FPSs, which indicates how the FPSs are deployed along the fiber link, is a significant factor for this PMD mitigation scheme. The performance of the bit error rate (BER) for the case with or without FPSs is investigated by simulations. Five different distribution patterns of FPSs along the fiber link are designed in this paper, and the performance for each pattern is depicted by a novel representation that is known as the “Ring Chart.” The results show that the property of PMD mitigation varies with different distribution patterns of FPSs.

PMD mitigation by LDPC codes with polarization scramblers

Low-density parity-check (LDPC) codes combined with polarization scramblers are used to mitigate polarization mode dispersion (PMD) in 40-Gb/s optical fiber system. The simulations are performed to compare the correction performance of LDPC codes and Reed–Solomon (RS) code used in this PMD mitigation scheme. Results show that LDPC codes can achieve a better performance than the RS code with the same redundancy. The scrambling speed of polarization scramblers for LDPC codes system is also discussed, and the optimal speed of 10 MHz is obtained.

Simultaneous PMD Mitigation for Two Polarization Tributaries of a PDM Signal using only One All-Optical Regenerator

A scheme of polarization-mode-dispersion (PMD) mitigation in a polarization-division-multiplexing (PDM) system is proposed and demonstrated with 2×10Gb/s return-to-zero on-off-keying (RZ-OOK) transmission. Simultaneous mitigation for two polarization tributaries of the PDM signal is achieved based on the self-phase-modulation (SPM) effect and offset filtering in a polarization nonlinear loop configuration. The improvement of eye-diagram-based signal-to-noise ratio (SNR) is 3.5 dB in the presence of a 7.2-ps differential-group delay (DGD) when the pulsewidth of the PDM signal is ∼16.6ps.

New Branch Metrics for MLSE Receivers Based on Polarization Diversity for PMD Mitigation

In this paper, we analyze the performance of polarization-diversity receivers employing maximum-likelihood sequence estimation (MLSE) to combat the effects of polarization mode dispersion (PMD) for both the intensity-modulation direct detection (IMDD) and duobinary modulation formats at 43 Gb/s. We propose and study several parametric branch metrics, showing that the use of MLSE receivers based on polarization diversity with appropriate branch metrics allows to cancel out the high penalty incurred by standard MLSE receivers in the presence of PMD.

Dynamic PMD Mitigation at 10 Gb/s Using Viterbi Equalization in DPSK Systems

Compensating dynamically changing polarization-mode dispersion (PMD) is important for optical fiber transmission systems. We present simulations of a Viterbi equalization for dynamic PMD mitigation in 10-Gb/s nonreturn-to-zero differential phase-shift keying systems. The equalizer can dynamically track fast varying differential group delay (DGD) and achieve similar performance to static DGD.

PMD Compensation/mitigation techniques for high-speed optical transport

In high-speed long-haul optical transport systems with channel data rates at 40Gb/s and beyond, polarization mode dispersion (PMD) is one of the major obstacles that limits system performance. It is desired or in most cases required to increase the system tolerance to PMD through PMD compensation and mitigation. In this paper, we review the techniques of PMD compensation and mitigation, including per-channel based optical PMD compensators (PMDCs), analog and digital electronic PMDCs, and all-channel PMD mitigation using distributed fast polarization scrambling and forward error correction (FEC). With the emergence of digital coherent detection, the signal optical field becomes digitally available, enabling powerful digital PMDC techniques to be applied. Digital PMDC techniques in optical single carrier coherent systems and orthogonal frequency division multiplexing (OFDM) systems are briefly reviewed.

Mitigation of Polarization Mode Dispersion in an Optical Heterodyne CPFSK Transmission System using Line Codes

A theoretical analysis for evaluating the performance of line codes in the polarization mode dispersion (PMD) mitigation of an optical heterodyne continuous phase frequency shift keying (CPFSK) transmission system with delay demodulation receiver is presented. It accounts for the combined effects of signal phase distortion due to PMD and chromatic dispersion in a single mode fiber. The analysis is carried out for three different linecoding schemes, i. e., alternate mark inversion, order-1 and delay modulation coding, to investigate the efficacy of the linecoding in counteracting the effect of PMD in CPFSK optical transmission system. Performance results are evaluated in terms of average bit error rate (BER) with line codes and compared with NRZ-CPFSK system at a bit rate of 10 Gbit/s considering Maxwellian probability distribution for the mean differential group delay (DGD) due to PMD. The results show that the penalty improvement of line coded systems is within 0.5 dB to 1.95 dB with respect to NRZ data for mean DGD 30 ps and at a BER of 10 -9 . .

Spun fiber Raman amplifiers with reduced polarization impairments

We report a novel vector model of Raman amplification in a fiber with randomly varying birefringence and unidirectional spin profile. Applying the model, we demonstrate for the first time simultaneous mitigation of polarization mode dispersion and polarization dependence of the Raman gain.

MLSE Equalizers for Frequency Discrimination Receiver of MSK Optical Transmission System

We propose maximum-likelihood sequence estimator (MLSE) equalizers based on either Viterbi algorithm or template matching temple matching (TM) for the equalization of impairments imposed on the minimum shift keying (MSK) modulation formats in long haul transmission without optical dispersion compensation. The TM-MLSE equalizer is proposed as a simplified alternative for the Viterbi-MLSE equalizer. It is verified that the Viterbi-MLSE equalizer can operate optimally when noise approaches a Gaussian distribution. Simulation results of the performances of the two MLSE equalizers for optical frequency discrimination receiver-based optical MSK systems are described. The transmission performance is evaluated in terms of: (1) the chromatic dispersion (CD) tolerance for both Viterbi-MLSE and TM-MLSE equalizers; (2) transmission distance limits of Viterbi-MLSE equalizers with various number of states; (3)the robustness to fiber polarization mode dispersion (PMD) of Viterbi-MLSE equalizers; and (4) performance improvements for Viterbi-MLSE equalizers when utilizing sampling schemes with two and four samples per bit over the conventional single sample per bit. With a small number of states (64 states), the non-compensating optical link can equivalently reach up to approximately 928 km SSMF for 10 Gb/s transmission or 58 km SSMF for 40 Gb/s. The performance of 16-state Viterbi-MLSE equalizers for optical frequency discrimination receiver (OFDR)-based optical MSK transmission systems for PMD mitigation is also numerically investigated. The performance of Viterbi-MLSE equalizers can be further improved by using the sampling schemes with multiple samples per bit compared to the conventional single sample bit. The equalizer also offers high robustness to fiber PMD impairment.

PMD mitigation and wavelength conversion using a SOA‐based interferometric switch

AbstractWe propose a new application of the SOA‐based wavelength conversion, which can realize polarization mode dispersion (PMD) mitigation for 10 GHz picosecond optical pulse. Both PMD mitigation and wavelength conversion are demonstrated by experiments. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1171–1173, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23312

PMD-Induced Outage Probability in an Optical Communication System With Fast Polarization Scramblers and Time-Varying PMD Sections

Polarization-mode-dispersion (PMD) tolerance of an optical communication system with distributed fast polarization scramblers (PS's) and time-varying PMD sections in terms of outage probability (OP) is investigated. We show that with a moderate number of PS's (up to 14), the PMD mitigation technique using distributed fast PS's and a typical forward-error correction increases the PMD tolerance by up to ~50% at an OP of 10-5. We provide a scaling rule to link the PMD tolerance in the system with fixed PMD sections to that with time-varying PMD sections. The implication of the Hinge model is briefly discussed.

40-Gb/s Adaptive Electronic Polarization-Mode Dispersion Compensator Using a Hybrid-MIC 3-Tap Linear Equalizer

We report a 40-Gb/s adaptive electronic dispersion compensator (EDC) for mitigation of polarization mode dispersion (PMD). The EDC employs a 3-tap linear equalizer acting as a transversal filter and manufactured on a substrate of duroid 5880 by using hybrid-monolithic-integrated-circuit (MIC) technology. The experimental results showed that for a given 20-ps differential group delay (DGD), the measured eye-opening penalty (EOP) after compensation was improved by 11 dB. This 40-Gb/s adaptive EDC demonstrated the possibility of its use for PMD compensation in a 40-Gb/s long-haul fiber-optic transmission system.

An experimental demonstration of a soft-failure approach to PMD mitigation in an installed optical link

We present a field-trial implementation of the soft-failure approach to polarization-mode dispersion (PMD) impairment mitigation, in which information about the PMD of the installed link is utilized by our modified control plane software to make decisions on data routing over available links. This allows us to maintain loss-free end-to-end data service, even at high PMD levels.

Effects of Nonlinearities on PMD-Induced System Impairments

It is well known that cross-phase-modulation-induced polarization rotation, cross-polarization modulation (XPolM), significantly degrades the performance of polarization-mode-dispersion (PMD) compensators. In this paper, the research on XPolM is reviewed, unique simulations of XPolM in the presence of walk off are presented, and some pitfalls are demonstrated with respect to choice of data streams in such simulations. Then, the authors discuss how XPolM affects PMD and PMD-induced outage probabilities (OP) in fiber-communication systems by providing analytical formulas for the OP with and without XPolM. Finally, the XPolM and PMD compensation are tied together by giving simple rules of thumb for when XPolM degrades PMD compensated systems, and PMD mitigation methods that are robust to XPolM are discussed

Optical technologies and techniques for high bit rate fiber transmission

The last few years have witnessed rapid advances in optical technologies and techniques for high-speed fiber transmission that have resulted in record-setting capacity-distance products and highly flexible and transparent optical networking. In this paper, we review some of the new key enabling approaches used in optical terminals, repeaters, and link designs. In particular, we summarize advances in modulation formats and their corresponding transmitter and receiver designs, broadband Raman amplification, chromatic dispersion compensation, polarization mode dispersion mitigation, and hybrid 10 Gb/s and 40 Gb/s dense wavelength division multiplexing (DWDM).

Polarisation mode dispersion mitigation in coherent optical orthogonal frequency division multiplexed systems

Coherent optical orthogonal frequency division multiplexing (CO-OFDM) to mitigate polarisation mode dispersion (PMD) in optical media is proposed. It is shown that PMD in deployed links can be overcome by CO-OFDM systems at 10 Gbit/s and beyond.

Autocorrelation function of the single PC polarization-mode dispersion emulator

The discrete structure of multisection polarization-mode dispersion (PMD) emulators is known to artificially correlate the PMD affecting different channels in a wavelength-division multiplexing system, thus limiting their usefulness in accurately emulating broad-band PMD. We report on the correlation properties of a novel single polarization controller (PC) PMD emulator, which offers scalability with the number of emulator sections through component reuse. We report a background level of the PMD frequency autocorrelation function of 0.66%, for a 50-section emulator, the lowest experimentally demonstrated for a PMD emulator, which makes the single PC PMD emulator an instrument of choice for research and development of broad-band PMD mitigation strategies.