Showing papers on "Polarization mode dispersion published in 2015"
TL;DR: In this paper, lower bounds on mutual information (MI) of long-haul optical fiber systems for hard-decision and softdecision decoding are studied. And the advantages of using MI over the prevailing Q-factor as a figure of merit of coded optical systems are also highlighted.
Abstract: Lower bounds on mutual information (MI) of long-haul optical fiber systems for hard-decision and soft-decision decoding are studied. Ready-to-use expressions to calculate the MI are presented. Extensive numerical simulations are used to quantify how changes in the optical transmitter, receiver, and channel affect the achievable transmission rates of the system. Special emphasis is put to the use of different quadrature amplitude modulation formats, channel spacings, digital back-propagation schemes and probabilistic shaping. The advantages of using MI over the prevailing Q-factor as a figure of merit of coded optical systems are also highlighted.
80 citations
TL;DR: A cascaded optical link of 1100 km for ultra-stable frequency distribution over an Internet fiber network and was extended to 1480-km with the same performance, a significant step towards a sustainable wide area ultra- stable optical frequency distribution and comparison network at a very high level of performance.
Abstract: We report a cascaded optical link of 1100 km for ultra-stable frequency distribution over an Internet fiber network. The link is composed of four spans for which the propagation noise is actively compensated. The robustness and the performance of the link are ensured by five fully automated optoelectronic stations, two of them at the link ends, and three deployed on the field and connecting the spans. This device coherently regenerates the optical signal with the heterodyne optical phase locking of a low-noise laser diode. Optical detection of the beat-note signals for the laser lock and the link noise compensation are obtained with stable and low-noise fibered optical interferometer. We show 3.5 days of continuous operation of the noise-compensated 4-span cascaded link leading to fractional frequency instability of 4x10(-16) at 1-s measurement time and 1x10(-19) at 2000 s. This cascaded link was extended to 1480-km with the same performance. This work is a significant step towards a sustainable wide area ultra-stable optical frequency distribution and comparison network at a very high level of performance.
72 citations
TL;DR: The results demonstrate successful identification among four modulation formats (MF) commonly used in digital coherent systems.
Abstract: In this paper, a simple novel digital modulation format identification (MFI) scheme for coherent optical systems is proposed. The scheme is based on the evaluation of the peak-to-average-power ratio (PAPR) of the incoming data samples after analog-to-digital conversion (ADC), chromatic dispersion (CD) and polarization mode demultiplexing (PMD) compensation at the receiver (Rx). Since at a particular optical-signal-to-noise ratio (OSNR) value different modulation formats have distinct PAPR values, it is possible to identify them. The proposed scheme and the results are analyzed both experimentally and through numerical simulations. The results demonstrate successful identification among four modulation formats (MF) commonly used in digital coherent systems.
60 citations
TL;DR: In this article, the frequency-domain optical fiber channel transmission model for PDM CO-OFDM/OQAM systems with the IMI effect induced by chromatic dispersion (CD) and polarization mode dispersion(PMD) was systematically analyzed.
Abstract: Intrinsic imaginary interference (IMI) induced by a multiple-path fading channel is an important impairment for orthogonal frequency division multiplexing/offset-quadrature amplitude modulation (OFDM/OQAM) systems. Therefore, the accurate channel estimation is highly desired for such a system. Recently both the simulation studies and the experimental demonstrations for coherent optical OFDM/OQAM (CO-OFDM/OQAM) have been reported. However, there are no theoretical discussions on the IMI effect and the channel estimation method for polarization-division-multiplexed (PDM) CO-OFDM/OQAM systems so far. In this paper, we systematically analyze the frequency-domain optical fiber channel transmission model for PDM CO-OFDM/OQAM systems with the IMI effect induced by chromatic dispersion (CD) and polarization mode dispersion (PMD). The full loaded (FL) and the half loaded (HL) frequency-domain channel estimation methods are discussed to mitigate the IMI effect. The computational complexities and robustness against CD and PMD are also compared for both of the FL and the HL methods. The theoretical analysis is validated by numerical Monte Carlo simulations of PDM CO-OFDM/OQAM systems.
59 citations
TL;DR: A formula is derived that relates the signal delay spread to the fiber geometry and to the statistical properties of the structural fiber perturbations that provides insight into the MD phenomenon and facilitates the design of low-MD multi-mode fiber structures.
Abstract: Contrary to single mode fibers, where random imperfections are responsible for polarization-mode dispersion, modal dispersion (MD) in multi-mode fiber structures for space-division multiplexed (SDM) transmission, originates chiefly from the intrinsic non-degeneracy of the propagating modes, also known as modal birefringence. The presence of random imperfections in such fibers has a positive aspect, as it reduces the intrinsic MD, and in the limit of strong coupling it causes the signal delay spread to increase with the square root of the propagation distance, rather than linearly, as would be the case in an ideal fiber. In this paper we derive a formula that relates the signal delay spread to the fiber geometry and to the statistical properties of the structural fiber perturbations. The derived formula provides insight into the MD phenomenon and facilitates the design of low-MD multi-mode fiber structures.
51 citations
TL;DR: In this article, a novel subcarrier coding scheme combined with pre-electrical dispersion compensation (pre-EDC) is proposed for fiber nonlinearity mitigation in coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems.
Abstract: In this paper, we demonstrate through computer simulation and experiment a novel subcarrier coding scheme combined with pre-electrical dispersion compensation (pre-EDC) for fiber nonlinearity mitigation in coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. As the frequency spacing in CO-OFDM systems is usually small (tens of MHz), neighbouring subcarriers tend to experience correlated nonlinear distortions after propagation over a fiber link. As a consequence, nonlinearity mitigation can be achieved by encoding and processing neighbouring OFDM subcarriers simultaneously. Herein, we propose to adopt the concept of dual phase conjugated twin wave for CO-OFDM transmission. Simulation and experimental results show that this simple technique combined with 50% pre-EDC can effectively offer up to 1.5 and 0.8 dB performance gains in CO-OFDM systems with BPSK and QPSK modulation formats, respectively.
49 citations
TL;DR: Among these formats, Stokes vector direct detection (SV-DD) achieves the highest electrical spectrum efficiency, presenting itself as a promising candidate for future short-reach networks.
Abstract: The explosive growth of the traffic between data centers has led to an urgent demand for high-performance short-reach optical interconnects with data rate beyond 100G per wavelength and transmission distance over hundreds of kilometers. Since direct detection (DD) provides a cost-efficient solution for short-reach interconnects, various advanced modulation formats have been intensively studied to improve the performance of DD for high-performance short-reach optical interconnects. In this paper, we report the recent progress on the advanced DD modulation formats that provide superior electrical spectral efficiency (SE) and transmission reach beyond that of simple direct modulation (DM) based direct detection (DM/DD). We first provide a review of the current advanced modulation formats for high-performance short-reach optical interconnects. Among these formats, Stokes vector direct detection (SV-DD) achieves the highest electrical spectrum efficiency, presenting itself as a promising candidate for future short-reach networks. We then expound some novel algorithms to achieve high-performance SV-DD systems under severe impairments of either polarization mode dispersion (PMD) or polarization dependent loss (PDL).
49 citations
TL;DR: The good agreement between the theory and the previously published experiments provides solid foundations to the random coupling model of SDM fiber links, and provides a tool for efficient design of MIMO-DSP receivers.
Abstract: We study the response of space-division multiplexed fiber links to an excitation by a short impulse of the optical intensity. We show that, in the presence of full mixing, the intensity impulse response is Gaussian, confirming recently reported experimental observations, and relate its variance to the mean square of the mode dispersion vector of the link τ. The good agreement between our theory and the previously published experiments provides solid foundations to the random coupling model of SDM fiber links, and provides a tool for efficient design of MIMO-DSP receivers.
46 citations
TL;DR: It is found that a cascade of linear filters can be combined into a single, truncated, linear, adaptive filter with negligible impact on receiver sensitivity, and by utilizing a multiplier-free tap weight update algorithm, the overall complexity of a digital coherent receiver can be significantly reduced, making it attractive for use in an ONU.
Abstract: Coherent receivers offer a potential solution for implementing a high-capacity, long-reach (up to 100 km) passive optical network (LR-PON), due mainly to their high sensitivity, frequency selectivity, and bandwidth efficiency. When using coherent receivers, received signals can be post-processed digitally to mitigate the specific impairments found in access networks and, additionally, relax the optical complexity requirements of the coherent receiver. However, the digital signal processing must itself be low complexity in order to minimize the overall complexity and power consumption of the optical network unit (ONU). This paper focuses on the impact of reduced complexity equalization algorithms on receiver sensitivity in a LR-PON. It is found that a cascade of linear filters can be combined into a single, truncated, linear, adaptive filter with negligible impact on receiver sensitivity. Additionally, by utilizing a multiplier-free tap weight update algorithm, the overall complexity of a digital coherent receiver can be significantly reduced, making it attractive for use in an ONU. Matched filtering, chromatic dispersion compensation, and polarization tracking are all performed by the adaptive equalizer. The performance of this low-complexity, multiplier-free equalizer is experimentally verified for 3 GBd polarization division multiplexed quadrature phase shift keying (12 Gbit/s) in both a back-to-back configuration and transmission over 100 km standard single-mode fiber.
44 citations
TL;DR: In this article, a ghost-peak-free distributed polarization crosstalk analyzer (DPXA) was used to obtain all polarization related parameters of polarization-maintaining (PM) fibers.
Abstract: We present methods and processes of using a ghost-peak-free distributed polarization crosstalk analyzer (DPXA) to accurately obtain all polarization related parameters of polarization-maintaining (PM) fibers. We show that by first inducing a series equidistant periodic polarization crosstalk peaks along a PM fiber and then measuring the positions and the widths of these peaks using the analyzer, all birefringence related parameters of the PM fiber, including group birefringence, group birefringence variation along the fiber, group birefringence dispersion, and group birefringence temperature coefficient , can be accurately obtained. We further show that the DPXA has the ability to identify and eliminate polarization crosstalk contributions of connectors or splices in the measurement system and therefore can be used to obtain high accuracy measurement of the polarization extinction ratio (PER) of PM fibers. Finally, we propose a set of parameters based on the distributed polarization analysis to quantitatively evaluate the quality of PM fibers. We believe that the methods and processes described in this paper can be widely applied in the industry for the complete characterization of PM optical fibers.
41 citations
TL;DR: In this article, the authors proposed a mode dependent signal delay method to determine the principal modes of a multimode optical fiber (MMF) by measuring N 2−1 mean signal time delays at a MMF input for N 2 − 1 launch conditions generated at an output.
Abstract: Mode dispersion can negatively impact optical fiber communication over multimode optical fibers (MMFs). Principal modes are a basis of spatial modes that do not experience mode dispersion up to the first order in frequency. In this work, a method to determine the principle modes of a MMF is proposed. This method is referred to as the mode dependent signal delay method, being the extension to a MMF of the analogous method to determine the principal states of polarization of a single-mode optical fiber. Using this method, principal modes can be determined by measuring N2−1 mean signal time delays at a MMF input for N2−1 launch conditions generated at a MMF output. The differences of the mode dependent signal delay method from the polarization signal delay method and its experimental implementation are discussed.
TL;DR: In this article, a novel fiber nonlinearity compensation technique for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) systems based on the transmission of phase-conjugated pilots (PCPs) was proposed.
Abstract: In this paper, we demonstrate a novel fiber nonlinearity compensation technique for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) systems based on the transmission of phase-conjugated pilots (PCPs). In this scheme, a portion of OFDM subcarriers (up to 50%) is transmitted with its phase conjugates, which is used at the receiver to estimate the nonlinear distortions in the respective subcarriers and other subcarriers, which are not accompanied by PCPs. Simulation and experimental results show that by varying the PCP overhead, a performance improvement up to 4 dB can be achieved. In addition, the proposed technique can be effectively applied in both single polarization and polarization-division multiplexed systems, in both single channel and wavelength-division multiplexing systems, thus, offering highest flexibility in implementations.
TL;DR: In this paper, a random distributed feedback Raman fiber laser with linear polarized output at 1178nm is presented. Linear polarization is realized by fiber coiling in a half-opened cavity of a polarization maintaining random fiber laser structure.
Abstract: A random distributed feedback fiber laser with linear polarized output at 1178 nm is presented. Linear polarization is realized by fiber coiling in a half-opened cavity of a polarization maintaining random fiber laser structure. The single linear polarization laser output power reaches ∼3 W with polarization extinction ratio >14 dB. Further investigations on the coiling technique and additional feedback are also studied. So far as we know, this is the first reported linear polarized random distributed feedback Raman fiber laser.
TL;DR: In this paper, the design and characteristics of a three-mode 12-core fiber with low intercore crosstalk (IC-XT) and low differential mode group delay (DMD) were demonstrated.
Abstract: The design and characteristics of a novel three-mode 12-core fiber are demonstrated. This fiber has low intercore crosstalk (IC-XT) and low differential mode group delay (DMD). In order to produce such a fiber, three new techniques are introduced to few-mode multicore fiber. A heterogeneous core arrangement with two types of cores, is used to minimize IC-XT; a multistep index, which can control DMD without sacrificing intermode crosstalk, is adopted as a core profile to reduce DMD; and a square lattice structure allows for the inclusion of 12 cores within a cladding diameter of 230 μm. Optimum design of the fiber using these techniques is determined from calculations. Finally, detailed characteristics of a three-mode 12-core fiber based on the design are reported. A fabricated 40-km fiber is confirmed to have a DMD of less than |530| ps/km over the C + L band and an estimated worst-case IC-XT of less than –55 dB/100 km at 1550 nm. This low IC-XT allows for the transmission of 32 QAM signals.
13 Jul 2015
TL;DR: In this paper, the authors show that optical and electrical phase conjugation enable effective nonlinear compensation, and the impact of polarization mode dispersion and finite processing bandwidth on the ultimate limits are also considered.
Abstract: We show that optical and electrical phase conjugation enable effective nonlinear compensation, The impact of polarization mode dispersion and finite processing bandwidth on the ultimate limits are also considered.
TL;DR: A polarization sensitive endoscopic optical frequency domain imaging (PS-OFDI) system with a motorized distal scanning catheter with complex field averaging method based on the alignment of randomly pointing field phasors is developed to reduce speckle noise.
Abstract: A polarization sensitive endoscopic optical frequency domain imaging (PS-OFDI) system with a motorized distal scanning catheter is demonstrated. It employs a passive polarization delay unit to multiplex two orthogonal probing polarization states in depth, and a polarization diverse detection unit to detect interference signal in two orthogonal polarization channels. Per depth location four electro-magnetic field components are measured that can be represented in a complex 2x2 field matrix. A Jones matrix of the sample is derived and the sample birefringence is extracted by eigenvalue decomposition. The condition of balanced detection and the polarization mode dispersion are quantified. A complex field averaging method based on the alignment of randomly pointing field phasors is developed to reduce speckle noise. The variation of the polarization states incident on the tissue due to the circular scanning and catheter sheath birefringence is investigated. With this system we demonstrated imaging of ex vivo chicken muscle, in vivo pig lung and ex vivo human lung specimens.
TL;DR: In this article, the authors proposed a highly birefringent and highly nonlinear polarization maintaining single mode hybrid cladding circular photonic crystal fiber (HyC-CPCF) for compensation of chromatic dispersion of standard single mode fiber (SMF) over 1360 to 1640nm wavelength band.
Abstract: In this paper, we propose a highly birefringent and highly nonlinear polarization maintaining single mode hybrid cladding circular photonic crystal fiber (HyC-CPCF). The proposed structure is extremely attractive for compensation of chromatic dispersion of standard single mode fiber (SMF) over 1360 to 1640 nm wavelength band. Guiding properties are investigated using finite element method (FEM) with perfectly matched layer boundary condition. Simulation results confirm the possibility of large negative dispersion coefficient and relative dispersion slope of −650 ps/(nm km) and 0.0036 nm−1, respectively, at 1550 nm wavelength and effective dispersion coefficient of about ±0.5 ps/(nm km) from 1360 to 1640 nm wavelength. The proposed fiber also demonstrates a high birefringence of order 2.1 × 10−2 at 1550 nm wavelength that allows the fiber to maintain a single polarization. In addition, effective V parameter ensures the single mode operation of the designed fiber over the entire band of interest. To realize the practical feasibility, the sensitivity of the fiber dispersion properties to a ±2% of structural parameter variation around the optimum value is evaluated and reported. Moreover, effective dispersion and nonlinear coefficient are also presented and discussed. The proposed fiber can be a promising candidate in high speed transmission system for broadband dispersion compensation, sensing and nonlinear applications as well.
TL;DR: It is shown that, as the angle of a motorized polarization controller inside the cavity is swept, the laser eventually reaches a mode-locked regime and the values of the Stokes parameters undergo an abrupt change.
Abstract: A strategy to align a mode-locked fiber laser with nonlinear polarization rotation is presented. This strategy is based on measurements of the output polarization state. It is shown that, as the angle of a motorized polarization controller inside the cavity is swept, the laser eventually reaches a mode-locked regime and the values of the Stokes parameters undergo an abrupt change. The sensing of this sudden variation is thus used to detect the mode-locking condition and a feedback mechanism drives the alignment of the polarization controller to force mode locking.
TL;DR: A novel joint estimation method suitable for spectrally efficient Nyquist wavelength-division multiplexing (WDM), based on the cyclostationary property of linearly modulated signals, exploited both in the frequency and time domains is demonstrated.
Abstract: Software-defined transceivers can be reconfigured based on demand and existing channel impairments, and as such, monitoring of both signal and channel parameters is necessary. We demonstrate a novel joint estimation method suitable for spectrally efficient Nyquist wavelength-division multiplexing (WDM), based on the cyclostationary property of linearly modulated signals, exploited both in the frequency and time domains. Using a Nyquist superchannel composed of three 10 GBaud channels, we experimentally demonstrate the simultaneous monitoring of symbol-rate with 100% accuracy, roll-off, frequency offset (FO), chromatic dispersion (CD) and optical signal-to-noise ratio (OSNR) with root-mean-square errors (RMSE) of 20%, 4 MHz, 200 ps/nm and 1.5 dB respectively, when the roll-off factor is larger than 0.06 for DP-QPSK and 0.3 for DP-16QAM.
TL;DR: This work remotely control the polarization state of the light incident at the sample using the eigenpolarization states of a wave plate as a reference, and determines the Jones matrix of the output fiber.
Abstract: Fiber-based polarization-sensitive optical frequency domain imaging is more challenging than free-space implementations. Using multiple input states, fiber-based systems provide sample birefringence information with the benefit of a flexible sample arm but come at the cost of increased system and acquisition complexity, and either reduce acquisition speed or require increased acquisition bandwidth. Here we show that with the calibration of a single polarization state, fiber-based configurations can approach the conceptual simplicity of traditional free-space configurations. We remotely control the polarization state of the light incident at the sample using the eigenpolarization states of a wave plate as a reference, and determine the Jones matrix of the output fiber. We demonstrate this method for polarization-sensitive imaging of biological samples.
TL;DR: In this article, the differential modal group delay and absolute chromatic dispersion values of a few-mode optical fiber were obtained from a single measurement without spatial mode transformers.
Abstract: Few-mode optical fibers (FMFs) are useful for many applications such as space-division-multiplexing (SDM), high laser power generation and transport, dispersion compensation, etc. The emergence of SDM induces considerable requirements in terms of FMF characterization (chromatic dispersion, birefringence, modal content, bending losses). All LP modes of an FMF can be simultaneously characterized using phase-sensitive optical low-coherence interferometry. The differential modal group delay and absolute chromatic dispersion values of each mode are retrieved from a single measurement without spatial mode transformers.
TL;DR: In this article, the design principles of bit-interleaved-coded modulation with multi-dimensional mapping are reviewed and its performance in long-haul transmission experiments with different spectral efficiencies in both dispersion managed and dispersion unmanaged fiber optic systems.
Abstract: Multi-dimensional-coded modulation approaches the nonlinear Shannon limit due to its high SNR sensitivity and large Euclidean distance between multi-dimensional symbols. It also eliminates phase ambiguity to avoid cycle slips. In this paper, we review the design principles of bit-interleaved-coded modulation with multi-dimensional mapping, and its performance in long-haul transmission experiments with different spectral efficiencies in both dispersion managed and dispersion unmanaged fiber optic systems.
TL;DR: In this paper, a single-shot optical cross-correlation in nanowaveguides is proposed based on four-wave mixing (FWM) between two orthogonally polarized input signals propagating with different velocities due to polarization mode dispersion.
Abstract: We describe a novel technique for performing a single-shot optical cross-correlation in nanowaveguides. Our scheme is based on four-wave mixing (FWM) between two orthogonally polarized input signals propagating with different velocities due to polarization mode dispersion. The cross-correlation is determined by measuring the spectrum of the idler wave generated by the FWM process.
TL;DR: On comparing pre- and post-compensation methods, it is found that the latter is superior to the former and the system performance can be improved to compare with the system with either pre- or post-dispersion compensation.
TL;DR: In this paper, the relation between soil temperature changes on a buried optical fiber and frequency changes of an optical carrier through the fiber is modeled and compared with observed frequency variations through this model.
Abstract: Results of optical frequency transfer over a carrier-grade dense-wavelength-division-multiplexing (DWDM) optical fiber network are presented. The relation between soil temperature changes on a buried optical fiber and frequency changes of an optical carrier through the fiber is modeled. Soil temperatures, measured at various depths by the Royal Netherlands Meteorology Institute (KNMI) are compared with observed frequency variations through this model. A comparison of a nine-day record of optical frequency measurements through the 2×298 km fiber link with soil temperature data shows qualitative agreement. A soil temperature model is used to predict the link stability over longer periods (days-months-years). We show that optical frequency dissemination is sufficiently stable to distribute and compare, e.g., rubidium frequency standards over standard DWDM optical fiber networks using unidirectional fibers.
TL;DR: In this article, an intensity-modulated direct-detection link using four states of polarization is demonstrated for the first time, where the four data-independent tributaries are each assigned distinct states of polarization to enable the receiver to separate the signals.
Abstract: We demonstrate for the first time an intensity-modulated direct-detection link using four states of polarization. The four data-independent tributaries are each assigned distinct states of polarization to enable the receiver to separate the signals. Polarization rotation due to propagation over optical fiber is tracked and compensated with simple digital signal processing in Stokes space. Transmission below the forward error correction limit is shown for maximum net bitrates of 100 Gb/s (4 $\,\times$ 27 GBd) and 120 Gb/s (4 $\,\times$ 32 GBd) over 2-km standard single-mode fiber at a center wavelength of 1550 nm.
TL;DR: Simulations show that the proposed scheme can support a 224-Gb/s polarization-division-multiplexed offset-4QAM OFDM signal over 160,000 ps/nm without any CP under 128 subcarriers, and this tolerance scales with the square of the number of subcarrier.
Abstract: Discrete-Fourier transform (DFT) based offset quadrature amplitude modulation (offset-QAM) orthogonal frequency division multiplexing (OFDM) without cyclic prefix (CP) was shown to offer a dispersion tolerance the same as that of conventional OFDM with ~20% CP overhead. In this paper, we analytically study the fundamental mechanism limiting the dispersion tolerance of this conventional scheme. It is found that the signal and the crosstalk from adjacent subcarriers, which are orthogonal with π/2 phase difference at back to back, can be in-phase when the dispersion increases to a certain value. We propose a novel scheme to overcome this limitation and significantly improve the dispersion tolerance to that of one subcarrier. Simulations show that the proposed scheme can support a 224-Gb/s polarization-division-multiplexed offset-4QAM OFDM signal over 160,000 ps/nm without any CP under 128 subcarriers, and this tolerance scales with the square of the number of subcarriers. It is also shown that this scheme exhibits advantages of greatly enhanced spectral efficiency, larger dispersion tolerance, and/or reduced complexity compared to the conventional CP-OFDM and reduced-guard-interval OFDM using frequency domain equalization.
TL;DR: Polarization Pairwise Coding is investigated for adaptive PDL mitigation in PDM coherent optical systems by pre-coding across two polarizations, and shows improved performance than Walsh-Hadamard transform since it maximizes the coordinate diversity.
Abstract: Polarization dependent loss (PDL) causes imbalanced optical signal to noise ratio (OSNR) of the two polarizations, thus remains one of the major bottlenecks for next-generation polarization-division-multiplexed (PDM) coherent optical transmission systems. In this paper, we investigate Pairwise Coding for adaptive PDL mitigation in PDM coherent optical systems. By pre-coding across two polarizations, the PDL-induced performance degradation can be largely mitigated without any coding overhead. We present details of the coding and de-coding design, and also derive the analytical symbol/bit error rate of the Polarization Pairwise Coding scheme, which can be used to predict the performance gain as well as for optimal rotation angle calculation. Simulation results verify that Pairwise Coding achieves substantial system performance gains over a wide range of PDL values. Compared with other digital coding techniques, Polarization Pairwise Coding shows improved performance than Walsh-Hadamard transform since it maximizes the coordinate diversity; and also Pairwise Coding is computationally much simpler to decode compared with the Golden and Silver Codes, therefore is practical for current 100-Gb/s and future 400-Gb/s and 1-Tb/s digital coherent transceivers.
22 Mar 2015
TL;DR: An investigation on the group delay spread in few-mode fibers operating in the weak and strong linear coupling regimes, and for the first time, the transition region between them is studied.
Abstract: We report an investigation on the group delay spread in few-mode fibers operating in the weak and strong linear coupling regimes, and for the first time, we study the transition region between them. A single expression linking the group delay spread to the fiber correlation length is validated for any coupling regime, considering 3 guided modes.
TL;DR: Optical Nyquist pulse generation based on a time lens with subsequent optical filtering with simultaneous dual-wavelength pulse generation is proposed and nearly chirp-free Nyquist pulses over C band are obtained.
Abstract: Optical Nyquist pulse generation based on a time lens with subsequent optical filtering is proposed A nearly chirp-free 10-GHz 81-ps Nyquist pulse generator is experimentally demonstrated By inserting group velocity dispersion (GVD) between cascaded phase and amplitude modulators, 11 tones ultraflat optical frequency comb (OFC) of 10-GHz frequency spacing within 09 dB power variation is obtained The quasi-rectangular shape spectrum is then filtered out with a tunable rectangular-shaped optical band-pass filter (OBPF) and the quasi-linear chirp is compensated by a segment of standard single mode fiber (SSMF) By changing the wavelength of the continuous wave (CW) light, nearly chirp-free Nyquist pulses over C band are obtained Furthermore, simultaneous dual-wavelength pulse generation is also demonstrated