Showing papers on "Polarization mode dispersion published in 2005"
TL;DR: The ultra-flattened dispersion feature, as well as the low confinement losses and the small effective mode area are the main advantages of the proposed PCF structure, making it suitable as a chromatic dispersion controller dispersion compensator, or as candidate for nonlinear optical applications.
Abstract: The present paper describes a novel systematic solution to the problem of controlling the chromatic dispersion and dispersion slope in photonic crystal fibers (PCFs), using a structurally-simple PCF with a defected-core. By adjusting the size of the central air-hole defect we can successfully design an ultra-flattened PCF with low confinement losses, as well as small effective mode area. The design strategy is based on the mutual cancellation between the waveguide and the material dispersions of the PCF, by varying the size of the central defected region in the core. The verification of the ultra-flattened chromatic dispersion property of the proposed PCF is ensured with an accurate full-vector finite element method with anisotropic perfectly matched layers. The ultra-flattened dispersion feature, as well as the low confinement losses and the small effective mode area are the main advantages of the proposed PCF structure, making it suitable as a chromatic dispersion controller, dispersion compensator, or as candidate for nonlinear optical applications.
195 citations
TL;DR: The structure of MLSE-based optical receivers operating in the presence of dispersion and amplified spontaneous emission, as well as shot and thermal noise, are discussed, and a theory of the error rate of these receivers is developed, and computer simulations show a close agreement between the predictions and simulation results.
Abstract: This paper discusses the investigation of maximum-likelihood sequence estimation (MLSE) receivers operating on intensity-modulated direct-detection optical channels. The study focuses on long-haul or metro links spanning several hundred kilometers of single-mode fiber with optical amplifiers. The structure of MLSE-based optical receivers operating in the presence of dispersion and amplified spontaneous emission (ASE), as well as shot and thermal noise, are discussed, and a theory of the error rate of these receivers is developed. Computer simulations show a close agreement between the predictions of the theory and simulation results. Some important implementation issues are also addressed. Optical channels suffer from impairments that set them apart from other channels, and therefore they need a special investigation. Among these impairments are the facts that the optical channel is nonlinear, and noise is often non-Gaussian and signal dependent. For example, in optically amplified single-mode fiber links, the dominant source of noise is ASE noise, which after photodetection is distributed according to a noncentral chi-square probability density function. In addition, optical fibers suffer from chromatic and polarization-mode dispersion (PMD). Although the use of MLSE in optical channels has been discussed in previous literature, no detailed analysis of optical receivers using this technique has been reported so far. This motivates the study reported in this paper.
186 citations
01 Jan 2005
TL;DR: In this paper, the inverse PMD problem is modeled as an importance sampling problem and applied to polarization mode dispersion in optical communications systems, and three representations of PMD are presented.
Abstract: to polarization mode dispersion in optical systems.- Modelling of polarization mode dispersion in optical communications systems.- Statistical properties of polarization mode dispersion.- Three Representations of Polarization Mode Dispersion.- The inverse PMD problem.- Numerical modeling of PMD.- Applications of importance sampling to polarization mode dispersion.- PMD & PDL.- Interaction of nonlinearity and polarization mode dispersion.- PMD measurement techniques and how to avoid the pitfalls.- PMD measurements on installed fibers and polarization sensitive components.- Reflectometric measurements of polarization properties in optical-fiber links.- PMD impact on optical systems: Single- and multichannel effects.- Polarization effects and performance of fiber optic recirculating loops.- PMD compensation techniques.- Low-PMD spun fibers.- PMD emulation.
147 citations
TL;DR: A method for measuring the complete linear response, including amplitude, phase, and polarization, of a fiber-optic component or assembly that requires only a single scan of a tunable laser source is presented.
Abstract: We present a method for measuring the complete linear response, including amplitude, phase, and polarization, of a fiber-optic component or assembly that requires only a single scan of a tunable laser source. The method employs polarization-diverse swept-wavelength interferometry to measure the matrix transfer function of a device under test. We outline the theory of operation to establish how the transfer function is obtained. We demonstrate the enhanced accuracy, precision, and dynamic range of the technique through measurements of several components.
122 citations
06 Mar 2005
TL;DR: In this article, the longest unregenerated reach was achieved for a 10 Gb/s return-to-zero differential phase shift keying (RZ-DPSK) system on standard dispersion fiber (G652) with no optical dispersion compensation.
Abstract: We report the longest unregenerated reach achieved for a 10 Gb/s return-to-zero differential phase shift keying (RZ-DPSK) system on standard dispersion fiber (G652) with no optical dispersion compensation.
116 citations
TL;DR: Results of the authors' calculations show that technological imperfections significantly affect the fiber's birefringence, and a significant disagreement between theoretical and experimental values of cutoff wavelengths is observed.
Abstract: We have manufactured and characterized a birefringent holey fiber of a new construction. The birefringence in this fiber is induced by the highly elliptical shape of the core, which consists of a triple defect in a hexagonal structure. Using a hybrid edge–nodal finite-element method, we calculated the spectral dependence of phase and group modal birefringence for spatial modes E11 and E21 in idealized and in real fiber, whose geometry we determined by using a scanning-electron microscope. Results of our calculations show that technological imperfections significantly affect the fiber's birefringence. Normalized cutoff wavelengths for higher-order modes relative to the filling factor were also determined for the idealized structure. We observed a significant disagreement between theoretical and experimental values of cutoff wavelengths, which was attributed to high confinement losses near the cutoff condition. We also measured the spectral dependence of the phase and the group modal birefringence for spatial modes E11 and E21. The measured parameters showed good agreement with the results of modeling.
71 citations
Journal Article•
TL;DR: In this article, the effect of PMD on the performance of a high-speed transmission system was analyzed theoretically by solving the nonlinear Schrdinger equation (NLSE), and the simulation results showed that PMD becomes the main factor which caused the average Q value's decline.
Abstract: In this paper, the characteristics of PMD and the effect of PMD on communication system have been analyzed theoretically by computer simulation. By solving the nonlinear Schrdinger equation (NLSE), our simulation results show that in the high-speed transmission system of 40Gbit/s, when the first-order of the group delay of the chromatic dispersion has been complete compensated, PMD becomes the main factor which caused average Q value's decline; and the system's average Q value curve changes with various kinds of pulse's duty cycle, when the duty cycle is 1, the performance of the system is the worst; Average Q value of the system also changes with the variety of the input power, and we could found a optimum value, when P_0 deviates from the optimum value, average Q value will drop.
71 citations
TL;DR: It is demonstrated that surface modes supported within PBGFs are very sensitive to structural distortions, and that any asymmetric change in the structure can break their degeneracy resulting in associated changes in the anticrossing behavior of the orthogonally polarized core modes, and the development of polarization dependent transmission properties.
Abstract: We present the results of numerical simulations of the modal properties of Photonic Band Gap Fibers (PBGFs) in which a structural distortion of the silica ring surrounding the air core is gradually introduced. We demonstrate that surface modes supported within such fibers are very sensitive to structural distortions, and that any asymmetric change in the structure can break their degeneracy resulting in associated changes in the anticrossing behavior of the orthogonally polarized core modes, and the development of polarization dependent transmission properties. Our results provide insight into recent experimental observations of wavelength dependent PDL and birefringence in PBGFs.
68 citations
TL;DR: Theoretical simulation indicates that the backward injection of dark-optical comb results in a narrow gain window of 60 ps within one modulating period, providing a cross-gainmodulation induced mode-locking in the SOAFL with a shortest pulsewidth of 15 ps at repetition frequency of 1 GHz.
Abstract: Optically harmonic mode-locking of a semiconductor optical amplifier fiber laser (SOAFL) induced by backward injecting a dark-optical comb is demonstrated for the first time. The dark-optical comb with 60-ps pulsewidth is generated from a Mach-Zehnder modulator, which is driven by an electrical comb at a DC offset of 0.3Vπ. Theoretical simulation indicates that the backward injection of dark-optical comb results in a narrow gain window of 60 ps within one modulating period, providing a cross-gain-modulation induced mode-locking in the SOAFL with a shortest pulsewidth of 15 ps at repetition frequency of 1 GHz. The mode-locked SOAFL pulsewidth can be slightly shortened to 10.8 ps with a 200m-long dispersion compensating fiber. After nonlinearly soliton compression in a 5km-long single mode fiber, the pulsewidth, linewidth and time-bandwidth product become 1.2 ps, 2.06 nm and 0.31, respectively.
55 citations
TL;DR: The chapter reviews the techniques that are used in optical sampling systems to perform the ultrafast sampling of the signal under investigation and time-resolved measurements of the state-of-polarization.
Abstract: The optical sampling technique is a novel method to perform time-resolved measurements of optical data signals at high bit rates with a bandwidth that cannot be reached by conventional photodetectors and oscilloscopes. The chapter reviews the techniques that are used in optical sampling systems to perform the ultrafast sampling of the signal under investigation. In addition to the various nonlinear materials and effects used for the optical sampling gates and pulse sources, the realized optical sampling systems also differ in the way, in which the system is synchronized to the data signal. Systems have been reported using synchronous, random and software synchronized configurations. Applications of optical sampling systems include high bit rate waveform and eye diagram measurements, measurements of constellation diagrams of phase modulated data signals, time-resolved measurements of the state-of-polarization as well as investigations of fiber transmission impairments.
48 citations
TL;DR: A novel idea for achieving highly efficient dispersion-compensating Bragg fiber by exploiting a modified quarter-wave stack condition is reported, which could be adopted for the design of a dispersion compensator across any desired wavelength range.
Abstract: We report a novel idea for achieving highly efficient dispersion-compensating Bragg fiber by exploiting a modified quarter-wave stack condition. Our Bragg fiber yielded an average dispersion of approximately -1800 ps/(nm km) across the C band for the fundamental TE mode and an ultrahigh figure of merit of approximately 180,000 ps/(nm dB), which is at least 2 orders of magnitude higher than that of conventional dispersion-compensating fibers. The proposed methodology could be adopted for the design of a dispersion compensator across any desired wavelength range.
10 Jan 2005
TL;DR: A 160-Gb/s OTDM network comprising switching and demultiplexing through field deployed fiber and the impact of fiber chromatic and polarization-mode dispersion (PMD) is discussed.
Abstract: This paper reports a 160-Gb/s OTDM network comprising switching and demultiplexing through field deployed fiber. The 160-Gb/s signal was obtained by time-interleaving 16 channels of a 10-Gb/s signal. The add-drop node was realized by using a gain-transparent operation of a semiconductor optical amplifier (SOA). A subharmonic clock recovery with a prescaled electrooptical phase locked loop employing an electroabsorption modulator was applied. An OTDM receiver employed a four-wave mixing principle in an SOA. The impact of fiber chromatic and polarization-mode dispersion (PMD) is discussed. Switching and demultiplexing performance are shown for a fiber link of 275 and 550 km, respectively. Excellent operation of clock recovery, drop-through-add function, and transmission was achieved.
TL;DR: In this article, the effect of temperature change on chromatic dispersion was analyzed in terms of the eye opening penalty and it was shown that for systems operating at 40 Gbit/s and above temperature effects have to be considered in system design.
TL;DR: It is found that a bilevel receiver provides 3-dB gain in optical signal-to-noise ratio sensitivity and is more robust against chromatic dispersion for either nonreturn-to -zero or return- to-zero modulation.
Abstract: We examine the performance of optical 8-ary differential phase-shift keying transmission systems according to the type of receiver structure and modulation format. Compared with the approach based on a multilevel decision, we found that a bilevel receiver provides 3-dB gain in optical signal-to-noise ratio sensitivity and is more robust against chromatic dispersion for either nonreturn-to-zero or return-to-zero modulation.
05 Dec 2005
TL;DR: In this paper, the authors monitor the polarization activity of operating light wave systems in urban and suburban areas and detect fast polarization fluctuations, which are not expected to trigger protection, or to affect performance of slower polarization mode dispersion (PMD) mitigating devices.
Abstract: This study monitors the polarization activity of operating light wave systems in urban and suburban areas. In 6 months of observation, multiple fast polarization fluctuations are detected, which are, however, not expected to trigger protection, or to affect performance of slower polarization mode dispersion (PMD) mitigating devices.
10 Jan 2005
TL;DR: A magneto- and electrooptically tuned dynamic polarization-mode dispersion (PMD) compensator that enabled error-free single-channel 160-Gb/s RZ-DPSK transmission over a 75-km SMF link with a mean differential group delay (DGD) of more than 30% of the bit period is reported.
Abstract: We report on a magneto- and electrooptically tuned dynamic polarization-mode dispersion (PMD) compensator that enabled error-free single-channel 160-Gb/s RZ-DPSK transmission over a 75-km SMF link with a mean differential group delay (DGD) of more than 30% of the bit period. Polarization scrambling and DOP measurements were utilized to automatically adapt the compensator. We present bit error rate (BER) measurements and describe the operation of the compensator in detail.
TL;DR: An all solid-state polarization-state generator that uses magneto-optic polarization rotators that can generate either five or six distinctive polarization states uniformly across a Poincaré sphere with repeatability better than 0.1 degrees is reported.
Abstract: We report an all solid-state polarization-state generator that uses magneto-optic polarization rotators. The device can generate either five or six distinctive polarization states uniformly across a Poincare sphere with repeatability better than 0.1°. It is ideal for polarization analysis, swept-wavelength measurement, and monitoring of polarization-related parameters and signal-to-noise ratios of optical networks.
TL;DR: This paper analyzes the statistics of the PMD and PDL vectors and derives explicit formulas for their mean-square magnitudes and shows that, in systems with realistic parameters, the waveform-distorting effects of PDL are of very limited significance.
Abstract: This paper presents a study on the effect of polarization-dependent loss (PDL) as a waveform-distorting mechanism in the presence of polarization-mode dispersion (PMD) and assesses its significance in fiber-optic communications links. A simple model is introduced that illustrates the joint effect of PDL and PMD on the transmitted waveforms within the first-order approximation in the transmitted bandwidth, and the nature of possible distortions is discussed. This paper analyzes the statistics of the PMD and PDL vectors and derives explicit formulas for their mean-square magnitudes. These formulas are used to show that, in systems with realistic parameters, the waveform-distorting effects of PDL are of very limited significance.
TL;DR: It is shown that polarization independence in the transmission mode can be achieved in such a configuration and that maximum transmittance occurs when a half-wave plate is used for the polarization-converting element.
Abstract: We analyze the transmission characteristics of a Sagnac loop interferometer containing a polarization-dependent loss element and lossless polarization-converting elements by use of Jones matrices. We show that polarization independence in the transmission mode can be achieved in such a configuration and that maximum transmittance occurs when a half-wave plate is used for the polarization-converting element. The result is verified experimentally for a fiber acousto-optic tunable filter and cascaded long-period fiber gratings with either intrinsic or process-induced polarization-dependent filtering characteristics.
TL;DR: In this paper, the effect of chromatic dispersion and nonlinearity in the presence of polarization-mode dispersion (PMD) was investigated for the first time in the case of 10-Gb/s nonreturn-to-zero (NRZ) transmission.
Abstract: In this paper, we investigate for the first time chromatic dispersion and nonlinearity tolerances in the presence of polarization-mode dispersion (PMD) for polarization-multiplexed (POLMUX) 2 /spl times/ 10-Gb/s nonreturn-to-zero (NRZ) transmission. In polarization-multiplexing, the interaction between fiber nonlinearity and PMD can lower the nonlinear tolerance beyond the tolerances evident when considering both transmission penalties separately; the combined penalties are significantly worse than in the case for non-POLMUX transmission. In this paper, we show, through simulations comparing POLMUX with non-POMUX transmission in the presence of nonlinearity, a reduction of about a factor of three in PMD tolerance. In addition, we show that the dispersion tolerance of POLMUX transmission is severely limited in the presence of PMD. For example, a 40-ps differential group delay (DGD) with worst case coupling of the polarization channels into the fiber lowers the dispersion tolerance, resulting in a 1-dB eye-opening penalty (EOP), from 1200 to 450 ps/nm. We conclude that the interaction between PMD, chromatic dispersion, and nonlinearity leads to the worst signal impairments in POLMUX transmission and increases the effort of using polarization-multiplexing as a modulation format.
TL;DR: In this article, a nondestructive method to monitor chromatic dispersion and polarization-mode dispersion in traffic-carrying wavelength-division-multiplexing optical systems is proposed and experimentally demonstrated.
Abstract: We propose and experimentally demonstrate a nondestructive method to monitor chromatic dispersion (CD) and polarization-mode dispersion (PMD) in traffic-carrying wavelength-division-multiplexing optical systems. Coherent heterodyne detection is used to down convert the spectrum of digitally modulated signal from optical domain into radio-frequency (RF) domain. By analyzing group delay difference and polarization walkoff between different frequency components through proper RF signal processing, both CD and PMD can be precisely determined. Good agreement between experimental results and theoretical values has been obtained.
TL;DR: It is shown 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.
Abstract: 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.
TL;DR: In this paper, the phase and group modal birefringence in photonic crystal fibres with an elongated core is discussed and a fully vectorial mode solver is used to tune the parameters.
Abstract: We discuss the phase and group modal birefringence in photonic crystal fibres (PCFs) with an elongated core. Owing to large form birefringence, these two types of birefringence in such PCFs may not only have opposite signs, but their absolute value can also differ by several orders of magnitude. We also show that PCFs offer the unique possibility of having a large phase birefringence and a negligible polarization mode dispersion at the same time. Using a fully vectorial mode solver, we show how these parameters can be tailored by a proper choice of the geometry of the PCF. We demonstrate both numerically and experimentally the strong wavelength dependence of phase and group modal birefringence in triple-defect photonic crystal fibres (PCFs).
Patent•
02 Aug 2005TL;DR: In this paper, a length ratio for the multimode optical fibers that obtains the maximum band of the optical transmission path is determined, and the multi-modal optical fibers are coupled according to this length ratio.
Abstract: In an optical transmission path including multimode optical fibers, modal dispersion is reduced so that signal light can be transmitted at high speed and across a broad band, at low-cost and over a long distance. To reduce modal dispersion, when the transmission path is constructed by coupling a plurality of multimode optical fibers, a length ratio for the multimode optical fibers that obtains the maximum band of the optical transmission path is determined, and the multimode optical fibers are coupled according to this length ratio. The multimode optical fibers that are used have specific refractive index profiles as mode dispersion-compensating fibers. The compensated fiber and the mode dispersion-compensating fiber are coupled with specific lengths.
TL;DR: In this article, an endless reset-free polarization controller implemented with planar lightwave circuits using phase shifters for tuning is proposed and demonstrated, and the proof of concept is demonstrated by implementing the equivalent of a rotating waveplate using Ge-doped silica-on-silicon waveguides and thermo-optic phase shiftters.
Abstract: An endless, reset-free polarization controller implemented with planar lightwave circuits using phase shifters for tuning is proposed and demonstrated. By avoiding the need for tunable polarization mode converters, simple fabrication processes and a large range of material systems can be used, since neither the electrooptic effect nor a rotatable birefringence axis are necessary for device operation. The proof of concept is demonstrated by implementing the equivalent of a rotating waveplate using Ge-doped silica-on-silicon waveguides and thermooptic phase shifters. The polarization controller is shown to have excellent tolerance to fabrication variations. Fast thermooptic control (on the order of 10 kHz) is achieved using high-index-contrast (4%) waveguides.
TL;DR: In this article, a simple method to monitor both optical signal-to-noise ratio (OSNR) and polarization-mode dispersion (PMD) simultaneously using a polarization-scrambling module followed by polarization beam splitting is proposed.
Abstract: This paper proposes a simple method to monitor both optical signal-to-noise ratio (OSNR) and polarization-mode dispersion (PMD) simultaneously using a polarization-scrambling module followed by polarization beam splitting. OSNR and PMD are obtained from interaction terms between two orthogonal polarization arms. Monitored OSNR and PMD are independent of each other. Experimental results are demonstrated in a 10-Gb/s nonreturn-to-zero (NRZ) system with OSNR from 18 to 36 dB and PMD from 0 to 70 ps.
Patent•
16 Nov 2005TL;DR: In this article, a method of providing dispersion compensation includes providing a dispersion signal indicative of an amount of dispersion for at least one channel of a multi-channel optical signal.
Abstract: A method of providing dispersion compensation includes providing a dispersion signal indicative of an amount of dispersion for at least one channel of a multi-channel optical signal. A dispersion compensator is controlled in accordance with the dispersion signal to optically compensate for the dispersion of the optical signal.
TL;DR: In this paper, the impact of the polarized nature of stimulated Raman scattering on RIN transfer in a forward-pumped Raman amplifier using polarization-combined diodes is measured and analyzed.
Abstract: Pump-to-signal relative-intensity-noise (RIN) transfer in a forward-pumped Raman amplifier using polarization-combined diodes is measured and analyzed. For the first time, by means of experiment and simulations, we call attention to the impact of the polarized nature of stimulated Raman scattering on RIN transfer. We show that measuring the RIN at the output of a depolarized Raman pump and inserting this figure in the commonly used RIN transfer equation is not sufficient for good signal RIN prediction. Although depolarizing the Raman pump enables polarization-independent signal gain, proper modeling of RIN transfer should include the polarization dependence of the Raman effect and the polarization mode dispersion of the fiber.
01 Jan 2005
TL;DR: In this article, the results of simulations of long-haul 10 Gb/s transmission, investigating simultaneous compensation of chromatic dispersion and intra-channel nonlinearity are presented.
Abstract: The development of CMOS-based digital signal processors, A/D and D/A converters operating at rates exceeding 20 GSa/s is enabling advances in the performance of electronic techniques to mitigate optical transmission impairments at bit-rates of 10 Gb/s and above. Digital processing techniques can be used to overcome signal distortion caused by fibre dispersion and nonlinearity, polarization mode dispersion, WDM crosstalk, and optical and electrical filtering. In this paper, recent advances in the use of signal predistortion using DSP are described, and results of simulations of long-haul 10 Gb/s transmission, investigating simultaneous compensation of chromatic dispersion and intra-channel nonlinearity are presented. Practical digital filter architectures are proposed to achieve nonlinear compensation. (6 pages)
TL;DR: This work demonstrates soliton trapping and collisions and also the ability to control the separation and shape of soliton pulses by varying the power at the input of the fiber.
Abstract: Propagation of two orthogonally polarized time-delayed optical solitons in low-birefringence optical fiber is studied experimentally. We demonstrate soliton trapping and collisions and also the ability to control the separation and shape of soliton pulses by varying the power at the input of the fiber.