Showing papers on "Polarization mode dispersion published in 2004"

Angular and polarization properties of a photonic crystal slab mirror

Abstract: It was recently demonstrated that a photonic crystal slab can function as a mirror for externally incident light along a normal direction with near-complete reflectivity over a broad wavelength range. We analyze the angular and polarization properties of such photonic crystal slab mirror, and show such reflectivity occurs over a sizable angular range for both polarizations. We also show that such mirror can be designed to reflect one polarization completely, while allowing 100% transmission for the other polarization, thus behaving as a polarization splitter with a complete contrast. The theoretical analysis is validated by comparing with experimental measurements.

Impact of chromatic and polarization-mode dispersions on DPSK systems using interferometric demodulation and direct detection

Abstract: We study the impact of chromatic dispersion (CD) and first-order polarization-mode dispersion (PMD) on systems using binary differential phase-shift keying (2-DPSK) or quaternary DPSK (4-DPSK) with nonreturn-to-zero (NRZ) or return-to-zero (RZ) formats. These signals are received using optical preamplification, interferometric demodulation, and direct detection. We consider the linear propagation regime and compute optical power penalties at fixed bit-error ratio (BER). In order to evaluate the BER precisely taking account amplifier noise, arbitrary pulse shapes, arbitrary optical and electrical filtering, CD, and PMD, we introduce a novel model for DPSK systems and compute the BER using a method recently proposed by Forestieri for on-off keying (OOK) systems. We show that when properly applied, the method yields highly accurate results for DPSK systems. We have found that when either the NRZ or RZ format is used, 2-DPSK exhibits lower power penalties than OOK in the presence of CD and first-order PMD. RZ-2-DPSK, as compared with NRZ-2-DPSK, incurs smaller penalties due to PMD, but offers no advantage in terms of CD. 4-DPSK, as it has twice the symbol duration of OOK or 2-DPSK for a given bit rate, incurs much lower CD and PMD power penalties than either of these techniques. RZ-4-DPSK is especially promising, as it offers CD and PMD penalties significantly smaller than all other techniques, including NRZ-4-DPSK.

Spectral broadening of a partially coherent CW laser beam in single-mode optical fibers

Abstract: The nonlinear propagation of a partially coherent continuous-wave laser beam in single-mode optical fibers is investigated both theoretically and experimentally, with a special attention to the zero-dispersion wavelength region where modulation instability is expected. Broadband asymmetric spectral broadening is reported experimentally and found in fairly good agreement with a numerical Schrodinger simulation including a phase-diffusion model for the partially coherent beam. This model shows in addition that the underlying spectral broadening mechanism relies not only on modulation instability but also on the generation of high-order soliton-like pulses and dispersive waves. The coherence degradation which results from these ultrafast phenomena is confirmed by autocorrelation measurement.

Principles for electronic equalization of polarization-mode dispersion

Abstract: System performance of optical fiber transmission in the presence of polarization-mode dispersion (PMD) can be improved by various types of electronic equalizers, which will be discussed in this paper. After a brief review of equalization and detection theory, equalizer concepts are adapted to the nonlinear optical channel and the architecture is optimized for high bit rate applications. Simulation results accounting for implementation losses in state-of-the-art technologies and realistic transmission conditions indicate that these concepts provide adequate solutions for equalization in lightwave transmission systems.

Simple multichannel optical equalizer mitigating intersymbol interference for 40-Gb/s nonreturn-to-zero signals

Abstract: We present a simple, silica waveguide optical equalizer that significantly mitigates intersymbol interference (ISI) impairments for many wavelength-division multiplexed (WDM) channels simultaneously. We study the mitigation of ISI arising from band-limited transmitters, narrow-band optical filtering, chromatic dispersion, and polarization-mode dispersion (PMD). We demonstrate significant improvements, both single- and multichannel, at 40 Gb/s with a single, potentially set-and-forget device.

Optical performance monitoring using nonlinear detection

Abstract: A definitive goal for optical performance monitoring in an optical communications network is to provide comprehensive signal quality information in a cost-effective manner. This paper explores in detail the possibility of using nonlinear optical detection to achieve this goal. Sensitive nonlinear detection techniques commonly used in the field of ultrafast optics are applied to the problem of performance monitoring and are shown to allow quantitative measurements to be made of quantities such as accumulated chromatic dispersion, polarization-mode dispersion impairment, optical signal-to-noise ratio, and extinction ratio. Experiments performed on a 40-Gb/s transmission system demonstrate the immediate viability of this approach for measuring these quantities of interest at practical optical power levels.

Monitoring and control of polarization-related impairments in optical fiber systems

Abstract: Polarization-related impairments have become a critical issue for high-data-rate optical systems, particularly when considering polarization-mode dispersion (PMD) and polarization-dependent loss (PDL). In general, polarization effects are stochastic processes and can occur on short or long time scales. Therefore, control and monitoring of these effects may be crucial in any systems-level mitigation. This tutorial will highlight the following key issues: PMD and PDL, monitoring schemes, emulation of proper statistics, interaction, and applications of polarization scrambling.

Planar photonic crystal polarization splitter.

Abstract: The differential dispersion relation for the E and H modes (TM-like and TE-like, respectively) in planar photonic crystals is used to control the polarization-dependent propagation of light. E- and H-polarized beams were separated by 10 degrees after propagating through a 20-microm-long planar photonic crystal in the wavelength range from 1250 to 1300 nm. The plane-wave expansion calculation matches well with the experimental results. This result represents the first demonstration, to our knowledge, of a polarization splitter realized in a planar photonic crystal configuration in the near-infrared wavelength range operating solely in transmission mode.

Spatially resolved PMD measurements

Abstract: Spatially resolved measurements of polarization properties of fiber optic link-such as birefringence, polarization-mode dispersion (PMD) and polarization dependent loss (PDL)-may be effectively performed using polarization sensitive reflectometric techniques. In particular, this paper focuses on polarization-OTDR and reviews its theory and applications. Special emphasis is given to the use of optical reflectometry as a tool to characterize fiber birefringence. This allows to inspect the fiber while cabled and, consequently, to test and improve the cabling process. In addition, it also allows to define reliable mathematical models, which are essential for the design of low polarization mode dispersion fibers. The application of polarization-OTDR to polarization mode dispersion and polarization dependent loss measurements is also discussed.

Fibers with low polarization-mode dispersion

Abstract: Fibers with low polarization-mode dispersion (PMD) enable high-bit-rate time-division-multiplexed optical communication systems. These fibers are becoming increasingly important with the growing implementation of wavelength-division-multiplexing (WDM) transmission with channel bit rates of 40 Gb/s. Important to the realization of low PMD fibers are the fiber's index and stress profiles, polarization-mode coupling, and the evolution of the polarization state with length. This paper reviews recent progress in the understanding of the fabrication and characteristics of these fibers. The paper also discusses the important fiber physical parameters, including the fiber index profile and fiber spinning parameters and their impacts on the realization of low PMD performance.

Effects of polarization-mode dispersion on fiber-based parametric amplification and wavelength conversion.

Abstract: We present a vector theory of four-wave mixing in optical fibers and use it to discuss the effect of polarization-mode dispersion (PMD) on the performance of parametric amplifiers and wavelength converters. We show that PMD distorts the gain spectrum and makes it less uniform than that expected in the absence of residual birefringence. PMD also induces large fluctuations in the amplified or wavelength-converted signal.

High spectral density long-haul 40-Gb/s transmission using CSRZ-DPSK format

Abstract: This paper presents an experimental investigation of 40-Gb/s DWDM transmission technologies that can potentially transport multiple terabits of aggregate capacity with ultrahigh spectral efficiency over several thousand kilometers of fiber in a terrestrial optical network. By using carrier-suppressed return-to-zero (CSRZ) differential-phase-shift-keyed (DPSK) modulation format with optimized signal filtering, we have demonstrated transmission of 6.4-Tb/s capacity with 0.8-bit/s/Hz spectral efficiency over 3200 km of fiber using 100-km amplified spans. This transmission was conducted using 160 50-GHz-spaced wavelength channels, each at 42.7 Gb/s, in the standard C + L wavelength bands. Low dispersion-slope TrueWave REACH fiber plus slope-matched dispersion compensating fiber with all-Raman amplification were also employed to achieve this record 20-Pbit/s/km capacity-distance product for terrestrial 40-Gb/s systems. In addition, we used a loop-synchronous polarization controller (PC) to better emulate the polarization effects of a straight-line system.

Importance sampling for polarization-mode dispersion: techniques and applications

Abstract: The basic theory of importance sampling (IS) as relevant to polarization-mode dispersion (PMD) in optical fibers is discussed, and its application to Monte Carlo (MC) simulations of PMD-induced transmission impairments is demonstrated. The use of IS allows rare PMD events to be simulated much more efficiently than with standard MC methods. As a consequence, methods employing IS provide natural and effective tools to assess PMD-induced impairments and outages in optical transmission systems at realistic probability levels.

Adaptive digital equalization in the presence of chromatic dispersion, PMD, and phase noise in coherent fiber optic systems

Abstract: Chromatic dispersion (CD) and polarization mode dispersion (PMD) severely limit the performance of optical transmission systems operating at and above 10 Gb/s. Electrical equalization techniques have been proposed to compensate dispersion in both coherent and intensity modulation/direct-detection (IM/DD) systems. We investigate the combined adaptive digital equalization of all-order PMD, CD, and laser phase noise in high-speed coherent optical transmission systems. Simultaneous equalization of these impairments has not been reported previously and is particularly important in modulation systems that exploit polarization to increase modulation efficiency. We propose a novel 4-dimensional equalizer structure for joint polarization modulation and M-ary differential phase shift keying (JPMDPSK) systems. The specific example considered is 40 Gb/s transmission with a 10 GBaud symbol rate, using DQPSK modulation on each axis of polarization. Our results show that the new four-dimensional equalizer can compensate channel dispersion of up to 1000 km of standard single-mode fiber, with less than 3 dB penalty in signal-to-noise ratio (SNR). This is a dramatic improvement over 40 Gb/s IM/DD systems. The feasibility of the very large scale integration (VLSI) of coherent receivers in current technology is also discussed.

Volume holographic grating-based continuously tunable optical filter

Abstract: We propose and demonstrate a widely tunable optical filter, realized by angle tuning a volume holographic grating. The volume holographic grating selectively drops a narrow portion of the signal bandwidth into a fiber while passing through the rest of the signals. The demonstrated 1510- to 1590-nm tuning range covers the entire erbium-doped fiber amplifier (EDFA) C band, with small bandwidth variation and low insertion loss (<1 dB). Group delay, polarization-dependent loss, and polarization mode dispersion are measured and investigated for optimizing the filter characteristics.

RZ-DPSK transmission using a 42.7-Gb/s integrated balanced optical front end with record sensitivity

Abstract: We have demonstrated a record sensitivity of -37.0 dBm (38 photons/bit) for a BER of 10/sup -9/ at 42.7-Gb/s using an integrated balanced optical front end. Results were obtained using optical preamplification of RZ-DPSK modulation and an external delay-interferometer. The OSNR requirement was measured to be 16.9 dB in a 0.1-nm bandwidth. The impact of polarization-mode dispersion (PMD) and chromatic dispersion on the optical front end performance has been measured. Performance for enhanced forward error correction has been projected based on 10/sup -3/ BER performance.

Polarization-mode dispersion detecting method, and a dispersion compensation controlling apparatus and a dispersion compensation controlling method

Abstract: A dispersion compensation controlling apparatus used in a very high-speed optical communication system adopting optical time division multiplexing system comprises a first specific frequency component detecting unit (2 a) detecting a first specific frequency-component in a baseband spectrum in a transmission optical signal inputted to a receiving side over a transmission fiber as a transmission line (6 a), a first intensity detecting unit (3 a) detecting information on an intensity of the first specific frequency component detected by the first specific frequency component detecting unit (2 a and a polarization-mode dispersion controlling unit (220 a) con trolling a polarization-mode dispersion quantity of the transmission line (6 a) such that the intensity of the first specific frequency component detected by the first intensity detecting unit. (3 a) becomes the maximum, thereby easily detecting and compensating polarization-mode dispersion generated in a high-speed optical signal.

Effects of polarization-mode dispersion on cross-phase modulation in dispersion-managed wavelength-division-multiplexed systems

Abstract: This paper develops a vector theory of cross-phase modulation (XPM) in optical fibers and use it to investigate the impact of polarization-mode dispersion (PMD) on the crosstalk induced by XPM in wavelength-division multiplexed lightwave systems. Under certain reasonable approximations, the theory permits us to obtain an analytic expression for the amplitude of probe fluctuations induced by a copropagating pump channel through XPM. We use this expression to calculate the average level of XPM-induced crosstalk together with its variance for several dispersion maps. We show that PMD not only reduces the crosstalk on average, but also impacts the efficiency of a commonly used polarization-interleaving technique.

Quaternion approach to PMD and PDL phenomena in optical fiber systems

Abstract: In this paper, we introduce the concept of quaternions (which is a generalization of the complex numbers) and quaternion calculus and demonstrate how this theory may be used to simplify the treatment of polarization phenomena in optical fibers. We apply quaternion calculus to two examples: 1) the description of polarization-dependent loss (PDL) elements and concatenation of such and 2) the description of pulse dynamics and broadening in transmission lines with both polarization-mode dispersion (PMD) and PDL. Finally we present some novel results from the investigation of pulse broadening in a simple system comprising a PMD element, followed by a perfect polarizer.

Polarization-mode dispersion of installed recent vintage fiber as a parametric function of temperature

Abstract: We report the first polarization-mode dispersion measurement of installed 0.05-ps/km/sup 1/2/ fiber over 150-km span and 100-nm bandwidth. The apparent randomness of differential group delay (DGD) spectral components over time is removed when the DGD is considered as a function of temperature.

Effects of polarization-mode dispersion in dual-pump fiber-optic parametric amplifiers

Abstract: Effects of polarization-mode dispersion (PMD) on dual-pump parametric amplifiers are investigated numerically using a set of four vector equations. It is found that PMD induces large fluctuations in the signal power that can affect the system performance by enhancing the outage probability. The average gain itself is reduced by more than 10 dB even for a relatively small value of 0.05 ps//spl radic/km for the PMD parameter. For larger values of the PMD parameter, the gain spectrum begins to distort and loses its flatness. We also show that the polarization dependence of gain cannot be eliminated by using orthogonally polarized pumps.

70-GHz-spaced 40/spl times/42.7 Gb/s transpacific transmission over 9400 km using prefiltered CSRZ-DPSK signals, all-Raman repeaters, and symmetrically dispersion-managed fiber spans

Abstract: 70-GHz-spaced 40/spl times/42.7 Gb/s prefiltered carrier-suppressed return-to-zero differential phase-shift keying (CSRZ-DPSK) signals have been transmitted over transpacific distances for the first time, using all-Raman repeaters with two pump-wavelengths, dispersion-managed fiber commercially available in volume, and an ETDM receiver. In this paper, first, in order to enhance the spectral efficiency, the impact of bandlimitation to a CSRZ-DPSK signal was experimentally investigated in comparison to a conventional CSRZ-on-off-keying (OOK) signal, and we found that the bandlimitation tolerance of CSRZ-DPSK signal was smaller than that of CSRZ-OOK signal in back-to-back condition. We also confirmed that the prefiltering CSRZ-DPSK signal with up to 65 GHz bandlimitation potentially had better transmission performance than the prefiltered CSRZ-OOK signal. In addition, we found that, although the nonlinear transmission penalty was increased by bandlimitation, this penalty for CSRZ-DPSK signal was smaller than that for CSRZ-OOK signal. Through this study, long-term stability of the transmission performance was also evaluated with low-speed signal polarization scrambling without using any polarization mode dispersion (PMD) compensation.

Polarization-mode-dispersion emulator using variable differential-Group-delay (DGD) elements and its use for experimental importance sampling

Abstract: We demonstrate a practical polarization-mode-dispersion (PMD) emulator using programmable differential-group-delay (DGD) elements. The output PMD statistics of the emulator can be chosen by varying the average of the Maxwellian DGD distribution applied to each element. The emulator exhibits good stability and repeatability in a laboratory environment. In addition, we demonstrate how this emulator may be used to experimentally employ the powerful technique of importance sampling to quickly generate extremely low probability events. This technique is used to measure the Q-factor degradation due to both average and rare PMD values in a 10-Gb/s transmission system.

First dispersion-flattened transpacific undersea system: from design to terabit/s field trial

Abstract: The 8991-km-long transpacific segment of the Tyco Global Network (TGN) [TGN is a trademark of Tyco Telecommunications, Eatontown, NJ 07724 USA], connecting Hillsboro, Oregon, USA to Toyohashi, Japan, is the first installed dispersion-flattened dense wavelength division multiplexed (DWDM) system. In this paper, we describe the development path bringing this system from the computer design stage to a field trial, which confirms that the installed segment can support the design capacity of 96/spl times/10 Gb/s customer channels per fiber pair. Commercial channels have been provisioned on this segment with satisfactory system margins. Exploratory transmission results at 128/spl times/12.3 Gb/s over this segment are also reported here. The experimental results agree well with our expectations based on the results from our system design simulator.

Statistics of the DGD in PMD emulators

Abstract: We give the statistics of the differential group delay at the output of a polarization-mode dispersion emulator made of a chain of fiber sections with constant birefringence, fixed and arbitrarily selected lengths, and randomly oriented polarization controllers in between.

Introduction to polarization mode dispersion in optical systems

Abstract: This introduction covers concepts important to the understanding of polarization mode dispersion (PMD), including optical birefringence, mode coupling in long optical fibers, the Principal States Model, and the time and frequency domain behavior of PMD. Other topics addressed include the concatenation rules, bandwidth of the Principal States, PMD statistics and scaling, PMD system impairments, and PMD outage probability calculations.

Adaptive distortion compensation with integrated optical finite impulse response filters in high bitrate optical communication systems

Abstract: In high-bit-rate optical transmission systems, distortions due to dynamic chromatic dispersion, polarization mode dispersion, and power changes are larger than the distortion tolerances of the system. To meet the tolerances and the desired quality of service, an adaptive equalizer is necessary. We demonstrate the capabilities of planar lightwave circuit integrated optical finite impulse response filters for mitigating distortions of the transmission channel, and we investigate two adaptive equalization approaches. The first approach uses an adaptive feedback generated from electrical spectrum monitoring; the second one uses intersymbol interference minimization with a least mean square error algorithm. We successfully demonstrated adaptive equalization of chromatic dispersion, self-phase modulation, and polarization mode dispersion, as well as combinations of these distortions.

A novel dispersion monitoring technique based on four-wave mixing in optical fiber

Abstract: We propose a novel dispersion monitoring method based on four-wave mixing (FWM) or parametric amplification effect in optical fiber. The signal pulse stream, which is used as a parametric pump, is mixed with a weak continuous wave light at a different wavelength in a fiber. Due to the FWM effect, a so-called idler light is created at a wavelength symmetric in respect to the pump. The output idler power can be measured and is dependent on the pulsewidth and, therefore, accumulated residual dispersion of the input signal. The concept was successfully demonstrated with 40-Gb/s return-to-zero signal. This approach potentially works for data rates up to terabits per second and can be applied to provide a feedback for automatic dispersion compensation.

Numerical study on dispersion compensating property in photonic crystal fibers

Abstract: The dispersion compensating property in photonic crystal fibers (PCFs) is simulated with a vectorial effective=index approach in this paper. It is found that the dispersion, dispersion slope, and Kappa parameter of PCFs can be designed neatly by changing the air hole size and the pitch in PCFs cladding. We can obtain PCFs with large absolute value of normal dispersion and negative dispersion slope at the wavelength of 1.55μm.Conventional communication nonshifted single-mode fibers (G652) and nonzero-dispersion shifted fibers (NZ-DSF,G655) can be compensated efficiently at wavelengths around 1.55μm low-loss optical communication window. It is demonstrated that there are huge potentials in designing dispersion compensating PCFs.