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The research object: data transmission in optical communication lines. The subject of research is algorithms for the construction of digital data and methods of their transmission over buses in optical computer systems and in backbone fiber-optic systems. The problem to be solved is the need to devise new methods that ensure increased reliability and cryptographic stability of optical transmission systems. To solve the task, the issue of expanding the theory of timer signal structures and the system of residual classes for the organization of multifactorial multiplex data transmission through the channels of modern information transmission systems was investigated. The factor space is defined (as an example) for fiber optic transmission systems where different multiplexing options are used or may be used. The possibility of adapting algorithms for the construction of digital signal structures for their further transmission in the system of residual classes by various methods of multiplexing has been substantiated. The main principles of transmission were considered: the principle of independence of multiplexing the transmission of residues on each module and the principle of logical dependence and physical independence of the system of channels for transmission of residue values for a specific module of a specific system of residue classes. The basic principle is that at each specific point in time in the multivariate binary space, only one of the possible values of each factor can be equal to unity. A comparison with existing transmission systems shows that the proposed technique could provide data transmission at a speed of up to 16 Tbit/s in a transmission bandwidth of 200 THz. At the same time, the capacity of the alphabet of transmitted characters will be 39468 different characters. It also provides a significant increase in the reliability of the entire transmission system. [ABSTRACT FROM AUTHOR]

Summary: The bit error rate (BER) in optical communication systems is often get degraded due to various factors like launch power, dispersion, modal noise, and so on. Finding the most optimal launch power for a signal to provide acceptable BER is usually difficult on an installed link. Therefore, in this paper, an attempt has been made to use machine learning‐based linear regression technique for predicting the optimal signal quality for spatial division multiplexed (SDM)‐based fiber optical transmission system for a fixed distance. This technique helps in predicting the optimal value of continuous launch power. Therefore, to demonstrate the given concept in this research work, the generic setup of an SDM optical long‐haul system of 20 km in length has been designed and simulated in Optisystem‐14.0. The light sources in our experiments are two spatial optical transmitters with an emission wavelength of around 1550 nm. Abiding to the first step for the regression analysis, that is the data preparation, normality and correlation checks were performed. After this, a linear regression model is developed which was validated through a summary report, coefficients and diagnostic plots. Furthermore, the accuracy of the model is improved by employing Cook's distance. These tests help in dealing with the influence points that hinders the prediction ability of the proposed model. The results show that the R‐squared value is 0.9366, and value of adjusted R2 comes out to be around 0.9344; we therefore came to infer that the model explains nearly 94% variations in the dependent variables. [ABSTRACT FROM AUTHOR]

A novel two-stage coded modulation (TSCM) scheme based on the 8-QAM signal is proposed. In the proposed scheme, three bits in the same symbol are protected by different codes in order to fully utilize 8-QAM’s ring characteristic and obtain the more coding gain in optical transmission systems. The two simulation experiments with two groups of quasi-cyclic low-density parity-check (QC-LDPC) codes are performed. The simulation results show that the proposed scheme, compared with the traditional parallel independent scheme which has similar code-rate, can bring about 0.5dB and 0.1dB net coding gain (NCG) respectively at the bit error ratio (BER) of 10 -6 . In addition, the applied QC-LDPC codes need less times of iterations and have low error floor. The proposed scheme can implement the transmission without time delay, and the number of addition operations is also only 2/3 of the traditional scheme while calculating the log-likelihood ratio (LLR) algorithm of a symbol. Therefore, the proposed TSCM scheme combined with the QC-LDPC codes has the better comprehensive performance and can better be suitable for high-speed optical transmission systems. [ABSTRACT FROM AUTHOR]

We present the concept and design of a 100 GHz PIC-based nonlinear frequency division multiplexed transmission system in which four b -modulated spectrally overlapping channels are spectrally stitched without frequency guard bands to obtain a continuous spectrum. Neural network-based equalizers are used at the receiver for improved performance. Simulations show that the proposed system alleviates the problem of nonlinear interaction between neighboring channels, that would, otherwise, be out of reach even for neural network equalization to solve on its own. The system achieves a 960 km transmission distance with a raw data rate of 333 Gbps per polarization and a BER well below the SD-FEC limit for every subcarrier. • New concept and design of a 100 GHz PIC-based nonlinear frequency division multiplexed transmission system. • b -modulated spectrally overlapping channels are stitched to obtain a continuous spectrum without nonlinear interaction between channels. • Neural network-based equalizers are used at the receiver for improved performance. • The system achieves a 960 km transmission distance with a raw data rate of 333 Gbps per polarization and a BER well below the SD-FEC limit for every subcarrier. [ABSTRACT FROM AUTHOR]

We outline a formalism for modeling interferometers, such as asymmetric Mach-Zehender interferometers used in both microwave photonic links and modern transmission systems. The formalism permits modeling elements with birefringence and polarization-dependent loss. By introducing a coordinate transformation between the standard “waveguide” view (coupled polarizations and independent waveguides) and the “coupler” view (coupled waveguides with independent polarizations), we reduce modeling to a concatenation of block diagonal operators and coordinate transformations. This connects to, and generalizes, an earlier approach. We illustrate the formalism by calculating the phase shift in a birefringent interferometer suffering differential normal mode losses in the couplers. Such phase shifts can be a significant source of even-order distortion in phase-modulated links employing an interferometer-based receiver. [ABSTRACT FROM PUBLISHER]

The search for schemes that minimize the energy associated with the transmission of information is a longstanding fundamental issue in communication theory. In this paper we extend fundamental limits to the energy consumption per unit of information, as given by Shannon's theory, to the quantum domain. Unlike previous studies, we address a scenario where the signal may be manipulated in an arbitrary way while propagating from the transmitter to the receiver. This situation characterizes many realistic scenarios, such as multi-span fiber-optic communication systems. We obtain the ultimate quantum limit on the energy consumption in this scenario and propose a simple binary energy modulation scheme that approaches this limit within one order of magnitude for practically relevant values of spectral efficiency. Under the same conditions, the quantum energy consumption limit of the standard optically amplified coherent communication scheme is three orders of magnitude above the ultimate identified limit. Throughout the paper we consider transmission of classical information over a quantum channel. [ABSTRACT FROM PUBLISHER]

A compact indium phosphide (InP)-based integrated transmitter assembly consisting of a tunable laser and a double-nested Mach-Zehnder modulator (vector modulator) was successfully used for the generation of Nyquist-prefiltered quadrature phase shift keying (QPSK) and 16-ary quadrature amplitude modulation (16-QAM) signals at 32 Gbaud. With external polarization division multiplexing (PDM) emulation and digital coherent detection, we realized data rates of 128 Gb/s with PDM-QPSK and 256 Gb/s with PDM-16-QAM from a commercially available small-form factor device originally designed for 40-Gb/s direct-detection differential QPSK applications. We transmitted these two signals over 8000 and 960 km of standard single mode fiber, respectively. We also compared the performance of the integrated transmitter with a LiNbO3 based vector modulator, using a high-performance 100-kHz external-cavity laser and a low-cost 200-kHz to 400-kHz integrated laser assembly as optical local oscillators. The all-InP integrated laser-vector-modulator transmitter was found to be a viable solution for long-haul 100 and 200-Gb/s coherent optical transmission systems. [ABSTRACT FROM PUBLISHER]

Abstract: Based on Galois Field (GF(q)) multiplicative group, a new coding scheme for Quasi-Cyclic Low-Density Parity-Check (QC-LDPC) codes is proposed, and the new coding scheme has some advantages such as the simpler construction, the easier implementation encoding, the lower complexity of the encoding and decoding, the more flexible adjustment of the code length as well as the code rate and so forth. Under the condition of considering the characteristics of optical transmission systems, an irregular QC-LDPC (3843,3603) code to be suitable for optical transmission systems is constructed by applying the proposed new coding scheme. The simulation result shows that the net coding gain (NCG) of the irregular QC-LDPC (3843,3603) code is respectively improved 2.14dB, 1.19dB, 0.24dB and 0.14dB more than those of the classic RS (255,239) code in ITU-T G.975, the LDPC (32640,30592) code in ITU-T G.975.1, the regular SCG-LDPC (3969,3720) code constructed by the Systematically Constructed Gallager (SCG) coding scheme and the regular QC-LDPC (4221,3956) code at the bit error rate (BER) of 10-8. Furthermore, all the five codes have the same code rate of 93.7%. Therefore, the irregular QC-LDPC (3843,3603) code constructed by the proposed new coding scheme has the more excellent error-correction performance and can be better suitable for optical transmission systems. [Copyright &y& Elsevier]

A method of quantitative determination of the parameters of distortions in a pulse that arise as a consequence of birefringence in an optical fiber is considered. Existing methods of estimating this type of distortion that are used in communication networks are analyzed. A measurement approach by means of which the effective displacement and broadening of the pulse may be determined for each wavelength of incoming radiation is developed. The method may be used for polarized mode dispersion analysis in networks with wavelength division multiplexing. [ABSTRACT FROM AUTHOR]

A high-scale integrated optical receiver including a preamplifier, a limiting amplifier, a clock and data recovery (CDR) block, and a 1:4 demultiplexer (DEMUX) has been realized in a 0.25 μm CMOS technology. Using the loop parameter optimization method and the low-jitter circuit design technique, the rms and peak-to-peak jitter of the recovered 625-MHz clock are 9.4 and 46.3 ps, respectively, which meet the jitter specifications stipulated in ITU-T recommendation G.958. The recovered and frequency divided 625 MHz clock has a phase noise of −83.8 dBc/Hz at 20 kHz offset in response to 2.5 Gb/s PRBS input data (2-1), and the 2.5 Gb/s PRBS data has been demultiplexed into four 625 Mb/s data. The power dissipation is only 0.3 W under a single 3.3 V supply (excluding output buffers). [ABSTRACT FROM AUTHOR]

This paper presents the circuit designs and measured performance of two ultrahigh-speed low-power 6-b digital-to-analog converters (DACs) using InP-based heterojunction bipolar transistors (HBTs) for beyond-100-Gb/s/ch optical transmission systems. The first design is based on an R-2R ladder-based current-steering architecture with a novel double-sampling technique that relaxes the speed restraints for the DAC and helps achieve ultrahigh-speed operation. The DAC with the double-sampling technique achieves an excellent sampling speed of up to 32 GS/s with low power consumption of 1.4 W. The second design is based on a new timing alignment technique. The DAC with the timing alignment technique operates at a sampling rate of 28 GS/s with very low power consumption of 0.95 W and achieves an excellent figure of merit (0.53 pJ per conversion step). It provides a clear multilevel modulated signal for QAM transmission and can be applied to beyond-100-Gb/s/ch optical transmission systems. [ABSTRACT FROM AUTHOR]

This paper presents the transmission performances, by simulation, of optical communication systems over 10 spans of dispersion compensated and optically amplified fiber distance with a bit rate of 100 Gb/s, by employing modulation formats of two amplitude levels and 8 phase states per amplitude level, the 2R-16-Star QAM constellation under direct and coherent detection with and without phase estimation. Different ring ratios of the amplitude levels are examined and associate transmission performances are reported. Optical signal to noise ratio is achieved with 18 dB and 23 dB for back to back and long haul transmission cases with a dispersion tolerance of ±67 ps/nm at 2 dB power penalty of the eye opening at 100 Gb/s. Monte–Carlo simulation is also performed and a receiver sensitivity of − 15 dBm is achieved for a BER of 10−5under direct detection after 1100 km of dispersion-compensated and optically amplified transmission. Transmission performances, bit error rate versus receiver sensitivity, are also confirmed with the use of the eye diagram and associate multiple-peaks statistical spectral density distribution. For 100 Gb/s 2R-16-Star QAM coherent transmission, an improvement of the receiver sensitivity of 2.5 dB and 3.5 dB is obtained for coherent detection without phase estimation and respectively. Under coherent detection with phase estimation, the chromatic dispersion tolerance reaches ±100 ps/nm for a 2 dB eye opening penalty at 100 Gb/s bit rate. Comparative studies of the transmission performances of the Star and Square QAM modulation formats are also conducted under the fiber linear and nonlinear effects and detection with and without phase estimation. [ABSTRACT FROM AUTHOR]

This paper analyzes optical transmission systems based on high-order modulations such as phase-shift keying signals and quadrature amplitude modulations. When the channel is affected by group velocity dispersion (GVD), polarization mode dispersion (PMD), and phase uncertainties due to the laser phase noise, the optimal receiver processing based on maximum-likelihood sequence detection and its practical implementation through a Viterbi processor is described without a specific constraint on the receiver front end. The implementation issues are then faced, showing that at least a couple of widely known front ends, with proper modifications, can be used to extract the required sufficient statistics from the received signal. The aspects related to the receiver adaptivity, the complexity reduction of the Viterbi processor, and the possibility of employing polarization diversity at the transmitter end are also discussed. It is demonstrated that, as long as a sufficient number of Viterbi processor trellis states is employed, GVD and PMD entail no performance degradation with respect to the case of no channel distortions (the back-to-back case). [ABSTRACT FROM PUBLISHER]

The 25 years since the founding of the Journal of Lightwave Technology have seen more than three orders of magnitude increase in the capacity of optical transmission systems. This dramatic increase was brought about by the deployment of WDM and advances in high-speed transmission technologies. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents experimental results of the introduction of FEC (forward error correction) in optical access network architectures operating at 625 Mb/s. We have first tested a Reed Solomon code on a point to point architecture to confirm the theoretical 3 dB gain in link budget. The innovative architecture is a wavelength division multiplexed passive optical network (WDM PON) using spectrum slicing and a reflective semiconductor optical amplifier (RSOA) to generate upstream signals. Optical carrier supply by spectrum slicing and modulation and amplification by RSOA is a way of reducing costs in WDM PON but it gives a noisy transmission due to excess intensity noise of broadband sources, Amplified Spontaneous emission of the SOA and beat noise at detection. In this case, adding FEC has more effect and it results in an increased link budget of 5.5 dB. FEC are a simple and efficient solution to compensate for penalties introduced by low cost components in innovative architectures like WDM PON. [Copyright &y& Elsevier]

Abstract: The statistical property of intra-channel four-wave-mixing (IFWM) is studied numerically for return-to-zero differential-phase-shift keying transmission. The distributions of IFWM-induced pulse power and phase fluctuations depend on the relative strength of pulse broadening and nonlinear interactions, which can be characterized with a dimensionless parameter. We thus offer a general criterion to understand the stochastic nature of IFWM effect. [Copyright &y& Elsevier]

Abstract: We compare the Q parameter obtained from scalar, semi-analytical and full vector models for realistic transmission systems. One set of systems is operated in the linear regime, while another is using solitons at high peak power. We report in detail on the different results obtained for the same system using different models. Polarisation mode dispersion is also taken into account and a novel method to average Q parameters over several independent simulation runs is described. [Copyright &y& Elsevier]

This paper presents a simple and effective design of taper-based higher order mode (HOM) filters that can effectively remove HOMs from the few-mode fibers. For this purpose, a taper manufacturing technique that allows the production of long and highly uniform tapers was developed. A filter performance was demonstrated on a standard single-mode telecommunication fiber operating at 850 nm. The HOM suppression was better than -39 dB, and the insertion loss of the fundamental mode was less than 0.15 dB [ABSTRACT FROM PUBLISHER]

This paper thoroughly investigates the maximum-likelihood sequence detection (MLSD) receiver for the optical ON-OFF keying (OOK) channel in the presence of both polarization mode dispersion and group velocity dispersion (GVD). A reliable method is provided for computing the relevant performance for any possible value of the system parameters, with no constraint on the sampling rate. With one sample per bit time, a practically exact expression of the statistics of the received samples is found, and therefore the performance of a synchronous MLSD receiver is evaluated and compared with that of other electronic techniques such as combined feedforward and decision-feedback equalizers (FFE and DFE). It is also shown that the ultimate performance of electronic processing can be obtained by sampling the received signal at twice the bit rate. An approximate accurate closed-form expression of the receiver metrics is also identified, allowing for the implementation of a practically optimal MLSD receiver [ABSTRACT FROM PUBLISHER]

In this paper, we compare performance of three classes of forward error correction schemes for 40-Gb/s optical transmission systems. The first class is based on the concatenation of Reed-Solomon codes and this is employed in the state-of-the-art fiber-optics communication systems. The second class is the turbo product codes with Bose-Chaudhuri-Hocquenghen component codes. The application of these codes in optical communication systems was extensively studied by Sab and Lemarie, and Mizuochi The third class is the low-density parity-check (LDPC) codes that have attracted much attention over the past decade. We present enhanced decoding algorithms for Turbo product codes and LDPC codes that use probability density function of output sequences instead of calculating initial likelihood ratios assuming (inaccurate) Gaussian or chi-square approximation. The analysis in this paper shows that the LDPC codes perform better than the other codes in the waterfall region at bit error rates as low as 10-9. We also presented error floors results obtained by analyzing decoding failures of hard-decision iterative decoders [ABSTRACT FROM PUBLISHER]

Frequency performances and sensitivities for three types of organic photo-detector (OPD) were studied for an opto-electrical conversion device. A high efficiency of 19.4 % of the external conversion efficiency and a high cutoff frequency response of 16 MHz were achieved using a mixed-layer between copper phthalocyanine (CuPc) and N, N'-bis (2,5-di-tert-butylphenyl) 3,4,9,10-perylene dicarboximide (BPPC) at a reverse bias voltage of 8 V under red incident light. These results were achieved by increasing exciton dissociation and charge carrier generation and to reduce the number of trapped carriers at the interfaces between CuPc and BPPC. The transmission of a moving picture was successfully demonstrated using mixed-layer OPD as an opto-electrical conversion device. These results indicate that it is possible for an OPD to be used as an opto-electrical conversion device in high-speed optical transmission systems [ABSTRACT FROM PUBLISHER]

Coherent optical transmission systems offer enhanced possibilities concerning multilevel modulation and the electronic compensation of transmission impairments. One of the key components in a homodyne in-phase/quadrature (IQ) receiver is a 2 times 4 90deg hybrid. However, this component is only commercially available in a form that requires an additional active control loop. This paper presents the different possible alternatives for the realization of the 2 times 4 90deg hybrids and discusses their availability and properties, as well as the practical implementation considerations [ABSTRACT FROM PUBLISHER]

In-fiber devices enable a vast array of critical photonic functions ranging from signal conditioning (amplification, dispersion control) to network management (add/drop multiplexers, optical monitoring). These devices have become mainstays of fiber-optic communication systems because they provide the advantages of low loss, polarization insensitivity, high reliability, and compatibility with the transmission line. The majority of fiber devices reported to date are obtained by doping, designing, or writing gratings in the core of a single-mode fiber (SMF). Thus, these devices use the fiber only as a platform for propagating light-the device effect itself is due to some extraneously introduced material or structure (dopants for amplification, gratings for phase matching, etc.) There exists another, relatively less explored degree of freedom afforded by fibers-the ability to copropagate more than one mode. Each mode may have a uniquely defined modal dispersion and propagation characteristic. In this paper, we will describe the variety of fiber devices enabled by few-mode fibers-fibers that typically support two to four modes with suitably tailored dispersive properties. We will show that the unique dispersive properties of various modes, in conjunction with the ability to couple between them with gratings, leads to devices that offer novel solutions for dispersion compensation, spectral shaping, and polarization control, to name a few. [ABSTRACT FROM PUBLISHER]

In this paper, we show that the nonlinear parametric gain (PG) interaction between signal and noise is a nonnegligible factor in the design and analysis of long-haul dispersion-managed optical 10-Gb/s on-off keying nonreturn to zero transmission systems operated at small signal-to-noise ratios (OSNRs) such as those employing forward-error correction (FEC) coding. In such a regime, we show that the in-phase noise spectrum exhibits a large gain close to the carrier frequency, which is due to the higher order noise terms accounting for the noise-noise beating during propagation that is usually neglected in the nonlinear Schrödinger equation. With a novel stochastic analysis that keeps such higher order terms, we are able to analytically quantify the maximum tolerable signal power after which PG unacceptably degrades system performance. We verify such an analytical power threshold by both simulation and experiment. We finally quantify the needed extra OSNR, or equivalently FEC coding gain, required when taking PG into account. [ABSTRACT FROM PUBLISHER]

This paper describes an adaptive dispersion equalizer (ADE) that uses an asynchronous dispersion-induced chirp monitor and the detailed study of the first demonstration of 160-Gb/s adaptive dispersion equalization. The device successfully equalized the dispersion change over a 40°C temperature range (from 5°C to 45°C) and the dispersion slope of an 80-km dispersion-shifted fiber (DSF). The ADE will enhance the feasibility of 160-Gb/s optical transmission systems. [ABSTRACT FROM PUBLISHER]

Abstract: The Q parameter scales differently with the noise power for the signal–noise and the noise–noise beating terms in scalar and vector models. Some procedures for including noise in the scalar model largely under-estimate the Q parameter. We propose a simple method for including noise within a scalar model which will allow both the noise–noise dominated limit and the signal–noise dominated limit to be treated consistently. [Copyright &y& Elsevier]

Taking into account the influence of group-velocity dispersion (GVD) and the nonlinear Kerr effect, the nonlinear amplification of the amplified spontaneous emission (ASE) noise in fiber transmission systems using optical phase conjugation (OPC) is studied. Under a path-averaged power approximation for long-haul transmission systems, an equivalent system is developed to evaluate ASE noise amplification and accumulation in OPC systems. Combining the theoretical analysis and numerical simulations, the noise suppression effect in OPC systems is demonstrated and discussed. By using the numerical calculation method, the power variation along the system is involved in the evaluation of noise amplification. It is shown that the power variation through the system results in an imperfect compensation of the modulation instability (MI) effect, which furthermore causes the degradation of the noise suppression performance in OPC systems with anomalous dispersion. [ABSTRACT FROM PUBLISHER]

We investigate the estimation of the bit-error rate (BER) performance of optical transmission systems with forward error correction (FEC) coding using a proposed uniformly quantized symbol error probability model. This model has been verified by the measurement of BER characteristics of coded and uncoded 10 Gb/s optical signals transmitted over 100 km. The measured results are very similar to the calculated results from the proposed model as well as Monte Carlo (MC) simulations. Our results suggest that the proposed uniformly quantized symbol error probability model using more than 8-decision levels can be applied to estimate BER performance for coded systems without degrading accuracy. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

This paper describes the analysis, simulations, and proof-of-principle experiment on transparent monitoring of relative rise time using asynchronously sampled amplitude histograms in optical transmission systems. The method described is based on the count in a selected amplitude window between the mark and space levels. The method is evaluated under various amplitude windows and Q-factor values and is compared with synchronously sampled eye-diagram-based measurements. The results demonstrate that the 40-60% amplitude window is generally suitable for system rise-time monitoring purposes without clock information. [ABSTRACT FROM PUBLISHER]

The understanding and development of 160-Gb/s transmission systems requires the study of the impact of different dispersion compensation schemes on pulse propagation in nonlinear fiber. In this paper, we present an investigation of 160-Gb/s optical transmission systems, focusing on optimal propagation regimes, and in particular, we analyze different transmission limitations and dominant nonlinear effects by comparing quasi-linear and dispersion managed soliton systems. Two quasi-linear systems, one using nonzero dispersion-shifted fiber (NZDSF) and the other single-mode fiber (SMF), and one short-period (1 km) dispersion managed soliton (DMS) system are studied, both for single-channel and wavelength-division-multiplexed (WDM) transmission. First, the performance of the two quasi-linear systems in single-channel transmission are compared and it is shown that the NZDSF and SMF systems allow similar error-free transmission distances with only small differences in the intrachannel four-wave mixing (IFWM) induced amplitude jitter. The effect of pulsewidth on transmission performance in this regime was investigated and the use of shorter pulses was found to result in lower amplitude jitter. We analyzed the behavior of the DMS system and showed that the reduced pulse broadening during transmission allowed a significantly longer single-channel transmission distance with a smaller impact of nonlinearities compared to quasi-linear propagation. The sensitivity of the DMS system performance to statistical fluctuations in the fiber dispersion was studied and the results show the level of accuracy in the dispersion management map which must be ensured in these systems. Finally, the performance of the DMS in WDM transmission was investigated and it was found that it was subject to very large penalties increasing the minimum channel spacing possible because of the strong impact of interchannel cross-phase modulation (XPM). [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

We analyze the performance of four different modulation formats in ultrahigh spectral efficient wavelength-division multiplexing (WDM) systems. Besides standard nonreturn-to-zero intensity modulation, we analyze duobinary, differential phase-shift keying (DPSK), and carrier-suppressed return-to-zero (CSRZ)-DPSK and, for each of them, optimize several system parameters, such as filtering and dispersion map. First, we optimize transmitter and receiver parameters in back-to-back condition, then we study the performance in a multispan scenario and its dispersion map optimization. Duobinary, DPSK, and CSRZ-DPSK show high suitability for ultrahigh spectral efficient WDM systems and high resilience to dispersion compensation tolerances and fiber nonlinearities. The investigation is based on detailed simulative analyses. [ABSTRACT FROM PUBLISHER]

The low-frequency intensity modulation in optical transmission systems can occurred by optical performance monitoring or dynamic devices such as acoustooptic tunable filters. Using a conventional receiver model, we derived the optical signal-to-noise ratio (OSNR) and Q penalties due to the low-frequency intensity modulation. The penalty is a function of the extinction ratio, OSNR, the modulation index, and the number of pilot-tone signals. The analytic results show good agreement with the experimental results. [ABSTRACT FROM PUBLISHER]

The last decade has witnessed wide-scale deployment of optical networks to support the growing data traffic. This success can be traced back to advances in optical transmission systems such as dense wavelength-division multiplexing, Raman amplification, etc., which allow a single fiber to carry several wavelengths very far, while sharing expensive equipment. However, these cutting-edge technologies require careful placement of amplifiers and other network elements to ensure error-free propagation of the signal and to minimize costs. In practice, it is common to use a set of constraints to ensure valid configurations for deployment. It is nontrivial to identify the optimal configuration under all but the simplest constraints. In this paper, we consider a set of constraints with varying flexibilities and present algorithms for efficiently computing the cost-optimal configuration under them. We also present experimental and theoretical results to evaluate the various constraints and algorithms. [ABSTRACT FROM PUBLISHER]

Self phase modulation (SPM) and amplified spontaneous emission noise (ASE) are the most important degradation effects in optical transmission systems [1–3]. SPM is caused by the Kerr-effect, which describes the signal power dependence of the refractive index. SPM leads to irreversible signal distortions, which can be kept small by an optimised system design. The erbium doped fibre amplifiers (EDFA) create ASE, which accumulates over several transmission spans and degrades the optical signal to noise ratio (OSNR) at the receiver. In this paper, we investigate the signal quality when using non-return-to-zero (NRZ) and return-to-zero (RZ) modulation due to both degradation effects. We further present design rules for the achievable transmission distance in high data rate transmission systems, and give an outlook for the design of future transmission systems. [ABSTRACT FROM AUTHOR]

An original approach to the solution of the nonlinear Schrodinger equation (NLSE) is pursued in this paper, following the regular perturbation (RP) method. Such an iterative method provides a closed-form approximation of the received field and is thus appealing for devising nonlinear equalization/compensation techniques for optical transmission systems operating in the nonlinear regime. It is shown that, when the nonlinearity is due to the Kerr effect alone, the order n RP solution coincides with the order 2n + 1 Volterra series solution proposed by Brandt-Pearce and co-workers. The RP method thus provides a computationally efficient way of evaluating the Volterra kernels, with a complexity comparable to that of the split-step Fourier method (SSFM). Numerical results on 10 Gb/s single-channel terrestrial transmission systems employing common dispersion maps show that the simplest third-order Volterra series solution is applicable only in the weakly nonlinear propagation regime, for peak transmitted power well below 5 dBm. However, the insight in the nonlinear propagation phenomenon provided by the RP method suggests an enhanced regular perturbation (ERP) method, which allows the first order ERP solution to be fairly accurate for terrestrial dispersion mapped systems up to launched peak powers of 10 dBm. [ABSTRACT FROM PUBLISHER]

We present a novel linearization method to calculate accurate eye diagrams and bit error rates (BERs) for arbitrary optical transmission systems and apply it to a dispersion-managed soliton (DMS) system. In this approach, we calculate the full nonlinear evolution using Monte Carlo methods. However, we analyze the data at the receiver assuming that the nonlinear interaction of the noise with itself in an appropriate basis set is negligible during transmission. Noise-noise beating due to the quadratic nonlinearity in the receiver is kept. We apply this approach to a highly nonlinear DMS system, which is a stringent test of our approach. In this case, we cannot simply use a Fourier basis to linearize, but we must first separate the phase and timing jitters. Once that is done, the remaining Fourier amplitudes of the noise obey a multivariate Gaussian distribution, the timing jitter is Gaussian distributed, and the phase jitter obeys a Jacobi-Θ distribution, which is the periodic analogue of a Gaussian distribution. We have carefully validated the linearization assumption through extensive Monte Carlo simulations. Once the effect of timing jitter is restored at the receiver, we calculate complete eye diagrams and the probability density functions for the marks and spaces. This new method is far more accurate than the currently accepted approach of simply fitting Gaussian curves to the distributions of the marks and spaces. In addition, we present a deterministic solution alternative to the Monte Carlo method [ABSTRACT FROM PUBLISHER]

This paper proposes a maintenance method for optical fiber cable networks that uses 1650-nm wavelength band light. We determined the maintenance wavelength of 1650-nm after considering the maintenance system requirements and the future trends in optical transmission systems. We improved the conventional maintenance system by adding appropriate system components including a narrow wavelength light source and a fiber-grating filter for the 1650-nm wavelength band. We designed the system and undertook manufacturing trials. The characteristics of our proposed maintenance method indicate good practical performance levels [ABSTRACT FROM PUBLISHER]

Polymer optical fiber (POF) is a promising transmission medium to provide broad-band telecommunication services within the customer's premises. POF offers several attractive features for data transmission such as broad bandwidth and low cost for in-house, access, and local-area-network (LAN) applications. This paper presents a review on optical transmission systems using POF and their enabling technologies. A summary is given of experimental data links with record capacity over record transmission distances. To conclude, we discuss trends for further development and research [ABSTRACT FROM PUBLISHER]