NRZ Pulse Research Articles

Impact of optimized pulse shaping on optical transmission performance in the availability of different dispersion maps

One of the most detrimental effects of an optical communication network that can strongly restrict the bit rate and thus reduce the transmission performance is the nonlinear effect. In this work, the effect of the optimized pulse on the optical transmission system with different dispersion maps i.e. post, pre, and symmetric dispersion compensation for 240 km is investigated. Furthermore, the system performance in terms of max quality factor (Q-factor) is performed under the influence of input power changing and applying bit rate equal to a 40 Gb/s. The results state that the optimized shaper brought an improvement in the performance compared to other pulse shapes at the same conditions. Also, the post-compensation shows better performance compared to pre and symmetrical at the same time. For instance in the case of post compensation at 10 dBm input power and 240 km distance, the optimized pulse shape offered better performance compared to others where the Q-factor equal to 67.65. As well as it is clear when NRZ, RZ and Sine pulse are used, the quality factors were decreased to 66.53, 50.92, 51.34 sequentially at the same input conditions.

Measuring clock jitter and data signals for bit error detection in optical transceiver systems

AbstractThis work demonstrates how to measure jitter using the eye diagram Analyzer histogram feature. Bit sequence generator is employed with the NRZ Pulse generator with the electrical jitter in order to measure the signal amplitude level. We have modulated the light signal from CW Laser with the electrical signal by Mach-Zehnder Modulator through 5 km fiber cables. The signal can be amplified with a gain of 7 dB with the presence of transimpedence amplifier. The combination of electrical signal and signal from noise source can be filtered by using the low pass Gaussian filter.

Transmitting audio via fiber optics under nonlinear effects and optimized tuning parameters based on Co-simulation of matlab and optisystemTM

Limitations of conventional wires such as copper wires are causing dispersion and distortion of the message signal for long distances communication especially for the wide bandwidths. The ability of fiber optic to overcome this problem is making it a dominant transmission medium. Despite of this major positive attribute of optic fibers, there is still a downside for using the fiber optic communication; that is the nonlinearity problem especially at the very high frequency bandwidth. For the first time, a desigen of an audio signal is suggested and executed in MatLab with an integration with OptiSystemTM software to discuss and solve this issu. The audio signal is then transmitted in different shapes of modulation signals (NRZ, RZ & RC) for different distances (100 km & 75 km) via a fiber optic media to be received in a receiving part of the simulated system. Three tests are used to do so. The first is the Quality-factor (Q-Factor) against the received power, second test is eye diagram performance and finally is the measuring of the amplitude of output (received) signal for each modulation signal shape using the Oscilloscope Visualizer. The NZR modulation signal was found to be the best one of the three used signals’ types in all three tests. The Q-factor for NRZ pulse shape (=12) was higher than that for RZ (=10) and RC (=8) for a 100 km distance at the same received power level.

Design and Analysis of Single-Channel High-Speed RoF System Using Different Coding Techniques

In this paper, we have discussed the single-channel radio over fiber system using single-mode Optical Fiber. In this article, we compared RZ, NRZ, and Gaussian pulse techniques. For performance analysis, we have used a 10 Gbps data rate and transmitted the ON-OFF signal using 60 GHz (V band) millimeter-wave over various optical lengths between 25 Km and 80 km. We successfully demonstrated that Gaussian pulse and NRZ provide better performance as compared to RZ for long-distance up to 80 km. RZ performs better for short-distance communication up to 50 km of a fiber link. The system performance is evaluated using the BER curve, Q factor, eye diagram, and output of the spectrum analyzer.

Simulation of Comparison from NRZ and RZ Pulse in Free Space Optics with Different Weather Conditions

FSO (Free Space Optic) is a form of optical technology communication by transmitting light to media free space. In the FSO system, the data transmission can be larger, namely 1-100 Gbps, and this is due to the large bandwidth width. FSO runs at a wavelength of 850 nm and 1550 nm. FSO is usually with a maximum distance of 2-4 km. This paper simulates the FSO optical transmission system using NRZ and RZ line coding in bright and rainy weather conditions. The parameters analyzed are Eye diagram, Optical Spec-trum, photocurrent, and received signal power. In the FSO line coding system, NRZ has an eye height value, received signal power and received photocurrent is greater than the RZ line coding at a distance of 1 km and 5 km in bright and rainy conditions. In the trial of this FSO communication system, it is better to use it at a distance of 1 km, because the received signal power is above 20 dBm and received photocurrent is still above 800 mA for NRZ and RZ line coding. This is due to the attenuation value of sunny weather conditions that are smaller between 0.2-3 dB/km, while in rain conditions between 4-17 dB/km.

Hitless Rate Switching for Dynamically Reconfigurable Optical Systems

We propose a set of techniques to enable hitless rate switching for reconfigurable optical systems and validate, by computer simulations, their applicability to NRZ, RZ, and Nyquist pulse shapes. The polarization-multiplexed quadrature phase-shift keying (PM-QPSK) and 16 quadrature amplitude modulation (16QAM) modulation formats are investigated. Error transients that appear during lower-to-higher rate switching are avoided by sufficiently long equalizer training periods. The robustness of the proposed scheme to polarization mode dispersion (PMD) and signal phase noise is also demonstrated.

A 0.039 mm<formula formulatype="inline"><tex Notation="TeX">$^2$</tex> </formula> Inverter-Based 1.82 mW 68.6<formula formulatype="inline"><tex Notation="TeX">$~$</tex> </formula>dB-SNDR 10 MHz-BW CT-<formula formulatype="inline"><tex Notation="TeX">$\Sigma\Delta$</tex> </formula>-ADC in 65 nm CMOS Using Power- and Area-Efficient Design Techniques

We present design techniques for the realization of compact, low-power CT- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\Sigma\Delta$</tex> </formula> -ADCs in ultra-deep-submicron CMOS: A resonant single-opamp third-order integrator with loss compensation, an inverter-based opamp with digitally assisted biasing and common mode control, a pseudo-differential modulator topology with quasi-1.5-bit quantization, a jitter-noise-reduction DAC with NRZ pulse shape, a mismatch-tolerant IIR quantizer, linearized single-ended FIR-DACs with passive DT compensation, and a rail-to-rail dynamic latched comparator. A highly compact 41.4 fJ/conv.-step, 77 dB-SFDR, 1.1 V ADC has been implemented to prove these concepts. The entire active analog circuitry in this minimalistic third-order modulator consists of only ten CMOS inverters.

바이폴라 델타 신호에 대한 GMSK 변조

기본적으로 GMSK는 NRZ 펄스열을 가우시안 저역 통과 필터로 전 처리한 후에 GMSK 신호를 생성하지만, 본 논문에서는 델타 펄스열에 대한 GMSK 변조 시스템을 제안하였다. 제시된 시스템은 바이폴라 델타 펄스로 가우시안 펄스를 발생시키는 가우시안 펄스 생성기, <TEX>$+T_b/2$</TEX>와 <TEX>$-T_b/2$</TEX> 사이의 차분기, 그리고 주파수변조 함수를 위한 정합 필터로 구성한다. 기본적인 GMSK 변조와의 비교를 통해 스펙트럼은 40[dB] 감쇠 대역폭에서 약 35[%] 협소하며, 스펙트럼의 중심은 더 낮고, 제로 크로싱 성질이 있는 것으로 나타났다. In the basic GMSK, the modulated signals are generated by the preprocessing of NRZ pulse trains with the gaussian low pass filter. In this paper, we proposed the GMSK modulation system with the delta pulse trains. The proposed system constructed with the gaussian pulse generator triggered by the bipolar delta pulse, the differentiator between <TEX>$+T_b/2$</TEX> and <TEX>$-T_b/2$</TEX>, and then a matched filter for frequency-modulation function. The spectrum of proposed system was found to be smaller than about 35[%] at 40[dB] attenuated bandwidth, and the center spectrum to be lower than the basic GMSK with zero-crossing property.

Investigation of optimum pulse shape for 112 Gbps DP-DQPSK in DWDM transmission

This paper reports the simulative analyses to investigate the impact of different pulse shapes on DP-DQPSK modulation for high-spectral efficient DWDM transmission at 112Gbps per channel. In the simulation model we have considered three different pulse shapes viz. NRZ, 50% duty cycle RZ (RZ50) and 67% duty cycle RZ (RZ67) in symbol-aligned and symbol-interleaved format. The analysis has been carried out for various linear and nonlinear system impairments where the pulse is subjected to degradation under the influence of amplified spontaneous emission (ASE) noise, group velocity dispersion (GVD), cross-phase modulation (XPM) and polarization mode dispersion (PMD) and thus, limiting the system performance. Results show that the RZ50 pulse shape for DP-DQPSK with symbol interleaving shows the maximum tolerance for the various system degradations in long haul DWDM transmission. Even the system based on the NRZ pulse shape can gain significant improvement from the symbol-interleaving.

Silicon-Organic Hybrid MZI Modulator Generating OOK, BPSK and 8-ASK Signals for Up to 84 Gbit/s

We report on high-speed multilevel signal generation and arbitrary pulse shaping with silicon-organic hybrid (SOH) Mach-Zehnder interferometer (MZI) modulators. Pure phase modulation exploiting the linear electrooptic effect allows the generation of multiple modulations formats at highest speed such as 40-Gbit/s on-off-keying (OOK) and binary-phase-shift keying (BPSK) and 28-Gbd 4-ASK and 8-ASK with data rates up to 84 Gbit/s. Additionally, beside NRZ pulse shaping, for the first time, Nyquist pulse shaping with silicon modulators is demonstrated to enable multiplexing at highest spectral efficiency.

Application of a digital non-linear compensation algorithm for evaluating the performance of root-raised-cosine pulses in 112 Gbit s−1 DP-QPSK transmission

In this paper, we numerically investigate the non-linear tolerance of root-raised-cosine (RRC) pulse shaping by interpolating finite impulse response (FIR) filters in conjunction with digital backward propagation (DBP) in coherent 112 Gbit s−1 dual-polarization quadrature phase shift keying (DP-QPSK) transmission. The results depict that RRC pulses are more tolerant to intra-channel non-linearities, i.e. self-phase modulation (SPM), as compared to standard RZ-33 and NRZ pulses. The non-linear threshold point is improved by using RRC pulses by a factor of 2 dB signal input power as compared to RZ pulses and by 4 dB signal launch power as compared to NRZ pulses. The behavior of RRC pulses is also investigated with standard single mode fiber (SMF), non-zero dispersion shifted fiber (NZDSF) and next-generation large Aeff pure silica core fiber (LA-PSCF). Most importantly multi-span DBP is implemented and in the case of RRC pulses the computational efforts of the conventional DBP algorithm are reduced by 80% with a diminutive Q-penalty of 0.74 dB. The duty cycle of the RRC pulses is further optimized for efficient system performance. We have also compared the performance of single-channel transmission with the multi-channel transmission, where the performance is limited due to inter-channel non-linear effects. Furthermore, the non-linear tolerance of RRC pulses is investigated with; (a) different amplifier spacing and (b) variation in transmission link design information for the DBP algorithm.

Investigation of RZ and NRZ pulse shape for optimum Duobinary transmission at 40 Gbps

This paper reports a simulative investigation on the RZ and NRZ pulse shape for optimum optical duobinary transmission in amplified spontaneous emission (ASE)-noise-limited system at 40Gbps. By deploying electrical low-pass filtering at the transmitter end and optical filtering at the receiver end, we achieved the desired duobinary pulse shape that provides optimum performance suppressing the ASE noise. Further analysis in the system with optimized filter parameters shows that NRZ duobinary provides better receiver sensitivity as compared to RZ duobinary in a channel limited by fiber chromatic dispersion.

Investigation of Pre-, Post- and Symmetric-Dispersion Compensation Techniques (DCF) using Different Modulation Formats over High-Speed Optical Link

The focus of this paper is to report a detailed investigation of dispersion compensated optical communication system of different optical pulses such as RZ super Gaussian, NRZ and RZ pulses using pre-, post- and symmetrical-dispersion compensation techniques. The dispersion compensated optical communication system consists of standard single-mode fiber (SSMF) of 16 ps/nm/km after, whose dispersion is compensated using different DCF compensation schemes with proportionate length of dispersion compensated fiber of −80 ps/nm/km. The performance of these three compensation schemes is compared by computing Q-parameter, Eye-closer penalty and required optical power at sensitivity at varied values of Laser line width from 100 MHz to 100 KHz to underscore the best possible performance. A relationship among the attributes laser line width, different optical pulses and different DCF schemes implemented at high transmission rate.

Complementary Detection Technique to Performance Analysis of RZandNRZ on MDW Code in FTTH Network

double weight (MDW) code is presented here to support Fiber-To-The-Home (FTTH) access network in point-to-point (P2P) and point-to- multipoint (P2MP) application. The Bit Error Rate (BER) performance is evaluated based on Modified Double Weight MDW code. Optical Code Division Multiple Access (OCDMA) system is considered a promising technique for Fiber-To-The-Home (FTTH) access networks. The performance of RZ against NRZ is compared through simulation by using opt system software version 7. We used two networks designed as follows, one used RZ pulse generator and the second used NRZ pulse generator, and both systems are tested with and without Erbium Doped Fiber Amplifier (EDFA). It is found that NRZ pulse generator in this system is better than RZ pulse generator for all simulation results. The conversion used a Mach- Zehnder interferometer (MZI) wavelength converter. Also, we are proposing a detection scheme known as complementary subtraction detection technique implemented with fiber Bragg Grating (FBG) acts as encoder and decoder. The performances are characterized through BER and bit rate (BR), also, the received power at a variety of bit rate.

Impact of DP-QPSK Pulse Shape in Nonlinear 100 G Transmission

This paper reports results of an extensive Monte Carlo simulation analysis on the impact of DP-QPSK pulse shape in high-spectral efficiency WDM transmission at 112 Gb/s per channel. The pulse shapes studied include NRZ, 50% duty cycle RZ and 67% duty cycle RZ. Both symbol-aligned and symbol-interleaved formats are investigated and compared for nonlinear transmission tolerance on common dispersion maps used in terrestrial long-haul systems. The RZ pulse shape shows the greatest improvement in nonlinear tolerance with symbol-interleaving. However, symbol-interleaving only provides significant benefit in optical line systems designed to preserve the pulse shape during transmission, such as systems based on distributed dispersion compensating fiber (DCF). The duty cycle of the RZ pulse has only a minor impact on nonlinear performance, and even systems based on the NRZ pulse shape can gain significant benefit from symbol-interleaving.

Comparison and optimisation of optical single sideband transmitters

A detailed comparison and optimisation of three different techniques to generate optical single sideband (OSSB) signals is presented. Three techniques are investigated: phase-shift (PS), optical filtering and Weaver&apos;s method (WM). The conventional binary and alternate mark inversion (AMI) coding formats are used to assess the transmitter performance for signals with different spectral properties. Different duty-cycles are considered for each format to analyse the generation of OSSB signals from signals with enhanced tolerance to inter-symbol interference.The optimisation of each transmitter parameter is carried out by maximising the amount of accumulated dispersion, using 40 Gb/s bit rate signals, for a specific eye opening penalty. With the binary format, an increase by more than 150 ps/nm of the accumulated dispersion is observed using the WM and NRZ pulses, compared to a reference double sideband signal with NRZ pulses. The optical filtering and PS techniques present lower accumulated dispersion improvements, although the PS allows significant sideband suppression near the carrier frequency. With the AMI format, an increase of 35 ps/nm is achieved by most OSSB transmitters and considerable high sideband suppression is observed using the optical filtering technique.

Implementation of non-linearity management for Gaussian pulses in a fiber-optic link by means of second-harmonic-generating modules

We introduce a model for the non-linearity compensation (“management”), based on second-harmonic-generating [ χ (2)] elements, integrated with amplifiers, which are periodically inserted into a fiber-optic link. The link features the Kerr [ χ (3)] non-linearity, group-velocity dispersion (GVD), and loss. Simulations demonstrate that the system can directly provide for effective compensation of the fiber non-linearity for quasi-Gaussian pulses over the propagation distance z up to 10 fiber spans between the χ (2) modules, and the interaction between adjacent pulses does not manifest itself over the same propagation distance, provided that the separation between them is ≃5 widths of the pulse or more. The results are sensitive to the correct choice of the mismatch parameter in the χ (2) module, but not to variation of other parameters (for instance, peak power of the pulses). For larger values of z, distortion of the pulses commences under the action of GVD. This can be prevented by periodic dispersion compensation. Although the latter is not directly included into the model, it is demonstrated that the non-linearity and dispersion compensation can be implemented independently, as they take place at essentially different scales of z for typical NRZ pulses. Thus, the stable-transmission distance can be expanded much farther.

Analysis of the Collocation Method for Simulating the Propagation of Optical Pulse Sequences

Summary In analogy to the standard Split-Step Fourier algorithm for calculating the signal transmission through optical fibers, a Split-Step collocation algorithm is applied and analyzed in terms of its capability to calculate the propagation of pulse sequences in optical fibers. The method uses a point matching technique for the representation of short optical pulse sequences with Hermite-Gauss functions as basis. This special basis renders time consuming Fast Fourier Transformations (FFT) within the calculation unnecessary. The method is analyzed using realistic NRZ pulse sequences in the simulations. Accuracy and computational effort are evaluated in comparison to the Split-Step Fourier method.

Comparison among RZ, NRZ, and CRZ Pulse Evolutions in Birefringent Nonlinear Fibers with Third-order Dispersion Effect

Article Comparison among RZ, NRZ, and CRZ Pulse Evolutions in Birefringent Nonlinear Fibers with Third-order Dispersion Effect was published on October 1, 2001 in the journal Journal of Optical Communications (volume 22, issue 5).

Marked increase in power margin through the use of dispersion-allocated soliton and evaluation of transmission characteristics using Q map: Comparison between D-A soliton, NRZ pulse, and RZ pulse at zero GVD

When fiber routes for optical soliton transmissions are dispersion allocated, higher order solitons cannot be formed even at power levels reaching the higher-order soliton power determined by the average dispersion, since the group velocity dispersion (GVD) in the individual fiber is large and the phase matching necessary to form higher-order solitons cannot be obtained. Therefore, solitons with intensity higher than that of N = 1 can still be propagated with a simple and clean pulse waveform without splitting. In this paper, it is first shown that the power margin of the dispersion-allocated (D-A) soliton is 6–9.5 dB larger than that of the soliton with a uniform GVD. Next, a new method (Q map method) for the evaluation of optical transmission systems using the Q value is described, which indicates the signal-to-noise ratio of the received eye pattern. By using this method, the power margins and dispersion tolerances of the soliton, NRZ, and zero-dispersion RZ pulse transmissions are discussed and it is found that the D-A soliton transmission has the highest power margin. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(12): 17–27, 1997