WDM Optical Communication Systems Research Articles

Performance investigation of geometric constellation shaping-based coherent WDM optical fiber communication system supported by deep-learning autoencoder

Geometric constellation shaping (GCS) has been proposed to enhance the performance of wavelength-division multiplexing (WDM) coherent optical fiber communication (OFC) systems. This paper presents a comprehensive simulation platform to design and simulate these systems' performance using an advanced autoencoder (AE) technique. The design of the AE is based on end-to-end deep learning and takes into account the system parameters, especially those related to the OFC channel. The system design uses identical AEs, one in each WDM channel, and only the AE of the central channel is trained to achieve the required performance target. The developed AE simulation platform is capable of assessing the bit error rate characteristics, signal-to-noise ratio, and mutual information for long-haul coherent OFC-WDM systems operating with various modulation formats. The simulation results indicate that using a multilayer perceptron neural network to design AE requires four hidden layers, sixteen nodes per hidden layer, and a “16x modulation order” batch size to achieve optimum system performance. The AE's behaviour is investigated to identify the allowed ranges of the optimal launch power using two different procedures that achieve better system performance for 2D and 4D constellations.

A Fast and Effective MIMO Algorithm Using CLR-RNN for Hybrid MDM and WDM Optical Communication System

A Fast and Effective MIMO Algorithm Using CLR-RNN for Hybrid MDM and WDM Optical Communication System

Design of Ultra Dense WDM Optical Communication System to Reduce Signal Impairments Using DCF and Repeater Techniques

Linear and non-linear impairments are the major problems that affected the dense wavelength division multiplexing (DWDM) system performance. In this simulation designs, two different compensation techniques have been proposed to eliminate signal impairments. The repeater technique was proposed to reduce non-linear effects like four-wave mixing (FWM) which cause transfer power from DWDM channels to another new channels. The dispersion compensation fiber (DCF) technique was used to reduce dispersion effects which cause signal pulse broadening over long transmission distances. Also, three different modulation formats and four frequency separations were used to determine which modulation scheme is more compatible with the compensation techniques. The results is calculated in term of quality factor against power and noetic that the carrier suppressed return to zero (CSRZ) format offers the best performance with the DCF technique with 32.1804 Q-factor at 15dBm threshold power then, the differential phase shift keying (DPSK) format is compatible with the repeater technique with 27.7959 quality factor and 14dBm threshold power. Index Terms— Dense Wavelength Division Multiplexing (DWDM), Dispersion Compensation Fiber DCF, Repeater, and Non-linear Effects.

Nonlinear effects on WDM optical communication system

Abstract A dense wavelength division multiplexing (DWDM) system improves the capacity of an optical communication system. On the other hand, nonlinear effects are critical issues that limit the performance of the DWDM system. The nonlinear effects of self-phase modulation, cross-phase modulation, and four-wave mixing affect optical communication’s capacity. This paper focuses on mitigating the nonlinear effect of cross-phase modulation in the DWDM system with a suitable technique.

Symmetrical and post dispersion compensation in WDM optical communication systems

In this paper, new symmetrical and post dispersion compensation schemes are proposed and investigated. Each scheme has many cases. Each case has a certain connection for the proposed model used in narrowing the linewidth, Δλ, of the optical signal. The new schemes in WDM systems are implemented and simulated with Optisystem 15 up to 200 km. The new proposed schemes are evaluated through the Q-factor and BER, showing a performance enhancement by 21% in the symmetrical and 19% in the post compensation as compared to the previous work.

An enhanced WDM optical communication system using a cascaded fiber Bragg grating

In this paper, a cascaded fiber Bragg grating (FBG) system is proposed to reduce the dispersion in the optical signal in single mode optical fibers. This consequently enhances the system performance, which is evaluated by the bit error rate (BER) and quality factor (Q-factor). The proposed model consists of four uniform cascaded FBGs connected at the transmitter to get narrow linewidth, Δλ, of the optical signal, which is a major cause of the delay. The Optisystem7 is used to simulate the proposed model in a WDM system with and without the model for distance 200 km. The system parameters are investigated showing an enhanced performance with 12%, including eye diagram, Q-factor and BER. A 10−6–10−10 BER is achieved with a quality factor in the range 7–14, including the effects of fiber length, input power and FBG length.

Analysis of Four Wave Mixing Effects in 16 ×10 Gb/S WDM Optical Communication System

Abstract The fiber nonlinearities are one of the main performance limiting factors in any optical communication system. There are several parameters that effectively contribute in mitigation of these fiber nonlinearities such as fiber dispersion, effective area of fiber core, etc. Here, we have investigated the four wave mixing (FWM) nonlinear impairments in 16-channel WDM system. The FWM crosstalk becomes very critical to handle for long haul transmission systems at high power levels. Here, 16 channels WDM is being implemented and its performance is evaluated in terms of bit error rate (BER), Q factor, etc. for distance transmission upto 500 km.

Raman Amplification in WDM Optical Communication Systems: A System Perceptive

AbstractStatistical study on stimulated Raman scattering (SRS) crosstalk has been done by many researchers while ignoring pulse walk-off effect due to analytically unsolvable nonlinear coupled equations. To our knowledge there is no treatise, which deals with pulse walk-off effect except statistically for few cases in case of wideband WDM Raman amplification systems. In this paper, we investigate the effect of group velocity dispersion induced crosstalk. We have tried to solve nonlinear coupled Raman gain equations for few channels by using the numerical technique called finite difference method. Finally we have provided results of the simulation for few cases. It is ever known that pulse walk-off effect (time-dependent effect) is responsible for transient effects hence the modeling has also done in this paper to simulate the effect of abrupt channel addition and removal response.

Switching solutions for WDM-SDM optical networks

Over the last few decades, network traffic has consistently grown at an exponential rate and was efficiently satisfied using WDM and more efficient coding schemes requiring coherent detection. There is no indication that the network traffic growth trend will cease anytime soon, and we are nearing the day when the capacity of the ubiquitous single-mode fiber will be fully exploited. Space-domain multiplexing (SDM) for high-capacity transmission is the promising solution with the scaling potential to meet future capacity demands. However, there is still a large technological gap between current WDM optical communication system designs and SDM network implementations. In this article we lay the foundation of switching node designs for future WDM-SDM optical networks.

Analysis of fiber Bragg grating with exponential–linear and parabolic taper profiles for dispersion slope compensation in optical fiber links

In this paper, the effect of various taper profiles on dispersion slope compensation in optical fiber links is studied. Theoretical and numerical investigation of the linear and nonlinear group delays of tapered fiber Bragg grating's (T-FBG) under strain is made. Calculation is performed using Matlab code based on solving the coupled mode equation using transfer matrix method. Our study shows that the linear tapered FBG profile provide the best result than the linear-exponential profile which can compensate up to 500km. As result, the spectral characteristics of tapered grating allow them to be used efficiently in high bit rates WDM and long-haul optical communication systems for chromatic dispersion of single-mode fiber.

Theoretical Modeling and Simulation of Higher Order FWM Crosstalks in Multichannel WDM Optical Communication Systems

In this paper, we derive a theoretical model for the higher order FWM power in WDM networks with NZDSF fibers for the first time. We have investigated the higher order FWM power theoretically and by numerical simulations. Dividing the fiber into finite number of elements and applying the boundary conditions, allow us derive an expression for second order power penalty. At the end of each element we derive the first order FWM power for all wavelengths and use these values to calculate the second order FWM power in the next element. Consequently, for each channel we can compute the total second order FWM power penalty at the end of the fiber.

Ultra-broadband indoor optical wireless communication system with multimode fiber

In this paper we experimentally demonstrate an ultra-broadband indoor full-duplex WDM optical wireless communication system with multimode fiber. The multimode fiber is used because it is employed in most of the already installed in-building fiber distribution networks. Simultaneous error-free (BER<10(-9)) transmission of 4×12.5 Gbps downlink and 800 Mbps uplink has been successfully demonstrated. The experimental results show that, although the use of multimode fiber will induce ~2.4 cm reduction in the maximum error-free beam footprint in the downlink, the bit rate of the uplink can be much higher compared to the system with single-mode fiber.

Technology for EDFA Gain Flattening Based on Long Period Fiber Grating

EDFA is an important component in WDM optical communication systems. But the uneven characteristic will lead to reduced effective transmission bandwidth and system performance degradation. This paper studies on issues of EDFA gain flattering based on long period fiber grating, and provides detailed analysis of the method of using LPFG to achieve flat EDFA output gain. Numerical simulation result shows that this method can reduce unevenness to 0.2dB and below.

4$\,\times\,$12.5 Gb/s WDM Optical Wireless Communication System for Indoor Applications

A novel high-speed optical wireless communication system incorporating wavelength division multiplexing technology for indoor personal area networking applications is proposed in this paper. Even with the simplest single wide field-of-view (45°) nonimaging receiver, bit rate as high as 4 × 12.5 Gb/s has been successfully demonstrated by experiments. It is shown that error-free reception (bit error rate <; 10-9) can be achieved over the entire beam footprint of about 1 m, so limited mobility can be provided to subscribers. In addition, a new localization system based on this optical wireless communication system has also been proposed and verified by experiments. When these two systems are incorporated together, high-speed optical wireless communication with mobility feature can be provided to users over the entire room.

Investigation Of Fwm Effect On Ber In Wdm Optical Communication System With Binary And Duobinary Modulation Format

This paper simulates two channel WDM optical communication system to investigate the effect of FWM on Bit Error Rate for Duo-binary & binary modulation like NRZ Rectangular at different dispersion value ,core effective area of fiber & channel spacing for 100km long optical communication system. BER got improved with duobinary modulation format & by increasing core effective area which will offer a significant performance benefit in digital systems.

The Nonlinear Impairments Due to the Data Correlation Among Sub-Carriers in Coherent Optical OFDM Systems

Resulted from the narrow frequency interval, the nonlinear impairments are strongly related with the data correlation of the optical orthogonal frequency division (OFDM) symbol in coherent optical OFDM (CO-OFDM) system, which is very different from the traditional WDM optical communication systems. The concept of normalized accumulative correlation coefficient (NACC) is proposed to evaluate the data correlation of the OFDM symbol. The parameter phi is presented to describe the influence of the systematic physical configuration on the nonlinear impairments. The dependence of the nonlinear impairments on the data correlation is investigated and revealed analytically. Closed form expressions are presented to calculate the noise spectrum, total nonlinear noise energy and noise signal ratio (NSR) under the condition that phi les 0.2, which is valid for most practical CO-OFDM system. The NSR is proportional to the NACC and phi2. Simulation results are well consistent with analytical calculations when phi les 0.2.

Four-wave mixing analysis in WDM optical communication systems with higher-order dispersion

Four-wave mixing (FWM) is one of the major limiting factors in WDM optical fiber communication systems. In this paper, we analyze the individual and combined effect of second-, third-, fourth- and fifth-order dispersion parameters on FWM at different input channel powers and core effective areas, which have not been calculated earlier. FWM power versus channel power graphs for individual and combined effects of dispersion parameters have been presented, and it has been observed that FWM reduces for combined effect of dispersion parameter.

Investigation on reflection spectr a of chirped and phase-shifted fiber Bragg gratings

The characteristics of chirped and phase-shifted fiber Bragg gratings have been investigated by the use of transfer matrix formulation. While the characteristics of a chirped and phase-shifted fiber Bragg grating are the same as those of non-chirped one in some important aspects, both the reflection and transmission windows of a chirped and phase-shifted fiber Bragg grating can be broadened in a wide range. Therefore, chirped and phase-shifted fiber Bragg gratings will have applications in WDM or DWDM optical communication systems. The work in this paper can be used to design the new devices based on chirped and phase-shifted fiber Bragg gratings.

Analysis and minimization of cross phase modulation in semiconductor optical amplifiers for multichannel WDM optical communication systems

A theoretical model for crosstalk in multichannel wavelength division multiplexing communication systems due to cross phase saturation in semiconductor optical amplifier structure is developed. This theoretical model is used to analyze the impact of the cross phase noise on the performance of semiconductor optical amplifiers in saturation region for WDM communication system by using differential phase shift modulation format. It is shown that by increasing the carrier life time, width and thickness while reducing the confinement factor, differential gain and bias current in the SOA structure mitigates the cross talk due to cross phase saturation. The impact of penalty and cross phase noise imposed on multichannel WDM links have been investigated for different parameters of the SOA with the variation in transmission distance. With the slight increase in differential gain of 200.2 × 10 −18 cm 2 and confinement factor 0.41, the maximum transmission distance observed is 5220 km with good quality and nil power penalty for 10 × 40 Gb/s soliton RZ-DPSK WDM signals for the first time.

Realization of an optical communication tunable filter using a diffraction-based optical system

Optical bandpass tunable filters are key elements for dense WDM optical communication systems. Recently, a realization of optical linear transformation using a spatial diffraction optical system was presented and theoretically analyzed [J. Opt. Soc. Am. A21, 732 (2004)]. We present an optical bandpass tunable filter based on this optical system and a spatial light modulator. The mathematical analysis and additional computer simulations for testing the filter's basic parameters using the Fresnel diffraction theory are presented. Some newly obtained laboratory experimental results of the device in the optical visible spectrum will be shown.