Channel WDM System Research Articles

Minimization of dispersion and non-linear effects in WDM based long-haul high capacity optical communication systems

Abstract Chromatic dispersion and nonlinear impairments pose challenges in high-capacity optical transmission systems, leading to signal distortions, channel interference and diminished the transmission performances. This paper explores the utilization of dispersion compensating fibers (DCF) using different schemes to mitigate the dispersion that accumulates along the length of a fiber in a 16 × 10 Gbps high-capacity long haul WDM system over a range of 500 km. When different wavelengths of light pulses are transmitted through an optical fiber, they experience varying speeds due to the refractive index’s wavelength dependency. As a result, the light pulses become temporally spread out as they travel through the fiber, and this dispersion persists throughout the fiber’s length. Considering non-linear effects such as self-phase modulation (SPM) and cross-phase modulation (XPM), this paper analyze and compare the three compensation schemes of DCF in a 16 channel WDM system. Moreover the impact of non-linearities based on fiber length are also analyzed and compared. The results are evaluated by comparing metrics such as Q-factor, bit error rate (BER) and eye height. The analysis concludes that the symmetrical compensation scheme of DCF outperforms the pre- and post-compensation scheme. This finding suggests that the symmetrical compensation method offers a promising solution for high-capacity access networks, providing high spectral efficiency, cost-effectiveness, and improved flexibility.

Demonstration of 5.12-Tbps THz-over-fiber transmission in 80 channel WDM system

Demonstration of 5.12-Tbps THz-over-fiber transmission in 80 channel WDM system

Investigation of FSO Using Polarization Diversity Under Clear Weather, Haze and Rain

Free space optical communication (FSO) is cost effective and potential technology for realization of transmission in hilly areas and for roof top communication in congested areas. In this work, a 32 channel WDM system employing polarization diversity technique is proposed in free space optical communication. Atmospheric turbulences plays vital role in system performance such as clear weather, haze and rain. Investigation has been done for different turbulences and effects are analysed. It is observed that system performs worst and better in case of rain and clear weather respectively.

Analysis of Four Wave Mixing In Ultra Dense WDM-Hybrid Optical Amplifier Systems

Abstract Amplification through hybrid optical amplifiers (HOAs) is a propitious and proficient technology for high speed and high capacity dense wavelength-division-multiplexing (DWDM) systems. HOAs are intended to improve system reach and to accomplish wide gain bandwidth with enhanced flatness of gain. In this work, an ultradense 16 channel WDM system is demonstrated and performance of diverse hybrid amplifiers is evaluated in terms of output power, Q-factor, gain flatness and BER. Spacing among the WDM channels is 25 GHz in order to make system bandwidth efficient and scrutinized its effect on four wave mixing (FWM) in case of EDFA-EDFA, Raman-EDFA and SOA-EDFA. It is observed that SOA-EDFA is more and Raman-EDFA is less prone to FWM. Moreover, for distance 20 Km–140 Km, Raman-EDFA is optimal configuration for amplification and from 150 Km–200 Km, SOA-EDFA shows better performance. For prolonged link lengths such as beyond 200 Km, EDFA-EDFA is a right hybrid amplifier. In order to achieve maximum gain flatness in proposed architecture, EDFA-EDFA is recommended to use.

Influence of Conventional Optical Amplifiers for 64×10 Gbps WDM System

Abstract In this work we have investigated semiconductor optical amplifier (SOA), erbium-doped fiber amplifier (EDFA) and RAMAN Amplifier separately under 64 channels WDM system at 10 Gbps data rate. A comparison is made based upon the values of Q- factor, bit error rate (BER), and power received for different values of laser (present at the transmitter) power. The eye diagram for the three optical amplifiers has also been analyzed. Also the performance factors (Q- factor, BER, and power received) are evaluated for different values of fiber length. In general it is observed that with respect to the power received for a particular laser power (at the transmitter) and up to a fiber length of about 120 km Semiconductor optical amplifier (SOA) gives the best result among all the three amplifiers. With respect to the quality (Q) – factor the RAMAN Amplifier gives slightly better result for a given laser power and for a short fiber length (up to a fiber length of 50 km). For long distance (fiber length greater than 160 km) the Q – factor for all the three optical amplifier saturates and become equal. In terms of Bit Error Rate, RAMAN amplifier is best as it gives minimum BER at a given laser power but up to the fiber length of 70 km EDFA provides minimum BER.

Performance Analysis of 16 Channel WDM System with Modulation Formats

Performance Analysis of 16 Channel WDM System with Modulation Formats

Nonlinear effects in WDM Networks

This paper studies nonlinear effects in WDM Network. The focus is on both the propagation of a unique signal as well as a set of them in optical fibers in a WDM network. The paper presents an analytical model to study the effects of having nonlinearities in a WDM system. Three main nonlinear effects are studied here are Cross Phase Modulation, Self-Phase Modulation, and Four Wave Mixing. Simulations are performed on up to 265 channels WDM System.

Automatic Gain-Controlled HOA with Residual Pumping

AbstractThe interminable need of number of channels in communication systems escorts more number of wavelengths to be used. This broad spectrum of wavelengths when expands in both C and L band, the need of hybrid optical amplifiers (HOA) comes into play. In this work, we proposed an automatic gain-controlled HOA using Residual pumping for C/L band. The desired gain is fixed at 27 dB at pump power swinging between 300 and 400 mW. The input powers are automatically adjusted so as to provide invariable and flat gain eliminating the wavelength dependency of optical amplifier to great extents. Analysis is carried out in a 32 channel WDM system and power transients are also measured in terms of powers of surviving channels and excursion amplitudes by adding and dropping up to 28 channels. The output is adjudicated in terms of maximum gain achieved, OSNR, BER, gain flatness, noise figure and power transient excursion amplitudes.

Performance Analysis of Hybrid Optical Amplifiers for 32 Channel WDM System at 10 Gbps Bit Rate for WAN Applications

Abstract In this paper, we have simulated an optical 32 channel WDM system with 10 Gbps data rate for various hybrid amplifiers at varying lengths. Stand-alone EDFA gives better performance than other individual amplifiers but when hybrid with Raman amplifier, the performance of the WDM system is enhanced. A lot of researchers are working on the hybrid amplifiers like EDFA and Raman. In this research paper we have also included latest amplifier such as Ytterbium and Praseodymium amplifiers and the performance of the various hybrid combinations is compared. So, different hybrid amplifiers such as Raman-EDFA, EDFA-Yb, Raman-Yb, EDFA-Pr and Raman-Pr have been analyzed for performance parameters like quality factor, bit error rate, eye height and channel power. The analysis shows that EDFA-Pr has maximum Q-factor of 15.4883 at 80 km. EDFA-Pr has a maximum eye opening of 0.00534 at 80 km of length but at 120 km transmission distance EDFA-Yb shows maximum eye opening of 0.00154. Below 100 km of transmission distance, EDFA-Pr shows minimum BER value ranging from 10–54 to 10–20 but as the length is increased above 100 km EDFA-Yb shows better performance with values ranging from 10–16 to 10–09.

Performance of a 32 Channels WDM System using Gain Flattened EDFA

Performance of a 32 Channels WDM System using Gain Flattened EDFA

Simulation Analysis of 32 Channel WDM System using SMF 28 Optical Fiber at Various Power Levels

Optical communication in case of WDM system is processing at an astonishing due to high transmission capacity. In this paper, we developed 32 channels WDM system at 40 Gbps is used to improve the system quality at different power levels and frequency spacing at the length of 50 km using single mode fiber (SMF). EDFA is used for better gain. In this work we enhance the system efficiency and system capacity by using DCF (dispersion compensating fiber). Also, BER an analysis has been shown through simulation at various power levels and frequency levels, the results are shown in terms of BER, Q-factor and Eye height using optisystem 7.0

IJARCCE - Computer and Communication Engineering

2 Abstract: In this paper, the 32 channel WDM system at 20 Gb/s has been investigated for the different channel spacing. The performance has been analyzed on the basis of dispersion. The comparison of BER, Q-factor and eye opening for WDM and DWDM systems at different dispersion is done. It is observed that at different dispersion 2-10 ps/nm/km the 32 × 20 Gb/s WDM system provides better results than the 32 × 20 Gb/s DWDM (dense wavelength division multiplexing) system in the presence of nonlinearities. The analysis is done using OptiSystem 7.0 simulator.

Performance analysis of optical WDM system based on unequal spaced channel allocation (USCA) scheme

Unequal spaced channel allocation (USCA) is a technique to reduce Four wave mixing (FWM). In this paper, system performance of 8 channel WDM system considering different optical transmitter formats (RZ, NRZ, Raised cosine and Gaussian) using USCA has been evaluated in terms of Q-factor. The simulation results reveal that four wave mixing is minimum for NRZ format. Also the effect of changing the laser power and increasing the bit rate has been observed.

Comparison of PMD Compensation in WDM Systems

The need for larger capacities in long haul optical digital transmission lead to greater channel density which can be achieved by wavelength division multiplexing and increasing the bit rate of each channel. As data rates increases, certain phenomena such as dispersion began to show up as obstacles. At higher bit rates beyond 2.5Gbps polarization mode dispersion (PMD) becomes a main factor in the degradation of the transmission characteristics. PMD occurs when slightly different planes of light inside a fiber travel at slightly different speeds and make it impossible to transmit data reliably at high speed in single mode fibers. PMD is caused due to optical birefringence in the fiber due to which the two modes within a single mode fiber travel with different group velocities and the random change of this birefringence along the fiber length results in random coupling between the modes. This effect of PMD results in broadening of transmitted pulses that limit the transmission capacity of the fiber. In high-speed optical communication systems working at data rates of 10Gbps and beyond, signal distortion caused by PMD is also a major limitation of the transmission distance. This paper intends to analyze the performance of PMD compensation by optical compensation technique and using DCF in a two channel WDM system. The analysis is done through eye diagrams from which the Q value and bit error rate can be determined by simulating with OptSim5.3, which includes the latest simulation algorithms to guarantee the highest possible accuracy and real world results. Keywords- Birefringence, Data rate, Deterministic Differential Group Delay (DDGD), Dispersion compensating fibers (DCFs) Polarization Mode Dispersion (PMD Principal State of Polarization (PSP), Q value.

Characterization of cross-polarization modulation on a two channel WDM system

This article contributes experimental corroboration of cross-polarization modulation (XPolM). A continuous wave probe signal is remotely controlled by a modulated pump signal. Experimental results show that the state of polarization (SOP) evolution of the probe signal resembles that of the pump signal to a confined region on the Poincaré sphere. Further a bit pattern is transmitted on the probe signal by making use of cross-phase modulation induced nonlinear polarization rotation of the probe signal. The article also gives evidence to the detrimental effect cross phase modulation may have on polarization mode dispersion compensators. The results show that the degree of polarization degradation of a probe signal in a two model wavelength division multiplexing system deteriorates with an increase in the power ratio between the pump and probe signal.

Distribution of DVB-C Channels over an Externally Modulated Optical Link

Amplification through hybrid optical amplifiers (HOAs) is a propitious and proficient technology for high speed and high capacity dense wavelength-division-multiplexing (DWDM) systems. HOAs are intended to improve system reach and to accomplish wide gain bandwidth with enhanced flatness of gain. In this work, an ultradense 16 channel WDM system is demonstrated and performance of diverse hybrid amplifiers is evaluated in terms of output power, Q-factor, gain flatness and BER. Spacing among the WDM channels is 25 GHz in order to make system bandwidth efficient and scrutinized its effect on four wave mixing (FWM) in case of EDFA-EDFA, Raman-EDFA and SOA-EDFA. It is observed that SOA-EDFA is more and Raman-EDFA is less prone to FWM. Moreover, for distance 20 Km–140 Km, Raman-EDFA is optimal configuration for amplification and from 150 Km–200 Km, SOA-EDFA shows better performance. For prolonged link lengths such as beyond 200 Km, EDFA-EDFA is a right hybrid amplifier. In order to achieve maximum gain flatness in proposed architecture, EDFA-EDFA is recommended to use.

Filtering of an Optical WDM Signal by using Wavelet Analysis

Wavelength division multiplexing WDM is on promising approach that can be used to exploit the huge bandwidth of optical fiber. In WDM, the optical transmission spectrum is divided into a number of wavelength bands, with each wavelength supporting a single communication channel. Thus, by allowing multiple WDM channels to coexist on a single fiber, we can tap into the huge fiber bandwidth, with the corresponding challenges being the design and development of appropriate network architectures and optical devices. This paper presents a novel signal processing technique based on the wavelet transformation of a received signal from two channels WDM system. Therefore the wavelet analyse is used for decoding and de-noising the received signal. We found that the signal filtering (de-noising) by using wavelet analysis is more optimal than filtering by utilizing the classical filter from the point of attenuation, phase shifting and signal spectrum deformation. The continues wavelet transform is successfully employed to decode and de-noise the received signal for different wavelengths separation (3,1 and 0.5 nm). Furthermore the selection of the wavelet type and the decomposition level is one of the most important parameters. We noted that in our case the haar and db wavelets are the most appropriate ones. Otherwise the decomposition level depends on the noise form.

L-band erbium-doped fibre amplifier with clamped- and flattened-gain using FBG

A gain clamped long wavelength band erbium-doped fibre amplifier (L-band EDFA) based on a ring laser cavity is demonstrated using a fibre Bragg grating (FBG) at the output end of the amplifier. This new design provides a good gain clamping as well as a gain flattening. The gain is clamped at 16.9 dB with gain variation of less than 0.1 dB from input signal power of −40 to −18 dBm by setting the VOA=5 dB. Also, the amplifier has the flattest gain spectrum at VOA=5. The gain variation is less than 1.0 dB within the wavelength range from 1570 to 1600 nm. This gain clamped amplifier also can support a 12 channel WDM system.

Polarization mode dispersion in WDM systems

The coupled nonlinear Schrodinger equations for two wavelength optical pulses in a birefringence fiber are given. The model for treating polarization mode dispersion in two channel (WDM) system is established. Based on this model, optical signal propagation behaviors in two channel WDM with polarization mode dispersion are numerically simulated. The influences of polarization mode dispersion on two channel WDM system are also analyzed.

Advances in multichannel MultiGbytes/s bit-parallel WDM single fiber link

For ultra-high-speed single media parallel interconnects, an all optical single fiber WDM format of transmitting parallel bits rather than a fiber ribbon format-where parallel bits are sent through corresponding parallel fibers in a ribbon format, can be the media of choice. Here, we discuss the realization of a multi-km/spl times/Gb/s bit-parallel WDM (BP-WDM) single fiber link. The distance-speed product of this single fiber link is more than several orders of magnitude higher than that of a fiber ribbon link. The design of a 12 b parallel channels WDM system operating at 1 Gb/s per channel rate through a single fiber is first presented. Experimental results for a two channel system operating at that rate are given. Further improvement of distance-speed product for the BP-WDM link can be obtained with JPL's newly developed 20 Gb/s per channel laser diode array transmitter. Also, new computer simulation results on how a large amplitude co-propagating pulse may induce pulse compression on all the co-propagating data pulses, thereby improving the shaping of these pulses for a WDM system, are presented and discussed. The existence of WDM solitons is also shown.