DWDM Channels Research Articles

Performance Analysis of Designing a Hybrid Optical Amplifier (HOA) for 32 DWDM Channels in L-band by using EDFA and Raman Amplifier

Performance Analysis of Designing a Hybrid Optical Amplifier (HOA) for 32 DWDM Channels in L-band by using EDFA and Raman Amplifier

Investigation of Power Transients in 45 Channel DWDM Ring Optical Network

Erbium doped fiber amplifiers (EDFA) are most commonly used in optical networks for the most assorted applications. The fast power transient effect of the cascaded erbium-doped fiber amplifiers (EDFA) in 45 channels optical ring network is investigated. The power transient effect of EDFA’s are observed when channels are added and dropped. It is shown that, for low channel adding/dropping frequency closed to EDFA transient rate, the transmission performances of the surviving channels are impaired severely. And also ring laser configuration technique has been reported to mitigate the effect of power transients. Optsim simulation was utilized for simulation of the designed DWDM OADM ring network.

Low-cost hybrid ROADM architectures for scalable C/DWDM metro networks

CWDM networks have proven to be a promising first-step metro and access network architecture, offering a significant cost advantage over DWDM due to the lower cost of lasers and the filters used in CWDM modules. If demand grows beyond the capacity covered by CWDM channels, DWDM network elements can be introduced to merge CWDM and DWDM traffic at the optical layer. This ensures two advantages: reduced initial investment and scalability for deploying DWDM channels in the future. This article presents various ROADM architectures, and explores the novel optical node architecture of hybrid C/DWDM networks, consisting of CWDM, hybrid C/DWDM, and junction nodes connecting two rings. Evaluation has shown that the hybrid ROADM architecture is superior to other conventional ROADM architectures in terms of scalability and the initial cost of optical nodes and networks.

Correlation of nonlinear noises from different spans in 100 Gb/s multi-span fiber optic lines

The accumulation of nonlinear noise in multi-span communication lines was investigated by numerical modeling and experimentally for different values of accumulated dispersion at input of each span. One coherent 100G channel was investigated (wavelength 1549.32nm, DWDM channel C35). It has been established that interaction of nonlinear noises from two different spans can be described by a correlation function that depends only on values of input dispersion for these spans. It confirms the idea that the nonlinear noise in a fiber optic line is formed mainly due to signal to signal interaction, and the influence of the signal to noise interaction can be neglected. The shape of correlation function was investigated by numerical modeling and experimentally, and its simple approximation was offered. The nonlinear noise in any multi-span line with arbitrary dispersion plan can be calculated based on the investigated correlation function for two spans. It was shown that in a compensated line the offered theoretical model based on correlation function corresponds well to simpler theoretical model based on superlinear dependence of total noise on number of spans.

Performance Evaluation of Hybrid amplifiers for 16 × 20 and 32 × 20 Gbps DWDM System

In this paper, the 16 channel and 32 channel DWDM systems at 20 Gbps have been investigated for hybrid amplifiers. The performance has been analyzed on the basis of transmission distance. The comparison of BER and Q-factor for two hybrid amplifiers EDFA+RAMAN and RAMAN+EDFA at different transmission distance is done. It is observed that for 16 × 20 Gbps and 32×20Gbps DWDM system using EDFA+RAMAN provides better results than the DWDM system using RAMAN+EDFA. The analysis is done using OptiSystem 7.0 simulator.

Performance Analysis of DWDM System Having 0.8- Tbps Date Rate with 80 Channels

Objectives: The main aim of this research paper is to design a 80 channel DWDM system with each channel having 10 Gbps data rate multiplexed with frequency spacing 100 GHz. Methods/Statistical analysis: Dispersion is an important factor to be considered while designing a DWDM system. Dispersion affects the penalties due to various types of fiber nonlinearities. Single mode fiber is preferred for long distance communication over Multimode fiber. In this proposed work Optisystem 7.0 simulator is used to analyze dispersion effect. The system performance is optimized by using Dispersion compensation fiber to compensate for the dispersion produced by single mode fiber. Findings: The system performance is limited by the dispersion. In order to compensate this we have used Dispersion compensation fiber. Between amplifier spans is standard single-mode fiber, but at each amplifier location, dispersion compensating fiber having a negative chromatic dispersion is introduced. By using this we have successfully designed a DWDM system with 80 channels each 10 Gbps data rate multiplexed with frequency spacing 100 GHz. Application/Improvements: It is realized that, in coming future, DWDM can emerge as a promising technique to increase the capacity and meet the bandwidth requirement. This work can further be extended to more number of channels i.e. 100 channels or more with even smaller frequency spacing.

New method to obtain optimum performance for 100Gb/s multi-span fiber optic lines

Design of DWDM lines requires calculation of optimal input powers for each span. It is called “optimization of DWDM network”. Different approaches are currently used to solve this task including maximization of optical signal-to-noise ratio (OSNR) margin and minimization of bit error rate (BER). Within last years there is a particular interest to DWDM lines based on uncompensated links with coherent transmission. We analyze benefits and drawbacks of existing approaches and offer a new method of optimization that guarantees sufficient OSNR margin for bringing into service such DWDM lines.The proposed method combines the advantages of two previously known methods. For short lines, it works like BER criterion. It does not overestimate values of power, and does not require the recalculation after each stage of expansion of the line. For long lines, it works like OSNR margin criterion. It guarantees that calculated values of powers will enable bringing the line into service; and if the optimization is failed it means that it is impossible to commission the line by any other method.Discussion and comparison of different methods are based on a general phenomenological model for multi-span fiber optic line that takes into account both linear and nonlinear noises. The proposed phenomenological model is a consequence of the GN model where a number of parameters characterizing nonlinear interaction of DWDM channels are determined experimentally.

Field trial of a quantum secured 10 Gb/s DWDM transmission system over a single installed fiber.

We present results from the first field-trial of a quantum-secured DWDM transmission system, in which quantum key distribution (QKD) is combined with 4 × 10 Gb/s encrypted data and transmitted simultaneously over 26 km of field installed fiber. QKD is used to frequently refresh the key for AES-256 encryption of the 10 Gb/s data traffic. Scalability to over 40 DWDM channels is analyzed.

Performance Analysis of TDAF Using 1050nm Pumping Power for 1479nm-1555nm Range

A model of TDFA has been proposed based on simulation after considering all the major parameters like pump and signal power, without considering ASE. Through this analysis of TDFA the optimum value of pump power and the range of fiber length (TDF) have been evaluated. In this section, an effort has further been made to use the least possible fiber length of TDF so as to maximum possible gain and in turn cheaper amplifier. The present research claims to support 96 DWDM channels across 1479nm- 1555nm wavelength range with a channel spacing of 0.8nm. The optimum range of fiber length of TDFA has been evaluated between 8m-16m. The peak gain of ranging from 22 dB to 30.5dB has been attained for selected optimum fiber lengths ranging from 8m to 16m of TDF.

Performance Analysis of TDFA using 1050nm Pumping Power for 1479nm-1555nm Range

A model of TDFA has been proposed based on simulation after considering all the major parameters like pump and signal power, without considering ASE. Through this analysis of TDFA the optimum value of pump power and the range of fiber length (TDF) have been evaluated. In this section, an effort has further been made to use the least possible fiber length of TDF so as to maximum possible gain and in turn cheaper amplifier. The present research claims to support 96 DWDM channels across 1479nm- 1555nm wavelength range with a channel spacing of 0.8nm. The optimum range of fiber length of TDFA has been evaluated between 8m-16m. The peak gain of ranging from 22 dB to 30.5dB has been attained for selected optimum fiber lengths ranging from 8m to 16m of TDF.

Amplification of DWDM channels at 128 Tb/s in a bidirectional fiber optical parametric amplifier

We experimentally demonstrate amplification of 1.28 Tb/s DWDM channels using a bidirectional fiber optical parametric amplifier. The amplifier can provide more than 13 dB on-off gain on all 32 DWDM channels. Error-free operation has been achieved for all data streams, with an average power penalty of 2.5 dB compared with conventional unidirectional configuration.

Investigation of Fiber Optical Parametric Amplifier Performance in DWDM Transmission Systems

During the last decade, due to the growing demand on high capacity transmission, the evolution of optical transmission systems is moving into the focus of dense and cost-effective solutions. This has resulted in stricter requirements for the elements used in optical transmission systems, including optical amplifiers (FOPAs). One of the innovative and most promising types of amplifiers is fiber optical parametric amplifiers. In this article the authors implement a lumped single pump FOPA in a 8 channel DWDM transmission system and investigate the performance of the FOPA in order to obtain a configuration that would ensure higher level of amplification coped with less amplifier produced signal impairments. DOI: http://dx.doi.org/10.5755/j01.eee.20.1.6170

Performance Comparison of Single & Hybrid Optical Amplifiers for DWDM System Using Optisystem

In this paper, single and hybrid amplifier configurations are implemented with FRA and EDFA amplifiers for 160 channel DWDM systems at 10 Gbps & 25 GHz frequency spacing for L-band. These configurations are transmitted and measured over different distances for 50, 100, 150, 200 and 250 km. The performance of single and hybrid optical amplifiers evaluated in terms of output power, BER, eye height and Q factor. Among these setups EDFA-EDFA performed better than other optical amplifiers at 150 km distance. It provides output power (36.55 to -3.45 dBm), least BER (-38.96 to 0), large Q factor (12.71 to 0) and good eye diagram for different transmission distance ranging from 50 to 250 km. These are all setups are arranged without using any gain-flattening technique and receiver filters. Keywords-FRA, EDFA, DWDM, Transmission Distance, Output Power, BER, Eye Height, Q factor.

10-Gbit/s direct modulation of a TO-56-can packed 600-μm long laser diode with 2% front-facet reflectance

A 600-μm long-cavity laser diode with a front-facet reflectance of 2% is demonstrated as a colorless OC-192 transmitter for the future DWDM-PON, which is packed in a TO-56-can package of only 4-GHz frequency bandwidth but can be over-bandwidth modulated with 10-Gbit/s non-return-to-zero data-stream. The coherent injection-locking successfully suppresses its side-mode intensity and noise floor level, which further improves its modulation throughput at higher frequencies. With increasing the coherent injection-locking power from -12 to -3 dBm, the side-mode suppression ratio significantly increases from 39 to 50 dB, which also suppresses the frequency chirp from -12 to -4 GHz within a temporal range of 150 ps. The dense but weak longitudinal modes (with 0.6-nm spacing) in the long-cavity laser diode suppresses to one single-mode in a 100-GHz wide DWDM channel for carrying the OC-192 data at 9.953 Gbit/s. Such an over-bandwidth modulated laser diode still exhibits an on/off extinction ratio of 6.68 dB and a signal-to-noise ratio of 4.96 dB, which can provide a back-to-back receiving power sensitivity of -12.2 dBm at BER of 10⁻⁹. After 25-km DSF transmission of the OOK data-stream at a bit rate up to 10 Gbit/s, the receiving power sensitivity is -10.1 dBm at a requested BER of 10⁻⁹.

Analysis and Compensation of Polarization Mode Dispersion in Single Channel, WDM and 32-channel DWDM Fiber Optic System

One of the most serious impairments which limit the data rate in long distance and high speed transmission systems is Polarization Mode Dispersion (PMD). PMD is negligible when data rate is low (i.e. in Mb/s or few Gb/s) but it will affect the high data rate transmission systems (10s of Gb/s, Tb/s etc.), as the pulse broadening severely distorts the signal during transmission. Thus it is necessary to compensate the PMD in both single and multichannel fiber optic transmission system due to increase in the traffic demand. This paper deals with a Deterministic Differential Group Delay (DDGD) method to compensate the PMD in single channel, by delaying the fast polarization component and wavelength independent Polarization Maintaining Fiber (PMF) method for multichannel PMD compensation. The DDGD method efficiently compensates the PMD upto 45 ps in single channel 40 Gb/s transmission systems. The State of Polarization (SOP) before and after the PMD and after compensation is analyzed by means of Poincare Sphere. By using PM Fiber method, simultaneous and effective compensation of PMD in multichannel system is achieved. Here, the simulation has been carried out for 4-channel (40 Gb/s), 8-channel (80 Gb/s), 16-channel (160 Gb/s) WDM systems and 32-channel (320 Gb/s) DWDM fiber optic system with each channel having the data rate of 10 Gb/s and the results of PMD compensation for all the channels are analyzed. It is seen that the PMD compensation is achieved upto 90 ps 87 ps, 84 ps and 80 ps in 4-channel, 8-channel, 16-channel WDM systems and 32-channel DWDM systems respectively. As very high data rate of 100 Gb/s and above are in practice now-a-days, compensation of PMD is enhanced to 1.6 Tb/s (16×100 Gb/s) data rate for 16-channel by PMF method and 74 ps of broadening is compensated effectively.

Performance evaluation of 16 channel DWDM radio-over-fiber link

In this article, generation of DWDM-RoF signal utilizing an SOA-MZI multichannel frequency up-conversion is demonstrated. The simulation results of a 16 channel, 10km DWDM-RoF link at baseband signal of 500Mbps, over the wavelength range 1545.80–1552.20nm are reported. BER of the order of e−18 and Q factor above 18dB over the entire bandwidth signify negligible crosstalk and error free transmission of radio signal.

High-capacity optical transport networks

Network traffic demands are forecast to increase for the foreseeable future, with the challenge being to meet the demand while maintaining or lowering network costs. Simply increasing capacity will not be sufficient; overall bandwidth utilization also needs to improve. A combination of improved transport capacity through increased spectral efficiency and bit rate along with better network utilization by integrating subchannel electrical grooming into the transmission system will be required. Smarter ways to utilize optical capacity are key since transmission costs have been decreasing slower than grooming and switching costs. Integrated transport and switching can improve the efficiency of the client network using techniques such as port virtualization and transit traffic reduction. The baseline for transport networks will be 100 Gb/s PM-QPSK using 50 GHz channel spacing. Moving from a fixed DWDM channel arrangement to support flexible grid and super channels will allow tighter channel (carrier) spacing and should increase capacity by 30 to 50 percent. For shorter distances higher-order modulation such as 16-QAM can double network capacity. To better optimize network efficiency, an architecture that flexibly combines lower rate (sub-100 Gb/s) clients to form channels (carriers) and then superchannels will be required.

Gain flattening of DWDM channels for the entire C & L bands

A hybrid amplifier consisting of one stage of Erbium Doped Fiber Amplifier and two stages of Raman amplifiers is constructed. Two Raman fibers are cascaded in series to suppress the intensity noise due to double Rayleigh scattering. Backward pumping is applied at all stages in order to increase the gain of Erbium Doped Fiber Amplifier and to decrease the polarization dependent gain of Raman fiber amplifier. In our previous experiment a 16 channel Wavelength Division Multiplexed system with channel spacing of 5 nm was considered. In this experiment a Density Wavelength Division Multiplexed system having 80 channels and a channel spacing of 0.8 nm was taken in to account. Gain Flattening is achieved for the entire C-band and L-bands. Experimental results showed that the hybrid amplifier has the average Gain of more than 19 dB in the wavelength range between 1530 and 1600 nm, with the Noise Figure of less than 6 decibels. The Gain of the Erbium Doped Fiber Amplifier and Raman was optimized to minimize the ripple value as low as 0.045 decibels with an output power of 15.265 decibel-milli.

Comparison of pre-, post- and symmetrical compensation for 96 channel DWDM system using PDCF and PSMF

In this paper, we investigate pre-, post-, symmetrical dispersion and power compensation in parallel for 96 channels×10Gbps non-return to zero DWDM system using pumped dispersion compensating fiber (PDCF) and pumped single mode fiber (PSMF). The results of three compensation methods have been compared in the term of bit error rate, eye closure penalty and Quality factor and it is found that both post-, and symmetrical compensation methods are provide better results for short haul communication but for long haul communication post-compensation method is the best alternative among other. The impact of bit error rate and eye closure penalty is also observed for large transmission distances and cover 420km using post-compensation method with acceptable bit error rate (2.3×10−10) and eye closure (1.73dB).

Field-Trial of an All-Optical PSK Regenerator/Multicaster in a 40 Gbit/s, 38 Channel DWDM Transmission Experiment

The performance of future ultra-long haul communication systems exploiting phase-encoded signals is likely to be compromised by noise generated during signal transmission. One potential way to mitigate such noise is to use Phase Sensitive Amplifiers (PSAs) which have been demonstrated to help remove phase as well as amplitude noise from phase-encoded signals. Recently, we showed that a PSA-based signal regenerator based on degenerate four-wave mixing can be implemented in a network-compatible manner in which only the (noisy) signal is present at the device input (black-box operation). The developed regenerator was also able to perform simultaneous wavelength conversion and multicasting, details/analysis of which are presented herein. However, this scheme was tested only with artificial noise generated in the laboratory and with the regenerator placed in front of the receiver, rather than in-line where even greater performance benefits are to be expected. Here, we address both theoretically and experimentally the important issue of how such a regenerator, operating for convenience in a multicasting mode, performs as an in-line device in an installed transmission fiber link. We also investigate the dispersion tolerance of the approach.