Impact Of Four-wave Mixing Research Articles

Development of a Technique for Mitigating Four-Wave Mixing Effect in Dense Wavelength Division Multiplexing System Using DP-QPSK with Channel Spacing

A Dense Wavelength Division Multiplexing (DWDM) system is a vital component in the optical network for the transmission of high data over a long distance. However, the non-linear effect of Four-Wave Mixing (FWM), one of the critical non-linear effects, limits the channel capacity and the amount of data that the DWDM system transmits. Intensity Modulation formats and Channel Shuffling algorithms being used to overcome the impact of FWM in DWDM are unable to sufficiently suppress the FWM effect due to limited capacity. This research, therefore, examined the mitigation of the FWM effect in the DWDM system using Dual Polarization Quadrature Phase Shift Keying (DP-QPSK) and channel arrangement. The DP-QPSK was designed and implemented using 100 GHz for both Equal Space Channel Allocation (ESCA) and Unequal Space Channel Allocation (USCA). It was analysed on a 64-channel DWDM system operating at 100 Gbps capacity over a transmission distance of 1000 km. The DP-QPSK-based ESCA and USCA techniques were simulated using OptiSystem 17 simulation software and Python for data analysis. The performance of the system was evaluated using bit error rate (BER), optical signal-to-noise ratio (OSNR) and Electrical Constellation Diagram. Validation was done with other advanced modulation formats: Quadrature Phase Shift Keying (QPSK) and Differential-Quadrature Phase Shift Keying (D-QPSK). The DWDM system using DP-QPSK gave better performance due to the highest OSNR and BER values obtained when compared with ESCA-based QPSK and D-QPSK techniques. The technique can be used to suppress the effect of FWM in optical communication systems.

Mitigation of nonlinearities in long-haul DWDM soliton-based communication system

Abstract The ongoing challenge of research and development is focusing on increasing the overall capacity of the transmission medium, achieving a high bit rate, and designing long-haul optical communication systems. The main requirement of the transmission system in supporting high bit rates in optical communication systems is their tolerance to nonlinear fiber impairments. Optical soliton pulses that preserve their shape over long distances are the straightforward solution to this problem. In this paper, DWDM soliton-based optical communication system is designed to mitigate the nonlinear effects at a data rate of 10 Gbps with channel spacing of 100 GHZ by using a microring resonator (MRR) device which acts as an add/drop filter that generates a filter narrowband wavelength from a wider optical spectrum. The transmission link of the optical fiber has a total length of 180 km and MRR is inserted at the end of the loop which provides the required bandwidth. The high bit rate signals can be transmitted through this MRR system to get the filtered signal which is less affected by the nonlinearities. This filtered signal is observed at a total transmission distance of 54,000 km. Also, by using dispersion compensation techniques, the impact of four-wave mixing (FWM) is mitigated. The performance of the designed system is evaluated based on the quality factor (Q-factor) along with the bit error rate (BER) obtained.

Minimizing FWM Impact in DWDM ROF DP-DQPSK System for Optical

The demonstration of a higher data rate transmission system was a major aspect to be considered by researchers in recent years. The most relevant aspect to be studied and analyzed is the need for a reliable system to handle nonlinear impairments and reduce them. Therefore, this paper examines the influence of Four-Wave Mixing (FWM) impairment on the proposed high data rate Dual polarization–Differential Quadrature phase shift keying (DP-DQPSK) system using the Optisystem software. In the beginning, the impact of varied input power on the proposed system’s performance was evaluated in terms of QF and BER metrics. More power is used to improve system performance. However, increasing power would raise the FWM effects. Accordingly, a −10 dBm input power and the proposed system are used to reduce the impact of FWM. Additionally, a hybrid amplification method is proposed to enhance system performance by utilizing the major amplification methods of erbium-doped fiber amplifier (EDFA): semiconductor optical amplifier (SOA) and Radio optical amplifier (ROA). The evaluation demonstrates that the OA-EDFA outperformed the other two key amplification techniques of (EDFA-SOA) and (EDFA-ROA) in improving Quality factor (QF) and Bit error rate (BER) system results for all distances up to 720 km. Consequently, the method contributes to minimizing the impact of FWM. In the future, other forms of nonlinearity will be investigated and studied to quantify their impact on the proposed system.

Impact of FWM on Optical Scheme Performance under Different Limitations Factors and Modulation Formats

Four-wave mixing (FWM) has been shown to be the leading nonlinear consequence in long transmission distance that can cruelly border the wavelength division multiplexing (WDM) and minor the scheme performance. In this work, the system analyze with performance under the effect of wavelength spacing in the case of normal RZ, NRZ intensity modulation - direct modulation (IM-DD) and in the existence of phase shift keying-modulation format, which comprised of (8-PSK and 16-PSK). In addition, the effect of wavelength spacing on FWM is evaluated through 4 kinds of optical fiber, SMF, DSF, NZDF and Large Effective Area Fiber (LEAF) for three channels. The outcomes show that the SMF presents minimum FWM power up to -40.88 dBm, while DSF offers maximum FWM power of -30.99 dBm. It is observed that for NZDF and LEAF, the FWM powers are -31.99dBm and -35 dBm, respectively. In the case of system quality with the channel spacing tuning after 150 Km, BER is 3.3×10−11 on received power of -12 dBm using 16-PSK modulation. Nevertheless, in the existence of NRZ arrangement the BER was originated to be worse and equal to 8×10−3 at same received power.

SRS VE FWM OLAYLARININ DWDM-GPON SİSTEMLERİN AŞAĞI YÖNLÜ KANAL PERFORMANSLARI ÜZERİNDEKİ BİRLEŞİK ETKİSİ

In this paper the combined impact of stimulated Raman scattering (SRS) and four-wave mixing (FWM) on the downlink channel performance of dense wavelength division multiplexed-gigabit passive optical networks (DWDM-GPONs) has been compared with the single impact of FWM via signal-to-crosstalk ratio (SXR) simulations performed on center downlink channels of 7-, 15- and 31-channel DWDM-GPON systems. Simulation results show that SRS compensates negative impacts of FWM and compensation significance enhances with increasing channel numbers and channel spacing values. At high channel spacing values of 50 GHz and 100 GHz, variation of SXR can display a strong oscillatory behavior in very short channel length variations of 0.5 km. The combined impact of SRS and FWM enhances the maximum oscillation amplitude of SXR variation with respect to the single impact of FWM at those channel spacing values. It has been observed that Raman gain exhibits an approximately linear variation with channel input powers in 0.1-5 mW range and it increases with increasing fiber lengths, channel spacing values and channel numbers. Results of this research emphasize the significant difference between the combined impact of SRS and FWM and the single impact of FWM on DWDM-GPON systems and give important hints for current DWDM-GPON implementations.

Impact of FWM on the Performance of 2-D Time-Wavelength OCDMA Systems

A derivation of a general formula for the bit error rate of 2-D time-spreading wavelength-hopping optical code division multiple access systems under the impact of four-wave mixing (FWM) is presented. The effect of many system parameters such as the transmitted power per chip, code properties, wavelength spacing, and transmission fiber length is investigated. The analysis reveals that the generated FWM light contributes not only as an additional crosstalk component, but also produces as extra three noise terms, namely, signal-FWM, interferer-FWM, and FWM–FWM noise. Theoretical results show the detrimental effect of FWM on the system performance at high chip power levels; resulting in a 4-dB penalty at a power of 15 dBm. Furthermore, the paper presents many aspects useful in the system design.

Analysis of the four-wave mixing impact on the most heavily affected channels of dense and ultra-dense wavelength division multiplexing systems using non-zero dispersion shifted fibers

In this paper, the impact of four-wave mixing (FWM) phenomenon on the system performance has been analyzed via focusing on effects of FWM products falling into the center channels, i.e. the most heavily affected ones among all, of equally spaced 9-, 11-, 13- and 15-channel DWDM systems having channel spacing values of 12.5GHz, 25GHz, 50GHz and 100GHz, and UDWDM systems having 6.25GHz channel spacing value. DWDM and UDWDM systems using four different single-span commercially available NZDSFs, i.e. TeraLight™, LEAF®, TrueWave®-Reach and TrueWave®-RS, have been considered in simulations. Results show that for all NZDSF types, input powers even as low as 1mW do not satisfy a minimum 23dB signal-to-crosstalk ratio (SXR) criterion in UDWDM and DWDM systems using 6.25GHz and 12.5GHz channel spacing values, respectively. Furthermore, for all DWDM and UDWDM systems, the lowest and the highest FWM crosstalk values belong to the TeraLight and the TrueWave-RS fibers, respectively, at all input powers, channel numbers and channel wavelengths while the minimum and the maximum SXR variations with varying channel wavelengths are obtained in the TrueWave-Reach and the LEAF fibers, respectively.

A Time-Domain Extended Gaussian Noise Model

From first-order perturbation theory, we derive the autocorrelation function of the nonlinear interference in coherent optical links. We show that the fundamental assumptions of the Gaussian noise (GN) model regarding stationary Gaussian statistics of the transmitted signal can be removed for a more complete model accounting for the fine details of the cyclostationary modulation format. We first give an intuitive presentation of the theory, and then provide a formal mathematical treatment based on symbol cumulants and discuss its key assumptions and limitations. The proposed model includes dual polarization effects, wavelength-division multiplexing and the nonlinear signal to amplified spontaneous emission noise interaction along the line, thus neglecting only the impact of four-wave mixing.

Determining influence of four-wave mixing effect on quantum key distribution

We consider the possibility of multiplexing the classical and quantum signals in a quantum cryptography system with optical fiber used as a transmission medium. If the quantum signal is located at a frequency close to the frequency of classical signals, a set of nonlinear effects such as FWM (four-wave mixing) and Raman scattering is observed. The impact of four-wave mixing (FWM) effect on error level is described and analyzed in this work in case of large frequency diversity between classical and quantum signals. It is shown that the influence of FWM is negligible for convenient quantum key distribution.

A bandwidth-efficient channel allocation scheme for mitigating FWM in ultra-dense WDM-PON

In this paper, we investigate four-wave mixing (FWM) effects in the ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON) system and propose an efficient channel allocation scheme to mitigate the FWM impact. This scheme is formed by grouping signal channels into several blocks with different channel spacing. Through numerical analysis and simulations, our proposed scheme is verified to be able to reduce the FWM effects and have higher bandwidth efficiency than the traditional unequal channel allocation scheme. The simulation results also demonstrate that our proposed scheme can achieve nearly 4dB increases in optical power budget of the UDWDM-PON systems at the BER of 1e−3, in comparison with the equal spaced channel scheme.

Impact of four-wave mixing on dispersion-managed frequency-shift-keying dense-wavelength-division-multiplexing system including various light-propagating effects

We describe a semi-analytic model used to deterministically and exactly calculate the variance of degenerate and nondegenerate four-wave mixing (FWM) noises for 128×10 Gb/s return-to-zero frequency-shift-keying dispersion-managed dense-wavelength-division-multiplexing system. The analytic model includes various important light-propagating effects such as walk-off between channels, oscillation of pulse width with transmission distance, and stochastic variation of birefringence strength and orientation along fiber. The achievable maximum Q -factor and allowed maximum input powers for different dispersion management schemes and transmission distances are shown including overall FWM noises from different channel combinations, signal-amplified spontaneous emission (ASE) beat noise, and others. Achievable maximum transmission distances for such systems are studied. The upper limit of local dispersion of the dispersion map is discussed. In the case of allowed maximum input powers for the system, the variances of overall FWM noise are observed to be about half of those of signal-ASE beat noise when averaged for different transmission distances. It is found that for high-local dispersion, when transmission distance is long enough, effect of nondegenerate FWM noise, compared with degenerate FWM noise, can be ignored.

Lightpath Topology Design for Wavelength-Routed Optical Networks in the Presence of Four-Wave Mixing

For optical communication links using wavelength-division multiplexing over a long-haul fiber optic backbone, four-wave mixing (FWM) may lead to significant transmission impairment. Lightwaves traversing through a wavelength-routed optical network (WRON) encounter progressive linear and nonlinear interactions and periodic loss/gain mechanisms through lossy fiber segments and noisy optical amplifiers. In this paper, the FWM power accumulated and received at the end of each lightpath in a WRON is estimated through analytical modeling of lightwaves. While estimating FWM interference for a given lightpath, various feasible lightpath topology scenarios, such as the possibility of any other lightpath joining the given lightpath or departing the given lightpath at any intermediate node, or co-propagating along with the given lightpath till the given lightpath end, are taken into account. The transmission impairments from the accumulated FWM crosstalk along with the amplified spontaneous emission (ASE) noise components from the inline optical amplifiers are considered for evaluating the overall optical signal-to-noise ratios (OSNRs) at the receiving ends of lightpaths. The values of FWM contributions and the OSNR for each lightpath, estimated by using the proposed analytical model, help in setting up lightpaths in a WRON, as one can predict whether the lightpath under consideration could offer a desirable physical-layer performance. From our earlier work [Opt. Switching Networking, vol. 6, pp. 10-19, 2009], though we observe that the count-based assessment of FWM interference (wherein the total number of generated FWM components is estimated from the co-propagating lightpaths) offers a simple method, the power-based evaluation of FWM, as developed in this paper, gives a more precise estimate of the FWM impact of the lightpath in a WRON setting. In view of this, we also carry out FWM-aware and FWM-unaware lightpath topology designs (LTDs) and compare the results of the two LTDs, based on the count-based and the power-based estimates of FWM.

The Reduction of FWM effects using Duobinary Modulation in a Two-Channel D-WDM System

This papers show that the adoption of a duo binary Modulation scheme reduces the impact of FWM in a DWDM system. The levels of the FWM products are reduced by around 10 dB which will offer a significant performance benefit in digital systems. We have taken into consideration great demand for high data rate & have designed optical fiber system for 40 Gbps. Keywords-dispersion shifted fiber (DSF), Dense wavelength division multiplexing (DWDM), Four wave mixing (FWM), Bit error rate (BER).

Light storage in an optically thick atomic ensemble under conditions of electromagnetically induced transparency and four-wave mixing

We study the modification of a traditional electromagnetically induced transparency (EIT) stored-light technique that includes both EIT and four-wave mixing (FWM) in an ensemble of hot Rb atoms. The standard treatment of light storage involves the coherent and reversible mapping of one photonic mode onto a collective spin coherence. It has been shown that unwanted, competing processes such as four-wave mixing are enhanced by EIT and can significantly modify the signal optical pulse propagation. We present theoretical and experimental evidence to indicate that, while a Stokes field is indeed detected upon retrieval of the signal field, any information originally encoded in a seeded Stokes field is not independently preserved during the storage process. We present a simple model that describes the propagation dynamics of the fields and the impact of FWM on the spin wave.

Performance analysis of incoherent multi-wavelength OCDMA systems under the impact of four-wave mixing

In this paper, we comprehensively analyze the impact of four wave mixing (FWM) on the performance of incoherent multi-wavelength optical code-division multiple-access (MW-OCDMA) systems. We also consider many other interferences and noises, including multiple access interference, optical beating interference, and receiver noise, in the analysis. From the numerical results, we can find the power ranges of different MW-OCDMA systems, in which the impact of FWM is dominant and consequently results in an increase in the bit-error rate of the systems. We also find that the impact of FWM becomes more severe when the frequency spacing is small and/or dispersion-shifted fiber is used. In addition, we quantitatively discuss the impact of FWM on the number of supportable users and power penalty in the MW-OCDMA systems.

Non-linear transmission effects in duobinary and dicode optical systems

This paper presents optical duobinary and dicode signalling, as alternatives to the binary format, in order to improve the transmission performance in the presense of non-linear effects in a dense wavelength division multiplex (WDM) optical system. Duobinary signalling is applied to an optical system to explore the reduction of stimulated Brillouin scattering (SBS) effects. Duobinary signalling suppresses the SBS effects, and an eye-opening improvement of 0.25 to 1.2 dB is achieved relative to binary transmission over a range of input power levels. An experimental study demonstrates that duobinary modulation suppresses the four wave mixing (FWM) products of a dense WDM system by a maximum of 3 dB. The suppression is maintained over a range of channel spacings. An investigation of the impact of fibre dispersion on FWM products under binary, duobinary and dicode modulation in a dense WDM system is then performed, with interchannel spacing and optical power variation. This leads to the development of a set of guidelines for the application areas, in which it is appropriate to use duobinary or dicode modulation in WDM systems as a means of mitigating the impact of FWM.