Wavelength Division Multiplexing Systems Research Articles

Designing and controlling a single-mode dual concentric core fiber with nearly zero ultra-flattened chromatic dispersion for linear or nonlinear application

For a number of applications, it is essential to design fibers that exhibit nearly zero ultra-flattened chromatic dispersion. Moreover, the nearly zero ultra-flattened chromatic dispersion fiber should ensure the single mode operation to avoid the multimode dispersion as it is responsible for signal degradation. In order to control the nearly zero ultra-flattened chromatic dispersion and single-mode regime, the present paper describes a new controlling technique of a dual concentric core fiber (DCCF). The finite element method (FEM) is used to investigate the properties. By introducing a varying index profile (alpha) in the core region of the DCCF, we can successfully design a single-mode operation fiber with nearly zero ultra-flattened chromatic dispersion in linear or nonlinear application. Other important guiding characteristics such effective mode area (Aeff), effective nonlinear refractive index (n2) are also discussed. The proposed DCCFs can be applicable in digital optical communication (dense wavelength division multiplexing (WDM) systems, for long-haul telecommunications networks and super continuum generation (SCG)).

Enhanced CSPR for a multichannel Kramers-Kronig receiver by self-seeded stimulated Brillouin scattering.

We demonstrate carrier-to-signal power ratio (CSPR) enhancement by self-seeded stimulated Brillouin scattering to improve the performance of Kramers-Kronig (KK) detection for multichannel single-sideband (SSB) signals. By virtue of low-CSPR transmission and high-CSPR detection, our proposed scheme effectively advances system performance by reducing propagation-induced distortion while maintaining the minimum phase condition. We experimentally demonstrate the improvement in CSPR and bit error rate of 5×10-Gbaud 16-QAM SSB signals by applying the carrier recovery block after 80-km transmission. Under optimum pump power, the average Q factor improvement of all five channels is 3.0 dB. We also analyze the performances of different channels and the major limiting factor. The results verify that our scheme offers a promising solution to enhance SSB self-coherent KK detection in wavelength-division multiplexing systems.

Up to 50 Gb/s modulation of an EAM integrated widely tunable DBR laser

An electro-absorption modulator (EAM) integrated widely tunable distributed Bragg reflector (DBR) laser working at 1.5 µm is reported. By utilizing the RF resonance between the bonding wire and the EAM, a 28 GHz modulation bandwidth is obtained. The device is modulated with up to 50 Gb/s NRZ data. At 28 Gb/s, the power penalty to obtain a 10-10 bit error rate (BER) after a 5 Km standard single mode fiber transmission is less than 0.7 dB. Because the DBR material has a long bandgap wavelength, the wavelength tuning range of the laser is larger than 12 nm. The DBR laser is a promising low cost tunable light source for future high capacity wavelength division multiplexing (WDM) optical communication systems.

Four-Wave Mixing Effect and Its Security Implications on a WDM System

The data yearning of the world is expanding massively with time and it is convincing media transmission organizations tomount up procedures to satisfy the high information need just as giving a proficient support. During the exponentialdevelopment of data hungry clients, media transmission organizations fantasize about giving nature of administrations ata lower cost to their clients to endure the challenge in the market. Transmitting products of signs through a solitary directin perspective on serving a huge number of clients all the while by wavelength division multiplexing (WDM) is theappropriate response. Four-wave multiplexing (FWM) is the optical sign float from one channel to the next. This impacthas the inclination of forcing a danger on the fiber correspondence organize consequently undermining the security andsecrecy of the data sent by the clients. In this work, FWM impact and its security issues are broken down. The differentTangle lab reenactment consequences of this FPM is contemplated utilizing optical.
 Citation: Anita Antwiwaa, Seth Okyere-Dankwa, Mensah Sitti and Anil Kumar, Four-Wave Mixing Effect and Its SecurityImplications on a WDM System, 2020; 5(4): 1－11.
 Received: October 3, 2020Accepted: December 31, 2020

An Optimal Framework for WDM Systems Using Analytical Characterization of Refractive Index-Related Nonlinear Impairments

Nonlinear effects in the optical transmission systems (OTSs) are considered as the major performance limiting factor to provide high transmission rates over ultra-long distances. As the demands for system capacity, transmission range and the number of users is increasing exponentially with the development of mobile broadband, new challenges are being faced by the backbone optical networks. Mainly, the refractive index related non-linearities (RIrNLs) need to be characterized to design an optimal OTS for error-free transmission with provision of wavelength division multiplexing (WDM) to support for multiple channels. This paper provides an estimation technique of RIrNLs for long-haul transmission and their treatment for different channel spacing and the number of channels in a WDM system operating frequency domain multiple in multiple out (FD-MIMO) equalizer based digital signal processing (DSP) receiver and microstrip Chebyshev low pass filter. The main focus of this work is to utilize the existing structure of OTS for RIrNLs treatment with a low cost solution. Thus, by varying the parameters of the third order dispersion parameters, group velocity dispersion parameters, phase modulation dispersion and nonlinear refractive index, the impact of RIrNLs is investigated in detail to enhance the transmission range and capacity of the current OTS. The proposed system is analyzed in terms of range of input power, fiber length and received power for OTS figure of merits including bit error rate (BER) and optical signal-to-noise ratio (OSNR). Using duo-binary modulation, the BER achieved in this work is <10−5 till 500 km range, for maximum number of 32 channels, with 100 Gbps aggregate data rate, which shows the feasibility and effectiveness of our proposed model.

Physical Layer Encryption for WDM Optical Communication Systems Using Private Chaotic Phase Scrambling

Protecting the security of optical network is a major worldwide challenge. The conventional schemes for securing communications are based on cryptography at the MAC layer and its higher layers, which are facing a great threat with the development of quantum computers. Optical encryption is a promising way for building security on the physical layer of optical communications. In this work, we propose a novel optical encryption scheme for wavelength division multiplexing (WDM) fiber-optic communication systems, by utilizing the private chaotic phase scrambling. Secure transmission of 50 Gbps signal over 50-km standard single-mode fiber is experimentally and numerically demonstrated. The results show that the WDM signal is efficiently encrypted into a noise-like signal, due to the spectral broadening effect of chaotic phase scrambling. Since the processes of encryption and decryption are totally implemented in the optical domain, the proposed scheme can encrypt the entire network traffic with low latency and high speed. Moreover, the proposed encryption scheme is compatible with the existing WDM optical networks, and only one pair of encryption and decryption devices is sufficient to encrypt all WDM channels, thus the scheme can be easily implemented at low hardware cost.

A Novel Gold Film-Coated V-Shape Dual-Core Photonic Crystal Fiber Polarization Beam Splitter Covering the E + S + C + L + U Band.

In this paper, a novel gold film-coated V-shape dual-core photonic crystal fiber (V-DC-PCF) polarization beam splitter (PBS) based on surface plasmon resonance effect is proposed. The coupling lengths of the X-polarization (X-pol) and Y-polarization (Y-pol) and the corresponding coupling length ratio of the proposed V-DC-PCF PBS without gold film and with gold film are compared. The fiber structure parameters and thickness of the gold film are optimized through investigating their effects on the coupling lengths and coupling length ratio. As the propagation length increases, the normalized output powers of the X-pol and Y-pol of the proposed V-DC-PCF PBS at the three wavelengths 1.610, 1.631, and 1.650 are demonstrated. The relationships between the extinction ratio (), insertion loss () and wavelength for the three splitting lengths () 188, 185, and 182 are investigated. Finally, it is demonstrated that for the proposed V-DC-PCF PBS, the optimal is 188 , the of the X-pol and Y-pol are less than 0.22 dB, and the splitting bandwidth () can cover the E + S + C + L + U band. The proposed V-DC-PCF PBS has the ultra-short , ultra-wide , and ultra-low , so it is expected to have important applications in the laser, sensing, and dense wavelength division multiplexing systems.

Performance optimization of OADM based DP-QPSK DWDM optical network with 37.5 GHz channel spacing

Advanced modulation formats like dual-polarization quadrature phase-shift keying (DP-QPSK) along with the digital coherent receiver are enabling optical networks to provide high spectral efficiency (SE) over long-haul transmission reach. The DP-QPSK based dense wavelength division multiplexing (DWDM) system with 37.5 GHz channel spacing can provide extra throughput of 33% compared to 50 GHz channel spacing. However, at 37.5 GHz channel spacing, optical add-drop multiplexers (OADMs) at intermediate nodes, impact the performance of WDM based optical networks in terms of increased BER, thereby reducing transmission reach drastically. In this paper, we have analyzed with the help of numerical simulations, the performance of a differentially encoded eight-channel 112 Gb/s, OADM based DWDM optical network with a channel spacing of 37.5 GHz. We propose that the selection of optimum values of system parameters can result in reducing the impact of crosstalk propagation and narrowband optical filtering introduced by a chain of OADMs at 37.5 GHz channel spacing. The paper exhibited that the selection of optimum values of parameters like filter order of multiplexer and demultiplexer, launch power per channel and filter taps of adaptive equalizer (AE) result in achieving minimum BER on all the channels over a long transmission reach up to 3600 km.

Multichannel tunable polarizing filter properties of one-dimensional ternary photonic crystal containing single-negative materials

Angle and polarization-dependent tunable transmission properties of a one-dimensional (1D) ternary photonic crystal (TPC) whose period consists of three alternate layers of two different kinds of single-negative [Epsilon-negative (ENG) and mu-negative (MNG)] media are theoretically investigated by using the transfer matrix method (TMM). It has been shown that the proposed polarizing filter is capable of transmitting multiple polarized transmission peaks (called as channels) by adjusting the incident angle from 21° to 89° as per need. The resonant frequencies of these respective transmission channels are completely different for the case of TE and TM polarizations. The proposed structure contains only twelve SNG material layers corresponding to the period number N = 4. This structure filters 18 separate transmission channels for TE and TM waves each at incident angle $$ \theta_{0} = 21^{\circ} $$ . The number of polarization dependent channels can be further increased to 35 and 37 for TE and TM polarizations, respectively, when the period number of 1D TPC increases from 4 to 8 at $$ \theta_{0} = 89^{\circ} $$ . This eight-period 1D TPC structure requires only 24 SNG material layers. The effect of lossy SNG materials on the performance of the filter is also investigated. This study may find its application in the field of optical communication for accommodating a large number of optical channels in the same bandwidth. Such types of filters may have their applications in integrated optics for dense wavelength division multiplexing systems and ultrafast light information processing.

Performance Evaluation of Diverse Hybrid Pulse Width Reduction Modules in WDM systems

Long reach wavelength division multiplexing (WDM) systems are required to cater the remote locations and to cover the maximum distances. Dispersion is prominent factor for distance limitation and should be addressed with high efficiency as well as using low cost pulse width reduction (PWR) modules. In this research work, hybridization of different PWR is proposed such as FBG-DCF, OPC–DCF (optical phase conjugation), FBG-DCF-OPC to analyse the PWRE and total cost of the modules. Further, in order to get optimal hybrid PWR module and amplification unit, different optical amplifiers are also investigated at 10 Gbps over 300 km. An ultra dense WDM system with 25 GHz channel spacing using 32 channels is demonstrated and PWRE is analysed using different hybrid PWR modules. Results revealed that FBG-DCF having least cost with PWRP of 55%, OPC-DCF show PWRE of 45% with moderate cost, and FBG-DCF-OPC provide maximum PWRE of 70% with little bit higher cost. Performance sequence of investigated PWR modules is give as: FBG-DCF-OPC (70% PWRE)> FBG-DCF (55% PWRE)>OPC-DCF (45% PWRE)> and performance of amplification unit with FBG-DCF-OPC is depicted as EDFA>RFA>SOA). This module can be used in passive optical networks for long reach systems.

WDM Network Issues: QOT Impairments, Dynamic Bandwidth Allocation, Modeling and Monitoring Schemes based on ML

Machine Learning (ML) has recently drawn the interest of both academics and professionals in the optical networking area to solve several problems. This trend has been triggered largely by the vast amount of available data (i.e., signal strength metrics, network alerts, etc.) and the large range of optimization criteria available in today's optical networks (such as modulation format, light path routes, transport wavelength, etc.). WDM systems are popular in the telecommunications industry. It increases network bandwidth without laying more cable. WDM technology in optical communication transports multiple optical carrier signals on a single fibre using various wavelengths of laser light. Wavelength division multiplexing (WDM) is an efficient strategy for leveraging the wide bandwidth of optical fibres to meet the rapid rise in demand for bandwidth on the Internet. WDM plays an essential role in both core and access networks in the communication network and faces various issues like its network performance is affected due to QoT impairments, Dynamic Bandwidth Allocation problem, Modeling, and Monitoring issues. Physical impairments are an issue in WDM and can cause calls to be blocked if the transmission quality is calculated in terms of minimum bit-error-rate. Dynamic allocation of bandwidth in WDM provides a crucial challenge for the effective and equal usage of the passive optical network upstream bandwidth when supporting the QoS specifications of various traffic groups. Fast attack monitoring can prevent the failure of vast volumes of data on all-optical networks. So, monitoring and modeling in a WDM network is also a critical issue. To solve these issues in WDM networks, more intelligence resources in scalable optical networks are necessary. ML techniques are demonstrating superiority in solving these issues. In this paper, a small detail about the WDM network is presented. Then, some WDM issues like QOT impairments, Dynamic Bandwidth Allocation, and modeling and monitoring are discussed, and then, in the next section focus on some ML techniques for solving these issues are presented.

Double-trench assisted thirteen-core five-mode fibers with low crosstalk and low non-linearity

Information technology has an increasingly strong demand for high-speed and large-capacity optical fiber networks. Space division multiplex(SDM) is a new generation of optical fiber communication technology which can be several times in communication capacity higher than the wavelength division multiplexing systems. In this paper, we present a kind of 13-core 5-mode fiber with double trench structure to meet the demand for high-speed and large-capacity information transmission in the future. In order to solve the crosstalk problem in SDM, a double-trench structure is adopted to better limit the light energy in the fiber core, thus reducing the crosstalk between cores and modes. The crosstalk and transmission characteristics of multi-core fiber are calculated and analyzed by the full vector finite element method and coupled power theory. After the optimization of structural parameters, the fiber can stably transmit LP<sub>01</sub>, LP<sub>11</sub>, LP<sub>21</sub>, LP<sub>02</sub> and LP<sub>31</sub> in the band of 1.3–1.7 μm; when the signal is transmitted at the 1.55 μm for 60 km, the inter-core crosstalks corresponding to the adjacent fiber cores in the above five modes are –122.37 dB, –114.76 dB, –106.28 dB, –100.68 dB and –92.813 dB, respectively; the effective refractive index difference between adjacent modes is greater than 1.026 × 10<sup>–3</sup>; inter-core and inter-mode crosstalk can be effectively suppressed. The corresponding non-linear coefficients of the 5-modes are 0.74 W<sup>–1</sup>·km<sup>–1</sup>, 0.82 W<sup>–1</sup>·km<sup>–1</sup>, 0.88 W<sup>–1</sup>·km<sup>–1</sup>, 1.26 W<sup>–1</sup>·km<sup>–1</sup>, 0.93 W<sup>–1</sup>·km<sup>–1</sup>, which can maintain low non-linear transmission. The structure of fiber is simple and compact, and the preform can be fabricated by vapor deposition method and stack method, then the 13-core five-mode fiber with low crosstalk and low nonlinear can be further drawn, which can be used in a long distance high-speed and large-capacity fiber transmission system.

Evaluation and Analysis of Different Spectrum Slicing Techniques in Free Space Optical Systems

Free space optical communication systems are competent in the context of supporting high data rate, license free operation, absence of Electromagnetic interference (EMI), cost effective operation etc. Wavelength division multiplexed systems (WDM) provide high capacity but at the cost of multiple number of laser sources which inturn increase the overall cost of the system. Spectrum slicing is emerged as an optimal method to reduce the cost of the multi channel systems and also increase the performance. In this work, different spectrum slicing techniques such as Light emitting diodes (LEDs), Arrayed waveguide grating (AWG), Highly nonlinear fiber (HNLF), and Semiconductor optical amplifier (SOA) are used and compared in terms of Q factor and BER at 5 Gbps. It is perceived that SOA provide best performance followed by HNLF and LED is least performing.

Semi-Active Wavelength Division Multiplexing System Based on Pilot-Tone Relay Detection for 5G Centralized Front-Haul Network

A semi-active wavelength division multiplexing (WDM) system based on pilot-tone relay detection is proposed and experimentally demonstrated for 5G centralized front-haul network, which is composed of a passive WDM multiplexer at active antenna unit (AAU) side, an active WDM equipment at distributed unit (DU) side, and several WDM optical modules in AAU and DU, respectively. In this semi-active WDM scheme, WDM technology is applied as an optical transport layer to save fibers and the semi-active architecture based on pilot-tone modulation is capable of flexible deployment with lite operation, administration and maintenance (OAM) functions. The experimental results show that the sensitivity penalty is lower than 0.3 dB and the extinction ratio is still higher than 4.2 dB by using 4 % amplitude depth of pilot-tone modulation. The bit rate of the OAM signal is 1024 bps to reuse the existing micro-controller unit in the optical modules for generating and detecting OAM signals. The robustness of the pilot-tone signals is further demonstrated as the sensitivities of the 25-Gbps eCPRI signals and the 1024-bps OAM signals are −16 dBm and −23 dBm, respectively. Compared with the OAM demodulation both in upstream and downstream direction for the active WDM equipment, the number of OAM demodulation unit can be reduced by 50% and the sensitivity requirement of OAM demodulation can be improved by 11.5 dB by using only downstream OAM demodulation unit. Error-free 24-hour transmission of real-time 12-channel 25-Gbps eCPRI signals combined with 1024-bps pilot-tone OAM signals over 10-km single mode fiber is obtained.

Supervised regression modelling for mitigation of four-wave mixing in dense wavelength-division multiplexing systems

A recent global crisis associated with COVID-19 has encouraged millions of people to work from home, thus causing a drastic increase in overall network traffic, data-rate requirements and end network capabilities. This has also produced more noise, cross-talk and undesirable optical-fibre nonlinearities, especially a four-wave mixing (FWM) effect that deteriorates performance of dense wavelength-division multiplexing (DWDM) systems. A presence of FWM in the DWDM systems imposes increasing complexity and latency of networks, and decreases their spectral efficiency. In its turn, this degrades efficient utilization of optical bandwidth. To mitigate the above problems, we suggest a supervised regression modelling (SRM). A relevant SRM-DWDM approach performs self-parametric optimization of the DWDM systems with machine-learning techniques and finds real trade-offs among various factors that affect the FWM. Our model reduces complexity of modelling and computational time, resulting in accurate and reliable prediction of parameter values. We also evaluate the performance of our SRM-DWDM technique by comparing its data with the iterative results obtained for different parameters (e.g., output signal-to-noise ratio, Q-factor, signal power and noise power). Finally, we specify the procedures necessary for global optimization of DWDM systems

Design and simulation of polarization-insensitive ring resonator based on subwavelength grating and sandwiched structure

Ring resonator fabricated on a silicon-on-insulator is versatile in optical integration, which can be used to realize filters, modulators and switches. However, silicon-on-insulator is difficult to control the polarization dependence, and thus its application is greatly limited. The polarization dependence of the ring resonator is caused mainly by two factors: the coupling coefficients of the coupling region at the same wavelength for the two orthogonal polarization modes are different, and the birefringence effect of curved waveguide results in the different resonant wavelengths of TE and TM polarization modes. When the coupling region polarization independence and the resonant wavelength polarization independence are simultaneously satisfied, the polarization independence of the ring resonator can be realized. In this paper, a new type of polarization-insensitive ring resonator on a silicon-on-insulator is designed based on subwavelength grating and sandwiched structure. Firstly, by adjusting the duty cycle of the subwavelength grating and the refractive index of SiN<i><sub>x</sub></i> in the coupling region, polarization independence of the coupling region is achieved. Secondly, the refractive index of SiN<i><sub>x</sub></i> in curved waveguides is designed to make the resonance wavelengths for orthogonal polarization modes equal. Thirdly, the parameters of the coupling region are optimized to reduce the insertion loss. The three-dimensional finite-difference time-domain method is used for simulation. The results show that the radius of the ring is only 10 μm, the 3-dB bandwidth of the device is less than 0.8 nm, and the insertion loss is lower than 0.8 dB. It has potential applications in the future dense wavelength division multiplexing systems.

Optical performances analysis and structure parameters optimization design of dense arrayed waveguide grating

The core device of dense wavelength division multiplexing (DWDM) system is a wavelength division multiplexer/demultiplexer, among which the arrayed waveguide grating (AWG) device has the most superior optical performances. The optical performances of AWG are mainly affected by the structure parameters such as the waveguide spacing, the width and length of the tapered waveguide and the number of arrayed waveguides. Taking the 40-channel AWG as the research object, by combining theory with simulation, this paper analyzed the influence mechanisms and laws of AWG structure parameters on its optical performances including insertion loss, loss non-uniformity, adjacent crosstalk, and 3 dB bandwidth. Then, the sensitivities analysis of AWG optical performance was carried out by using the direct derivation method and the finite difference method in the sensitivities analysis method, so as to obtain the influence degree of each structure parameter on the optical performances. Finally, based on the influence rules and sensitivities of structure parameters on optical performances, this paper adopted some methods to optimize the structure parameters of AWG, and optimized the insertion loss, loss non-uniformity, adjacent crosstalk, and 3 dB bandwidth to about 1 dB, 0.35 dB, −30 dB, and 0.42 nm, respectively. The research methods and conclusions of this paper can provide references for the optimization of optical performances and layout design of other types of AWG.

Inter-Channel Fiber Nonlinearity Mitigation in High Baud-Rate Optical Communication Systems

Kerr nonlinearity in long distance fiber-optic link imposes a fundamental limitation to the capacity of wavelength division multiplexed (WDM) optical communication systems. Solving the inverse-propagating nonlinear Schrodinger equation (NLSE) is in principle a fundamental methodology to mitigate fiber nonlinear impairments. However, solving multi-channel coupled NLSE is too complexed to be implemented commercially. It is of great importance to compensate for nonlinear distortions in high baud-rate WDM systems based on the information of one single target channel. In this article, we experimentally study fiber nonlinearity mitigation in an 8 × 512 Gb/s (64Gbaud) polarization division multiplexed (PDM) 16-ary quadrature amplitude modulation (16-QAM) Nyquist-WDM system with 960 km standard single mode fiber (SSMF) loop transmission. The digital back-propagation (DBP) algorithm based on the target channel is applied, which can compensate for intra-channel nonlinearity. The inter-channel nonlinearity of cross phase modulation (XPM) induces nonlinear polarization scattering and nonlinear phase noise, which are partially correlated over adjacent pulses in high baud-rate systems. We propose an advanced nonlinear polarization crosstalk canceller (NPCC) with a novel decision feedback (DF) update strategy that is called the DF-NPCC, which incorporates the iterative process of the least mean square (LMS) algorithm and can thus mitigate the correlated nonlinear polarization crosstalk and nonlinear phase noise. Through nonlinearity mitigation, the DBP together with the DF-NPCC can achieve a 0.77 dB Q2 factor promotion. The DF-NPCC can suppress the remaining nonlinear distortions after the single channel DBP, which corresponds to a 0.36 dB Q2 factor improvement due to inter-channel nonlinear mitigation. Our work indicates XPM distortions can be mitigated with low complexity digital signal processing such as the DF-NPCC based on the single channel information, which provides an attractive solution to compensate inter-channel fiber nonlinearity in high baud-rate Nyquist-WDM systems.

Programmable High-Resolution Spectral Processor in C-band Enabled by Low-Cost Compact Light Paths

The flexible photonics spectral processor (PSP) is an indispensable element for elastic optical transmission networks that adopt wavelength division multiplexing (WDM) technology. The resolution and system cost are two vital metrics when developing a PSP. In this paper, a high-resolution 1 × 6 programmable PSP is investigated and experimentally demonstrated by using low-cost compact spatial light paths, which is enabled by a 2 K (1080p) liquid crystal on silicon (LCoS) and two cascaded transmission gratings with a 1000 line/mm resolution. For each wavelength channel, the filtering bandwidth and power attenuation can be manipulated independently. The total insertion loss (IL) for six ports is in the range of 5.9~9.4 dB over the full C-band. The achieved 3-dB bandwidths are able to adjust from 6.2 GHz to 5 THz. Furthermore, multiple system experiments utilizing the proposed PSP, such as flexible spectral shaping and optical frequency comb generation, are carried out to validate the feasibility for the WDM systems.

Mitigation of non-linear four-wave mixing phenomenon in a fully optical communication system

This paper aims to point out the nonlinear phenomenon occurring in coarse/dense wavelength division multiplex (C/D-WDM) systems. This phenomenon has to betaken into account during the design of the optical network itself, as wavelengthsin the optical fiber are constantly densified. The paper points out the emergence of the non-linear four-wave mixing (FWM) phenomenonand how it relates to the dispersion in the optical fiber together with the transmit power. The output of the paper is a proposed design of the system that points to the improvement of the bit error rate (BER) with a suitable choice of dispersion and suitable transmission power.