# Optimal Analysis of 40 Gbps Dispersion Compensated Optical Fiber System +
###### Abstract  
Dispersion is one of the main factors that limit the development of optical fiber communication systems regarding data rate and long distance transmission of the signal. This is because of increases in dispersion with the increase in data rate and distance, resulting in signal degradation. In this work, we propose an optimal dispersion compensated optical fiber system, which is designed on the basis of Q-factor, eye height, and bit error rate. The system operates at a bit rate of 40 Gbps and a distance of 100 km. According to the optimization scheme, the system is simulated using the modulation format Non Return to Zero (NRZ) with uniform and Linear Chirped Apodized Fiber Bragg Grating (LCAFBG) as dispersion compensator. After deciding the Fiber Bragg Grating (FBG) structure, other key parameters are simulated to meet the requirements. The simulation results show that using NRZ modulation format with a LCAFBG Tanh profile gives better performance.  
dispersion; optimal; chirped; apodized; fiber bragg grating (FBG); non return to zero (NRZ); linear chirped apodized fiber bragg grating (LCAFBG) +
Footnote †: Copyright © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([[https://creativecommons.org/licenses/by/](https://creativecommons.org/licenses/by/)]([https://creativecommons.org/licenses/by/](https://creativecommons.org/licenses/by/))).  
Footnote †: Copyright © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([[https://creativecommons.org/licenses/](https://creativecommons.org/licenses/)]([https://creativecommons.org/licenses/](https://creativecommons.org/licenses/))).  
Footnote †: Copyright © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([[https://creativecommons.org/licenses/by/](https://creativecommons.org/licenses/by/)]([https://creativecommons.org/licenses/by/](https://creativecommons.org/licenses/by/))).  
Footnote †: Copyright © 2021 by the authors. Licensee MDPI, BaselA severe limitation faced by engineers is the fiber chromatic dispersion in long-distance optical transmission systems. The fiber chromatic dispersion is directly proportional to the fiber transmission length, resulting in an unendurable amount of distortion that eventually leads to errors. Therefore, it is compulsory to use dispersion compensator devices to reduce unwanted distortion [4]. The simple optical communication system comprises transmitters, optical fibers, and receivers.  
Optical amplifiers are used to transmit terabits of data over long distances by overcoming the fiber loss limitation to longer distances. The deployment of a Wavelength Division Multiplexing (WDM) system boosts the capacity, which requires an EDFA optical amplifier [5]. The core concept in EDFA technology is the use of silica fiber doped with erbium. Another element used to compensate dispersion is a Fiber Bragg Grating (FBG) filter device. FBG is applied for removing dispersion and used as an economical filter for wavelength selection [6]. The FBG is able to reflect specific wavelengths because of recurring variations in Refractive Index (RI) of fiber core.  
The major factors that determines the quality of the communication system depends on formatting of codes and modulation of the signal. The modulated signal is added with an external electrical signal; for this purpose, the two most used RZ and NRZ modulation techniques are used [7]. The modulated signal is transmitted to the receiver through single-mode fiber SMF.