In this paper, a cascaded fiber Bragg grating (FBG) system is proposed to reduce the dispersion in the optical signal in single mode optical fibers. This consequently enhances the system performance, which is evaluated by the bit error rate (BER) and quality factor (Q-factor). The proposed model consists of four uniform cascaded FBGs connected at the transmitter to get narrow linewidth, Δλ, of the optical signal, which is a major cause of the delay. The Optisystem7 is used to simulate the proposed model in a WDM system with and without the model for distance 200 km. The system parameters are investigated showing an enhanced performance with 12%, including eye diagram, Q-factor and BER. A 10−6–10−10 BER is achieved with a quality factor in the range 7–14, including the effects of fiber length, input power and FBG length.

An enhanced WDM optical communication system using a cascaded fiber Bragg grating

Abstract The fundamental issue limiting long-distance and high-speed optical fiber transmission is dispersion. Dispersion impairs system performance, the signal-to-noise ratio (SNR), and the bit error rate (BER). To address this, numerous dispersion modification techniques have been developed. The use of fiber Bragg grating (FBG) is one of the efficient strategies for dispersion compensation. The FBG is frequently used as a filter. The proposed model uses uniform fiber Bragg grating UFBG. Two cascaded FBGs with varying lengths, a constant grating period, and a constant spacing between FBGs are employed in the proposed thesis. The input signal for the stage that follows is the output signal from the previous stage. The best performance and many applications are considered while modeling, analyzing, and comparing this system. Transmission and reflection in two cascaded stages of fiber Bragg grating using first and second order are studied. The mathematical equations for the proposed model are simulated in MATLAB. 

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Design of multistage FBG with variable filter parameters

/pdf/analytic-model-for-the-transmission-and-reflection-in-two-iqevvgwy.pdf

Analytic model for the transmission and reflection in two cascaded stages of fiber Bragg grating

Abstract The fundamental issue limiting long-distance and high-speed optical fiber transmission is dispersion. Dispersion impairs system performance, the signal-to-noise ratio (SNR), and the bit error rate (BER). To address this, numerous dispersion modification techniques have been developed. The use of fiber Bragg grating (FBG) is one of the efficient strategies for dispersion compensation. The FBG is frequently used as a filter. 

/pdf/analytic-model-for-the-transmission-and-reflection-in-two-3v78de8c.pdf

Abstract Dispersion is the main problem that limits long-distance and high-speed optical fiber transmission. Bit error rate, the signal-to-noise ratio, and system performance all suffer from dispersion. Many dispersion adjustment strategies have been created to combat this. One of the effective methods for compensating for dispersion is the usage of fiber Bragg grating (FBG). In the suggested thesis, cascaded uniform fiber Bragg grating (UFBGs) with various lengths, a constant grating period, and a constant gap between FBGs are used. This system is modeled, analyzed, and compared for the best performance and different applications. The control parameters affecting the system are the coupling coefficient, number of FBGs, grating period, and the number of grating periods. The control parameters for this system are studied to compensate for the effect of dispersion. A trade-off between increasing bandwidth and roll-off factor. Another trade-off between flatness and roll-off factor. These trade-offs can be considered according to applications. MATLAB is used to simulate the mathematical equations for the suggested model. 

/pdf/design-of-multistage-fbg-with-variable-filter-parameters-hb396849.pdf

Objectives: WDM systems are high-performance systems. Light signals can be transmitted to longer distances by using WDM systems. The efficiency of light signals is reduced by optical effects such as dispersion and attenuation. Attenuation can be reduced by using powerful optical amplifiers. Dispersion causes errors in optical communication systems. So dispersion has to be minimized to obtain better performance of WDM systems. This paper analyzes the different types of dispersion compensation techniques that can be used in WDM Systems to minimize dispersion. Methods/Statistical analysis: In dispersion compensation technique, dispersion compensation fiber (DCF) is placed at different positions of optical fiber to reduce dispersion. The negative dispersion in DCF removes the dispersion in SMF. The three dispersion compensation techniques pre-compensation, post-compensation, and symmetric compensation techniques are analyzed with Optisystem. The structure of FBG also helps to compensate dispersion in optical systems. Dispersion compensation by FBG is also analyzed with Optisystem. Findings: Pre-compensation technique shows good performance for very shorter distances. Performance of pre-compensation is reduced for long distances. Post-compensation also do not show good quality factor for longer distances. Symmetric compensation shows the best performance and quality factor for longer distances and is the best method out of the three compensation techniques. FBG also compensates the dispersion very effectively in long-distance communication. Application/Improvements: Symmetric compensation is the best technique to reduce dispersion in all three dispersion compensation techniques. By using FBG, dispersion can be reduced effectively. These methods can be used in WDM systems to minimize errors and to improve performance.

Analysis of Dispersion Compensation Methods in WDM Systems

In this study, we employed a non-invasive approach based on the collisional radiative (CR) model and optical emission spectroscopy (OES) measurements for the characterization of gas tungsten arc welding (GTAW) discharge and quantification of Zn-induced porosity during the GTAW process of Fe–Al joints. The OES measurements were recorded as a function of weld current, welding speed, and input waveform. The OES measurements revealed significant line emissions from Zn-I in 460–640 nm and Ar-I in 680–800 nm wavelength ranges in all experimental settings. The OES coupled CR model approach for Zn-I line emission enabled the simultaneous determination of both essential discharge parameters i.e. electron temperature and electron density. Further, these predictions were used to estimate the Zn-induced porosity using OES-actinometry on Zn-I emission lines using Ar as actinometer gas. The OES-actinometry results were in good agreement with porosity data derived from an independent approach, i.e. x-ray radiography images. The current study shows that OES-based techniques can provide an efficient route for real-time monitoring of weld quality and estimate porosity during the GTAW process of dissimilar metal joints.

S. Sesha Sai Srikar

Papers

Analysis of Dispersion Compensation Methods in WDM Systems

Non-invasive optical characterization and estimation of Zn porosity in gas tungsten arc welding of Fe–Al joints using CR model and OES measurements