The optimal TDFA length is also calculated and the parameters are compared with existing state-of-the-art EDFAs. It summarizes and compares the results obtained through simulation in Simulink with that of.
Optical Communication Wavelengths
The lowest attenuation of optical signal in the C-band motivated the optical scientists and engineers in the development of optical fiber operation in this band. Extending gain bandwidth from the narrow C-band "Erbium-Window" to L-band has been a subject of research in the recent past to meet the need for bandwidth demand.
Fiber-Optic Communication System
It is one of the crucial parts of a fiber optic communication system to improve the overall system performance. Therefore, signal recovery is an important aspect for the optical system designers to manage the BER value to an acceptable limit of the fiber optic communication system.
Advantages and Applications of Fiber-Optic Communication System
Depending on the type of modulation scheme, the demodulation format is designed in the fiber optic communication system. In addition, the low power requirements of the fiber optic communication system further optimize operating costs in the long run.
Dopant based Classification of RE-DFAs
As a result, the pump absorption and signal emission transitions involve the energy levels from 4F3/2 ↔4I9/2, 11/2, as shown in Fig. The process is allowed by inter-system energy transfer mechanism between ligand and Europium (Eu3+) chelate as shown in Fig. The graphical illustration regarding the latest achieved power levels for fiber optic lasers and amplifiers is shown in Fig.
Applications of TDFAs
The emission bands at ~ 2 µm and ~ 3 µm can be effectively used in human tissue ablation and welding. This aspect of TDFAs can be used as a tool for semiconductor wafer processing and add an application in the fields of research and industry. The importance of TDFAs in the field of military defense can be observed in the infrared-guided missile countermeasure applications.
Working Mechanism of TDFAs in S and near-C bands
Research Motivation and the Problem Formulation
However, research has been done on shifting the S-band gain more towards the near-C-band to achieve better synchronization with the existing 1550 nm EDFA's C-band gain [163]. the input signal is over-modulated with some distortions. Similar analysis should be performed for TDFAs operating in S and near-C bands to ensure its in-situ applicability with EDFAs for increasing data rates. Exclusive analysis for loss factor and non-linear parameter effect should be regarded as an essential part and planned to be performed. iii).
Thesis Contribution
The feasibility of the optical pulse train is observed by simulation through the developed model on the OptiSystem® simulator.
Thesis Overview
Related mathematical modeling and simulation studies related to the utility of TDFAs in current infrastructure as presented in the literature. A comparison of loss effects and non-linear effects is shown with respect to the lossless case corresponding to the integrated gain and interference frequency. A special case, considering the practical scenario, has been solved and presented numerically when perturbations become comparable to the input signal amplitude.
Introduction
S-band and near-C TDFA operation can be used with existing C-band EDFAs to increase the capacity of an optical fiber system by nearly a factor of four. This can be an additional application of TDFA in hybrid EDFA-TDFA fiber optic communication systems in addition to conventional S-band and near-C band communication. This chapter provides a brief overview of the main components of S-band and near-C TDFA, followed by a discussion of studies on the above mentioned new researches mentioned in the literature.
Main Components of S and near-C band TDFAs
One of the most important and frequently used insulators in optical communication systems is the Faraday insulator [222,223]. The percentage output power of the corresponding port is mentioned on the right vertical axis. the output is determined using coupled mode theory. The geometric parameters of the coupling region and the selection of the input signal wavelength play an important role in the output power division ratio as shown in Figure iii) Passive fiber: the input-output signal together with the optical pump travels in a passive silicon fiber that is coupled to the TDFA with other corresponding essential components.
Literature Survey
However, the analysis does not include the effects of the ASEs on the system's performance. A summary of the overmodulation of signal gain dynamics in RE-DFAs discussed in this section is given in the Table 2.1. The configuration of the setup is in a ring shape with dual mode locking mechanisms as shown in the graphical summary of Fig.
Summary
TTDP represented as a function of dopant radius, profile roll-off factor and the radial position of the profile peak.
Introduction
As a result, dynamic modulation of the input signal has also been found to strongly influence the TDFA gain characteristics [253]. Optical filtering at different network nodes can dynamically transform the ASE spectrum to irregular levels depending on the operating wavelength. As a result, signal information may be corrupted if the ASE level becomes comparable to the signal level.
Analytical Model
Ignoring the scattering losses, the photon progression in the fiber along its length can be defined as This is required to represent N3(t) and N1(t) around their respective mean (unmodulated) steady-state solutions, which can be denoted as . Using the steady-state expression of (3.38) in (3.56), the modified expression can be written as.
Simulink Pedestal for TDFAs
Equations (3.64) and (3.65) are used to find the amplitude and phase characteristics of the output signal represented by (3.61). The dynamics of the energy levels with the corresponding population densities 3H4(N3) and 3F4(N1) are implemented on a Simulink model using (3.36) and (3.36). From the cascaded network of TDFAs in a fiber optic communication system, a single unit of the dynamics of TDFA is shown in Fig.
Results and Discussions
The modulation index of the input signal at the output was modified by the modulation frequency in expression (3.64). The variation of the modulation index of the output signal at different power levels of the input signal can be observed in the figure. As the input signal power is further increased, the output modulation index drops to zero, which can actually be seen in the figure.
Summary
Introduction
The non-linearity is caused by the doping concentration of ions in the optical fiber, which produces variations in the non-linear refractive index. As a result, lossy and nonlinear analysis for TDFAs and its comparison with its lossless counterpart becomes a significant factor to consider the viability of deploying it in the existing fiber optic communication network. In this chapter, the loss and non-linear factor effects on the behavior of MI in TDFAs operating in S- and near-C bands are observed.
Analytical Model
The longitudinal propagation of the field along the length of the fiber can be given by NLSE as in [256] which included the loss factor termα given as (4.1). By substituting (4.6) in (4.1), linearizing in and b, we get a set of coupled differential equations given as. 4.9) where (a0,b0) follows the slowly varying envelope condition, Ω is the interference frequency and K(z) is the wave number expressed as a function of space due to the gain characteristics of the signal while traversing within TDFA. The total gain of the perturbations, also called integrated gain F(Ω), can then be obtained by integrating the imaginary part of (4.10) along the length of the TDFA L, given as.
Results and Discussions
Similarly, from Fig.4.6 the other TDFA threshold lengths (L0) are calculated for various signal strengths for which the model followed the desired results. For example, at input signal power of 250 mW, a drop of 45 dB in maximum integrated gain was observed when lossless and lossless TDFA. The loss-factor effect for the fixed input signal power (P0 = 150 mW) is shown in Fig.
Summary
Introduction
The influence of the nonlinear fiber length is also reflected in the model results. The governing equations are solved numerically in MatLab® and the results are verified by including similar conditions on the OptiSystem® simulation test bench. The results conclude the findings on the optimal non-linear length (LNL) and the pulse-chirp parameter (C).
Mathematical Model
The optical pulse propagation in a single-mode heavily doped Tm3+ fiber amplifier can be described by nonlinear Schrödinger equation (NLSE) followed by slowly varying envelope [234]. The nonlinear parameter (γ) mentioned in (5.1) can be written as γ = 2πn2/λae f f with ae f f and λ as the effective mode area of the core of the TDFA and the signal wavelength (1460 nm), respectively. The corresponding spread and non-linear lengths of the TDFA are defined as LD and LNL which are given below as.
Simulation Setup
Its graphical user interface (GUI) controls the placement of optical components from its extensive and comprehensive library. Optimization can be easily performed by sweeping the parametric variables of the designed system [281]. Consequently, this simulation setup, as shown in Figure 5.2, is assigned the system parameters given in Table 5.1.
Results and Discussions
Apparently, the GVD effect on frequency spectrum spread is mainly observed in super-Gaussian pulses as shown in Fig.5.5 (g)-(i) making it unsuitable for long distance fiber optic communication systems. The results obtained from Fig.5.4 and Fig.5.5 give the optimal values of Nl and C for heavily doped Tm3+ fiber amplifiers to invoke the MI phenomenon and thus pulse compression. The image matrix shown in Fig.5.6 shows the variation of optical pulses with respect to nonlinear fiber lengths (L =0.5LD, 0.8LD and 1.0LD) keeping Nl = 12 and C = 12 as fixed parameters.
Summary
At 375 m TDFA length from the input end, the MI effect was initiated to produce a 4 ps, 500 MHz spaced pulse train, each with 8 nJ energy at a wavelength of 1460 nm. The effect of MI was considered to obtain 4 ps, 500 MHz spread pulses with 8 nJ energy each in the pulse train at a wavelength of 1460 nm. As this analysis dealt with heavily doped TDFAs, other ion-ion interaction effects may therefore also occur, requiring a deeper analysis, as presented in the next chapter of this thesis.
Introduction
These rates of inter-ionic interactions strongly depend on the distance between them and therefore the PIQ effect is more dominant over HUC. In this chapter, the constructive aspect of the IM effect with HUC and PIQ is studied in TDFA. The design parameters of the TDFA are studied by performing simulations based on the implementation of the mathematical model on the MatLab® and OptiSystem® platforms.
Mathematical Model
The cluster size of Tm3+ ions and the number of ions per cluster is held constant [244]. v) The absorption and emission CSAs must be the same for the clustered and the single ion. The doping profile plays a crucial role in determining the odds of occurrence of the IM effects. The shape of the doping profile, indicating its relative shift from the fiber axis and the slope of the profile, is defined.
Simulation Setup
With m > 3, the process becomes less likely than the single ion and two particle set.
Results and Discussions
Obviously, a constructive effect of IM was observed with respect to the optimal pump power corresponding to the maximum gain conditions. The noise value relative to the maximum gain conditions for both cases was found in the direction. 6.10: (a) IM effect on doping concentration for fixed radius Tm3+doping versus TDFA length and signal gain. b) shows a magnified section to observe optimal TDFA lengths.
Summary
