Design Of Erbium-doped Fiber Amplifiers Research Articles

Design of EDFA based 16 channel WDM system using counter directional high pump power

Abstract In this paper, design of erbium-doped fiber amplifiers (EDFA) based 16 channel wavelength-division multiplexing (WDM) system for different pump powers and input signal levels using counter propagating pumping scheme is reported. Wavelength range between 1548 and 1560 nm in C-band with channel spacing of 0.75 nm at a bit rate of 10 Gbps are used. Input power given to all the channels is taken between −20 and −35 dBm with 3 dBm variation. Pump power levels between 100 and 500 mW at 980 nm wavelength are used. Low gain flatness with high gains and low noise figures are achieved with the proposed scheme.

Analytical method for few-mode erbium doped fiber amplifiers

An analytical method for few-mode erbium doped fiber amplifiers (EDFAs) is proposed by introducing the uniformity coefficient of population inversion. The validity of the derivation process of the analytical method is identified by the numerical method. It is shown that the more uniform the transverse distribution of erbium ion population density at the metastable level, the closer the analytical solution is to the numerical result. The optimized uniformity coefficient is also applied to the case of varying pump power to some extent. The analytical method is especially suitable for the design of the gain-saturated EDFAs.

Rigorous and optimized few-mode erbium-doped fiber amplifier design by using topology optimization and genetic algorithms

We develop a rigorous procedure for the optimum design of few-mode erbium (Er)-doped fiber amplifiers, which is tackled as a multiobjective optimization problem, in an approach based on the combination of the topology optimization and genetic algorithm techniques. We demonstrated that the usual ring-like doping distributions are necessarily the best choices only if the pump intensity shows no azimuthal dependence. Additionally, in general, the optimum doping distribution will be a function of the signal and pump azimuthal mode numbers. For the particular case of the LP11 pump, we also provide a triple-ring Er-doping profile that maximizes modal equalization for seven-group modes over the whole C-band, the highest modal count proposed in the literature so far.

Few-mode erbium-doped fiber amplifier design method based on the signal-pump overlap integral

Space-division multiplexing allows an increase of link capacity by using either multicore or single-core few-mode (FM) optical fibers. In the case of FM systems, each mode carries its own data stream and long-haul transmission can be hampered by the use of conventional erbium-doped fiber amplifiers (EDFAs), since because of distinct field profile configurations, each mode experiences a different value of optical gain. The role of the FM-EDFA designer, usually done by solving rate and propagation equations, is to define both the fiber cross-section and the pumping configuration to provide the best possible mode equalization of optical gain and noise figure. An optimization method is proposed here based on the definition of a figure of merit related to the equalization of the pump-mode signal overlap integral, significantly reducing computation time and allowing a multiobjective optimization approach. The results obtained were validated against the solution provided by the full set of rate and propagation equations and we conducted an FM-EDFA optimization case study. Our double-ring Er doping profile design requires a single 180-mW LP11 pump to provide a mean gain of 21.3 dB, within 0.6 dB of equalization for each of the four modes considered.

Unrepeatered Transmission of 6.3 Tb/s ( \(63 \times 128\) Gb/s) Over 402-km Fiber Link

We demonstrated 6.3-Tb/s (63 × 128 Gb/s) unrepeatered transmission over 402-km fiber link. This was achieved by employing a high-power Yb-free clad-pumped L-band erbium-doped fiber amplifier (EDFA) as a booster amplifier in the transmitter station, a combination of ultralarge-area fiber, low loss and zero-water-peak loss fibers, and a remote optically pumped amplifier (ROPA), which was counter-propagating second-order Raman pumped from receiver station. This letter also describes the design and characteristics of Yb-free cladpumped L-band EDFA, and discusses the system performance optimization of ROPA and Raman impact on large capacity long reach unrepeatered transmission.

Analysis of Augmented Gain EDFA Systems using Single and Multi-wavelength Sources

The scope of this paper is to analyze the performance of augmented gain EDFA systems using Single and Multiwavelength Input sources. The Performance of an Optical Communication system can be improved by the use of EDFAs as an Optical Amplifier. Erbium doped fiber amplifier (EDFA) is an important element in DWDM networks. We can achieve a flat gain spectrum by modeling the dynamic characteristics of an EDFA. This paper presents basic EDFA model operating on single (1550nm) and multi (1520-1610) nm wavelength operation with their simulation results. For the present work, we have used EDFA design software tool. It simulates various characteristics such as amplified spontaneous emission, gain, noise figure etc. in efficient manner. The working principle of this software provides accurate simulations and results. It confirms the excellent agreement between simulations and results obtained in real EDFA design. The proposed model consists of an input source, isolator, pump source, erbium fiber and WDM coupler. By changing the design parameters such as Input signal power and Pump Power, the different performance parameters (gain and noise figure) can be optimized. Without changing the values of isolator, erbium fiber length and WDM coupler and keeping the values of Input signal power -30dBm and Pump Power 80mW the obtained optimized gain is 34.45dB for single wavelength source and 32.924 dB for multi wavelength source. General Terms Spectrum, Networks, Multiplexing.

Optical characterization, 1.5 μm emission and IR-to-visible energy upconversion in Er 3+-doped fluorotellurite glasses

The optical properties of Er 3+ ions in a novel glass based on TeO 2–PbF 2–AlF 3 oxyfluoride tellurites have been investigated using steady-state and time-resolved spectroscopies as a function of the rare-earth doping concentration. Basic optical characterizations have been performed measuring and calculating the absorption and emission spectra and the cross-sections, the Judd–Ofelt intensity parameters, the radiative probabilities and the fluorescence decays and lifetimes. Special attention has been devoted to the broad 4I 13/2→ 4I 15/2 emission transition at around 1.53 μm since, with a wide broadening of around 70 nm and a relative long lifetime of around 3 ms compared to others glass hosts, it shows potential applications in the design of erbium-doped fiber amplifiers. The absorption, the stimulated emission and the gain cross-sections of this transition have been obtained and compared with that obtained in different hosts. Finally, infrared-to-visible upconversion processes exciting at around 800 nm have been analyzed and different mechanisms involved in the energy conversion have been proposed.

Temperature independent length optimization of L-band EDFAs providing flat gain

In this study, single stage (SS), double-stage (DS), and gain flattened (GF) DS L-band erbium-doped fiber amplifier (EDFA) configurations are designed in order to obtain a flat gain amplifier. Temperature dependence of the mentioned configurations is also analyzed. Maximum spectral dependence of EDFA gain with respect to temperature is obtained for SS EDFA design while smaller spectral dependence of gains is obtained for both DS and GF DS L-EDFA configurations. It is observed that the maximum temperature dependence is in the range of 1570–1580 nm band for all configurations. It has also been found that for all configurations, reducing the temperature has greater effect than raising the temperature on EDFA gain. The overall results show that a temperature independent L-band configuration has not been possible. However, for some signal wavelengths, the erbium-doped fiber (EDF) lengths at which the gain is temperature independent are observed.

Design optimization of erbium-doped fiber amplifiers using artificial neural networks

An artificial neural network (ANN)-based model for erbium-doped fiber amplifiers (EDFAs) is developed. For a network with two input neurons and a single hidden layer, the number of neurons in the hidden layers is optimized by monitoring the mean square error (MSE) at the outputs. The model is used to optimize the design of EDFAs for central signal gain, 3-dB bandwidth, and noise factors, taking into account the influence of amplifier constructional parameters in the amplifier performance. For a given pump power and pulse width that correspond to the two input neurons, the model computes the constructional parameters to obtain values of central signal gain, 3-dB bandwidth, and noise figures in optimal range. The effects due to intrapulse stimulated Raman scattering (ISRS) are also considered by varying pulse widths from subpicosecond regime to hundreds of picoseconds. Self frequency shift due to ISRS is found to be prominent in the subpicosecond regime. The proposed model generates results with a MSE of 1×10 -4 , and needs relatively very low computational time compared to other analytical models.

Gain enhancement in L-band loop EDFA through C-band signal injection

Gain enhancement provided in L-band erbium-doped fiber amplifier (EDFA) with loop configuration and through C-band signal injection is experimentally demonstrated and compared with conventional single-stage L-band EDFA design. Significant backward amplified spontaneous emission suppression in C-band and pump conversion efficiency increase in L-band were observed for varying C-band seed signal wavelength and power levels. Gain and noise figure (NF) performance of loop design L-EDFA is compared with the conventional bidirectionally pumped single-stage L-EDFA design. Gain and NF measurements in the loop configuration have resulted in an up to 9.5-dB increase in gain and up to 2.6-dB degradation in NF at a moderate signal wavelength of 1585 nm.

Application of preemphasis to achieve flat output OSNR in time-varying channels in cascaded EDFAs without equalization

In this paper, we present a new method for optical signal-to-noise ratio (OSNR) equalization of wavelength division multiplexed (WDM) channels at the end of a cascade of several erbium-doped fiber amplifiers (EDFAs) by use of preemphasis, as well as the proper choice of EDFA design parameters. Identical OSNR at the end of the cascade ensures better signal detection and quality of service. The dynamics of the equalizing method have been demonstrated by simulation for single- and double-stage amplifier designs using a numerical model incorporating time variation effects in EDFA. Calculations are based on the solution of a transcendental equation describing the dynamics of the reservoir, i.e., the total number of excited ions, for each EDFA. Traffic on eight WDM channels is modeled as statistically independent ON-OFF time-slotted sources. In addition, we investigate the effect of gain clamping of the first amplifier in the cascade-by implementing a ring laser and propagating the lasing power through the cascade-on the statistics of OSNR variation. We show that it is possible to achieve dynamic OSNR equalization for a WDM system by the use of preemphasis and an appropriate choice of EDFA parameters, without resorting to optical equalization filters. Most previous equalization methods are static with flat gain for a given inversion level in the amplifier. Changes in the input power (due to network reconfiguration or packetized traffic) will lead to a varying inversion level and hence non optimal equalization.

Optical channel upgradability of multiwavelength erbium-doped fiber amplifier for hybrid digital/analog dense wavelength-division-multiplexing systems

We investigate theoretically the impact of optical channel upgradability on the design of erbium-doped fiber amplifier (EDFA), in terms of guard band, channel number and input signal power level for simultaneously amplifying amplitude-modulated vestigial-sideband analog cable television signal and multiple optical digital baseband signals in hybrid dense wavelength-division-multiplexing (H-DWDM) systems. The single-staged forward and backward bidirectional pumping scheme for EDFA without using any inter-staged components is adopted because it is the best amplifier configuration to offer the highest output power with fairly low noise figure and highly satisfied carrier-to-noise ratio performance. In this work, we define the guard band Δλ GB as the channel spacing between the analog channel and the nearest digital channel. We find that various guard bands (Δλ GB =6.45–1.61 nm) do not affect the noise figure (3.36–3.38 dB) and channel gain variation (ΔG D =0.12–0.13 dB) . However, the channel number (10–32, Δλ D =0.8 nm) influences the gain variations (ΔG D =0.12–3.62 dB) evidently. The gain variation of H-DWDM EDFA for a launched 10, 16, 20 and 24 digital channels is 0.12, 0.65, 0.71 and 0.74 dB, respectively, but that for 28 and 32 digital channels is degraded to 2.47 and 3.95 dB, respectively, because the left-most digital channel is very close to the 1530 nm spectrum so as to degrade the gain flattening. This degradation can be improved by shifting the digital channels away from the 1530 nm band.

Optimum configuration and design of 1480-nm pumped L-band gain-flattened EDFA using conventional erbium-doped fiber

We theoretically investigate optimum configurations of 1480-pumped L-band (1570–1610 nm) gain-flattened erbium-doped fiber amplifier (EDFA), using conventional erbium-doped fiber, for multi-wavelength wavelength division multiplexing (WDM) systems. The design criterion of L-band EDFA is to achieve the highest channel output power while keeping the differential channel output power to be ≤0.7 dB among 32 digital baseband channels with low channel noise figure of ≤5.5 dB. A total of nine L-band EDFA configurations are examined and compared. These configurations considered include the dual-forward, dual-backward, and different bi-directional pumping schemes, each with and without the midway optical isolator. Among all configurations, we find that the pump-passed case in forward-and-backward pumping scheme is the best amplifier configuration to offer the highest channel output power with good channel gain uniformity and moderate low noise figure. In addition, the tolerance of the ratio of first-staged EDF length to the total EDF length, and the effects of optical isolation of midway isolator, and pump power degradation on the characteristics of the best configuration are also examined. This investigation provides the EDFA configuration selection for multi-wavelength WDM L-band lightwave systems.

A novel wideband erbium-doped fiber amplifier design

A novel wideband erbium-doped fiber amplifier utilizing a bidirectional amplification of conventional- and long-wavelength band signals is presented. Amplification of a four-channel wavelength-division multiplexing system (two channels for each band) is successfully demonstrated, with an average gain of 20 dB and a noise figure less than 7.5 dB. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 268–269, 2000.

Analysis of dual-stage erbium-doped fibre amplifiers with passive equalisation filters

The gain and noise properties of dual-stage gain flattened erbium doped fibre amplifiers (EDFA) are analysed. Simple expressions are derived to aid the design and understanding of the dual-stage EDFAs. Simulation is carried out to determine the behaviour of EDFAs when subject to different operating parameters. It is found that a dual-stage EDFA incorporating an equalisation filter, variable attenuator and gain control makes it ideal for use as an on-line optical amplifier in WDM networks.

Modeling, measurement, and a simple analytic approximation for the return loss of erbium-doped fiber amplifiers

When fiber-optic systems contain erbium-doped fiber amplifiers (EDFA), reflections are enhanced by the gain of the amplifiers and can degrade system performance. We present a simple approximate analytic expression for the return loss of pumped EDFAs, with and without discrete reflections that applies at both the signal and pump wavelengths. A novel return loss measurement test set is used to verify the validity of this expression for a particular EDFA design. Using a computer simulation, the return loss is computed as a function of EDFA design to assess the range of validity of the approximate expression. The expression serves as an easy way to chain amplifiers and accurately predict the effects of reflections in long systems.

Experimental investigation of the gain flatness characteristics for 1.55 /spl mu/m erbium-doped fluoride fiber amplifiers

The flat gain over a broad spectral width offered by fluoride-based Erbium-Doped Fiber Amplifiers (EDFA) appears very attractive for wavelength-multiplex systems operating near 1550 nm. The relevant parameters (input pump and signal powers, fiber length) that determine the gain flatness characteristics of fluoride-based EDFA have been experimentally investigated. It is found that hat gain operation requires an optimal, though not critical, population inversion within the doped fiber, which is somewhat lower than the maximum population inversion achievable with 1.48 /spl mu/m-pumping. Implications on the design and operating conditions of fluoride-based EDFA are discussed. >

Experimental verification of new EDFA gain-tilt distortion theory

Measurement of composite second-order distortion (CSO) for a 28-channel AM-TV system verifies a recent theory on erbium-doped fiber amplifier (EDFA) gain-tilt distortion. The fundamental difference between locked-inversion and continuous-wave (CW) gain-till is explained experimentally and theoretically. Good agreement between simulated and measured locked-inversion gain curves are found. The results confirm that gain-tilt distortion in optical AM-TV systems can be reduced to acceptable levels by proper EDFA design. The measurements indicate that EDFA-induced CSO cannot be used to compensate CSO generated by other mechanisms over the whole frequency band in multichannel systems. >

Analog video distribution system with three cascaded 980 nm single-pumped EDFA's and 73 dB power budget

A FTTH (fiber to the home)-system for 35 AM-VSB (amplitude modulation vestigial sideband) PAL TV-signals is presented with three cascaded EDFAs (erbium-doped fiber amplifiers) single-pumped with commercially available 980 nm semiconductor laser diodes, with only one optical isolator per amplifier and without any optical filter. This EDFA design leads to an optical distribution system that is cost competitive as compared to coax solutions. The high-optical output power (+13 dBm) in conjunction with the low noise performance (max NF=4.5 dB) allows a 73-dB power budget for a weighted video signal to noise ratio of 45 dB. A high split count of 4*32*64*64=524288 subscribers is realized.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The design of erbium-doped fiber amplifiers

An accurate model for the erbium-doped fiber amplifier is presented. The model is used to design the index profile of the doped fiber, optimizing with regard to efficiency for inline- and preamplifiers as well as for power booster amplifiers. The predicted pump efficiencies (maximum gain to pump power ratios) are in agreement with experimental results presented in the literature. The choice of codopant is shown to be very significant for the pump efficiency when pumping in the 0.98 mu m. The pump efficiency in the 0.98- mu m pump band is shown to be twice the pump efficiency in the 1.48- mu m pump band. >