Hybrid Fiber Amplifier Research Articles

Performance enhancement of L-shape hybrid fiber amplifier via combining of tunable optical filter and second-order stimulated Raman scattering

Performance enhancement of L-shape hybrid fiber amplifier via combining of tunable optical filter and second-order stimulated Raman scattering

Effects of L-shape and Raman second-order pumping scheme on the performance of double-pass hybrid fiber amplifier

Effects of L-shape and Raman second-order pumping scheme on the performance of double-pass hybrid fiber amplifier

Raman Pump Optimization for Maximizing Capacity of C+L Optical Transmission Systems

Within a context of C+L band transmission, this work proposes a design approach for Raman pumps in hybrid fiber amplifiers (HFAs) with the goal of maximizing the total system capacity. First, the optimization problem is constructed. The capacity of a system can be equivalently assessed by the mean generalized signal-to-noise ratio (GSNR) of all channels, which is chosen as the optimization objective. The powers of Raman pumps are chosen as the decision variable, and constraints on the Raman pump powers are added. Then, an optimization framework for Raman pump powers is proposed. An artificial neural network (ANN) is used to establish a differentiable model for GSNR and signal power after Raman amplification (RA). The gradient descent algorithm is adopted to perform the optimization. Simulations are conducted on a single-span link for modeling and on an 8-span link for optimization. Results show that the ANN can reach a high modeling accuracy with a prediction error of 0.16 dB for GSNR and 0.06 dB for signal power with specific link and signal parameters. Results also demonstrate the superior performance of the proposed optimization framework, and a gain of 0.54 dB on the mean GSNR can be achieved by the designed HFA compared with that of the design aimed at a flat gain profile.

Hybrid double-cladding Er/Yb co-doped fiber amplifier with Yb-ASE suppression

A single-frequency hybrid double-cladding Erbium-Ytterbium co-doped fiber amplifier (EYDFA) with Yb-band amplified spontaneous emission (Yb-ASE) suppression is demonstrated. Two segments of EYDFs, with core diameters of 6 μm and 12 μm, are fused in sequence to form a hybrid gain fiber. Theoretical analysis indicates that reducing the pump absorption in the initial part of the gain fiber is beneficial to avoid Yb-ASE boosting. A 4.79-W output laser with a linewidth of 1.67 kHz is obtained in the experiment. The Yb-ASE of the hybrid fiber amplifier is suppressed by more than 3 dB when compared to the uniform fiber amplifier with the same gain fiber length, and the slope efficiency is increased by 1.6 %. The loss characteristics of the hybrid gain fiber for backward transmitted light indicate its potential to suppress SBS effects. These results show a compact structure to suppress the Yb-ASE of the EYDF amplifier.

Broadband flat amplification based on fully double-pass configuration in serial hybrid fiber amplifier

A broadband amplification that utilizes a serial hybrid fiber amplifier is experimentally demonstrated in this paper. Two fully double-pass configurations, namely, setups A and B, are implemented. The difference between these two configurations is that the position of the two amplifiers (erbium and Raman) is swapped. These two configurations are tested under the same input parameter conditions. Two laser pump power wavelengths with a total pump power of 375 mW (1495 nm with 350 mW for Raman and 1480 nm with 25 mW for the erbium amplifier) were used. Under the optimum condition and under a small signal power of −30 dBm, a wide flatness gain bandwidth of 80 nm (1530–1610 nm) with an average gain level of 28.5 and 24 dB is achieved for setups A and B, respectively. A wide bandwidth is achieved by avoiding the amplification overlap between these two amplifiers through choosing the proper pump wavelength. In addition, A gain dynamic range values of 3 dB and more than 15 dB were recorded for setup A and B respectively.

All-polarization-maintaining and high-energy fiber optical parametric chirped-pulse amplification system using a solid core photonic hybrid fiber.

We present an all-fiber optical parametric chirped-pulse amplification integrated system delivering a single-mode polarized beam. The system makes use of a specifically designed solid-core photonic hybrid fiber (i.e., combining modified total internal reflection and photonic bandgap mechanisms) that ensures sufficient birefringence to maintain the signal polarization. Moreover, the fiber combines a large mode area to handle energetic pump pulses (without generating damage or unwanted nonlinear effects) and weak dispersion to generate parametric gain bands broad enough to amplify ultrashort pulses. An efficient parametric process allows for obtaining a very high gain (>45 dB) with an output pulse energy reaching µJ range at 1053 nm by using a single 5-m hybrid fiber amplifier.

Performance Comparison of Serial and Parallel Hybrid Fiber Amplifier under Optimum Pump Conditions

In this work, two different configurations of hybrid fiber optic amplifiers are investigated and simulated via OptiSystem 7.0 software, namely, serial and parallel hybrid fiber optical amplifiers (S– and P–HFOAs). The investigation involves performance comparison for the S– and P–HFOA under optimum pump conditions to demonstrate the advantages and disadvantages of each configuration. The simulation results show that the serial configuration has a high average gain level of 19.2 dB, an appropriate noise figure about 4.3 dB, but low saturation power, and limited gain bandwidth of approximately 40 nm, which is considered a primary issue in S–HOFA design, in addition to the pump conversion efficiency still insufficient in the Raman amplifier stage. While in P–HFOA design, a wide 3–dB gain bandwidth of more than 60 nm is maintained, along with an average gain level of 13.5 dB, high average noise figure about 8.3 dB and high saturation power due to the absent of cascading effect in parallel configuration

Design of broadband hybrid fiber amplifier based on particle swarm optimization algorithm

基于铒/镱共掺光纤放大器（erbium-ytterbium doped fiber amplifier, EYDFA）的理论模型和受激拉曼散射效应的分析理论，利用EYDFA和拉曼光纤放大器（Raman fiber amplifier, RFA）的增益谱互补特性，研究并设计了EYDFA与二阶多泵浦RFA相结合的混合放大器结构。为了得到高增益和低平坦度的混合放大器，引入了粒子群算法优化泵浦光波长和功率。仿真结果表明：在不使用增益均衡器的条件下，所设计的混合光纤放大器在输出端得到了近似相等的输出光功率，在90 nm的带宽范围内平均增益为38.78 dB，增益平坦度为1.1 dB，为混合放大器的设计和优化提供了参考。

Wideband full double-pass serial hybrid fiber amplifier utilizing L-shape configuration.

In this work, a new, to the best of our knowledge, full double-pass serial hybrid fiber amplifier is simulated on OptiSystem 7.0 software. A wideband flat gain spectrum covered both conventional and long communication bandwidth (C+L) from 1530 to 1590 nm, which is approximately 60 nm with high average gain of 23.6 dB; acceptable noise figure of 7 dB is achieved via the L-shape configuration. The main innovative step in the proposed design is decreasing the cascading amplification effect between the combined amplifiers, by making the individual full double-pass for the input signal in each amplifier stage.

An efficient wide flatness gain bandwidth with parallel hybrid fiber amplifier

AbstractIn this article, we experimentally propose an efficient wide flat gain bandwidth with a parallel hybrid fiber amplifier. The setup includes parallel amplifier branches. In the first branch, serial erbium‐doped and Raman fiber amplifiers are used. In the second branch, only a Raman fiber amplifier is used. Three Raman pump power units (i.e., 1410, 1480, and 1495 nm) are used to achieve Raman gain at different optical communication bands. At optimum pump powers and at a small‐signal power of −30 dBm, an average gain of 18.5 dB with a maximum gain variation of 3 dB and a gain flatness bandwidth of 83 nm, that is, from 1527 to 1610 nm, is achieved. This gain flatness is expanded to 92 nm (1525–1617 nm) at a large input signal power of −5 dBm with an average gain level of 13 dB. In our proposed amplifier, the Raman amplification peaks (1510 and 1595 nm) are chosen to be far from the erbium amplification peak (1530–1570 nm) in order to avoid the overlapping and the saturation in the first amplifier branch. Therefore, due to such wavelength optimization in addition to the recycling the residual Raman pump power, a wide flatness gain bandwidth is achieved for both of low and large input signal powers.

Yb-ASE Suppression in Single-Frequency Hybrid Double Cladding Erbium–Ytterbium Co-Doped Fiber Amplifier with SMS Structure

A hybrid double cladding erbium–ytterbium co-doped fiber (EYDF) amplifier with a single-mode-multimode-single-mode (SMS) active fiber is demonstrated in this study. The hybrid gain fiber with an SMS structure is composed of two kinds of EYDFs with 6 and 12 μm core diameters. The transmission spectra of the SMS fiber structure were theoretically analyzed and the simulation results indicated that the maximum loss in the 1~1.1 μm band where the Yb-band amplified spontaneous emission (Yb-ASE) located, was much larger than that of the 1.5-μm band because of the wavelength difference. The power performance and spectra properties of the hybrid fiber amplifier were theoretically and experimentally analyzed and compared with a typical uniform fiber amplifier under the same conditions. The experimental results demonstrated that this hybrid fiber amplifier can suppress the Yb-ASE by over 12 dB and increase the slope efficiency by more than 2%, but the ASE in the 1.5-μm band increases by 2~3 dB. This work provides a possible method to enable EYDF amplifiers to suppress the Yb-ASE and overcome the pump bottleneck effect.

Widely flatness gain bandwidth with double pass parallel hybrid fiber amplifier

A Widely flatness gainbandwidth with double pass parallel hybrid fiber amplifier is experimentally demonstrated in this study. The proposed design combines serial erbium–Raman fiber amplifier in one branch and Raman fiber amplifier in the second branch. Multiple Raman pump units with a maximum power of 800 mW (250 mW of 1410 nm, 225 mW of 1480 nm, and 325 mW of 1495 nm) are utilized. Pump recycling technique is applied to achieve acceptable pumping efficiency. A maximum flatness gain bandwidth of 80 nm (1525–1605 nm) and average gain level of 22.5 dB are obtained at a small input signal power of \(-25\) dBm and optimum pump power values. While, a wider flatness gain of 90 nm (1520–1610 nm) and average gain level of 11.5 dB are achieved at a large input signal power of \(-5\) dBm.

Gain-control technique in double-pass parallel hybrid fiber amplifier

In this paper, the effect of gain control technique in double pass parallel hybrid fiber amplifier in terms of gain level as well as pump powers optimization are simulated using Optisystem and experimentally validated. An average gain level of 22.8 dB and overall gain variation of 3 dB within C and L band regions are achieved. The gain flatness bandwidth of 60 nm from 1530 to 1590 nm are obtained. A comparison with a single pass parallel hybrid fiber amplifier is presented. This comparison showed an average gain level of 38.5% higher than single pass-structure utilizing only 650 mW of Raman pump which is 18.7% lower.

Pump power optimization for hybrid fiber amplifier utilizing second order stimulated Raman scattering

In this work, a wideband serial hybrid fiber amplifier based on second order stimulated Raman scattering (SO-SRS) is demonstrated. The optimum pumping power for Raman fiber amplifier with SO-SRS, is determined for six different Raman gain medium lengths. A wide flat gain bandwidth is achieved within the short, conventional and long band (S + C + L band) about 90 nm with average gain level of 25.165 dB and 19.649 dB for Raman gain medium length of 5 km and 15 km, respectively. According to the results, the average hybrid gain level is decreased as the gain medium length increased at optimum pumping condition. Furthermore, the Raman pumping power in which the lower Raman Stokes power reaches to the saturation region represent the optimum pumping power for the higher order Raman Stokes.

32 Channel × 40 Gb/s WDM optical communication system utilizing different configurations of hybrid fiber amplifier

In this paper, a simulation analysis of 40 Gb/s wavelength division multiplexing system of 32 channels is implemented through RZ modulation format by using a different hybrid fiber amplifier (HFA) configurations, namely, serial HFA, parallel HFA, and combined serial–parallel hybrid fiber amplifier (CSP-HFA). The performance of the proposed amplifiers is compared in terms of average gain level, average noise figure, flat gain bandwidth. In addition, quality factor, bit error rate, and eye diagram for the demonstrated 32 channel × 40 Gb/s wavelength division multiplexing optical communication system utilizing different configurations of the hybrid fiber amplifier is compared. The CSP-HFA shows better performance than serial and parallel hybrid amplifiers in terms of wider flat gain bandwidth, higher quality factor, lower bit error rate, and wider and clearer eye opening. Furthermore, CSP-HFA exhibits a flat gain bandwidth of 65 nm with an acceptable average gain of 16 dB and average noise figure of 7 dB.

Optimization of Hybrid Fiber Amplifier Utilizing Combined Serial-Parallel Configuration

In this paper, the optimum pump conditions are determined for C+L band combined serial-parallel hybrid fiber amplifier (CSP-HFA), utilizing gain control technique via OptiSystem 7.0. The optimization includes determining the optimum pump power (OPP), the optimum pump wavelength (OPW) and optimum coupling ratio (OCR), within the longest 3– dB flat gain bandwidth. The proposed HFA at optimum conditions, produced 65 nm flat gain bandwidth ranging from 1530 nm to 1595 nm within average gain of 16 dB and average NF of 7.29 dB. The proposed architecture provided two advantages over the conventional P-HFA includes; 1) improved flat gain bandwidth by 8.33 %, 2) constant optimum coupling ratio for both small and large signal at 0.7.

Physical Layer Strategies to Save Lightpath Regenerators

We investigate the viability of hybrid fiber amplifiers (HFA) and advanced digital signal processing (DSP)-based transceivers in translucent optical networks. We focus on the reduction of optical-electro-optical (OEO) regenerators required to support a 200 Gbps any-to-any traffic. In this paper, two network topologies, Pan-European and USNET, are quantitatively analyzed according to three different upgrade strategies. The first upgrade strategy includes selective placement of HFA in a network using different Raman amplification levels. The second upgrade strategy includes the use of two different DSP techniques of digital backpropagation and probability shaping (PS) at the transceivers. The third upgrade strategy involves a combination of both HFA and DSP techniques in a network. Our results indicate that by using these upgradation strategies, a prominent reduction in OEO regenerators can be obtained, which can lead to full transparency of a network. In the Pan-European topology, improving the equivalent noise figure (ENF) of the optical amplifiers by 5 dB, it is possible to reduce by 74% the amount of required regenerators. Then, by applying advanced DSP techniques like PS, this percentage grows up to 82%. In the USNET topology, by reducing the ENF by 2 dB, it is possible to reach full transparency. By using PS, it is enough to reduce the ENF by just 0.5 dB to reach the same results.

Performance Evaluation of DPSK System with Different Combination of Hybrid Optical Amplifiers by Using Equal and Unequal Channel Spacing

AbstractThis article investigates the performance of differential phase shift key system with different hybrid optical amplifiers with equal and unequal channel spacing. The differential phase shift key signals are transmitted with equal channel spacing of 0.1 THz and unequal channel spacing of 0.05, 0.075, 0.1 and 0.15 THz at 96×20 Gbps bit rate. The maximum transmission distance of 230 km is achieved with unequal channel spacing. It is observed that the interference between adjacent channels decreases due to unequal channel spacing and gives better results than equal channel spacing in terms of bit error rate and quality factor. It is found that the maximum distance of 220 km is achieved with equal channel spacing using Raman-erbium-doped fiber amplifier hybrid amplifier.

High power linearly polarized fiber laser: Generation, manipulation and application

Linearly-polarized (LP) fiber lasers, which could find wide potential applications such as coherent detection, coherent/spectral beam combining, nonlinear frequency conversion, have been a research focus in recent years. In this paper, we will present a general review on the achievements of various kinds of high power LP fiber laser and its applications for the first time. The recent progress in high power LP fiber oscillator, including fiber oscillator based on active fiber, Raman fiber laser and Random distributed feedback fiber laser are summarized. Power scaling of LP fiber laser by using active-fiber based power amplifier, passive-fiber based Raman amplifier, and active/passive fiber based hybrid fiber amplifier has been achieved. Polarization-maintained active fiber based power amplifier and non-polarization-maintained active fiber based power amplifier incorporating active polarization control are specially introduced in detail. High power LP fiber laser with diversified property, such as narrow-linewidth, wavelength-tunable and ultrashort pulse operation, are summarized. Various kinds application of high power LP fiber laser, including beam combining, supercontinumm generation, mid-infrared lasing, structured light field and ultrasonic generation, are presented at the end of this paper.

Flattened gain S + C + L Band RAMAN–Thulium-Doped Tellurite Fiber Amplifier Hybrid Optical Amplifier for Super Dense Wavelength Division Multiplexing System

Abstract In this paper we have examined the performances of 180×10 Gbps super dense wavelength division multiplexing (SD-WDM) system using the RAMAN–thulium-doped tellurite fiber amplifier (TDTFA) hybrid optical amplifier (HOA) with the channel spacing of 50 GHz in S+C+L band. Accepted rating flattened gain of 39.21 dB with the noise figure less than 5 dB is archived with the dual-pumping ( power level of 500 mW at 980 nm and at 1100 nm for RAMAN optical amplifier and similar, power level of TDTF amplifier is set to 500 mW and 350 mW at 1150 nm) technique. The effect of the proposed hybrid amplifier is evaluated in terms of gain and noise figure without using any coast effective technique. The outcome from the proposed model is also compared here with the existing optical amplifier.