Backward Pumping Research Articles

Bandwidth Extension in a Mid-Link Optical Phase Conjugation

In this paper, we investigate various designs of distributed Raman amplifier (DRA) to extend amplification bandwidth in mid-link optical phase conjugation (OPC) systems and compare bands 191–197 THz and 192–198 THz giving a total bandwidth of 6 THz using a single wavelength pump. We demonstrate the use of highly reflective fiber Bragg grating (FBG) to minimize gain variation across a WDM grid by optimizing forward and backward pump powers as well as the wavelength of FBGs for original and conjugated channels. Finally, we also simulate OSNR and Kerr nonlinear reduction as a product of signals asymmetry and nonlinear phase shift (NPS) for all channels.

Various pumping modes of high-power double clad fiber laser

As one of the first invented laser categories, fiber laser plays a crucial role in many specific fields, e.g., filed-optic communication, sensing, industrial processing, national defense, military. In order to effectively couple the pump light into the single-mode fiber, double-clad fiber laser was invented, i.e., the power and efficiency of fiber lasers have been significantly improved. There are two mainly categories of pumping mode for double clad fiber laser, named as end smoothing the gain curve pumping and side pumping. This paper will focus on the analysis and comparison of these two pumping modes in terms of the power, efficiency, relative population density, thermal load and feasibility. The experimental procedure will be achieved based on the MATLABR2021b and SFTool. The aim of the paper is to investigate the effects on the forward pumping and backward pumping in the process of side pumping and end pumping. According to the analysis, side pumping and bi-direction pumping smooth the gain curve effectively. Choosing appropriate pumping mode can reduce the loss and save the cost of optical transmission to a large extent. These results shed light on selection of pumping mode for high power fiber laser.

Raman pumps power distribution optimization for maximum overall gain and flatness of a hybrid SOA/EDFA/Raman optical amplifier

Abstract A hybrid optical amplifier (HOA) is designed and optimized for the transmission of 40 dense wavelength division multiplexed system (DWDM) channels modulated at 10 Gbps having 25 GHz spacing at the edge of the L and U wavelength bands over more than 250 km. Multi-parameter optimization process is used to achieve the highest gain and best gain flatness. Different power combinations distributed among four lasers of a total forward pumping power (1270 mW) and total backward pumping power of either 730 mW or 850 mW are investigated for their effect on the hybrid amplifier gain and flatness. The best power distribution among the pumps provides about 31 dB overall gain with a flatness about 0.8 dB and noise figure ∼5.7 dB. It is found that the red-shifted pumps’ wavelengths should be used in the forward direction, while the blue-shifted pumps’ wavelengths should be used in the backward direction.

Average-power (4.13 W) 59 fs mid-infrared pulses from a fluoride fiber laser system

We report a high-average-power mid-infrared ultrafast laser system consisting of a fluoride fiber mode-locked oscillator and a nonlinear amplifier. A backward pumping scheme was used in the amplifier to simultaneously realize pulse amplification and self-compression. The input signal polarization was demonstrated to play an important role in the self-compression process. Through the optimization of input polarization, a 4.13 W average-power 59 fs pulse at 2.8 µm was achieved, with an estimated pulse energy of 42.2 nJ and a peak power of 715 kW. To the best of our knowledge, this is the highest average-power pulse with sub-100-fs duration generated from a mid-infrared fiber laser system to date.

Phosphosilicate Fiber-Based Low Quantum Defect Raman Fiber Laser with Ultrahigh Spectral Purity.

The phosphosilicate fiber-based Raman fiber laser (RFL) has great potential in achieving low-quantum defect (QD) high-power laser output. However, the laser’s performance could be seriously degraded by the Raman-assisted four-wave mixing (FWM) effect and spontaneous Raman generation at 14.7 THz. To find possible ways to suppress the Raman-assisted FWM effect and spontaneous Raman generation, here, we propose a revised power-balanced model to simulate the nonlinear process in the low-QD RFL. The power evolution characteristics in this low-QD RFL with different pump directions are calculated. The simulation results show that, compared to the forward-pumped low-QD RFL, the threshold powers of spontaneous Raman generation in the backward-pumped RFL are increased by 40% and the Raman-assisted FWM effect is well suppressed. Based on the simulation work, we change the pump direction of a forward-pumped low-QD RFL into backward pumping. As a result, the maximum signal power is increased by 20% and the corresponding spectral purity is increased to 99.8%. This work offers a way for nonlinear effects controlling in low-QD RFL, which is essential in its further performance scaling.

Effects of ASE noise and dispersion chromatic on performance of DWDM networks using distributed Raman amplifiers

We investigate effects of amplified spontaneous emission noise (ASE), noise figure (NF) and dispersion chromatic on the performance of DWDM networks using distributed optical fiber Raman amplifiers (DRAs) in two different pump configurations, i.e., forward and backward pumping. We found that the pumping configurations, ASE noise, and dispersion play an important role in network performance improving since it reduces noise figure and bit error rate (BER) of the system. Simulation results show that the lowest bit error rate and noise figure when using forward pumping configuration. Moreover, we have also compared ASE noise powers of the simulation with these of the experiment, they are match.

Experimental study of spectral broadening in kW-level narrow linewidth FBG-based fiber amplifiers under different pumping configurations

In this work, experimental investigations were presented on the variation of spectral broadening and optical efficiency in a kW-level narrow linewidth MOPA fiber laser under different pumping configurations. The results revealed that the backward-pumping scheme could reduce the spectral broadening and enhance the optical efficiency compared with the forward-pumping scheme. For a detailed study, the bidirectional pumping setup was employed. It could be seen that by removing the pump diodes from the forward direction and adding them to the backward direction one by one, the spectral bandwidth and the optical efficiency gradually decreased and increased, respectively. By coiling the gain fiber on a plate with a bending diameter of 9-13 cm, a multi-peak and unstable spectrum was observed. When this fiber was coiled on a cylinder with a fixed diameter of 10.5 cm, the spectral instability was removed and a single-peak spectrum was observed. For forward pumping only, the spectral bandwidth, the optical efficiency, and the maximum output power were measured to be 0.121 nm, 78.92%, and 822 W, respectively, while for backward pumping only, these values were measured to be 0.084 nm, 82.65%, and 860 W.

Distributed Backward Pumped Raman Amplifiers Gain without Attenuation: A New Approach

Optical amplifiers have made a great achievement and a huge revolution in the world of optical communications, but some of the shortcomings must be occurs, for example, backward pump Raman amplifier suffers from decrease in gain. The main objective of this paper is to solve the problem of decrease that occurs in gain of backward pumped Raman amplifier. To solve this problem, we design a model of two of backward pumped Raman amplifiers are used in a cascaded form to overcome the attenuation in gain. We present the results in the case of using one backward pumped Raman amplifier compared to the model that we designed to show the difference between the two cases. Three types of fibers with different gain parameters are used. We also simulate and analyze the parameters that affect the Raman gain of fiber Raman amplifier for three different types of fiber. The gain depends heavily on the length of the fiber and the pumping power, according.

Protection Scheme for a Wavelength-Division-Multiplexed Passive Optical Network Based on Reconfigurable Optical Amplifiers

This paper demonstrates a wavelength-division-multiplexed passive optical network (WDM-PON) scheme based on novel reconfigurable optical amplifiers (ROAs). The measured switching characteristics of the ROA3 constructed with a 2 × 2 crossbar optical switch and a four-port reversible optical circulator (OC) and a conventional EDFA can meet the requirements of most network management and surveillance. The self-made four-port reversible OC’s response time is less than 2 ms, and its insertion losses are about 1 dB or less for all the transmission paths and switching states. An optimal design of ROAs is proposed and evaluated for bidirectional optical amplifier protection, in which ROA3 has an EDF length of 7.5 m long with a 1480 nm pump laser and possesses a backward or forward pumping configuration with the corresponding pump power of 200 mW or 50 mW. We verified the scheme’s feasibility through a simulation of WDM-PON systems with 40 downstream and upstream channels. This scheme enables the intelligent protection switching in practical operation scenarios for high-capacity multi-wavelength networks.

Analysis of gain and noise characteristics of O-band Bi-doped fiber amplifier under different pumping schemes

In this paper, the gain and noise characteristics of bismuth-doped fiber amplifiers in O-band (1260–1360 nm) under forward, backward and bidirectional pumping are comprehensively compared and optimized using numerical models. The validity of the model is verified. The results show that (1)the signal power is changed within a limited range does not have an effect on the noise figure. However, the noise figure will be worse while the power continues to increase, and the magnitude of the change is most pronounced under the backward pumping scheme. With an increase in signal power from − 25 dBm to − 10 dBm, the noise figure is relatively flat under all pumping schemes. While increasing from − 10–0 dBm, the noise figure under backward pumping increased by 0.9 dB; (2)Only if pump power is below a certain threshold, the gain obtained under bidirectional scheme is significantly higher than under forward and backward.With larger pump power, the gain obtained under all pumping schemes is almost the same. With pump power less than 1.2 W, the gain under bidirectional scheme is 0.9 dB higher than that under forward and backward schemes. With more than 1.2 W, the gain difference between bidirectional and forward and backward is only 0.2 dB. The analysis provides guidance for the selection and optimization of pumping structures in BDFA, thus helping to improve the performance of O-band transmission systems.

Investigations on the performance of distributed Raman amplifier in dense wavelength division multiplexed communication system using different modulation formats

AbstractHere, the amplification performance of distributed Raman amplifier in a dense wavelength division multiplexed (DWDM) system is analyzed. We aim to compare the performance of distributed Raman amplifier using different digital modulation formats accordant with the bit error rate (BER) and Q factor through simulations. The various pumping methods like forward pumping, backward pumping, and bidirectional pumping for different pump powers have been compared by varying the modulation formats. Binary phase shift Keying (BPSK), differential phase shift keying (DPSK), carrier suppressed DPSK (DPSK‐CS), and quadrature phase shift keying (QPSK) with RZ and NRZ are analyzed as their spectral efficiency is found to be better than OOK systems. Our simulation results indicate that the bit error rates are much lesser for Raman Amplifier systems with QPSK‐NRZ modulation format having SNR improvement of almost 6 dB.

Experimental investigation of short pulse Raman amplification with backward pumping.

We report an experimental study on the backward-pumped Raman amplification of short pulses into a 20.3 km long optical fiber. We demonstrate that the gain and the pump saturation depend on the pulse duration. We also reveal that for short enough pulses, the amplification process remains linear, and very high peak powers, even larger than the Raman pump, are achievable. Numerical simulations reproduce the experimental results with excellent agreement.

Raman Amplification Optimization in Short-Reach High Data Rate Coherent Transmission Systems.

We compared the transmission performances of 600 Gbit/s PM-64QAM WDM signals over 75.6 km of single-mode fibre (SMF) using EDFA, discrete Raman, hybrid Raman/EDFA, and first-order or second-order (dual-order) distributed Raman amplifiers. Our numerical simulations and experimental results showed that the simple first-order distributed Raman scheme with backward pumping delivered the best transmission performance among all the schemes, notably better than the expected second-order Raman scheme, which gave a flatter signal power variation along the fibre. Using the first-order backward Raman pumping scheme demonstrated a better balance between the ASE noise and fibre nonlinearity and gave an optimal transmission performance over a relatively short distance of 75 km SMF.

Nonlinear/dispersion compensation in dual polarization 128-QAM system incorporating optical backpropagation

Abstract In order to cater long distance optical network units (subscribers), optical networks with prolonged reach are needed. In this study, an optical back propagation (OBP) dual polarization (DP)-128 QAM-based system is proposed to cope with nonlinear impairments in wavelength division multiplexing (WDM) systems. In pre, post and symmetrical configurations, the OBP module consisting of the optical phase conjugator (OPC), Raman fiber amplifier (RFA) and erbium doped fiber amplifier (EDFAs) is examined. Using dispersion compensation fiber (DCF) as RFA with dual directional pumping, ideal OBP conditions are simulated. DP-128 quadrature amplitude modulation (QAM) system is proposed with symmetrical OBP and compared with single channel digital back propagation (DBP), wideband DBP, pre OBP-forward pumping, pre OBP with backward pumping, pre OBP with dual directional pumping, post OBP with dual directional pumping. It is observed that symmetrical OBP configuration with dual direction pumping provide enhanced results and successfully cover 6500 km at bit error rate (BER) 10−3.

Temperature Influence on the Radiation Responses of Erbium‐Doped Fiber Amplifiers

The gain degradations of an Er‐doped fiber amplifier (EDFA) during the exposure of its active Er‐doped fiber to 40 keV X‐rays (≈2.7 mrad(SiO2) s−1 up to 300 krad) at three different temperatures: −40, 25, and 120 °C, are characterized. The spectral dependence of the fiber radiation‐induced attenuation (RIA) is monitored in situ in the 900–1600 nm spectral range, highlighting a combined temperature and radiation effect on the near‐infrared RIA levels and kinetics. At the system level, the kinetics of EDFA gain degradation are only slightly affected by varying the irradiation temperature for the tested backward pumping EDFA configuration. On the theoretical side, a homemade computer code based on the particle swarm optimization and the rate equations to model the radiation behavior of EDFA is used, considering only the RIA impact on its gain. Despite a good agreement between experimental and simulation results below the dose of 70 krad corresponding to current space missions, the comparison between the modeled and measured gain degradation kinetics at higher doses shows that a more precise modeling of the temperature impact on the absorption properties of the erbium ions is necessary to better reproduce the EDFA radiation behavior for future space missions.

High power pump and signal combiner for backward pumping structure with two different fused fiber bundle designs by means of pretapered pump fibers.

We report on two high power backward (6 + 1) × 1 pump and signal combiners with different optical designs based on end-pumping technique, each achieving more than 95% coupling ratio of signal light, 98% coupling ratio of pump light, and a total pump power of 2.95kW. Both designs solve the problem of non-uniform arrangement in asymmetric fiber bundles by the pretreatment of the pump fibers and signal fiber. Asymmetric fiber bundle in backward pump and signal combiners means the pump input fibers and signal output fiber have different cladding diameters. Two 3D simulation models were built to calculate the parameters of the fused fiber bundles for matching the mode field diameter between the signal input and the output fibers. Both optical designs of backward combiners were developed based on the beam propagation method and confirmed by experimental results.

EDFA AND EYCDFA POWER BOOSTER FOR SECURED, HIGH SPEED AND MULTIPLE WAVELENGTH SERVICES IN OPTICAL COMMUNICATION SYSTEMS USING WDM AND QUAD-SINGLE FORWARD AND TRI BACKWARD PUMPING TECHNIQUE

Proposed the EDFA and EYCDFA power booster (Erbium Doped Fiber Amplifier- Erbium ytterbium co doped fiber amplifier) with quad pumping for high speed and multi wavelength services in an optical communication. The proposed EDFA and EYCDFA power booster with WDM(Wavelength division multiplexing) simulated by dual forward and Backward pumping, Dual-backward pumping, Tri-single forward and dual backward pumping and Quadsingle forward and tri-backward pumping with respect to Pump power and fiber Length. The parameters Input Optical power, Output Optical power, Forward Signal power, Backward Signal power measured and determined the speed of transmission in all types of pumping methods. From that the proposed EDFA- ans EYCDFA power booster with WDM quad pumping is the best suitable for secured high speed optical telecommunication systems. The results shown in Quad pumping Output optical power is maximum 25.2dB and optimum spectral forward Signal power is 30.5dBm and very less spectral optical backward signal power of -25.4dBm with Length 5m

Estimation of four wave mixing effect in pre-, post- and in-line configuration of EDFA using advanced modulation formats for 1.28 Tbps WDM system

This paper reported the effect of different EDFA configurations on the four wave mixing (FWM) effect in wavelength division multiplexed (WDM) system which is operating at 1.28 Tbps data speed. Also, the comparative analysis of pre-, post (booster) and inline configuration of EDFA using both forward pumping and backward pumping techniques at variable input signal power and pump signal power levels. Further, the effect of various modulation formats on the signal quality of WDM system is analyzed in presence of dispersion compensated fiber. The original contribution of this investigation is to check the effect of EDFA amplification on FWM for future high-speed optical access networks and it can be observed that in line EDFA amplification configuration gives the best amplification performance among other configurations.

Gain enhancement of polymer waveguide amplifier based on NaYF4 : Er[formula omitted], Yb[formula omitted] nanocrystals using backward pump scheme

Optical waveguide amplifiers based on NaYF4 : Er3+, Yb3+ nanocrystals prepared by high-temperature thermal decomposition method with forward and backward pump schemes are designed. The gain characteristics of the two schemes are compared through simulation and experiment. For an input signal power of 0.1 mW and a pump power of 270 mW, relative gains of 5 and 5.6 dB are obtained by forward and backward pumping, respectively, in a 9-mm-long waveguide at a wavelength of 1530 nm. Simulation and experimental results show that the gain of backward pumping was higher than that of forward pumping by 12%. The utilization rate of pump light power is greatly improved, which is beneficial to the optimization design of waveguide amplifiers.

Multi-wavelength Brillouin Raman random fiber laser with double Brillouin frequency shift

In this paper, a linear full-open-cavity Raman random fiber laser generating multi-wavelength Brillouin lines with double Brillouin frequency shift is proposed. The odd-order and even-order Stokes lights are respectively output from different end. Our contrastive experiments with forward and backward Brillouin pumping schemes reveal that the signal-to-noise ratio (SNR) of the laser output by backward pump is 24.5 dB, and the SNR of the laser output by forward pump is 19.5 dB under same Raman pump power of 831.8 mW. The SNR of backward-pumped laser output is higher and the wavelength number is more than that of forward-pumped case. But the Raman pump threshold for Brillouin Stokes light generation is higher for backward-pumped laser, which results in no stable Brillouin light generation at low Raman pump power. It is believed that the results not only can provide different ideas for the further optimization of random fiber laser structure, but also can help to further expand the application range of multi-wavelength Brillouin Raman lasers in optical communication systems and optical sensing fields.