Powerful 2 μm Silica Fiber Sources: A Review of Recent Progress and Prospects

A review on the progress of powerful 2 μm silica fiber sources in past decades is presented. We review the state-of-the-art records and representative achievements of 2 μm high-average-power continuous- wave, pulsed fiber lasers and amplifiers, and powerful superfluorescent sources. Challenges which limit the further power scaling of 2 μm silica fiber sources are discussed, including pumping brightness limitation, thermal problem and nonlinear effects. Potential and promising roadmaps to go beyond these limitations, like tandem pumping and beam combining, are discussed. Prospects of powerful 2 μm silica fiber sources are also presented in the end of paper.

A high-linearity InGaP/GaAs HBT power amplifier for IEEE 802.11a/n

A three-stage 4.8-6 GHz monolithic power amplifier（PA） compatible with IEEE 802.11a/n designed based on an advanced 2μm InGaP/GaAs hetero-junction bipolar transistor（HBT） process is presented.The PA integrates input matching and closed-loop power control circuits on chip.Under 3.3 V DC bias,the amplifier achieves a ~31 dB small signal gain,excellent wide band input and output matching among overall 1.2 GHz bandwidth,and up to 24.5 dBm linear output power below EVM 3%with IEEE 802.11a 64QAM OFDM input signal.

Enhanced multiple access schemes for future broadband satellite communications

A new structure of next generation integrated communication system was proposed, which is composed of space segment based on satellites and terrestrial segment. Moreover, the characteristics of enhanced multiple access schemes based on orthogonal frequency division multiplexing (OFDM) technique were analyzed for satellite links. However, OFDM is a doubtful candidate as its higher peak-to-average power ratio (PAPR) that causes the distortion of high power amplifier (HPA). Furthermore, different schemes were evaluated and compared in terms of the HPA nonlinearity and the link level performance in detail. And the pilot-aided channel estimation and equalization techniques were also considered for analyzing the problem. Simulation results show that the bit error rate (BER) and block error rate (BLER) performance of orthogonal frequency division multiple access (OFDMA) outperforms that of single carrier-frequency division multiple access (SC-FDMA) for the satellite links in the proposed structure, though discrete Fourier transform-spread OFDM DFT-S OFDM has low PAPR, especially the BER performance of OFDMA is 3.6 dB larger than that of SC-FDMA at the target BER.

Evolution of modes in double-clad Raman fiber amplifier

Stimulated Raman scattering in a double cladding optical fiber is studied with a continuous wave laser used as a pump source. Under various launch conditions, pump modes are differently excited. Considering the mode coupling effect among the pump modes, the evolution of the power in the Stokes modes is studied. The results show that the scattered waves （the Stokes waves） in the fiber core with 9%tm diameter and 0.14 NA could propagate predominantly in the fundamental mode of the fiber by carefully adjusting the pump light launching conditions.

Green Base Station Solutions and Technology

Base station power consumption is the biggest power issue concerning wireless networks. Saving power in base stations is therefore the primary focus in green wireless network development. This paper discusses green base stations in terms of system architecture, base station form, power saving technologies, and green technology applications. It explores effective ways of reducing power consumption in base stations.

A High Power Conversion Efficiency L-Band Erbium Doped Fiber Amplifier

By using two sections of erbium doped fiber and a fiber optical reflector, a novel, highly efficient L-band amplifier is demonstrated with significantly power-conversion-efficiency enhancement and the gain increasing of as much as 13 dB.

Design and Analysis of 120-μm Core Rod-Type Photonic Crystal Fiber for High Power 1.5-μm Band Amplifier

We report the design and analysis of a rod-type photonic crystal fiber with Er-Yb co-doped for the high power 1.5-μm band amplifier.The fiber structure is designed to be the 120-μm extreme large core diameter,300-μm inner cladding diameter,and 1.5-mm outer cladding diameter that ensure the single mode output during high power amplification.Both the continuous wave(CW) and pulsed amplification characteristics are analyzed based on the exact modeling and simulation under the designed geometry.The 4-mJ pulse energy and 400-kW peak power are obtained in theory,so the 1.5-μm band amplifier that achieves milojoule level pulse energy meanwhile keeping single mode is firstly designed.

A Model-Driven Approach to Enhance Faster-than-Nyquist Signaling over Nonlinear Channels

In order to increase the capacity of future satellite communication systems,faster-than-Nyquist(FTN)signaling is increasingly consideredI..Existing methods for compensating for the high power amplifier(HPA)nonlinearity require perfect knowledge of the HPA model.To address this issue,we analyze the FTN symbol distribution and propose a complex-valued deep neural network(CVDNN)aided compensation scheme for the HPA nonlinearity,which does not require perfect knowledge of the HPA model and can learn the HPA nonlinearity during the training process.A model-driven network for nonlinearity compensation is proposed to further enhance the performance.Furthermore,two training sets based on the FTN symbol distribution are designed for training the network.Extensive simulations show that the Gaussian distribution is a good approximation of the FTN symbol distribution.The proposed model-driven network trained by employing a Gaussian distribution to approximate an FTN signaling can achieve a performance gain of 0.5 dB compared with existing methods without HPA's parameters at the receiver.The proposed neural network is also applicable for non-linear compensation in other systems,including orthogonal frequency-division multiplexing(OFDM).