Highly Efficient S-Band Thulium-Doped Fiber Amplifier Employing High-Thulium-Concentration Doping Technique

In the paper, we describe in detail a highly efficient S-band thulium-doped fiber amplifier (TDFA) employing a high-thulium-concentration doping technique. A TDFA with a dual-pass configuration is superior to a TDFA with a single-pass configuration with regard to power-conversion efficiency, whereas it is inferior with regard to noise figure (NF). We propose a cascaded configuration consisting of a single- and double-pass configuration, which provides high efficiency and a low NF. The configuration generated no interference noise, which can result from multipass interference (MPI) with a double-pass configuration. We achieved gains exceeding 26 dB and NFs of less than 7 dB in the 1480-1510-nm wavelength region (30-nm bandwidth). Furthermore, an 8 times 10-Gb/s transmission experiment also confirmed that there was no MPI-induced excess noise.     

1kHz高倍率亚纳秒全固态激光放大器研究

高功率全固态亚纳秒激光器具有体积小、成本低、线宽窄、峰值功率高等优势,在诸多领域具有重要的应用价值。为获得高功率亚纳秒激光输出,首先通过被动调Q激光器得到亚纳秒种子激光,然后利用LD侧泵模块,采用双模块双通放大的实验设计,在重复频率为1 kHz时,获得了平均功率达10 W,脉冲宽度816 ps,线宽39 pm,光束质量M2小于1.8的激光输出,放大器整体放大倍率达95倍以上。     

双程激光脉冲放大系统的建模及仿真研究

为了提高脉冲放大系统模型的光光转换效率,采用建模及仿真的方法研究了双程脉冲放大模型的输出特性,得到了得到双程脉冲放大系统输出功率与抽运功率的关系、输出单脉冲能量与脉冲的重复频率的关系,以及双程放大系统转换效率与重复频率的关系。结果表明,在重复频率为40kHz时,仿真得到该脉冲激光放大模型的光光转换效率达到了29.1%。该双程脉冲放大模型有效地提高了能量转换效率。     

Wavelength-interleaving bidirectional circulators

We report a wavelength-interleaving bidirectional circulator, in which the even and odd ITU channels circulate in opposite handedness. Demonstrated three-port bidirectional isolation ranges from 45 dB for single-pass to 90 dB for dual-pass over the entire C-band with low loss, large flat-top bandwidth, low PDL, and good temperature stability. This new device technology is an enabler for bidirectional optical networks and opens up a range of possibilities for bidirectional fiber devices: isolators, circulators, add-drops, cross-connects, and uni- to bidirectional optical network interfaces     

光谱维编码中红外光谱成像系统的光学设计

基于双DMD提出了一种光谱维编码的中波红外光谱成像系统,利用空间维DMD完全补偿了光谱维编码DMD引起的像面倾斜。介绍了系统的组成和工作原理,设计了焦距为240 mm、F数为3的望远系统作为前置成像单元,采用双光路Offner光栅成像系统配合光谱维编码DMD同时实现了光线的色散、编码和合光等多个功能,设计了放大倍率为1的中继成像系统实现冷光阑匹配。通过整体优化设计实现了对双光路Offner光栅成像系统残余像差的补偿,设计结果表明,系统具有良好的空间成像和光谱性能,作用距离满足设计要求。     

Polarisation-dependent gain spectrum of a 1.5 ?m travelling-wave optical amplifier

We present high-resolution gain spectra measurements of a 1.5 ?m near-travelling-wave amplifier for both TE and TM polarisation. We use 49km of single-mode fibre at the amplifier input to demonstrate a reduction in the effective bandwidth of the amplifier caused by a combination of dichroism in the amplifier and the polarisation dispersion present in long lengths of fibre.     

Ultrafast characteristics of InGaP-InGaAlP laser amplifiers

We characterize a visible, 670 nm, diode laser amplifier with respect to parameters of interest in short pulse generation and amplification. With a single pulse in the amplifier, we measure the differential gain and saturation energy of the amplifier, and changes in the optical spectrum of a pulse traveling through the amplifier. We also measure the ultrafast gain dynamics using a pump and probe technique. We find the ultrafast gain recovery time due to carrier heating is 400 fs±30 fs. Our results differ quantitatively from those reported for InGaAsP and AlGaAs amplifiers     

Ultra-wide-band tellurite-based fiber Raman amplifier

We describe the first wide-band tellurite-based fiber Raman amplifier (T-FRA) for application to seamless ultra-large-capacity dense wavelength-division multiplexing (WDM) systems. First, we confirmed that the Raman scattering characteristics of the tellurite-based fiber has so large a gain coefficient and Stokes shift that we can achieve a wide-band tellurite-based fiber Raman amplifier with a shorter fiber length than when using silica-based fiber. Second, we investigated the small signal gain and the signal transmission characteristics for a high gain and high output power operation with a single-stage amplifier. Focusing on double Rayleigh scattering, we compared the high gain limit of tellurite- and silica-based fibers. We then studied the impact of nonlinear effects by measuring the bit error rate (BER) when using a two-stage amplifier with a high output power of 18.8 dBm in which we simultaneously amplified eight channel signals in the L-band located on the ITU 100-GHz grid. Finally, we designed a wide-band tellurite-based fiber Raman amplifier with a multiwavelength band pumping scheme. We constructed this amplifier with a tellurite-based fiber only 250 m in length pumped by four-wavelength-channel laser diodes, and it provided a 160-nm bandwidth with a gain of over 10 dB and a noise figure below 10 dB from 1490 to 1650 nm. We also measured the BER to confirm the transmission characteristics of the amplifier for single channel operation over the whole signal wavelength range of 160 nm. We thus confirmed that the amplifier could be employed in ultra-high-capacity WDM systems.     

High-Power 1.06-$mu{hbox {m}}$ Near-Diffraction-Limited Planar Tapered Amplifier Injected With Seed Light Through a Fiber Biconical Microlens

We designed a 1.06-mum single-quantum-well (SQW) InGaAs/AlGaAs planar tapered amplifier that was injected with seed light of a fiber Bragg grating stabilized laser diode through a fiber biconical microlens. To increase the amplifier output, the microlens with approximately 3- and 11-mum radii on vertical and horizontal axes, respectively, provides high coupling efficiency between the laser diode and the amplifier. The microlens also controls propagation in the tapered gain area to suppress the filament formation. In addition, the small radii of the microlens reduce near-end reflection at the amplifier input to prevent parasitic laser oscillation of the amplifier. We demonstrated near-diffraction-limited output of 5.5 W with the beam quality factor M² of 1.5 by using a 3-mm-long amplifier having an optical confinement factor of 1.2%.     

A multigigahertz Josephson-semiconductor interface circuit using77-K differential monolithic HEMT amplifier and 4.2-K JJ high-voltagedriver for superconductor-semiconductor electronic hybrid systems

We proposed and successfully demonstrated a high-speed Josephson IC to semiconductor IC output interface circuit combining a high electron mobility transistor (HEMT) amplifier and Josephson high-voltage drivers successfully. We developed a 0.5-μm gate 77-K wide-band analog monolithic HEMT amplifier for the interface. The HEMT device consisted of InGaP/InGaAs materials stable even at 77 K. The amplifier has a differential amplifier as a first stage to cancel out ground-level fluctuations in the Josephson IC and showed a voltage gain of 23 dB and ~3-dB frequency of 8 GHz. A 0.63-V_p-p output was obtained from a 5-GHz, 30-mV_p-p complementary input signal. We succeeded in transfer ring a voltage signal from 10-stack Josephson high-voltage drivers to a 50-Ω system at room temperature with 0.7-V_p-p amplitude at 300-MHz clock using the HEMT amplifier     

Elimination of signal distortion and crosstalk from carrier densitychanges in the shared semiconductor amplifier of multifrequency signalsources

The signals from multifrequency sources that utilize a shared semiconductor optical amplifier often exhibit distortion and crosstalk due to carrier density changes in the shared amplifier. We propose a technique that eliminates the signal distortion and crosstalk by keeping the carrier density in the shared amplifier constant via feedforward of the electrical drive signals. We demonstrate the technique using a waveguide grating router multifrequency laser     

An automatic-gain-controlled Raman fiber amplifier/gain-clamped SOA for metro WDM networks with changes in span loss

We propose an automatic-gain-controlled Raman fiber amplifier/gain-clamped semiconductor optical amplifier. The amplifier uses a feedforward gain-control scheme to maintain the channel output power. The signal power after the optical amplifier is automatically controlled to within 0.15 dB when the span loss changes from 16 to 26 dB.     

Comparison of noise characteristics of Fabry-Perot-type and travelling-wave-type semiconductor laser amplifiers

We report results of comparative noise measurements on AlGaAs semiconductor laser amplifiers of the Fabry-Perot and travelling-wave types. We show that, for the same net gain, the electrical baseband signal/noise ratio of a photodetector placed at the amplifier output (after an optical filter) is higher for a travelling-wave-type amplifier, especially at high-gain values where the Fabry-Perot amplifier is operated at oscillation threshold. For a net gain of 20.5 dB, the signal/noise ratio of the travelling-wave-type amplifier is 4?5 dB better.     

射频功率放大器前馈线性化技术研究

在移动通信等领域,功率放大器的性能是决定整个通信系统性能的关键因素。而功率放大器的高线性度尤为关键。在设计射频功率放大器时,通常采用前馈技术实现高线性的要求。介绍了功率放大器前馈线性化技术的基本原理,利用该技术设计了一个线性功率放大器,并对电路提出改进方案。实验表明,该设计实现了功率放大器高线性,大功率输出的要求,该技术对改善功放的线性度有一定的效果。     

前置掺铒光纤放大器的研究

本文简述了前置掺铒光纤放大器的结构与应用，重点分析了影响接收机灵敏度的主要因素，前置光纤放大器的优化设计方法以及我们的实验与技术指标。     

基于增益扩展现象的线性化技术在Doherty功放中的应用

在分析Doherty放大器特性基础上,研究了利用Doherty具有增益扩展特性的放大器线性化技术.深入分析了Doherty功放中辅助功放的栅压变化对增益扩展特性的影响,并讨论了据此将具有增益扩展特性的前级Doherty功放作为模拟射频预失真器与末级Doherty功放进行级联而构成的线性化功放.最后根据这一原理,采用一对MRF21010功放管所设计并优化的Doherty模拟预失真功率放大器与前级为平衡放大器、末级为相同Doherty功放的级联电路相对照,表明三阶互调可以改善15dB,效率提高2%.研究结果对高效率、高线性功放的设计具有实际意义.     

A 90-GHz InP-HEMT lossy match amplifier with a 20-dB gain using a broadband matching technique

We demonstrated a 90-GHz InP-HEMT lossy match amplifier (LMA) with a 20-dB gain for the first time. The power consumption was 220 mW, which is the smallest ever reported for a broadband amplifier with a bandwidth of over 80 GHz. The amplifier acts as a C-R coupled amplifier in the low to medium frequency range and as an L-C match amplifier at high frequencies. This configuration provides both high gain and wide bandwidth. The key to achieving a bandwidth of over 80 GHz is broadband matching in the L-C match amplifier. In this paper, we propose a broadband matching technique with a low-Q network and describe the design guideline we used to get excellent performance.     

Modeling the saturation induced by broad-band pulses amplified inan erbium-doped fiber amplifier

We theoretically study the saturation of a homogeneously broadened optical amplifier with a slow response time. This model approximates well the behavior of the erbium-doped fiber amplifier (EDFA). When a broad-band pulse propagates inside such amplifier the saturation is determined by the overlap between the amplifier gain profile and the pulse spectrum rather than by the energy of the pulse. This effect may significantly increase the output power of an EDFA that amplifies broad-band pulses     

Broadband Amplifier Module Used in 3MM IF-Switch Radiometer

This paper introduced the design procedure of a low-noise broadband amplifier module used in 3mm IF-Switch radiometer. We first analyzed the impact of IF amplifier on the overall performance of the radiometer and then illustrated the techniques used in broadband amplifier design. CAD software was used in the procedure of simulation and the circuit was implemented in hybrid microstrip format. The final amplifier module matched well with the simulation result.     

0-40 GHz GaAs MESFET distributed baseband amplifier ICs forhigh-speed optical transmission

We describe distributed amplifiers built using advanced circuit design techniques to improve gain and noise performance at low frequencies. Using these techniques we have developed an amplifier IC with a 0-36 GHz bandwidth and a noise figure of 4 dB at low frequencies. This frequency range starting from 0 Hz makes it possible to use the IC as a baseband amplifier for SDH optical transmission systems and this noise figure is about 1 dB better than conventional distributed amplifiers. We also present another amplifier IC built using our loss compensation technique to improve high-frequency performance of the amplifier. This IC has a 0-44-GHz bandwidth, which is the widest among all reported GaAs MESFET baseband amplifiers