20 GHz bandwidth low-noise HEMT preamplifier for optical receivers

A broadband, low-noise HEMT preamplifier is designed for very high-speed fibre-optic transmission systems. A 20 GHz 3 dB down bandwidth and 7.6 pA/√(Hz) averaged input equivalent noise current density from 100 MHz to 18 GHz are achieved using inductor peaking techniques and low stray capacitance chip resistors     

Variable bandwidth and tunable centre frequency filter usingtransversal-form programmable optical filter

The authors report the realisation of an integrated-optic variable bandwidth and tunable centre frequency filter using a transversal-form programmable optical filter with 32 taps. The bandwidth is varied from 44 to 84 GHz with a fixed centre frequency. Also, the centre frequency is tuned over 105 GHz with a fixed bandwidth     

GaAs monolithic integrated optical preamplifier

A GaAs monolithic integrated optical preamplifier has been developed based on the transimpedance principle. By associating the amplifier with an external p-i-n diode, a sensitivity of -38 dBm was measured at 140 Mbits/s and 10^-9error rate with a signal wavelength of 1.3 μm. A TiWSiN-integrated technology was used to realize larger than 100-kω feedback resistors and gate leakage could be minimized by improving Schottky contact deposition and employing selective implantation. The optimization details of the FET and resistor elements, as well as the design techniques for integrated transimpedance amplifiers are presented.     

System performance of optical fibre preamplifier

An optical fibre amplifier has been used as an optical preamplifier for a PIN detector-based receiver. A maximum amplifier gain of 22 dB has been measured and, at this gain with no additional optical filtering, an improvement of 10.5 dB in receiver sensitivity has been achieved.<>     

Nonlinear feedback preamplifier for optical trigger circuits

A nonlinear preamplifier system to improve the performance of a zero-crossover optical trigger circuit is presented. The network is based on a low-noise operational amplifier with a Zener diode feedback. It is proposed to exploit the nonlinear characteristic of this network to reduce timing measurement uncertainty. Accordingly the circuit has been developed and tested in operation.     

Ultrawide bandwidth optical receivers

Low-noise p-i-n/HEMT optical receivers with bandwidths in excess of 16 GHz have recently been developed using advanced microwave design and packaging techniques. Here, state-of-the-art receiver technology, including design tradeoffs and implementation techniques for this class of ultrawide bandwidth receiver, is discussed. Some directions for future research are explored     

一种可变带宽FRM滤波新结构

设计窄过渡带FIR滤波器的一种非常有效的方法是采用频率响应屏蔽技术(FRM).但是如果过渡带要求过窄,经典FRM滤波器各子滤波器的阶数会变得很高.据此,本文提出一种可变带宽镜像半带滤波FRM滤波新结构,通过增加两个镜像半带滤波器,将原型滤波器及其互补滤波器的镜像分别分成奇偶两部分,使得原型滤波器和屏蔽滤波器的设计更加灵活,并降低了滤波器的计算复杂度,达到了设计高效窄过渡带滤波器的目的.理论分析和实例均验证了该结构的有效性.     

Transimpedance optical preamplifier having a common-collector front end

A simple PIN photodiode-bipolar transistor (PIN-BJT), direct-coupled, transimpedance, optical preamplifier suitable for fabrication in monolithic IC form is described. The preamplifier basically consists of a common-collector, common-emitter configuration with shunt feedback. Measurements indicate that the receiver is capable of a sensitivity of ?35.8 dBm at 140 Mbit/s for an error rate of 10?9.     

Optical preamplifier using optical modulation of amplified spontaneous emission in saturated semiconductor optical amplifier

This paper demonstrates a novel optical preamplifier using optical modulation of amplified spontaneous emission (ASE) emitted from a saturated semiconductor optical amplifier (SOA). Requirements on optical alignments and antireflection coating for SOAs can be relaxed and the elimination of an optical filter gives us a large tolerance of an input light wavelength in the proposed optical preamplifier. A small-signal gain of a fabricated preamplifier was over 13.5 dB for an input power of below -20 dBm. An optical gain bandwidth was over 60 nm. We measured the small-signal response of the optically modulated ASE. The 3 dB bandwidths at SOA bias currents of 200, 300, and 400 mA were 5.8, 12.6, and 16.5 GHz, respectively. We also investigated improvements in receiver sensitivities with the proposed optical preamplifier. Our calculation shows a possibility of 10 dB improvement in receiver sensitivities by using the optical preamplifier at 10 Gb/s. The measured receiver sensitivity was -22.7 dBm at 10 Gb/s with the optical preamplifier, which is corresponding to an improvement of 2.5 dB in the receiver sensitivity. Further improvements of the receiver sensitivity can be expected by optimizing the structure of SOAs for saturating ASE.     

A current-mode gain-control scheme with constant bandwidth andpropagation delay for a transimpedance preamplifier

This paper presents a current-mode gain-control scheme that significantly increases the input dynamic range of a wideband optoelectronic receiver without affecting its bandwidth or delay or deteriorating its noise properties. A current buffer with variable attenuation is placed between the photodetector and the transimpedance preamplifier. In this way, the input dynamic range of the receiver can be increased, or alternatively, the signal dynamics can be reduced, by over 20 dB. A BiCMOS test circuit designed for a pulsed time-of-flight laser rangefinder has a measured bandwidth of 170 MHz and an input dynamic range of ~80 dB. The delay varies only ±5 ps when the gain is varied by 24 dB (1:15)     

40 dB fibre optical preamplifier in 1064 nm laser Doppleranemometer

With a neodymium-doped fibre amplifier a small signal gain of 40 dB at 1064 nm has been achieved. Using the same amplifier as an optical preamplifier in a conventional 1064 nm laser Doppler anemometer (LDA), an improvement in the SNR of the LDA radiation and sensitivity enhancement in comparison to that for direct detection with a highly sensitive avalanche photodiode was obtained     

DCG窄带反射滤光片再现波长和带宽的控制方法

本文从DCG的成像特性出发 ,讨论了用DCG制作全息窄带反射滤光片时 ,干板制备、曝光记录、显影处理以及暗反应和后光化反应对全息滤光片的再现波长和反射带宽的影响 ,并给出了控制再现波长和带宽的方法。     

Variable bandwidth birefringent filter for stable femtosecondlasers

A design for a birefringent filter is described, which is suitable for tunable femtosecond lasers. Using a single plate, which has a steeply diving optic axis, two-octave tunability is attained with negligible deterioration of the stopband rejection. For a specific wavelength region, it means that the filter's bandwidth can be changed by a factor of four. Another characteristic of the design is that, for the same bandwidth, the proposed plate is five times thicker than a conventional plate in which the optic axis is parallel to the surface. Thus, etalon effects can be avoided. Tuning characteristics of color center lasers utilizing the new filter are also presented     

Inflection of shock response spectrum of filter bandwidth

目前利用冲击响应谱作为参考的冲击实验在国防事业、国家经济生活中得到广泛的应用,冲击响应谱也成为国防事业和经济生活中重要的参考标准,分析对冲击响应谱造成影响的因素,将有利于对冲击响应谱,规范,为更好实现冲击实验提供精确的参数设置。实验过程中为了得出冲击信号滤波带宽对冲击响应谱的影响,利用霍普金森杆产生高g值,窄带宽的冲击信号,再结合信号分析软件对得到的数据进行处理,得出滤波带宽影响冲击响应谱的等冲区的结论。     

滤波带宽对冲击响应谱的影响研究

目前利用冲击响应谱作为参考的冲击实验在国防事业、国家经济生活中得到广泛的应用,冲击响应谱也成为国防事业和经济生活中重要的参考标准,分析对冲击响应谱造成影响的因素,将有利于对冲击响应谱,规范,为更好实现冲击实验提供精确的参数设置。实验过程中为了得出冲击信号滤波带宽对冲击响应谱的影响,利用霍普金森杆产生高g值,窄带宽的冲击信号,再结合信号分析软件对得到的数据进行处理,得出滤波带宽影响冲击响应谱的等冲区的结论。     

电调滤波器Q值与带宽分析

在甚高频频段,电调滤波器的构成以集中参数元件为主。通常情况下,高频瓷介质电容都有较高的Q值,不会对带宽产生过大的影响,怎样对一个频带够窄的电调滤波器进行设计,电感的Q值起着一定的决定性作用。文章基于电路品质因数(Q值)与匹配带宽之间的理论关系,利用ADS软件对窄带电调滤波器的Q值与带宽进行了仿真分析。     

High-gain low-noise mid-infrared quantum cascade optical preamplifier for receiver

Optical preamplifier (OPA) in the mid-infrared can boost weak signals in systems such as lidars or optical wireless links to improve the receiver sensitivity. Quantum-cascade-based traveling-wave OPA with off-normal Bragg-grating (BG) coupled surface-emitting configuration have been developed with a net small-signal gain up to 13 dB over a spectral range /spl sim/70 nm around 4.7 /spl mu/m, limited by the wafer gain bandwidth, and the linear dynamic range was >20 dB. Amplified spontaneous emission (ASE) was measured and the spontaneous emission factor was determined N/sub sp//spl sim/1, indicating near quantum-limit noise behavior. Surface-emitting BG devices yielded diffraction-limited output beam, and provided simultaneous wavelength dispersion and ASE filtering. The OPA was coupled with a detector to form a receiver that is polarization-selective, has a net gain 8-13 dB with a corresponding optical filter bandwidth 25-50 GHz. These results suggest that BG-coupled OPA receivers can be useful for multispectral/wavelength-division-multiplexing systems in free space applications.     

Transimpedance optical preamplifier with a very low input resistance

A PIN photodiode-bipolar transistor transimpedance optical preamplifier with a very low input resistance is described that exhibits certain advantages over more conventional designs using common-emitter or common-collector input stages. The common-base input configuration enables optimum performance to be maintained with lower-cost photodiodes exhibiting a moderate capacitance of 2-7 pF.     

Optical preamplifier using antireflection-coating-free semiconductor optical amplifier with signal-inverted ASE

We fabricated an antireflection (AR)-coating-free semiconductor optical amplifier (SOA) with an absorbing region for an optical preamplifier. In the fabricated SOA, the resonance of light was fully suppressed so that the amplitude of the ripple of amplified spontaneous emission (ASE) spectra was as small as 0.36 dB, which is comparable to conventional SOAs with AR coating at both facets. We formed an optical preamplifier using the AR-coating-free SOA. The gain saturation of the SOA gives us the signal conversion to ASE and the amplification of the signal. The small-signal fiber-to-fiber and chip gain of the preamplifier were 11.4 and 20.0 dB, respectively. The 3-dB optical gain bandwidth of the preamplifier was about 30 nm.