A.P. Freundorfer

A 10 Gb/s AlGaAs/GaAs HBT high power fully differential limiting distributed amplifier for III-V Mach-Zehnder modulator

High power, high frequency linear distributed amplifiers are available commercially which provide high power single-ended drive capability from a single-ended source. The signal source can be either analog or digital. Such amplifiers must have stringent gain and phase response requirement over a wide bandwidth in order to maintain good eye quality of the signal. A limiting amplifier, with less stringent bandwidth requirement than analog amplifiers, can be used to amplify pure digital signal source. The purpose of this paper is to present a high power, fully differential limiting distributed amplifier operating at 10 Gb/s. The amplifier has been fabricated with both AlGaAs/GaAs and InGaP/GaAs heterojunction bipolar transistor (HBT) processes. The amplifier is designed to drive any 50 /spl Omega/ system. In particular, this amplifier is intended to drive a III-V Mach-Zehnder modulator.

MMIC adaptive transversal filtering using Gilbert cells and is suitable for high-speed lightwave systems

An adaptive transversal filter (equalizer), which has positive and negative tap weights, will be discussed. Measured results will be presented that show an increased passband control. An example of pulse shaping/generation of a modified duobinary signal is also shown.

Adaptive transversal preamplifier for high speed lightwave systems

A nine-tap transversal preamplifier using cascode MESFETs in a distributed structure has been designed for pulse shaping data, AGC and group delay control in high speed lightwave systems. The circuit was fabricated in a microwave monolithic integrated circuit (MMIC) implementation using 0.8 /spl mu/m GaAs MESFET technology. The AGC capability was demonstrated. The best noise measured for this preamplifier was 15 pA//spl radic/(Hz).

A low-noise broad-band GaAs MESFET monolithic distributed preamplifier

It is shown that the equivalent input noise current density of a distributed preamplifier of an optical receiver can be improved by using large gate, line matching impedance. A monolithic GaAs MESFET distributed preamplifier, utilizing this design consideration, was fabricated. Using a 35 /spl mu/m InGaAs p-i-n photodiode, it was shown to have an equivalent input noise current density of 8 pA//spl radic/(Hz) and an 8 GHz bandwidth. To date, this is the best known result for a 0.8 /spl mu/m GaAs MESFET process.<<ETX>>

An active transversal filter MMIC for very high-speed lightwave systems

An equalizer using cascode MESFETs in a distributed structure has been designed for pulse shaping data in high speed lightwave systems. Pulse shaping is accomplished by controlling the gain of each individual cascode stage separately in the distributed circuit. The circuit was fabricated in a microwave monolithic integrated circuit (MMIC) implementation using Nortels 0.8 /spl mu/m GaAs MESFET technology. Frequency response measurements demonstrate that the bandwidth can be controlled up to 8 GHz. Eye pattern measurements demonstrate the ability to control the pulse shape at 5 Gb/s.

A 10 Gb/s AlGaAs/GaAs HBT high power fully-differential limiting distributed amplifier for III-V Mach-Zehnder modulator

High power, high frequency linear distributed amplifiers are available commercially which provide single-ended drive capability from a single-ended source. The purpose of this paper is to present an AlGaAs/GaAs HBT high power fully-differential limiting distributed amplifier operating at 10 Gb/s. The amplifier is designed to drive a III-V Mach-Zehnder modulator also developed at Bell-Northern Research.

A coherent optical network analyzer

A novel measurement instrument is presented for evaluation of optical components. The proposed instrument is able to measure the scattering parameters of a two-part optical device under test (ODUT) for a given optical probe wave. The optical scattering parameters are vectors and this implies that polarization, phase, and, magnitude detection are important. The ODUT may be optical material, optical components, or fiber optical communication components. This instrument is also capable of polarization measurements. Heterodyne mixing and small linewidth lasers with large tunable range make it a flexible tool for optical device evaluation and design. Experimental results are also presented. >

Noise analysis of a photoreceiver using a P-I-N and GaAs HBT distributed amplifier combination

A noise analysis for a common-collector-cascode traveling wave HBT preamplifier is developed. The photoreceiver, consisting of a P-I-N and GaAs HBT MMIC distributed amplifier, was implemented using Nortels f/sub T/=70 GHz GaAs HBT process, is the first to have a P-I-N mounted on the MMIC chip. The P-I-N preamplifier, having a measured bandwidth of 22 GHz, displayed a measured average equivalent input noise current density of 24 pA//spl radic/Hz. Good agreement was obtained between the predicted and measured noise performance.

A low noise broadband GaAs MESFET monolithic distributed preamplifier

It is shown that the equivalent input noise current density of a distributed preamplifier of an optical receiver can be improved by using large gate line matching impedance. A monolithic GaAs MESFET distributed preamplifier utilizing this design consideration was fabricated. Using a 35 /spl mu/m InGaAs p-i-n photodiode, it was shown to have an equivalent input noise current density of 8 pA//spl radic/(Hz) and an 8 GHz bandwidth. To date, this is the best known result for a 0.8 /spl mu/m GaAs MESFET process.<<ETX>>

MMIC adaptive transversal filtering for optical communication systems

An adaptive transversal filter (equalizer), which has only positive tap weights, will be discussed. It has a measured bandwidth that can be controlled from 2 GHz to 8 GHz. AGC and phase shift function of this circuit for microwave applications are presented. A new adaptive transversal filter with negative and positive tap weights can be operated in a bandpass mode. When integrated with a MSM photodetector on the same chip, one could in principle make a photo receiver that can AGC and control phase shift.