Yuhki Imai

Loss-compensated distributed baseband amplifier IC's for optical transmission systems

We describe a distributed baseband amplifier using a new loss compensation technique for the drain artificial line. The new loss compensation circuit improves a high-frequency performance of the amplifier and makes the gain bandwidth product of the amplifier larger than that of conventional ones. We also use dc matching terminations and dumping resistors for the gate and drain artificial lines to obtain flat gain from frequencies as low as 0 Hz. One IC fabricated using 0.1 /spl mu/m-gatelength InAlAs/InGaAs/InP HEMTs has a gain of 16 dB over a 0-to-50 GHz band, resulting in a gain bandwidth product of about 300 GHz. Another IC has a gain of 10 dB over a 0-to-90 GHz band. These are the highest gain bandwidth product and the widest band reported for baseband amplifier ICs applicable to optical transmission systems.

40-Gbit/s ICs for future lightwave communications systems

This paper reviews recent advances in 40-Gbit/s class analog and digital ICs developed at our laboratories for future lightwave communications systems. A 0.1-/spl mu/m gate InAlAs/InGaAs HEMT with InP recess etch stopper was adopted mainly for IC fabrication. Fabricated ICs demonstrate excellent data-multiplexing, demultiplexing and amplifying operation at 40 Gbit/s.

1.25 Gb/s burst-mode receiver ICs with quick response for PON systems

This paper describes burst-mode receiver ICs with quick response for 1.25-Gb/s optical access networks. In a point-to-multipoint fiber access system, such as a passive optical network (PON) system, the receiver should be able to handle burst-data packets with different amplitudes. In burst-mode transmission, a receiver with a quick response is desired for high efficiency in data transmission. In addition, high sensitivity is also required for such a shared access system. To achieve a quick response and high sensitivity at the same time, a transimpedance amplifier (TIA) with three gain modes has been designed. The use of a hysteresis comparator enables fast gain mode switching. A limiting amplifier with feed-forward auto-offset compensation (AOC) is also used for quick response to burst data. These circuit techniques require no external adjustment. Using these design techniques, optical receiver ICs were fabricated in SiGe-BiCMOS technology. The optical receiver built with the ICs exhibits a settling time of under 20 bits and a sensitivity of -30 dBm with wide dynamic range of over 26 dB using a p-i-n photodiode (PD) for burst-mode optical input at 1.25 Gb/s. These fast-response receiver chips improve the data transmission efficiency. The use of a conventional p-i-n PD and the freedom from external adjustment make it possible to build an inexpensive receiver.

A 0.2 mu m GaAs MESFET technology for 10 Gb/s digital and analog ICs

A 0.2 mu m gate length GaAs IC technology is reported. This technology enables the fabrication of both digital and analog ICs using the same process. A 10 Gb/s decision circuit with a 130 mV sensitivity and 215 degrees phase margin, and an amplifier with a 20 dB gain and 13 GHz bandwidth were successfully fabricated using this unified process technology.<<ETX>>

Design and performance of wideband GaAs MMIC's for high-speed optical communication systems

Advanced design techniques for GaAs wideband direct-coupled amplifiers are described. The amplifier achieved a 20 dB gain with a 3 dB bandwidth of 13 GHz and a 5-7 dB noise figure. An equalizing amplifier module consisting of amplifier and variable attenuator monolithic microwave integrated circuits (MMICs) exhibited a high gain of 43 dB over a 10 GHz band with a controllable gain of 20-43 dB. >

A design technique for a high-gain, 10-GHz class-bandwidth GaAs MESFET amplifier IC module

A design procedure is proposed for a high-gain and wideband IC module, using stability analysis and a unified design methodology for ICs and packages. A multichip structure is developed using stability analysis and the requirements for stable operation are determined for each IC chip, package, and interface condition between them. Furthermore, to reduce the parasitic influences, several improvements in the interface and package design are clarified, such as wideband matching and LC resonance damping. IC design using effective feedback techniques for enlarging the bandwidth are also presented. The ICs are fabricated using 0.2- mu m GaAs MESFET IC technology. To verify the validity of these techniques, an equalizer IC module for 10-Gb/s optical communication systems was fabricated, achieving a gain of 36 dB and a bandwidth of 9 GHz. >

Ultrafast monolithic receiver OEIC composed of multimode waveguide p-i-n photodiode and HEMT distributed amplifier

A multimode waveguide p-i-n photodiode (WGPD) and a distributed baseband amplifier consisting of high-electron mobility transistors (HEMTs) were monolithically integrated on InP substrate using a stacked layer structure for both components. The multimode WGPD has a 3-dB bandwidth of 49 GHz. The distributed baseband amplifier has a 3-dB bandwidth of 47 GHz, though its 0.5-/spl mu/m gate-length HEMTs have modest cutoff frequencies f/sub T//f/sub max/ of 47/100 GHz. The receiver optoelectronic integrated circuit has a bandwidth of 46.5 GHz. It was packaged into a fiber-pig-tailed module, and the WGPD in the module has a high responsivity of 0.62 A/W for 1.55-/spl mu/m wavelength. The module achieves a sensitivity of -22.7 dBm at 40 Gb/s and exhibits a clear eye-opening at 50 Gb/s.

Direct-coupled distributed baseband amplifier IC's for 40-Gb/s optical communication

We have developed GaAs MESFET baseband amplifiers using novel distributed amplification schemes. The key feature of their design is a direct coupling architecture employing two kinds of new distributed DC transformers. One is a distributed level-shift circuit and the other is a distributed source coupled FET logic (SCFL) level transformer. A two-stage distributed amplifier IC cascaded with the distributed level-shift circuit has a gain of 17 dB with a 0-to-30 GHz bandwidth. This is the best performance so far among all reported GaAs MESFET baseband amplifier ICs. A distributed baseband amplifier IC with the distributed SCFL level transformer connected by another distributed level-shift circuit also has a 0-to-30 GHz bandwidth with a gain of 7 dB. This is the first IC with an SCFL interface to have such broad-band characteristics.

Novel distributed baseband amplifying techniques for 40-Gbit/s optical communication

GaAs MESFET baseband amplifiers using novel distributed amplification schemes have been developed. The key feature of their design is a direct coupling architecture employing two new distributed DC transformers. One is a distributed level-shift circuit and the other is a distributed SCFL level transformer. A two-stage distributed amplifier IC cascaded with the distributed level-shift circuit has a gain of 17 dB with a DC-to-30-GHz bandwidth. This is the best performance so far among all reported GaAs MESFET baseband amplifier ICs. A distributed baseband amplifier IC with the distributed SCFL level transformer can be directly coupled with a GaAs SCFL circuit. This IC also has a DC-to-30-GHz bandwidth with a gain of 7 dB. This is the first IC with an SCFL interface to have such broadband characteristics.

Design and performance of clock recovery GaAs ICs for high-speed optical communication systems

Design and performance of clock-recovery GaAs ICs are presented. Four kinds of ICs were developed: a limiting amplifier, a tuning amplifier, a rectifier, and a differentiator. The cascaded limiting amplifier together with a tuning amplifier achieved a 58-dB gain and a 10-degree phase deviation with 20-dB input dynamic range at 10 GHz. A clock-recovery circuit successfully extracts a low-jitter 10-GHz clock signal of 1-dBm constant power from 10-Gb/s NRZ pseudorandom bit streams using a pulse pattern generator. >