RZ-DPSK transmission using a 42.7-Gb/s integrated balanced optical front end with record sensitivity

We have demonstrated a record sensitivity of -37.0 dBm (38 photons/bit) for a BER of 10/sup -9/ at 42.7-Gb/s using an integrated balanced optical front end. Results were obtained using optical preamplification of RZ-DPSK modulation and an external delay-interferometer. The OSNR requirement was measured to be 16.9 dB in a 0.1-nm bandwidth. The impact of polarization-mode dispersion (PMD) and chromatic dispersion on the optical front end performance has been measured. Performance for enhanced forward error correction has been projected based on 10/sup -3/ BER performance.     

Demonstration of enhanced performance of an InP/InGaAsheterojunction phototransistor with a base terminal

The optical gain and the small-signal frequency response of an InP/InGaAs heterojunction phototransistor (HPT) with a base terminal are investigated in detail for the first time. When operated under an optimally chosen external base current, the optical gain is enhanced more than five times over that of the same device operated as a two-terminal device, over a 17-dB range of input optical power. The small-signal 3-dB bandwidth of the three-terminal device is enhanced 15 times over that of the two-terminal device over the same range of input optical power. For a pseudorandom NRZ bit stream at 100 Mb/s, a clear eye opening is observed at an incident optical power of -33 dBm (500 nW)     

Functional sites and evolutionary connections of acylhomoserine lactone synthases

Acylhomoserine lactone (AHL) synthases act as chemical communicationsignals or pheromones in Gram-negative bacteria and regulatediverse physiological events in a cell density-dependent manner.The recent crystal structure determination of EsaI, a key enzymein this pathway, shows that the AHL synthase superfamily membersadopt the fold of the N-acetyltransferase superfamily. We suggest,by the identification of intermediate sequences, that the twosuperfamilies are evolutionarily related. Evolutionary traceanalyses of aligned sequences and docking studies have beenused to discuss functionally important residues of EsaI homologues.     

A parallel polygon-clipping algorithm

We describe a new parallel polygonclipping algorithm based on a novel technique that allows a processor to compute output vertices independently of the results of the other processors. The basis for the method is a collision-free labeling scheme to compute the labels of the vertices of the output polygon. This labeling scheme depends only on the id of the vertices of the output polygon. This labeling scheme depends only on the id of the vertex in the input polygon. This procedure allows us to defer the synchronization between processors to the final stages of the algorithm, reduces the amount of overhead due to fine-grain synchronization, and helps makes the algorithm efficient.     

Tunable dispersion compensation at 40-Gb/s using a multicavity etalon all-pass filter with NRZ, RZ, and CS-RZ modulation

We present a multichannel tunable dispersion compensator (TDC) based on multicavity all-pass etalons that is capable of operation at 40 Gb/s. The device has a tuning range of +200/-220 ps/nm with a group delay ripple < /spl plusmn/5 ps over a channel bandwidth of 80 GHz, an overall loss of < 5.2 dB, very low insertion loss ripple, and can operate on any channel on a 200-GHz grid over the C-band. In addition, we present system performance results at 40 Gb/s using NRZ, RZ, and CS-RZ modulation, compensating up to 45 km of nonzero dispersion shifted fiber (NZDSF). Our results show that this device introduces very little excess system penalty with signal frequency drifts of up to 20 GHz when operated near the center of its tuning range. For single channel experiments with fiber, the system penalty increase versus signal detuning is more significant, but can be reduced by dynamically optimizing the device dispersion during detuning. Finally, we demonstrate simultaneous compensation of 4 channels across the C-band over 25 km of NZDSF.     

Modeling and characterization of the polymer stud grid array (PSGA) package: electrical, thermal and thermo-mechanical qualification

We characterize the polymer stud grid array (PSGA) package electrically, thermally and thermo-mechanically for successful commercial application. For the electrical characterization, we extract lumped parameter resistance-inductance-capacitance (RLC) models for the interconnects from simulations. We also measure the RF performance of the package on printed circuit board (PCB) test structures. The average self-inductance from the wirebond pad to the bottom of the stud is 0.53 nH and the total capacitance to the ground is 0.26 pF for an interconnection of the periphery of the over the edge (OTE) type PSGA. The lumped RLC model is verified by full three-dimensional (3-D) EM simulations. Simulation models also indicate that the "Micro-via" (/spl mu/-via) type of interconnection on the PSGA package improves performance by decreasing the inductance on an average by 60%. Thermal characterization involves the development of a steady-state thermal compact model with six nodes for the 72-pin PSGA. We also perform transient thermal measurements on test packages to fine-tune the detailed model. For the thermo-mechanical case we test the first level and second level reliability by experiments and optimize them using simulations. The board level reliability for the 72-pin PSGA mounted on a PCB is very high (N50%>10000 cycles). Simulations also show a higher reliability for the PSGA than the plastic ball grid array (PBGA).     

Continuous wave cavity ring down spectroscopy measurements of velocity distribution functions of argon ions in a helicon plasma

We report continuous wave cavity ring down spectroscopy (CW-CRDS) measurements of ion velocity distribution functions (VDFs) in low pressure argon helicon plasma (magnetic field strength of 600 G, T(e) ≈ 4 eV and n ≈ 5 × 10(11) cm(-3)). Laser induced fluorescence (LIF) is routinely used to measure VDFs of argon ions, argon neutrals, helium neutrals, and xenon ions in helicon sources. Here, we describe a CW-CRDS diagnostic based on a narrow line width, tunable diode laser as an alternative technique to measure VDFs in similar regimes but where LIF is inapplicable. Being an ultra-sensitive, cavity enhanced absorption spectroscopic technique; CW-CRDS can also provide a direct quantitative measurement of the absolute metastable state density. The proof of principle CW-CRDS measurements presented here are of the Doppler broadened absorption spectrum of Ar II at 668.6138 nm. Extrapolating from these initial measurements, it is expected that this diagnostic is suitable for neutrals and ions in plasmas ranging in density from 1 × 10(9) cm(-3) to 1 × 10(13) cm(-3) and target species temperatures less than 20 eV.