2.488 Gb/s-318 km repeaterless transmission using erbium-dopedfiber amplifiers in a direct-detection system

The authors have achieved a 2.488 Gb/s, 318 km repeaterless transmission without any fiber dispersion penalty through a nondispersion-shifted fiber in a direct detection system. The system was loss limited with a T-R power budget of 57 dB. Three key components enabled the authors to achieve this result: (1) a Ti:LiNbO₃ external amplitude modulator enabling a dispersion-free transmission, (2) erbium-doped fiber amplifiers increasing the transmitting power to +16 dBm, and (3) an erbium-doped fiber preamplifier enabling a high-receiver sensitivity of -4.1 dBm for 10^-9 BER. To the author's knowledge, this result is the longest repeaterless transmission span length ever reported for direct detection at this bit rate. From the experimental results and a theoretical model, the authors identified the sources of the receiver sensitivity degradation from the quantum limit (-48.6 dBm) and estimated the practically achievable receiver sensitivity of ~-44 dBm (~-124 photons/bit) for 2.5 Gb/s optical preamplifier detection     

Performance evaluation of waveguide phase modulators for coherent systems at 1.3 and 1.5 µm

This article describes the fabrication and performance evaluation ofX-cut andZ-cut Ti:LiNbO3traveling wave waveguide phase modulators designed for coherent systems applications at 1.3 and 1.5 μm. Details of device fabrication and measurements of phase shift as a function of optical wavelength, input polarization, modulation voltage, and modulation frequency are reported. Phase modulator performance in a 40-Mbit/s self-heterodyne coherent DPSK experiment is also discussed.     

1.3 mu m semiconductor laser power amplifier

The performance of a 3.4-Gb/s system using a low-power 1.318- mu m distributed-feedback (DFB) laser transmitter and a traveling-wave semiconductor laser power amplifier is studied. The -14.5-dBm, input from a directly modulated DFB laser is boosted to +10.3 dBm, of which +4.8 dBm is coupled into the transmission fiber. The penalty, caused by amplifier noise and pattern effects due to gain saturation, is less than 0.5 dB.<>     

Crosstalk and prefiltering in a two-channel ASK heterodynedetection system without the effect of laser phase noise

The authors present an experimental and theoretical study on the crosstalk in a two-channel amplitude-shift keying (ASK) heterodyne detection system in which the effect of laser phase noise is negligible. Three results are described: (1) the dependence of the crosstalk penalty on the ratio of channel separation to bit rate and on the optical power level of the image band (2) comparison of the measured crosstalk penalities with the ones obtained from a simple model, and (3) the effect of electrical prefiltering on the crosstalk penalty. It is concluded that the channel separation can be as low as four times the bit rate without incurring any crosstalk penalty as long as the optical power of the image band is comparable to the optical power of the desired channel. In addition, electrical prefiltering of the transmitted signals significantly reduces the crosstalk penalty in multichannel ASK heterodyne systems in which the effect of laser phase noise is negligible     

Evaluation of agitation within circuit board through — holes

A method is presented for determining the rate and uniformity of solution mass transport to the outer surfaces and within the through-holes of multilayer printed circuit boards. The method is based on the measurement of the diffusion-limited currents for a fast redox reaction at strategically located inert electrode probes. A specially fabricated test board and an electrolyte which hydrodynamically simulates the copper pyrophosphate system are described. Results are presented for a typical agitation scheme based on gas sparging and slow board motion. The method provides the basis for evaluating and improving bath agitation schemes and should be applicable to a variety of systems.     

Enhanced tensile strength for electrodeposited nickel-copper multilayer composites

The tensile strength of electrodeposited layered composites of the nominal overall composition 90 pct Ni-10 pct Cu is shown to increase sharply to the 1300 MPa range as the thickness of the Cu layers is decreased below ~0.4 ώm. This tensile strength value is almost a factor of three greater than that measured for Ni itself, and more than a factor of two greater than the handbook value for Monel 400.     

Solderability assessment via sequential electrochemical reduction analysis

A recently-developed sequential electrochemical reduction analysis method permits nondestructive assessment of solderability loss associated with surface oxides on metals and can be applied to almost any part geometry, including printed wiring board through-holes and surface pads. Preliminary results indicate that metal sulphides can also be detected, at least in some cases. The type and amount of oxides detected for tin coatings are shown to correlate with solderability determined by the wetting balance method. The data indicate that formation of excessive amounts of Sn02 in the surface oxide is a primary cause of Sn solderability degradation.     

1.7 Gb/s-419 km transmission experiment using a shelf-mounted FSKcoherent system and packaged fiber amplifier modules

Experiments to assess the commercial viability of long-span FSK coherent systems with fiber amplifiers were performed. Transmission spans of 253, 365, and 419 km with integrated shelf-mounted modules have been demonstrated in repeaterless systems and in single-fiber and two-fiber amplifier repeatered systems, respectively     

High-temperature tensile properties of Cu-Ag composites prepared by solution-precipitation of electroformed multilayered alloys

Appropriate heat treatments have been shown to convert Cu-Ag multilayered structures, obtained by a new electrochemical periodic displacement process, into homogeneous alloys or dispersed particle composites. The high-temperature tensile properties of the latter are comparable to those obtained for similar materials prepared by conventional metallurgical techniques. Preliminary data also indicate that the as-deposited material may exhibit superplastic behaviour under stress applied immediately at high temperature.