Performance comparison of parallel optical interconnects for enterprise servers
There is an emerging need in the computing industry for higher bandwidth, longer distance, and increased density interconnections within clusters of high performance enterprise-class computer systems. Many of these servers share a common set of high level requirements which lend themselves to the use of parallel optical interconnects to either supplement or replace existing copper data buses. In this paper, we describe the results of application testing performed on 12-fiber parallel optical cables and connectors, including a relative comparison between three different multimode cable assembly sources. Assembly loss and effects of both axial and off-axis pull forces are measured for cable samples mated to a laser transmitter array. Significant variations exist in the performance of the same type of cable assembly from different manufacturing sources, particularly concerning their susceptibility to pull forces; we also investigate the effects of fiber strain relief to improve performance of these links. While currently available 12-fiber array connectors are not equivalent in performance to standard duplex connectors, this work suggests areas for future improvement and data communication application requirements which should be considered when using parallel fiber optic arrays.
Latent Electro-Static Damage in Vertical Cavity Surface Emitting Semiconductor Laser Arrays
We describe a novel type of failure mechanism for arrays of vertical cavity surface emitting lasers, such as those used in parallel optical interconnects for clustered computer systems. Conventional failure mechanisms related to electrostatic discharge (ESD) during laser manufacturing will cause multiple lasers in an array to fail at once, shortly after the ESD event. We have found that in some cases, latent ESD damage can occur; the ESD site serves as a nucleation point for dark line defects, which migrate under applied voltage. In this manner, individual elements in the laser array can fail randomly, without affecting adjacent lasers in the same array; furthermore, these failures can occur after 30-40 days of continuous operation. We report empirical data on the failure analysis used to identify this effect, including images of the latent damaged lasers, and recommend procedures for avoiding this damage during manufacturing.
Compact and durable MT-RJ connector
We have successfully developed the MT-RJ connector which is designed to be compact, easy to use and high performing. Optical characteristics measurements have revealed typical connector insertion loss values of less than 0.1 dB and return loss values of higher than 30 dB for 62.5/125 /spl mu/m multimode GI fiber, while respective values of 0.15 dB and 40 dB have been obtained for the 10/125 /spl mu/m singlemode fiber. A variety of mechanical and environmental tests based on the Bellcore and IEC standard specifications have also proven the reliability of the connector for field and premises use, with typical insertion loss changes of less than 0.1 dB. We have also developed a field installable version of the connector for fast and easy assembly in the field.