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.
Single-mode small-form-factor fiber optic connectors for enterprise computing systems
Advanced enterprise servers require dense packaging of their fiber optic input/output (I/O) interconnections. This can be accomplished using small-form-factor (SFF) optical connectors and transceivers such as the MT-RJ and LC. Previously, we presented a performance comparison between some of the major types of multimode SFF connectors; at the time, none of these designs was mature enough to offer equivalent performance to established connectors or to support a single-mode interface. We extend the previous work to include recent design enhancements in multimode connectors, as well as the first performance comparison between single-mode SFF connectors. Fiber optic jumper cables are tested using industry standard test procedures and bench marked against the industry standard SC Duplex connector. Initial loss data as well as stress testing are performed. Variations are found in the performance of the connectors types, with the mechanical stress tests of axial and off-axial pull being the most demanding application tests. Because SFF connectors are more susceptible to pull forces, we describe a new type of strain relief developed for high-density I/O interconnects. These connectors demonstrated for the first time design points that are suitable to replace the SC Duplex interface in both multimode and single-mode enterprise system applications.
Novel V-groove-based interconnect technology
A novel fiber optic interconnect technology based on injection molded V-grooves that uses the fiber’s inherent precision to provide a reliable, robust and consistent optical connection is described. This technology has been expanded and applied to optical transceivers that can now achieve the same port density as that of current copper-based systems. Both the interconnect and the optical transceivers are shown to have performance levels similar to current ferrule-based multimode technology. Testing was performed in an effort to accurately measure performance and qualify the connector design for field use. Test results for the interconnect met the performance requirements of Electronics Industry Association/Telecommunications Industry Association (EIA/TIA) 568, which represent test standards for local area networks. Results of insertion loss and return loss performance of the duplex ferrule-less connector design were measured when 400 unique links were tested using 62.5 mm multimode fiber. Mating durability performance tests were performed in which plugs were reconnected to the socket 500 times. A new generation of small form factor transceivers is discussed that were developed using the same V-groove technology. Optomechanical tests are reported that show the performance level of these new transceivers is comparable to existing ST transceiver technology.