Scalability Analysis of Optical Intrasystem Interconnects

Abstract

<p class="Abstract">Architecture of network elements such as large routers and switches is becoming more and more complex due to the constantly increasing requirements on both capacity and performance. Already today, high-performance routers having capacities of more than several Tb/s can not be packaged in a single rack of equipment. Complex and spatially distributed multirack routers comprising a large number of line cards, switching modules and high-speed ports have already become reality. A consequence of this trend is that internal interconnecting system also becomes large and complex. Interconnection distances, total number of cables and power consumption increase rapidly with the increase in capacity, which can cause limitations in scalability of the whole system. This paper addresses requirements and limitations of large-scale optical interconnects. Various point-to-point interconnects and two optically switched interconnection options were studied with regard to their scalability by considering various impairments on optical signal, required number of fiber links and power consumption. Results of this study are presented and discussed in this paper.</p

Limitations and Perspectives of Optically Switched Interconnects for Large-scale Data Processing and Storage Systems

“…Assuming a fixed network topology one can reduce the required number of fibers through increasing the data rate per channel, using wavelength-division multiplexing (WDM), and applying optically switched interconnects as presented on the example of a 3-stage Clos network in Figure 6a). The required number of fiber links can be reduced by up to 80 % through increasing the channel data rate, while using WDM and optically switched interconnects can lead to an even higher reduction of 95% [21]. However, the scalability of optically switched interconnects is mostly limited by physical impairments on optical signals that set limits on the maximum achievable size of switching elements without applied signal regeneration.…”

“…Figure 5. Examples of 4x4 switching elements based on a) semiconductor optical amplifiers, b) arrayed waveguide gratings with tunable wavelength converters, and c) 3D optical micro-electromechanical systems (MEMS) [21].…”

“…The EO, AO and TO effects rely on refractive index changes of the matter through application of an external physical field or action, while in OM switches, optical beams are reflected by electromechanical means. Foe a more complete overview of different options for implementing optical switches reader is referred to [21] In the EO effect, an applied electrical field induces change in the index of refraction, which then channels light to the appropriate port. LiNbO 3 is a unique crystal that shows large EO effect, AO effect, TO effect and nonlinear effects.…”

“…Each interconnection technology is upper-bounded regarding its transmission distance, channel data rate, and number of assigned channels [21]. Some of the technologies such as CEI-6G, CEI-11G and sRIO (Serial Rapid I/O) are only intended for electrical backplane applications, while others such as those based on Ethernet and InfiniBand (IB) also support board-to-board and rack-to-rack applications through using optical point-to-point interconnects.…”