A Scalable AWGR-Based Optical Switch

The energy-per-bit efficiency has quickly become the ultimate limiting factor in the design of a switching fabric for routers and data center networks. People are now turning to optics for solutions. If switch fabrics can be implemented with optics, many E/O and O/E conversions will be removed and tremendous power saving can be achieved. Arrayed waveguide grating routers (AWGRs) provide the most promising solution in this regard. But AWGRs have one fundamental limitation: poor scalability. While the realistic port count of an AWGR is likely to be less than 50, a switch for a data center network may need to interconnect one thousand racks, or more. This paper presents a novel AWGR-based switch architecture which, without using wavelength converters, can expand the switch size from N to $N^{2}$, where N is the number of wavelengths in the AWGR. Each port can transmit up to N wavelengths simultaneously. This makes the total capacity of the switch close to ($N^{3}$ × bandwidth of a wavelength channel). A detailed analysis of the performance of the switch is provided in this paper.

I. Introduction

The Internet's traffic growth shows no sign of abating [1]. To keep pace with the growth, the capacity of a single-rack router has grown about threefold every 18 months [2]. But the energy/bit efficiency has only decreased at a rate of about 10% per year since 2000 [3]. Since the power dissipation within a rack cannot substantially increase due to the present limitations of air cooling, the energy/bit efficiency is becoming the ultimate capacity limiting factor for future routers or data center networks. How to reduce the physical and carbon footprint of a data center network has been pushed to the forefront of networking research today.