The Best Paper Award
Monolithically Integrated Wavelength-Routing Switch Using Tunable Wavelength Converters with Double-Ring-Resonator Tunable Lasers
Toru Segawa 　・　Shinji Matsuo 　・　Takaaki Kakitsuka　・　Yasuo Shibata
Tomonari Sato 　・　Yoshihiro Kawaguchi 　・　Yasuhiro Kondo　・　Ryo Takahashi
（英文論文誌C　平成23年9月号掲載）
　With the explosive growth of data traffic in communication networks due to the Internet and its related services, the excessive increase in power consumption of large capacity routers has become a major concern. Optical packet-switching networks (OPS-NW) relying on optical packet routers are considered to be a potential solution that maximizes the flexibility and throughput of the network owing to the packet-level granularity which they can support. However, the construction of optical packet routers will require N×N optical switches that can operate on a packet-by-packet basis while maintaining data in the optical domain. Although various types of N×N optical switches have been considered and demonstrated so far, there are still several challenges including the speed of switching capability, power consumption, footprint and scalability to match the need in optical packet routers. Currently, the most promising candidate is a wavelength-routing switch (WRS), utilizing the wavelength of optical packets.
　 The WRS is composed of a set of tunable wavelength converters (TWCs) followed by an arrayed-waveguide grating (AWG). The TWC in WRS consists of a high-speed tunable laser and an optical gate. For the tunable laser, fast tuning of the lasing wavelength is critical in order to switch each packet within a guard time of several nanoseconds. In addition, wide and accurate tuning characteristic is required in order to fabricate large scale switches. In that paper, double-ring-resonator tunable lasers developed by the authors are employed; resulting in high-speed, stable and wide-band tunability with low tuning current. Since the ring resonator is basically a transmission-type filter, the fabrication technologies for mirrors essential to form a laser cavity on integrated switch are developed. Furthermore, the fabricated TWC can automatically remove the input signal from the converted signal before the AWG by using parallel amplifiers in symmetric Mach-Zehnder arms as an optical gate. An ultra-compact WRS is fabricated by integrating the TWCs and AWG with a size of only 2.1×4.8 mm2. A 1×8 high-speed wavelength routing operation with a switching time of less than 10 ns is demonstrated.
　 As stated above, the results of this paper are highly original based on the authors' previous developments and study. The device will be critical for realizing future environmentally friendly optical networks by reducing the power consumption and footprint of large capacity routers.

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