OREANDA-NEWS. June 22, 2012. Fujitsu today announced that it has worked with NTT Communications Corporation to conduct a successful test of 100 Gbps DWDM transmission using an advanced optical transmission technology called "digital coherent transmission"(1) over a commercial fiber-optic cable between Tokyo and Osaka, Japan's most heavily trafficked communications corridor.

Having confirmed commercial-grade transmission quality, Fujitsu plans to actively move forward with network construction using 100 Gbps DWDM systems.
1. Background

With the spread of cloud services and the rapid uptake in smartphones using advanced wireless communications, and as access-line capacity increases, communications traffic is experiencing explosive growth. Meanwhile, the impact of last year's Great East Japan Earthquake has focused attention not only on increasing the capacity of core networks, but also in improving their reliability and disaster tolerance.

Fujitsu has been developing 100 Gbps DWDM systems as a way to achieve economical, high-capacity, high-quality advanced core networks. With NTT Communications, it conducted a field test on the underlying technology, 100 Gbps digital coherent transmission.
2. Test Overview

Fujitsu has previously implemented 100 Gbps DWDM systems that use digital coherent transmission technology at 100 Gbps per wavelength in markets outside of Japan. Leveraging this expertise, Fujitsu and NTT Communications conducted a field test of DWDM transmissions on a commercial fiber-optic cable connecting Tokyo to Osaka. The test was conducted using dispersion-shifted fiber in the L-band(2), which is often used in Japan for long-haul transmissions (Figure 1).

In anticipation of the commercial deployment of 100 Gbps DWDM, the field test simulated real-world situations, such as fiber-optic cable changes in accordance with transmission-circuit route changes and adding/removing wavelengths. The results confirmed that a quality sufficient for commercial operation could be achieved at 8 Tbps (100 Gbps Ч 80 multiplexed wavelengths).

In addition, the test demonstrated that the system could compensate automatically when adding chromatic dispersion and polarization mode dispersion to actual transmission circuits, which could happen over a variety of networks. This proved that it would be possible to have operability with eased conditions of prior measurement of the fiber for each individual network and design customization—which are characteristic features of digital coherent transmission technology.

On December 14, 2011, Fujitsu announced the Packet Optical Networking Platform for building ultra-fast, ultra-capacity 100 Gbps networks. Since then, Fujitsu has continued to work on technologies that will bring more capacity, more speed, and more energy efficiency to core optical networks in Japan and around the world.

Digital coherent transmission technology makes use of results achieved in two previous research projects, "R&D on High-speed Optical Transport System Technologies" and "R&D on High-speed Edge Node Technologies," which were supported by the Ministry of Internal Affairs and Communications.