Reliability of Elastic Lambda Aggregation Networks (EλAN) Demonstrated

TOKYO — Six technology companies (NTT, Hitachi, OKI, Keio, KDDI Research, and Furukawa Electric) have demonstrated the reliability of elastic lambda aggregation network (EλAN) through a prototype network that utilizes optical path provisioning and switching technologies.

EλAN sets an adaptive modulation OFDM transmission system, which leads to the improvement of optical frequency utilization efficiency into the access (subscriber’s home-central office)-metro network that directly connects the subscriber’s home and the metro central offices via fiber and WSSs. Therefore, EλAN provides flexible assignment of the transmission speed and optical frequency bandwidth to support diversified services with different types of traffic, such as internet, enterprise line, and mobile services.

Optical Path Provisioning and Switching Technologies
The companies demonstrated the reliability of EλAN through a prototype network that utilizes optical path provisioning and switching technologies. The demonstration showed that the service accommodated in the failed office was automatically re-connected within 10 seconds to another office some 10 km away with the same transmission speed as before the failure. This research and development project was contracted with the National Institute of Information and Communications Technology (NICT) of Japan under a research contract titled “Research and development of elastic lambda aggregation network.”

Along with the wider penetration of FTTH services, efficient operation of a large number of network sets is essential in optical access networks. Moreover, the future access network must be able to support — in addition to conventional FTTH service — multiple access services, such as mobile, HD video and IoT (Internet of Things) services.

All Services Coexisting on the Same Service-adaptive Network
Until now, multiple access services have been provided using distinctly different network infrastructures to meet the disparate service requirements. However, to provide them more efficiently, all services should coexist on the same service-adaptive network that can flexibly meet individual service requirements. If multiple access services share an optical fiber network, high reliability is essential so that the network can keep providing services by autonomous reconfiguration of the network resources remaining after a disaster. Furthermore, high optical frequency utilization efficiency (transmission rate per unit of optical frequency) should also be provided to accommodate a large number of services and subscribers.

From this background, as advanced research studies targeting beyond 2030, the six institutions (NTT, Hitachi, OKI, Keio, KDDI Research, and Furukawa Electric) have been researching EλAN, a service adaptive access-metro network that provides multiple services with high reliability and high optical frequency utilization efficiency.

Transferring the OLT to a Metro Central Office
In conventional access networks, the central office equipment (OLT) is located at access central offices close to subscribers’ homes. EλAN, on the other hand, transfers the OLT to a metro central office that aggregates the traffic of metro networks. Moreover, EλAN improves the reliability of access-metro networking, which will need to accommodate a huge number of subscribers, by using WSSs to switch optical paths flexibly. This innovative architecture offers lower end-to-end latency and power consumption, since Optical-Electrical-Optical (O-E-O) conversion in the access central office is not needed.

EλAN employs a digital coherent OFDM system with adaptive modulation, a technique that can realize high optical frequency utilization efficiency and large-scale flexible service allocation by using the elastic control of transmission speed and optical frequency bandwidth. In addition, EλAN applies dynamic bandwidth allocation algorithm in OLTs. This makes it possible for the users to share the additional bits in a fair manner regardless of optical distribution network (ODN) conditions.