R&D toward “Access Networks––Building Trust, Connecting People”

3.1 Constructing a highly reliable and economical network

To reduce capital expenditure (CAPEX), we are working to optimize aggregation appropriate to user dispersion, construct facilities applicable to rural areas, promote the use of existing facilities, and simplify the work of installing new circuits and deploying new services. We are also working to reduce operating expenditure (OPEX) in relation to maintenance/operations and fault repair. Here, to supplement operations support technology based on existing operations systems, our plan is to simplify installation work through DIY facilities and skill-free procedures and introduce technology like remote fault troubleshooting and remote switching to make maintenance operations even more efficient. At the same time, we are working to make network facilities more reliable and to achieve long-life infrastructure facilities. The three technologies described below reflect these expenditure-reducing efforts.

(1) Small-diameter, low-friction indoor optical fiber cable

To promote the provision of optical services in multi-dwelling units and especially in existing structures, it became necessary to lay many cables using the spare space in existing conduits that already house telephone cables. In response to this need, we developed a small-diameter, low-friction indoor optical fiber cable having half the cross-sectional area and one-fifth the dynamic friction coefficient of existing products. More than 20 of these new cables can be deployed in the free space in existing conduits compared with only a few cables of the current type. Thus, optical services that could not be provided in the past owing to insufficient space in conduits can now be offered. This newly developed cable was also given an optimal amount of bending rigidity so that it could be installed in the conduit using the push-in method instead of the conventional pulling method using a pulling wire. The end result was a reduction in cable deployment time.

(2) Optical-media maintenance and operations technology (traffic monitoring tool)

We developed a traffic monitoring tool for monitoring signals from an optical network unit (ONU) and displaying service status. This tool enables on-site personnel to check the link status between optical fibers and an ONU. With this tool, the user’s usage conditions can be checked in real time and the media access control (MAC) address can be verified when fibers are switched to ensure that the user has been connected. This prevents erroneous cutoffs or connections in fiber switching activities while also reducing installation time.

(3) Operations visualization technology

This technology aims to make operations more efficient and improve security by systematizing business know-how possessed by individual employees. This know-how can be extracted from work logs that record the daily actions of operators and accumulated in a database so that it can be reflected in future operations. We can compare this approach to a high-performance car navigation system that uses a record of routes travelled by veteran drivers to advise novice drivers which roads to take or to guide a driver along an optimal route by means of an auto-cruise (auto-pilot) function.

Although this function could have been achieved in the past by embedding it in the system, the advantage of this technology is that information from work logs can be collected without having to revamp the base operations system. In this way, we aim to achieve functions such as automatic execution of routine operations, operation navigation, and controls on certain operations.

3.2 Creating new network services

NTT Access Network Service Systems Laboratories is researching and developing a high-reliability, next-generation access network to promote the creation of new network services.

3.2.1 10G-EPON

The demand for a faster optical access network is growing as broadband services spread and the Next Generation Network (NGN) expands.

The standardization of optical access systems tends to lag behind the Ethernet standardization process by a few years (Fig. 1). The GE-PON (Gigabit Ethernet passive optical network) optical access system, which is the one now in use, was standardized in 2004, while specifications for the physical layer and data-link layer of 10G-EPON (10-Gbit/s Ethernet PON) were standardized in 2009. In addition, discussions on NG-PON2 as the next next-generation optical access system providing several tens of gigabits per second have already begun.

Fig. 1. Progress and standardization of optical access systems.

At present, work is proceeding on standardizing interoperability between GE-PON and 10G-EPON at the system and network levels. Coexistence with the current GE-PON system is essential to the adoption and expansion of 10G-EPON. We are studying a system that has a 1G-10G dual-rate optical line terminal (OLT) to accommodate GE-PON ONUs (1G upstream, 1G downstream) and 10G-EPON ONUs (1G or 10G upstream, 10G downstream) connected to the same splitter. Such interoperability will enable users who desire faster speeds to migrate to new services smoothly.

3.2.2 Carrier-grade Ethernet technology

To achieve high reliability, maintainability, and operability, we are developing the following three network technologies as well as an operations system that can implement those technologies and applying them to commercial services (NTT’s Business Ether Wide).

3.3 Expanding the broadband service area

NTT Access Network Service Systems Laboratories is working to expand the broadband service area by providing a diverse lineup of access networks. There are many technologies that can link the creation of new network services with the expansion of the service area (Fig. 2).

Fig. 2. R&D for expansion of broadband service area.

3.3.1 Optical-amplification PON repeater (PON extender)

The maximum transmission distance of the current PON system is 20 km, which means that some sort of distance-extending technology is needed to provide services to rural areas. In response to this need, we are developing a PON repeater to achieve wide-area service coverage (with long-distance, multi-branching capabilities) through optical amplification. This repeater can be installed outdoors on poles so that transmission distances can be increased in rural areas and the number of branches and accommodated ONUs can be increased in urban areas.

3.3.2 Wireless technology

A personal wireless router (PWR) will enable a variety of devices equipped with wireless local area network functions to be automatically connected to the most optimal network (3G, Wi-Fi, optical access, etc.) without user intervention.

A wide-area ubiquitous network (sensor network) will make possible services for automatically collecting information over a wide area by attaching wireless terminals to all kinds of things. Various service concepts are now being studied: one application would be to enable gas and electricity meters to be read wirelessly from an office instead of visually by a person in the field.

3.4 Promoting green R&D

3.4.1 Activities toward preserving the global environment

At NTT Access Network Service Systems Laboratories, our R&D efforts follow the “NTT Group Energy Efficiency Guidelines” conforming to the “ICT Ecology Guidelines” established by the Telecommunications Carriers Association (ICT: information and communications technology). We are working to reduce power consumption in access-network equipment by steering our long-term research in the following three directions.

- Reduce power in devices and components

- Reduce power through a method/system approach

- Reduce power through a network-architecture approach

We are also developing cable-conduit repair technology, design technology for concrete poles, and optical-splitter compact housing technology to save resources including recycling access-network facilities.

3.4.2 Power-savings technology for PON systems

To reduce power consumption in the access network, we are researching the application of mechanisms like automobile idle-stop systems to PON systems. A sleep function will deactivate some ONU functions according to current operating conditions and a link-rate switching function will switch the link rate between OLT and ONU according to current traffic conditions. Achieving these mechanisms will require protocol for controlling communications between the OLT and ONU, and standardization activities to this end are proceeding.

3.4.3 Resource savings by cable-conduit repair technologies

These technologies make it possible to repair cable conduits though operations performed only in a manhole. This enables conduits to be reused while also reducing the use of asphalt conventionally required in cable-conduit excavation work and cutting down on earth, sand, and other waste (Fig. 3). Cable-conduit high-pressure washing technology removes rust and dirt inside a conduit by high-pressure washing without requiring the cable to be pulled out. Cable-conduit renovation technology secures space for accommodating additional cables by inserting lining material inside a conduit after it has been washed.

Fig. 3. Resource-saving technologies.

Up to now, the repair of a degraded conduit required excavation of the road surface, backfilling after completion of the repair, and the application of a new asphalt coating. Our new no-dig technologies, however, eliminate the need for roadwork to excavate and repair conduit cables. Once these technologies are fully implemented, the use of asphalt paving materials is forecast to drop by about 300,000 tons over a five-year period.

3.5 Expanding globally

To become more competitive on the world stage, NTT is actively promoting its researched and developed technologies and their products to a number of countries overseas. It is also involved in international standardization activities and relationship building with an eye to expanding business on a global scale. Three specific R&D achievements of NTT Access Network Service Systems Laboratories are contributing to the global expansion of the Japanese ICT industry.

In addition to providing technologies and products, NTT is also building relationships with overseas telecommunication carriers by receiving interns and holding technology seminars (Fig. 4). The initial focus here was Southeast Asia, but tie-ups with carriers in Central and South America have recently begun.

Fig. 4. Relationship building with overseas carriers.