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Study Group 15 at a glance

​​ITU-T Study Group 15 - Networks, Technologies and Infrastructures for Transport, Access and Home

The international standards (ITU-T Recommendations) produced by Study Group 15 detail technical specifications giving shape to global communication infrastructure. The group’s standards define technologies and architectures of optical transport networks enabling long-haul global information exchange; fibre- or copper-based access networks through which subscribers connect; and home networks connecting in-premises devices and interfacing with the outside world.


SG15 standardizes architectures of optical transport networks as well as physical and operational characteristics of their constituent technologies.

The Optical Transport Network (OTN), which provides a terabit-capable framework equipped to carry ever-rising volumes of data and video traffic, is rapidly supplanting its predecessor, Synchronous Digital Hierarchy (SDH), which has been the dominant transport protocol for the previous 20 years. OTN’s support for both optical (wavelength division or WDM) and digital multiplexing techniques improves network efficiency. The WDM aspects of OTN increase the traffic-carrying capacity of optical fibres by allowing simultaneous operation over multiple wavelengths. The digital hierarchy and mappings provide transport of new packet, data-centre and video protocols (for example, IP/MPLS, Ethernet, Fibre Channel, SDI, DVB_ASI), in addition to legacy protocols (such as SDH) which allows for the seamless convergence of operators’ networks. OTN also offers the flexibility required to support future protocols as they emerge.

Additionally, the Automatically Switched Optical Network (ASON) provides quick and reliable configuration of connections across the transport network. ASON gives operators a way to manage network traffic more dynamically than traditional connection management techniques. This enhanced capability allows, for example, the rerouting traffic away from points of failure to provide highly reliable connections.


SG15 produces the digital subscriber line (DSL) standards that provide broadband Internet connections to over 600 million households around the world. The group continues to challenge the existence of a ceiling to network capacity in the predominantly copper “last mile” (between the exchange and the customer premises). VDSL2 vectoring achieves access speeds of 250 Mbit/s, and the next update of DSL ( will raise the bar to 1 Gbit/s by combining the best aspects of optical networks and DSL.

SG15 also standardizes shared-access fibre-to-the-home (FTTH) technologies known as passive optical networks (PONs). PONs are a crucial step towards all-optical networks and, by eliminating the dependence on expensive active network elements, PONs enable carriers to make significant savings. 10-Gigabit-capable PON (XG‑PON) is ITU-T’s latest series of PON standards and achieves access speeds of up to 10 Gbit/s.

Smart Grid and home networking

SG15’s experience in optimizing the communication capabilities of wired infrastructure makes it the natural home of ITU’s work on Smart Grid. SG15 has produced a family of orthogonal frequency-division multiplexing (OFDM)-based narrowband powerline communication (NB-PLC) standards that reuse the electric grid as a telecommunication medium, primarily to monitor, analyse and control power supply/usage. This work builds on (ITU-T G.996x-series) which provides broadband home-networking over telephone wiring, coaxial cable and power-line wiring.​​​​