Optical Carrier
Encyclopedia
Optical Carrier transmission rates are a standardized set of specifications of transmission bandwidth for digital signals that can be carried on Synchronous Optical Networking
(SONET) fiber optic networks
. Transmission rates are defined by rate of the bitstream
of the digital signal and are designated by hyphenation of the acronym OC and an integer value of the multiple of the basic unit of rate, e.g., OC-48. The base unit is 51.84 Mbit/s. Thus, the speed of optical-carrier-classified lines labeled as OC-n is n × 51.84 Mbit/s.
: 1.728 Mbit/s) using optical fiber
.
(SDH
).
OC-12 lines are commonly used by ISPs
as WAN
connections. While a large ISP would not use an OC-12 as a backbone (main link), it would for smaller, regional or local connections. This connection speed is also often used by mid-sized (below Tier 2) internet customers, such as web hosting companies or smaller ISPs buying service from larger ones.
With relatively inexpensive interface prices, and being faster than OC-3, OC-12 connections, and even surpassing gigabit Ethernet
, OC-48 connections are used as the backbones of many regional ISPs
. Interconnections between large ISPs for purposes of peering
or transit are quite common. As of 2005, the only connections in widespread use that surpass OC-48 speeds are OC-192 and 10 Gigabit Ethernet
.
OC-48 is also used as transmission speed for tributaries from OC-192 nodes in order to optimize card slot utilization where lower speed deployments are used. Dropping at OC-12, OC-3 or STS-1 speeds are more commonly found on OC-48 terminals, where use of these cards on an OC-192 would not allow for full use of the available bandwidth.
A standardized variant of 10 Gigabit Ethernet
(10GbE), called WAN-PHY, is designed to inter-operate with OC-192 transport equipment while the common version of 10GbE is called LAN-PHY (which is not compatible with OC-192 transport equipment in its native form). The naming is somewhat misleading, because both variants can be used on a wide area network
.
As of 2005, OC-192 connections were most common for use on backbones of large ISPs.
On October 23, 2008, AT&T announced the completion of upgrades to OC-768 on 80,000 fiber-optic wavelength miles of their IP/MPLS backbone network
. OC-768 SONET interfaces have been available with short-reach optical interfaces from Cisco
since 2006. Infinera made a field trial demonstration data transmission on a live production network involving the service transmission of a 40 Gbit/s OC-768/STM-256 service over a 1,969 km terrestrial network spanning Europe and the U.S. In November 2008, an OC-768 connection was successfully brought up on the TAT-14/SeaGirt
transatlantic cable, the longest hop being 7,500km.
Synchronous optical networking
Synchronous Optical Networking and Synchronous Digital Hierarchy are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers or highly coherent light from light-emitting diodes . At low transmission rates data can also be transferred via an...
(SONET) fiber optic networks
Telecommunications network
A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections...
. Transmission rates are defined by rate of the bitstream
Bitstream
A bitstream or bit stream is a time series of bits.A bytestream is a series of bytes, typically of 8 bits each, and can be regarded as a special case of a bitstream....
of the digital signal and are designated by hyphenation of the acronym OC and an integer value of the multiple of the basic unit of rate, e.g., OC-48. The base unit is 51.84 Mbit/s. Thus, the speed of optical-carrier-classified lines labeled as OC-n is n × 51.84 Mbit/s.
Optical Carrier specifications
Optical Carrier classifications are based on the abbreviation OC followed by a number specifying a multiple of 51.84 Mbit/s: n × 51.84 Mbit/s => OC-n. For example, an OC-3 transmission medium has 3 times the transmission capacity of OC-1.OC-1
OC-1 is a SONET line with transmission speeds of up to 51.84 Mbit/s (payload: 50.112 Mbit/s; overheadOverhead information
Overhead information is digital information transferred across the functional interface between a user and a telecommunications system, or between functional units within a telecommunications system, for the purpose of directing or controlling the transfer of user information or the detection and...
: 1.728 Mbit/s) using optical fiber
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
.
OC-3
OC-3 is a network line with transmission data rate of up to 155.52 Mbit/s (payload: 148.608 Mbit/s; overhead: 6.912 Mbit/s, including path overhead) using fiber optics. Depending on the system OC-3 is also known as STS-3 (electrical level) and STM-1STM-1
The STM-1 is the SDH ITU-T fiber optic network transmission standard. It has a bit rate of 155.52 Mbit/s. Higher levels go up by a factor of 4 at a time: the other currently supported levels are STM-4, STM-16, STM-64 and STM-256...
(SDH
Synchronous optical networking
Synchronous Optical Networking and Synchronous Digital Hierarchy are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers or highly coherent light from light-emitting diodes . At low transmission rates data can also be transferred via an...
).
OC-3c / STM-1
OC-3c ("c" stands for "concatenated") concatenates three STS-1(OC-1) frames into a single OC-3 look alike stream. The three STS-1 (OC-1) streams interleaved with each other such that the first column is from the first stream, the second column is from the second stream, and the third is from the third stream. Concatenated STS(OC) frames carry only one column of path overhead because they cannot be divided into finer granularity signals. Hence, OC-3c can transmit more payload to accommodate a CEPT-4 139.264 Mbit/s signal. The payload rate is 149.76 Mbit/s and overhead is 5.76 Mbit/s.OC-12 / STM-4
OC-12 is a network line with transmission speeds of up to 622.08 Mbit/s (payload: 601.344 Mbit/s; overhead: 20.736 Mbit/s).OC-12 lines are commonly used by ISPs
Internet service provider
An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
as WAN
Wide area network
A wide area network is a telecommunication network that covers a broad area . Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations...
connections. While a large ISP would not use an OC-12 as a backbone (main link), it would for smaller, regional or local connections. This connection speed is also often used by mid-sized (below Tier 2) internet customers, such as web hosting companies or smaller ISPs buying service from larger ones.
OC-24
OC-24 is a network line with transmission speeds of up to 1244.16 Mbit/s (payload: 1202.208 Mbit/s (1.202208 Gbit/s); overhead: 41.472 Mbit/s). Implementations of OC-24 in commercial deployments are rare.OC-48 / STM-16 / 2.5G SONET
OC-48 is a network line with transmission speeds of up to 2488.32 Mbit/s (payload: 2405.376 Mbit/s (2.405376 Gbit/s); overhead: 82.944 Mbit/s).With relatively inexpensive interface prices, and being faster than OC-3, OC-12 connections, and even surpassing gigabit Ethernet
Gigabit Ethernet
Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second , as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks where it performed...
, OC-48 connections are used as the backbones of many regional ISPs
Internet service provider
An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
. Interconnections between large ISPs for purposes of peering
Peering
In computer networking, peering is a voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the customers of each network. The pure definition of peering is settlement-free or "sender keeps all," meaning that neither party pays the...
or transit are quite common. As of 2005, the only connections in widespread use that surpass OC-48 speeds are OC-192 and 10 Gigabit Ethernet
10 Gigabit Ethernet
The 10 gigabit Ethernet computer networking standard was first published in 2002. It defines a version of Ethernet with a nominal data rate of 10 Gbit/s , ten times faster than gigabit Ethernet.10 gigabit Ethernet defines only full duplex point to point links which are generally connected by...
.
OC-48 is also used as transmission speed for tributaries from OC-192 nodes in order to optimize card slot utilization where lower speed deployments are used. Dropping at OC-12, OC-3 or STS-1 speeds are more commonly found on OC-48 terminals, where use of these cards on an OC-192 would not allow for full use of the available bandwidth.
OC-192 / STM-64 / 10G SONET
OC-192 is a network line with transmission speeds of up to 9953.28 Mbit/s (payload: 9621.504 Mbit/s (9.621504 Gbit/s); overhead: 331.776 Mbit/s).A standardized variant of 10 Gigabit Ethernet
10 Gigabit Ethernet
The 10 gigabit Ethernet computer networking standard was first published in 2002. It defines a version of Ethernet with a nominal data rate of 10 Gbit/s , ten times faster than gigabit Ethernet.10 gigabit Ethernet defines only full duplex point to point links which are generally connected by...
(10GbE), called WAN-PHY, is designed to inter-operate with OC-192 transport equipment while the common version of 10GbE is called LAN-PHY (which is not compatible with OC-192 transport equipment in its native form). The naming is somewhat misleading, because both variants can be used on a wide area network
Wide area network
A wide area network is a telecommunication network that covers a broad area . Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations...
.
As of 2005, OC-192 connections were most common for use on backbones of large ISPs.
OC-768 / STM-256
OC-768 is a network line with transmission speeds of up to 39,813.12 Mbit/s (payload: 38,486.016 Mbit/s (38.486016 Gbit/s); overhead: 1,327.104 Mbit/s (1.327104 Gbit/s)).On October 23, 2008, AT&T announced the completion of upgrades to OC-768 on 80,000 fiber-optic wavelength miles of their IP/MPLS backbone network
Backbone network
A backbone network or network backbone is a part of computer network infrastructure that interconnects various pieces of network, providing a path for the exchange of information between different LANs or subnetworks. A backbone can tie together diverse networks in the same building, in different...
. OC-768 SONET interfaces have been available with short-reach optical interfaces from Cisco
Cisco Systems
Cisco Systems, Inc. is an American multinational corporation headquartered in San Jose, California, United States, that designs and sells consumer electronics, networking, voice, and communications technology and services. Cisco has more than 70,000 employees and annual revenue of US$...
since 2006. Infinera made a field trial demonstration data transmission on a live production network involving the service transmission of a 40 Gbit/s OC-768/STM-256 service over a 1,969 km terrestrial network spanning Europe and the U.S. In November 2008, an OC-768 connection was successfully brought up on the TAT-14/SeaGirt
TAT-14
TAT-14 is the 14th consortia transatlantic telecommunications cable system. In operation from 2001, it utilises wavelength division multiplexing. The cable system is built from multiple pairs of fibres—one fibre in each pair is used for data carried in one direction and the other in the opposite...
transatlantic cable, the longest hop being 7,500km.