Optical Carrier transmission rates are a standardized set of specifications of transmission bandwidth for digital signals that can be carried on

Synchronous Optical Networking Synchronous optical networking (SONET) and synchronous digital hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diode ...

(SONET)

fiber optic An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means t ...

networks Network, networking and networked may refer to: Science and technology * Network theory, the study of graphs as a representation of relations between discrete objects * Network science, an academic field that studies complex networks Mathematics ...

. Transmission rates are defined by rate of the

bitstream A bitstream (or bit stream), also known as binary sequence, is a sequence of bits. A bytestream is a sequence of bytes. Typically, each byte is an 8-bit quantity, and so the term octet stream is sometimes used interchangeably. An octet may ...

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 In telecommunications, data-transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...

. 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; overhead: 1.728 Mbit/s) using

optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass ( silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a mea ...

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-1 The STM-1 (Synchronous Transport Module level-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-1 ...

( SDH).

OC-3c / STM-1

(''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 interleave with each other so 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

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 An Internet service provider (ISP) is an organization that provides services for accessing, using, or participating in the Internet. ISPs can be organized in various forms, such as commercial, community-owned, non-profit, or otherwise private ...

wide area network A wide area network (WAN) is a telecommunications network that extends over a large geographic area. Wide area networks are often established with leased telecommunication circuits. Businesses, as well as schools and government entities, u ...

(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

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companies or smaller ISPs buying service from larger ones.

OC-24

is a network line with transmission speeds of up to 1244.16

(payload: 1202.208 Mbit/s (1.202208

Gbit/s In telecommunications, data-transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mu ...

); overhead: 41.472 Mbit/s). Implementations of OC-24 in commercial deployments are rare.

OC-48 / STM-16 / 2.5G SONET

is a network line with transmission speeds of up to 2488.32

(payload: 2405.376 Mbit/s (2.405376 Gbit/s); overhead: 82.944 Mbit/s). With relatively low interface prices, with being faster than OC-3 and OC-12 connections, and even surpassing

gigabit Ethernet In computer networking, Gigabit Ethernet (GbE or 1 GigE) is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use ...

, OC-48 connections are used as the backbones of many regional ISPs. Interconnections between large ISPs for purposes of

peering In computer networking, peering is a voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the "down-stream" users of each network. Peering is settlement-free, also known as "bill-and ...

transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1979 film), a 1979 Israeli film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countries in the world * ''Transit'' (2006 film), a 2006 ...

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 (10GE, 10GbE, or 10 GigE) is a group of computer networking technologies for transmitting Ethernet frames at a rate of 10 gigabits per second. It was first defined by the IEEE 802.3ae-2002 standard. Unlike previous ...

. OC-48 is also used as a transmission speed for tributaries from OC-192 nodes in order to optimize card slot utilization where lower speed deployments are used. Slower cards that drop to 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 terminal would not allow for full use of the available bandwidth due to the number of cards that would be required.

OC-192 / STM-64 / 10G SONET

is a network line with transmission speeds of up to 9953.28 Mbit/s (payload: 9510.912 Mbit/s (9.510912 Gbit/s); overhead: 442.368 Mbit/s). A standardized variant of 10 Gigabit Ethernet (

10GbE 10 Gigabit Ethernet (10GE, 10GbE, or 10 GigE) is a group of computer networking technologies for transmitting Ethernet frames at a rate of 10 gigabits per second. It was first defined by the IEEE 802.3ae-2002 standard. Unlike previous Eth ...

), called WAN PHY, is designed to inter-operate with OC-192 transport equipment while the common version of

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.

OC-768 / STM-256 / 40G SONET

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 Multiprotocol Label Switching (MPLS) is a routing technique in telecommunications networks that directs data from one node to the next based on labels rather than network addresses. Whereas network addresses identify endpoints the labels identif ...

backbone network A backbone or core network is a part of a computer network which interconnects networks, providing a path for the exchange of information between different LANs or subnetworks. A backbone can tie together diverse networks in the same buildin ...

. OC-768 SONET interfaces have been available with short-reach optical interfaces from

Cisco Cisco Systems, Inc., commonly known as Cisco, is an American-based multinational digital communications technology conglomerate corporation headquartered in San Jose, California. Cisco develops, manufactures, and sells networking hardware, ...

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,"First Transatlantic 40G IP-Router--(optics only)--IP-Router link"
(via archive.org). North American Network Operators Group, Merit Network Email List Archives. Accessed 28 January 2009. the longest hop being 7,500 km.

References

{{Telecommunications Synchronous optical networking Fiber-optic communications