View source for Optical Carrier transmission rates

{{Short description|Standardized set of specifications}}
'''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]] [[Telecommunications network|networks]].<ref name=IEC>{{cite web
|title=Synchronous Optical Network (SONET)
|work=Web ProForums
|publisher=International Engineering Consortium
|url=https://www.iec.org/online/tutorials/sonet/topic01.html
|access-date = 2007-05-25
|archive-url = https://web.archive.org/web/20070502045842/http://www.iec.org/online/tutorials/sonet/topic01.html |archive-date = 2007-05-02}}</ref> 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&nbsp;[[Megabit per second|Mbit/s]].<ref name=Cartier_2001>{{cite web
|author=Cartier C, Paynetitle T
|title=Optical Carrier levels (OCx)
|url=https://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci212685,00.html
|date=2001-07-30
|access-date=2007-05-25
}}</ref> Thus, the speed of optical-carrier-classified lines labeled as '''OC-n''' is ''n'' × 51.84&nbsp;Mbit/s.

==Optical Carrier specifications==
{{Outdated section|date=February 2016}}
Optical Carrier classifications are based on the abbreviation ''OC'' followed by a number specifying a multiple of 51.84&nbsp;Mbit/s: ''n'' × 51.84&nbsp;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&nbsp;Mbit/s ([[payload (computing)|payload]]: 50.112&nbsp;Mbit/s; [[Overhead information|overhead]]: 1.728&nbsp;Mbit/s) using [[optical fiber]].

===OC-3===
'''OC-3''' is a network line with transmission data rate of up to 155.52&nbsp;Mbit/s (payload: 148.608&nbsp;Mbit/s; overhead: 6.912&nbsp;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]] ([[Synchronous optical networking|SDH]]).

===OC-3c / STM-1===
'''{{vanchor|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 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&nbsp;Mbit/s signal. The payload rate is 149.76&nbsp;Mbit/s and overhead is 5.76&nbsp;Mbit/s.

===OC-12 / STM-4===
'''{{vanchor|OC-12}}''' is a network line with transmission speeds of up to 622.08&nbsp;Mbit/s (payload: 601.344&nbsp;Mbit/s; overhead: 20.736&nbsp;Mbit/s).

OC-12 lines were commonly used by [[internet service provider|ISPs]] as [[wide area network]] (WAN) connections, or connecting [[Digital subscriber line|xDSL]] customers to a larger internal network <ref>https://kitz.co.uk/adsl/BTCentrals.htm</ref> 

This connection speed was popular with mid-sized (below [[Tier 2 carrier|Tier 2]]) internet customers, such as [[web hosting]] companies or smaller ISPs buying service from larger ones.

===OC-24===
'''{{vanchor|OC-24}}''' is a network line with transmission speeds of up to 1244.16&nbsp;[[Mbit/s]] (payload: 1202.208&nbsp;Mbit/s (1.202208&nbsp;[[Gbit/s]]); overhead: 41.472&nbsp;Mbit/s).  Implementations of OC-24 in commercial deployments are rare.

===OC-48 / STM-16 / 2.5G SONET===
'''{{vanchor|OC-48}}''' is a network line with transmission speeds of up to 2488.32&nbsp;[[Mbit/s]] (payload: 2405.376&nbsp;Mbit/s (2.405376&nbsp;Gbit/s); overhead: 82.944&nbsp;Mbit/s).

With relatively low interface prices, with being faster than OC-3 and OC-12 connections, and even surpassing [[gigabit Ethernet]], OC-48 connections are used{{when?|date=April 2021}} as the backbones of many regional ISPs. Interconnections between large ISPs for purposes of [[peering]] or [[IP transit|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 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===
'''{{vanchor|OC-192}}''' is a network line with transmission speeds of up to 9953.28&nbsp;Mbit/s (payload: 9510.912&nbsp;Mbit/s (9.510912&nbsp;Gbit/s); overhead: 442.368&nbsp;Mbit/s).

A standardized variant of [[10 Gigabit Ethernet]], called [[WAN PHY]], is designed to inter-operate with OC-192 transport equipment while the common version of 10 Gigabit Ethernet 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 ===
'''{{vanchor|OC-768}}''' is a network line with transmission speeds of up to 39,813.12&nbsp;Mbit/s (payload: 38,486.016&nbsp;Mbit/s (38.486016&nbsp;Gbit/s); overhead: 1,327.104&nbsp;Mbit/s (1.327104&nbsp;Gbit/s)).<ref>{{cite web|website=itu.int|publisher=ITU|title=ITU G.707/Y.1322 - Network node interface for the synchronous digital hierarchy (SDH)|url=https://www.itu.int/rec/T-REC-G.707}}</ref><ref>{{cite web|website=telecom-info.njdepot.ericsson.net|publisher=Telecordia|title=GR-253-CORE, Issue 5 - SONET Transport Systems: Common Criteria|url=https://telecom-info.njdepot.ericsson.net/site-cgi/ido/docs.cgi?ID=SEARCH&DOCUMENT=GR-253&}}</ref>

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]].<ref>{{cite press release |url=https://www.att.com/gen/press-room?cdvn=news&newsarticleid=26230&pid=4800 |title=AT&T Completes Next-Generation IP/MPLS Backbone Network, World's Largest Deployment of 40-Gigabit Connectivity |date=October 23, 2008 |access-date=28 January 2009 |archive-url=https://web.archive.org/web/20081220075337/http://www.att.com/gen/press-room?pid=4800&cdvn=news&newsarticleid=26230 |archive-date=20 December 2008 |url-status=dead }}</ref>  OC-768 SONET interfaces have been available with short-reach optical interfaces from [[Cisco Systems|Cisco]] since 2006. [[Infinera]] made a field trial demonstration data transmission on a live production network involving the service transmission of a 40&nbsp;Gbit/s OC-768/STM-256 service over a 1,969&nbsp;km terrestrial network spanning Europe and the U.S. In November 2008, an OC-768 connection was successfully brought up on the [[TAT-14|TAT-14/SeaGirt]] transatlantic cable,<ref>[https://web.archive.org/web/20110614101510/http://www.merit.edu/mail.archives/nanog/2008-11/msg00532.html "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.</ref> the longest hop being 7,500&nbsp;km.

===OC-3072 / STM-1024 / 160G SONET===
'''{{vanchor|OC-3072}}''' is a network interface with transmission speeds of 159,252&nbsp;Mbit/s (payload 
153,944,064&nbsp;Mbit/s).
<ref>{{cite web|website=itu.int|publisher=ITU|title=ITU G.709/Y.1331 (2020) Amendment 3 (03/24)|url=https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.709-202403-I!Amd3!PDF-E&type=items}}</ref>

===OC-12288 / STM-4096 / 640G SONET===
'''{{vanchor|OC-12288}}''' is a network interface with transmission speeds of 639,009.92&nbsp;Mbit/s.
{{citation needed|date=July 2024}}

==See also==
* [[Optical transport network]]

==References==
{{Reflist}}

{{Optical communication}}
{{Telecommunications}}

[[Category:Synchronous optical networking]]
[[Category:Fiber-optic communications]]