Optical Carrier

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Optical Carrier levels describe a range of digital signals that can be carried on SONET fiber optic network.^[1] The number in the Optical Carrier level is directly proportional to the data rate of the bitstream carried by the digital signal.

The general rule for calculating the speed of Optical Carrier lines is when a specification is given as OC-n, that the speed will equal n × 51.8 Mbit/s.^[2]

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Optical Carrier specifications (in use)^[1]

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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. This base rate is multiplied for use by other OC-n standards. For example, an OC-3 connection is 3 times the rate of OC-1.

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OC-3 (STM-1x)

OC-3 is a network line with transmission speeds 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 (SDH).

When OC-3 is not multiplexed by carrying the data from a single source, the letter c (standing for concatenated) is appended: OC-3c.EDA中国门户网站(JT{q*XMvD

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OC-3c

OC-3c concatenates three STS-1(OC-1) frames. 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.EDA中国门户网站!c,f P v0@

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OC-12 (STM-4x)

,]Q!HoM.M pv0OC-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).EDA中国门户网站EAcJ'X$v8Hn|

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.

OC-24

OC-24 is a network line with transmission speeds of up to 1243.68 Mbit/s (payload: 1202.208 Mbit/s; overhead: 41.472 Mbit/s). Implementations of OC-24 in commercial deployments are rare.

OC-48 (STM-16x)

$_JG,i'OD%L4G!@0OC-48 is a network line with transmission speeds of up to 2488.32 Mbit/s (payload: 2405.376 Mbit/s; overhead: 82.944 Mbit/s).EDA中国门户网站LDFE^!w.xs}

$@I"Q,Y%p C6W*e0OC-48 connections are some of the fastest data connections in use today. 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.EDA中国门户网站)M g3~H,c4~i

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OC-96

OC-96 is a network line with transmission speeds of up to 4976.64 Mbit/s (payload: 4810.752 Mbit/s; overhead: 165.888 Mbit/s). Implementations of OC-96 in commercial deployments are rare, if ever used at all.EDA中国门户网站Pxd!hu(a

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OC-192 (STM-64x)

~d4^X;CMe5|R+s:F{8F0OC-192 is a network line with transmission speeds of up to 9953.28 Mbit/s (payload: 9621.504 Mbit/s; overhead: 331.776 Mbit/s). This is the fastest connection commonly available on the Internet.

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 are suitable for use on a wide area network.

bm&^\.n)y/G0As of 2005, OC-192 connections are the most common for use on the backbones of large ISPs.EDA中国门户网站5SWR5~@*s:{.{f1Q

OC-768 (STM-256x)

%Ccba`"zO0OC-768 is a network line with transmission speeds of up to 39,813.12 Mbit/s (payload: 38,486.016 Mbit/s; overhead: 1327.104 Mbit/s).

As of Sept 2007, CISCO will use OC-768 line cards from a third party. These line cards will plug into the CISCO chassis. These same line cards will also be made available to Siemens. These cards will use four Xilinx FPGA, a Power PC, a TI c6200 DSP, Four AMCC FEC, and two DeMux and two Mux.EDA中国门户网站h-cm{ lAdXV+j

Optical Carrier specifications (unused)

Note: All of the following OC lines are theoretical. None of these are currently in use.

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OC-256

OC-256, when launched, will be able to provide transmission speeds of around 13.27104 Gbit/s.EDA中国门户网站V+O Vw7\&c mO

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OC-384

OC-384, when launched, will be able to provide transmission speeds of around 19.90656 Gbit/s.

OC-1536

/X!@-J}M.i"w|;I0Will be able to provide transmission speeds of around 79.62624 Gbit/s. It is unknown if such standards will be implemented in the near future.

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OC-3072

0|(d3T!J7n Y"rX0Will be able to provide transmission speeds of around 159.25248 Gbit/s (20 Gbyte/s). Though it is unknown if such a standard will be implemented in the near future, research based chips from IBM and Intel indicate progress towards the standard.

References

^ ^a ^b Synchronous Optical Network (SONET). Web ProForums. International Engineering Consortium. Retrieved on 2007-05-25.
^ Cartier C, Paynetitle T (2001-07-30). Optical Carrier levels (OCx). Retrieved on 2007-05-25.