physics

Optical Carrier transmission rates

Optical Carrier transmission rates is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Optical Carrier transmission rates rather than just read about it. In short: 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.

Key takeaways

Optical Carrier transmission rates belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Optical Carrier transmission rates to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Optical Carrier transmission rates from memory before moving on to harder problems.

Reference excerpt

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.

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.

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 (SDH).

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 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 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 were commonly used by ISPs as wide area network (WAN) connections, or connecting xDSL customers to a larger internal network This connection speed was popular with 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 low interface prices, with being faster than OC-3 and 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 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 OC-192 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, 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 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. 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 7,500 km.

OC-3072 / STM-1024 / 160G SONET OC-3072 is a network interface with transmission speeds of 159,252 Mbit/s (payload 153,944,064 Mbit/s).

OC-12288 / STM-4096 / 640G SONET OC-12288 is a network interface with transmission speeds of 637,009.92 Mbit/s.

Worked examples

Example 1 — a first encounter with Optical Carrier transmission rates

Start with the simplest possible case. Write down what Optical Carrier transmission rates claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Optical Carrier transmission rates before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Optical Carrier transmission rates ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Optical Carrier transmission rates

In research: Optical Carrier transmission rates appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Optical Carrier transmission rates in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Optical Carrier transmission rates is common in secondary-school and first-year university syllabi. It links to neighbouring topics Data center technology, Fiber-optic communications, Leet, so understanding it makes those chapters shorter.
In everyday life: Look for Optical Carrier transmission rates outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Optical Carrier transmission rates in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Optical Carrier transmission rates means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Optical Carrier transmission rates out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Optical Carrier transmission rates in simple terms?

Why does Optical Carrier transmission rates matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Optical Carrier transmission rates?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Optical Carrier transmission rates.