An optical carrier is the standard unit used to measure the transmission bandwidth rate for the data carried by Synchronous Optical Networking (SONET) fiber-optic networks. Simply put, it’s a fiber-optic network speed abbreviated as “OCx,” where “x” represents a multiplier with a base rate of 51.85Mbps. So, an OC-3 fiber-optic network has a transmission rate of 155.52Mbps. That said, the higher the fiber-optic network rating, the faster it transmits data.

Read More about an Optical Carrier

Before we go into more detail about optical carriers, let’s discuss some technologies connected to them first.

What Optical Carrier-Related Terms Should You Know About?

Here are some technical terms related to optical carriers.

  • Bandwidth: The maximum amount of data you can transmit over an Internet connection within a specific period. While it’s often mistaken for Internet speed, it refers more to the volume of information you can send through a connection over a specified amount of time, calculated in megabits per second (Mbps).
  • SONET: A standardized protocol that transfers multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diodes (LEDs). You can also transfer data via an electrical interface at low transmission rates. It replaced the plesiochronous digital hierarchy (PDH) system for transporting large numbers of telephone calls and data traffic over the same fiber without encountering synchronization problems.
  • Fiber-optic cable: Much like an electrical cable but contains one or more optical fibers that are used to carry light. It is used for long-distance telecommunication or high-speed data connections between different building parts.

Now that we’ve dissected the definition of optical carriers, we can discuss them in greater detail.


Did you know that optical carriers are the oldest kind of audiovisual carriers? They’ve been used for analog image representation for more than 170 years. When it comes to storing audio and video signals, though, they are among the youngest carriers.

What Are the Different Optical Carrier Levels in Use Today?

The current list of optical carrier levels with their corresponding data transmission speeds is listed in the table below.

optical carrier levels

Note: 1000Mbps = 1Gbps

What Are the Practical Applications of Optical Carriers?

Optical carriers are used in various industries, including:

  • Telecommunications: Telcos use optical carriers to transmit various types of information to make voice and video calls as clear and without interference as possible. That results in less choppy voice calls and video calls that don’t hang no matter how far the participants are from one another.
  • Broadcasting: TV and radio networks and streaming service providers use optical carriers to ensure their shows are viewed without lags.
  • Computer networking: Optical carriers enable convenient long-distance information transfers by successfully plugging in gaps left by the more traditional telecommunications network. They offer higher bandwidth with far less attenuation and practically no interference.
  • Medical scanning: Optical carriers are especially useful in optical imaging, which uses light and the special properties of photons to obtain detailed images of organs, tissues, cells, and even molecules. The technique offers noninvasive methods for looking inside a patient’s body.
  • Military: Satellites and optical carriers allow military teams to obtain clear terrain and other images they need for tactical operations, apart from making always-on voice communication with field and base personnel possible.

What Benefits Do Optical Carriers Provide?

The following are some of the benefits optical carriers provide:

  • Speed and bandwidth: Unlike traditional telecommunications networks, fiber-optic cables offer much higher bandwidths and connection speeds. If you’ve ever wondered why they say “travels faster than the speed of light,” that’s the basic idea behind optical carriers.
  • Cloud access: Businesses that need to regularly transmit data to or store it in the cloud, then a fiber-optic network can offer faster uploads and downloads and cater to large amounts of transfers.
  • Symmetrical connectivity: While optical carriers can offer fiber-optic connections with different speed plans, they all come with symmetrical connection speeds, which means your upload speed will equal your download speed.
  • Strong signal even over long distances: Traditional copper wire cables are limited in transmitting voice or data over longer distances. Fiber optic cables offer a much lower signal loss rate, even over vast distances.
  • Reliability: Fiber-optic cables are physically more durable than traditional cables, allowing them to withstand severe climatic conditions.

Key Takeaways

  • An optical carrier is the standard unit that measures how fast a SONET fiber-optic network transmits data. It is abbreviated as “OC-x,” where “x” represents a multiplier with a base rate of 51.85Mbps.
  • To truly understand optical carriers, you must learn about bandwidth, SONET, and fiber-optic cables.
  • Eleven optical carrier levels exist today—OC-1 (51.84Mbps), OC-3 (155.52Mbps), OC-9 (466.56Mbps), OC-12 (622.08Mbps), OC-18 (933.12Mbps), OC-24 (1244.16Mbps), OC-36 (1866.24Mbps), OC-48 (2488.32Mbps), OC-192 (9953.28Mbps), OC-768 (40Gbps), and OC-3072 (160Gbps).
  • The telecommunications, broadcasting, computer networking, medical scanning, and military sectors greatly benefit from optical carriers.
  • Optical carriers offer more bandwidth and faster connection speeds, enable cloud access, provide symmetrical connectivity, and more.