Definition

optical network (photonic network)

Contributor(s): John Burke

An optical (photonic) network transmits information as optical rather than electronic signals: It uses light, not electrical currents, to convey data. 

In a truly optical network, every router, switch and repeater would work with light only; conversion to and from electrical impulses would only be done at a network packet's origin and destination.

Current commercial networks mix optical networking and electronic networking. Data signals are converted from light to electronic or electronic to light multiple times. They traverse long links and high-capacity connections within data centers and in campus and building backbones as light, but get converted to electrical signals in all routers and network appliances.

Why use optical networking?

Optical networks have three important attributes: speed, range and capacity.

Optical networking reduces latency between endpoints on the network. Where an electric current moves data at about 10% of the speed of light -- around 18,600 miles per second or 30,000 kilometers per second -- optical signals in fiber optic cable travel 10 times faster, at the speed of light -- 186,000 miles per second or 300,000 kilometers per second.

Optical networks can also move more data across a cable at longer distances: Using electronics and copper, speeds top out at around 100 Gbps over short distances. Fiber can move data at 100 Gbps over a single data channel and across multi-kilometer distances -- and even further with amplification. Even greater speeds can be obtained by dividing a single optical cable into multiple data channels.

Because light beams do not interfere with each other, a single strand of fiber-optic cable can carry optical signals on multiple wavelengths simultaneously, with each light beam carrying its own data content. This is known as wavelength division multiplexing (WDM). WDM networks can pack a single cable with anywhere from two -- called coarse wavelength division multiplexing, or CWDM -- to 160 channels -- known as dense wavelength division multiplexing, or DWDM -- with peak capacities at above 10 terabits per second (Tbps).

Optical networking for agility

Dynamic provisioning, whereby new optical channels are lit up on an existing fiber, enables network managers to rapidly increase the capacity of their optical network. Users can get more bandwidth in days -- hours, even -- rather than the weeks or months it might take a service provider to lay copper cable.

Another optical networking technology, free space optics (FSO), uses lasers without the optical fibers, transmitting data through the air. Although it has lower capacity than fiber-based optical networking and is subject to interference from certain types of precipitation, FSO can provide high-capacity wireless connectivity with very little lead time. FSO can also transmit data over longer distances than Wi-Fi and, in some use cases, it can do so for far less money than if fiber has to be pulled.

Optical networking for security

While it is relatively easy to tap into copper cables and read the data running over them, optical signals running over fiber are more difficult to decipher. Many organizations that need secure networks, such as government and defense installations, make extensive use of optical networks, sometimes connecting them right to the desktop. Newer generations of quantum networking will make it impossible for attackers to tap into optical signals undetected.

Who uses optical networking?

Everyone -- or at least, every kind and size of company.

Performance, capacity, agility and security make optical fiber a widely used choice for network backbones on campuses and even within buildings, where bandwidth demands are at their highest and where there is the greatest likelihood of electromagnetic interference from other building services, such as high-voltage power cables, which often run close to network cabling.

Fiber is also increasingly attractive to network service providers for last-mile connectivity. In addition to higher capacities and speeds, fiber easily accommodates dynamic bandwidth services, allowing service providers to offer a portal through which their customers can determine the amount of bandwidth they need.

This was last updated in October 2018

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