Optical networking

Optical networking is a way to send information using light. It works by encoding signals in light and sending them through special types of networks. These networks can be small, like those used in a school or office, known as local-area networks, or they can cover big areas, like cities or even whole countries, called wide area networks.

This kind of networking uses tools like optical amplifiers, lasers, LEDs, and a method called wavelength-division multiplexing to send huge amounts of data. The data travels through thin glass fibers, called fiber-optic cables. Because optical networking can handle so much information very quickly, it helps make the Internet and other communication systems work. Today, most of the information we send and receive—whether it’s a video call, a webpage, or data between machines—travels through these fast optical networks.

Types

Fiber-optic networks

Main article: Fiber-optic communication

Fiber-optic networks are a common way to send information over long distances. They use thin glass or plastic fibers to carry light signals. These networks can be set up in cities, countries, or even around the world. Some fiber-optic networks share one connection with many homes or businesses using special splitters.

Free-space optical networks

Free-space optical networks work like fiber-optic networks but they send signals through the air instead of using fibers. This can be done between satellites in space, like with SpaceX's Starlink, or between high-altitude balloons, such as in Google's Project Loon and Facebook Aquila. These networks can also connect computers over short distances on the ground, like on a school campus.

Components

An optical networking system uses several key parts to send information with light. First, it needs fiber, which can be either multi-mode or single-mode. A light source, such as a laser or LED, provides the signal. Other important components include devices that combine or separate signals, like multiplexers/demultiplexers, and tools that direct or split the light, such as optical switches and splitters. Optical amplifiers help strengthen the light signal as it travels through the fibers.

These parts work together to allow large amounts of data to move quickly over long distances through fiber-optic cables.

Main article: Multiplexer/demultiplexer

Main articles: Optical Add/Drop Multiplexer, Reconfigurable Optical Add/Drop Multiplexer

Main article: Optical switch

Main article: Optical splitter

Main article: Circulator

Main article: Optical amplifier

Main article: Wave division multiplexer

Transmission medium

In the past, networks used copper wires to send information, but these wires could only carry a limited amount of data. They also had problems when signals got too close together.

Later, scientists discovered that light could carry much more data without these problems. They developed special glass fibers that could guide light over long distances. These fibers could carry thousands of times more information than old copper wires, making modern communication faster and more efficient.

Optical amplification

Fiber optic networks can send more information because of better tools, such as optical amplifiers. These amplifiers make light signals stronger as they travel through the cables. One important type is the erbium-doped optical amplifier (EDFA), created in 1986 by David Payne at the University of Southampton. This amplifier uses special atoms to boost the light signal.

As networks grew, many kinds of amplifiers were developed, but EDFAs became very popular, especially for systems that need to send many signals at once. Today, these amplifiers are key parts of networks that handle lots of data.

Wavelength division multiplexing

Wavelength-division multiplexing (WDM) greatly increased how much information fibers could carry. It uses different colors of light, or wavelengths, to send many signals at once through a single fiber. Early systems had just a few channels, but new technology allowed many more.

Companies worked to improve this technology. In 1996, a system with 16 channels was deployed on a major network, showing how powerful WDM could be. This development helped start the field of optical networking.

Main article: Wavelength-division multiplexing

Bell Labs

Optelecom

General Instruments Corp

Ciena Corp

Sprint

Capacity

The density of light paths from wavelength-division multiplexing (WDM) was key to expanding fiber optic capacity, helping the Internet grow in the 1990s. Since then, WDM systems have improved a lot, with some systems now able to send very large amounts of data very quickly. For example, in 2018, a system could send enough data to stream over a million 4K Ultra HD videos at once.

Because WDM can carry so much information, it has become a foundation for most global communication networks and the Internet. People need more and more bandwidth for things like watching videos online, using mobile phones, and cloud computing. In fact, by 2022, the amount of data moving over the Internet was growing very fast, with most of it being video content sent through optical networking.

Standards and protocols

Synchronous optical networking (SONET) and synchronous digital hierarchy (SDH) are the main protocols used in optical networks. The optical transport network (OTN) protocol, created by the International Telecommunication Union, works with these protocols to help different networks communicate. These protocols can carry many types of data, including ATM, Ethernet, and TCP/IP.

Main article: Synchronous optical networking