Optical network is a technology that utilizes light to transmit data between devices. It provides high bandwidth and low latency, and has been the de facto standard for long-distance data communication for many years. Fiber optic is used for most long-distance voice and data communications worldwide.

  The history of optical networks is long, and as their services and use cases expand, the trend towards making them more flexible, intelligent, and efficient will continue to grow.

  Optical networks are important because they allow for long-distance high-speed data transmission. For example, optical networks ensure that New York users can access Nairobi servers as quickly as possible within the limits allowed by the laws of physics.

  The technology behind optical networks is based on the principle of total internal reflection. When light shines on the surface of media such as optical cables, some light will be reflected by the surface. The angle of light reflection depends on the characteristics of the medium and the incident angle (the angle at which light strikes the surface).
  If the incident angle is greater than the critical angle, all light will be reflected; This is called total internal reflection. Total internal reflection can be used to manufacture optical fibers, a type of glass or plastic that guides light along its length.
  When light passes through an optical fiber, it undergoes multiple total internal reflections, causing it to bounce off the fiber wall. This rebound effect causes light to propagate downward along the length of the fiber in a zigzag pattern.
  By carefully controlling the characteristics of optical fibers, engineers can control the amount of reflected light and the distance traveled before it is reflected again. This enables them to design optical fibers that can transmit data over long distances without losing any information.

  An optical network consists of several components: optical fibers, transceivers, amplifiers, multiplexers, and optical switches.

  1.optical fiber
  Fiber optic is the medium that carries optical signals. It is composed of various materials, including:
① Core: The center that carries light.
② Cladding: A material that surrounds the core and helps maintain the presence of optical signals.
③ Buffer coating: a material that protects optical fibers from damage.
  The fiber core and cladding are usually made of glass, while the buffer coating is usually made of plastic.
  2.transceiver
  A transceiver is a device that converts electrical signals into optical signals, and vice versa, typically implemented at the last mile of the connection. It is the interface between optical networks and electronic devices that use it, such as computers and routers.
  3.amplifier
  As the name suggests, amplifiers are devices that amplify optical signals, allowing them to propagate over long distances without losing their strength. The amplifier is placed along the fiber at regular intervals to enhance the signal.
  4.multiplexer
  A multiplexer is simply a device that receives multiple signals and combines them into a single signal. This is achieved by assigning different wavelengths of light to each signal, allowing the multiplexer to simultaneously send multiple signals along a single fiber without interference.
  5.optical switch
  Optical switch is a device that routes optical signals from one optical fiber to another. Optical switches are used to control traffic in optical networks, typically in high-capacity networks.

  The History of Optical Networks

  The history of optical networks began in the 1790s when French inventor Claude Chappe invented the optical signal telegraph, which was one of the earliest examples of optical communication systems.
  In 1880, nearly a century later, Alexander Graham Bell applied for a patent for an optical telephone system. Although Photophone was groundbreaking, Bell's early invention of the telephone was more practical and adopted a tangible form. Therefore, Photophone never left the experimental stage.
  It was not until the 1920s that John Logie Baird from the UK and Clarence W. Hansell from the US applied for a patent for the idea of using hollow tubes or transparent rod arrays to transmit images for television or fax systems.
  In 1954, Dutch scientist Abraham Van Heel and British scientist Harold H. Hopkins each published scientific papers on fiber bundle imaging. Hopkins focuses on non clad fibers, while Van Heel only focuses on simple clad fiber bundles - transparent cladding with lower refractive index around bare fibers.
  This protects the reflective surface of the fiber from external deformation and significantly reduces interference between fibers. The development of imaging bundles is an important step in the development of optical fibers. Protecting the surface of the optical fiber from external interference allows for more accurate transmission of optical signals through the fiber.
  By 1960, the loss of glass clad optical fibers was about 1 decibel (dB) per meter, suitable for medical imaging but too high for communication. In 1961, Elias Snitzer of the American Optical Company published a theoretical description of an optical fiber with a tiny core that can transmit light through only one waveguide mode.
  In 1964, Dr. Gao Kun proposed a light loss of 10 or 20 dB per kilometer. This standard helps to improve the scope and reliability of remote communication systems. In addition to his work on loss rate, Dr. Gao also demonstrated the need for a purer glass to help reduce light loss.
  In the summer of 1970, a group of researchers from Corning Glass Factory began to test a new material called fused silica. This substance is known for its extremely high purity, high melting point, and low refractive index.
  The team, composed of Robert Maurer, Donald Keck and Peter Schultz, soon realized that fused silica could be used to manufacture a new type of wire called "optical waveguide fiber". This type of fiber optic cable can carry 65000 times more information than traditional copper wire. In addition, light waves used to carry information can be decoded at destinations even a thousand miles away.
  This invention completely changed long-distance communication and paved the way for today's fiber optic technology. The team solved the decibel loss problem defined by Dr. Gao. In 1973, John MacChesney improved the chemical vapor deposition process for fiber production at Bell Labs. As a result, commercial production of fiber optic cables has become possible.
  In April 1977, General Telephone and Electronics Corporation first utilized fiber optic networks for real-time telephone communication in Long Beach, California. In May 1977, Bell Labs quickly followed suit and established a 1.5-mile optical telephone communication system in the downtown area of Chicago. Each pair of optical fibers can transmit 672 voice channels, equivalent to a DS3 circuit.
  In the early 1980s, the second generation of fiber optic communication was designed specifically for commercial use, using 1.3-micron InGaAs semiconductor lasers. These systems operated at a bit rate of up to 1.7 Gbps in 1987, with relay spacing of up to 50 kilometers.
  The system used in the third-generation fiber optic network operates at 1.55 microns with a loss of approximately 0.2 dB per kilometer.
  The fourth generation fiber optic communication system relies on optical amplification to reduce the number of required repeaters and on wavelength division multiplexing (WDM) to increase data capacity.
  In 2006, an optical amplifier was used to achieve a bit rate of 14 terabits per second (Tb) on a 160 kilometer line. As of 2021, Japanese scientists are able to transmit 319 Tbps over 3000 kilometers using a four core fiber optic cable.
  Although the capacity of these fourth generation fiber optic communication systems is much larger than previous generations, the basic principle is the same: converting electrical signals into optical pulses, sending them through optical fibers, and then converting them back into electrical signals at the receiving end.
  However, the components of each generation of products have become smaller, more reliable, and cheaper. Therefore, fiber optic communication has become an increasingly important part of our global telecommunications infrastructure.

The main trends of optical networks

1.Focusing on the edge of the network

  The edge of an optical network is where traffic enters and exits the network. In order to meet the demands of cloud based applications, optical networks are moving closer to end-users. This allows for lower latency and more consistent performance.

  2.Layer encryption
  As cyber attacks become increasingly common, dynamic data protection will continue to be a major issue. SASE (Secure Access Service Edge), which uses cloud native security features at service endpoints, has been receiving increasing attention recently. Endpoint protection may render security controls on the connected network unnecessary.
  Although this may not eliminate the need for encryption, it will protect sensitive data and applications. If there is no single security control, the first layer of protection will become increasingly difficult.
  We can better protect our resources by encrypting control, management, and user traffic. This makes it almost impossible for hackers to infiltrate the system, greatly reducing the chances of successful cyber attacks. As businesses become increasingly reliant on data and connectivity, powerful security solutions will only become more apparent.
  3.Open Optical Network
  Open optical network is an optical network that uses standard, open interfaces to allow integration of devices from different vendors. This provides more choices and flexibility for optical network components. In addition, it can also easily add new features and services when they become available.
  4.The growth of spectral services
  With the continuous growth of data traffic, the demand for higher bandwidth and capacity is also increasing. Spectral services provide this by using spectra to increase the capacity of existing fiber optic networks. These services are becoming increasingly popular because they provide an economically efficient way to meet the growing demand for data.
  5.More outdoor deployments
  With the increasing demand for higher bandwidth and capacity, outdoor deployment in street cabinets has become increasingly common. Outdoor fiber optic cables can run directly to the user's location, providing a more direct connection and lower latency.
  6.Compact modularity
  With the continuous development of optical networks, the demand for smaller and more compact components is becoming increasingly evident. This is because the space in data center environments is usually limited. Compact modular optical components provide a space saving approach while still delivering high performance.
  1.Intelligent Optical Network
  Intelligent optical network is an optical network that uses artificial intelligence (AI) to optimize performance. Artificial intelligence can be used to automatically identify and correct problems in networks. This allows for more efficient and reliable networks.
  In addition, artificial intelligence can be used to predict future transportation patterns and demands. These pieces of information can be used to configure capacity in advance, ensuring that the network can meet future needs.
  2.Flexible grid architecture
  Flexible grid architectures are becoming increasingly popular as they provide a way to increase existing fiber capacity. A flexible grid allows for the multiplexing of light of different wavelengths on a single optical fiber. This can carry more data on each fiber, thereby increasing network capacity.
  3.On-demand wavelength division multiplexing
  Wavelength division multiplexing is a technology that allows multiple wavelengths of light to be transmitted over a single optical fiber. On demand WDM is a type of WDM that allows for on-demand capacity provision. This means that capacity can be increased as needed without the need to install new fibers.
  4.Optical networks in an increasingly digitized world
  Optical networks have come a long way in their relatively short history. From an inconspicuous beginning, it has now become an important component of many large network infrastructures. It is a key pillar of the Internet, which has completely changed our way of communication and created an unprecedented era of technological progress.
  With the maturity of trends such as 5G, optical networks seem to have the potential to continue playing an important role in our increasingly digitized world.