Optical Networks Tutorial

Optical Networks are communication medium that make the use of signals encoded in the form of light for transmitting information. These networks are being widely used in a variety of communication and telecommunication systems.

Optical networks involve the optical communication in several local area networks (LANs) or wide area networks (WANs). The functioning of optical networks relies on devices like optical amplifiers, LASERs or LEDs, and wavelength-division multiplexing for efficiently transmitting large amount of data. The cables used in optical networks are referred to as fiber-optic cables.

In modern Internet and telecommunication networks, optical network technology is being used due to its extremely high bandwidth and speed.

This tutorial is designed to explain the structural features of optical fibers and their connections in networks. The nature of optical networks along with the recent developments in the Optical and Networking systems using optical sources and devices are also dealt with.

What is an Optical Network?

An optical network is a communication network using optical fiber technology for data communication or transmission. Optical fiber networks utilize optical fiber cables and light signals as their fundamental mechanism for conveying data and signals through a network. Where, an optical fiber cable consists of three main parts namely, a core that carries light signals, a glass cladding that keeps the light signals within the cable, and a coating that protect the optical fibers.

In an optical network, data travelling through the network are converted from electronic signals to light signals and vice-versa multiple times. Optical networks provide a cost-effective and high-speed mean for communicating voice and data signals over very long distances.

Why Use Optical Networks?

The following are some primary reasons that driving the adoption of optical networks in modern communication systems −

Optical networks provide very high bandwidth and allow for transmitting huge amounts of data simultaneously.
Optical networks have minimal signal losses when employed for long distance communications.
The immunity of optical networks against electromagnetic interferences is very high. Hence, optical networks provide reliable data communication in high electromagnetic areas and alongside high-voltage power lines.
Optical networks provide highly secure data transmission, as they are difficult to tap.
Optical networks are easily scalable, simply by upgrading the endpoint equipment like transmitters or receivers.
Due to low maintenance cost and higher energy efficiency, optical networks are cost effective in a long run.
Optical networks are compatible with emerging technologies like artificial intelligence (AI), internet of things (IoT), virtual reality (VR), etc.

Components of Optical Network

A typical optical network consists of the following key components −

Optical Fiber

It is a cylindrical non-conducting waveguide made up of glass or plastic fiber and is used to transmit light signals by using the process of total internal reflection. It provides a physical medium for transmission of signals.

In optical networks, the following two types of optical fibers are widely used −

Single-Mode Optical Fiber − Single-mode optical fiber can transmit only a single mode of light. It usually operates at a wavelength range between 1300 nm and 1550 nm. It has minimal dispersion and hence is suitable to use for long distance communication up to several hundred kilometers.
Multi-Mode Optical Fiber − Multi-mode optical fiber can transmit multiple modes of light at the same time. The wavelength range at which this optical fiber can operate is between 850 nm and 1300 nm. Since it has modal dispersion, thus it is suitable for short distance communication only.

Light Source

In optical networks, the primary function of a light source is to convert information signals from their electrical form to light form for transmitting them through optical fiber cables. The following two types of light sources are generally used in most optical networks −

LASER (Light Amplification by Stimulated Emission of Radiation) − It is used to produce a coherent light beam of high-power. It is mainly used in long distance, high-speed optical networks.
LED (Light Emitting Diode) − It is used to produce incoherent light beams of low power. It is suitable for short distance optical networks, where low cost is a primary concern.

Multiplexer and Demultiplexer

In optical networks, mux (multiplexer) and demux (demultiplexer) are used to increase the capacity of the optical fiber. This is done by providing multiple data channels on a single optical fiber. Mux is used for combining multiple wavelengths of light into a single optical fiber, while demux is used to separate multiple light wavelengths from the fiber.

Optical Switch

Optical switches are used in optical networks for dynamically routing and switching the paths for signal transmission. These switches provide routing of light signals among ports without need for converting them into electrical signals.

Optical Splitter

An optical splitter is a device that separates a single light into multiple light streams. This allows for signal distribution to multiple destinations in an optical network.

Circulator

Optical circulator is a device used to separate optical signals travelling in opposite directions in an optical fiber. It allows for bidirectional communication using the same optical network and helps integrating other components into the network.

Optical Amplifier

It is another important component in an optical network, as it makes the long-distance optical communication reliable. In an optical network, the optical amplifier is used for amplifying optical signals (i.e., increasing the power of optical signals) directly without converting them into electrical form.

Wave Division Multiplexer

A wave division multiplexer is a specially designed multiplexer used in optical networks for transmitting multiple wavelengths of light simultaneously over a single optical fiber. The primary objective of this device is to maximize the utilization of capacity of the fiber.

Applications of Optical Networks

Today, optical networks find their applications across various fields. Some examples highlighting the applications of optical networks are given below −

Optical networks are serving as the backbone of today's high-speed telecommunication systems. They are employed for providing real-time communication like voice and video conferencing, connecting multiple cities countries through internet, etc.
Optical networks are also used in data centers to provide high-speed connectivity between servers and storage systems.
Optical networks are used for providing ultra-fast internet connections to homes, offices, and businesses.
In healthcare sector, optical networks are used for real-time data transmission in advanced medical technologies like MRI, CT, medical imaging, remote surgery systems, etc.
In media and broadcasting, optical networks enable live broadcasting and media streaming in HD/FHD/UHD quality.
Optical networks are also used for transmitting high-frequency trading data in real-time with high security.
Optical networks are making the concept of smart city practical by interconnecting systems across cities for IoT and real-time monitoring.
Optical networks are also enhancing the security in miliary operations and providing robust communication links across defense systems.

What You Will Learn in Optical Networks

In this tutorial on Optical Networks, we have explained the following topics in detail −

Optical Networks - Introduction − This chapter provides an overview of optical networks and optical internet and their role in modern communication systems.
Convergence Networks − This section discussion about convergence network concepts such as todays network, next generation network, optical transport network, etc.
Optical Data Networking − In this chapter, you will learn about the concept of optical data networking and its key components.
Optical Devices − This chapter explains various optical networking devices such as optical ADM, modulators, isolator, filters, etc.
Single and Multi-hop Networks − In this chapter, you will get knowledge about single and multi-hope networks. It will also provide explanation about different network topologies.
Optical Networks - WDM Technology − This section explains the wavelength division multiplexing (WDM) in optical networks.
Optical Networks - ROADM − In this chapter, you will learn about elements, architecture, and working of Reconfigurable Optical Add-drop Multiplexer (ROADM).

Who Should Learn Optical Networks?

This tutorial is designed for readers who have interest in learning the networking concepts using optical sources. It is also a valuable resource on optical networks for any of the following −

Undergraduate or post graduate students having optical networks in their syllabus.
Professional technicians or engineers working in the field of optical networks and fiber optic communication.

Prerequisites to Learn Optical Networks

This optical networks tutorial is designed for absolute beginners, and a prior knowledge of the subject is not a necessity. However, readers will find this tutorial easy if they are aware of basic networking concepts. A fair idea on digital networking and digital communication systems will be a plus.

FAQs on Optical Networks

This section is included to briefly answer some of the most Frequently Asked Questions (FAQs) related to Optical Networks.

An optical network is a type of communication network used for data transmission using optical fibers and light signals. The working principle of optical network is based on the total internal reflection of light, which keeps the light signals within the optical fiber cable over long distances.

The four main components of an optical network are as follows −

Optical fiber cable − Transmits light signals from one point to another.

Optical transmitter − Converts electric signals into light signals and transmits to the optical fiber.

Optical amplifier − Amplifies the optical signals to compensate attenuations.

Optical receiver − Receives the optical signals from optical fiber cable and convert them into electric signals.

Some of the main protocols used in an optical networks include the following −

SONET − It stands for Synchronous Optical Networking. This is a standardized protocol used in optical networks for transmitting large amount of data over long distances.

SDH − It stands for Synchronous Digital Hierarchy. It is another important protocol in optical networks that allows for large amounts of data over very long distances. It is mainly used in international industries.

OTN − It stands for Optical Transport Network. It is used for transmitting data using optical networks. OTN is known for its built-in real-time latency measurement.

The key characteristics of optical networks are include the following: high-speed and long distance data transmission, real-time data communication with very small delay, higher bandwidth capacity, and less susceptible to losses and interferences, etc.

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