Basic Elements of a Fiber Optic Communication System

For gigabits and beyond gigabits transmission of data, fiber optic communication is the ideal choice. This type of communication is used to transmit voice, video, telemetry, and data over long distances and local area networks or computer networks. A fiber Optic Communication System uses lightwave technology to transmit the data over fiber by changing electronic signals into light. Some exceptional characteristic features of this type of communication system like large bandwidth, smaller diameter, lightweight, long-distance signal transmission, low attenuation, transmission security, and so on make this communication a major building block in any telecommunication infrastructure. The subsequent information on fiber optic communication systems highlights its characteristic features, basic elements, and other details.

What is a Fiber Optic Communication?

The technique of transmitting data from one location to another by transmitting infrared light pulses using optical fiber is known as fiber optic communication. Here, the light is in the form of a carrier signal that is changed to hold the data. The fiber optic cables replace the electrical cables whenever long distance, high bandwidth, and resistance to electromagnetic interference are necessary.

Fiber-optic communication is mainly used for transmitting voice, video & telemetry using LANs. In many telecommunication companies, optical fiber is used for transmitting the signals of telephone, cable TV signals, Internet communication. In Bell Labs, the researchers have investigated and reached a record of BW distance 100 petabit × kilometers for each second with fiber-optic communication.

How a Fiber Optic Communication Works?

Unlike copper wire-based transmission where the transmission entirely depends on electrical signals passing through the cable, fiber optics transmission involves the transmission of signals in the form of light from one point to the other. Furthermore, a fiber optic communication network consists of transmitting and receiving circuitry, a light source, and detector devices like the ones shown in the figure.

When the input data, in the form of electrical signals, is given to the transmitter circuitry, it converts them into a light signal with the help of a light source. This source is of LED whose amplitude, frequency, and phases must remain stable and free from fluctuation in order to have efficient transmission. The light beam from the source is carried by a fiber optic cable to the destination circuitry wherein the information is transmitted back to the electrical signal by a receiver circuit.

The Receiver circuit consists of a photodetector along with an appropriate electronic circuit, which is capable of measuring the magnitude, frequency, and phase of the optic field. This type of communication uses the wavelengths near the infrared band that is just above the visible range. Both LED and Laser can be used as light sources based on the application.

3 Basic Elements of a Fiber Optic Communication System

There are three main basic elements of a fiber optic communication system. They are

1. Compact Light Source
2. Low loss Optical Fiber
3. Photo Detector

Accessories like connectors, switches, couplers, multiplexing devices, amplifiers, and splices are also essential elements in this communication system.

Compact Light Source

Depending on the applications like local area networks and long-haul communication systems, the light source requirements vary. The requirements of the sources include power, speed, spectral linewidth, noise, ruggedness, cost, temperature, and so on. Two components are used as light sources: light-emitting diodes (LEDs) and laser diodes.

The light-emitting diodes are used for short distances and low data rate applications due to their low bandwidth and power capabilities. Two such LED structures include Surface and Edge Emitting Systems. The surface-emitting diodes are simple in design and are reliable, but due to their broader line width and modulation frequency limitation edge-emitting diodes are mostly used. Edge emitting diodes have high power and narrower linewidth capabilities.

For longer distances and high data rate transmission, Laser Diodes are preferred due to its high power, high speed, and narrower spectral linewidth characteristics. But these are inherently non-linear and more sensitive to temperature variations.

Nowadays many improvements and advancements have made these sources more reliable. A few of such comparisons of these two sources are given below. Both these sources are modulated using either direct or external modulation techniques.

Low Loss Optical Fiber

Optical fiber is a cable, which is also known as a cylindrical dielectric waveguide made of low-loss material. Optical fiber also considers the parameters like the environment in which it is operating, the tensile strength, durability, and rigidity. The Fiber optic cable is made of high-quality extruded glass (si) or plastic, and it is flexible. The diameter of the fiber optic cable is in between 0.25 to 0.5mm (slightly thicker than a human hair).

 A Fiber Optic Cable consists of four parts.

• Core
• Cladding
• Buffer
• Jacket

Core

The core of a fiber cable is a cylinder of plastic that runs all along the fiber cable’s length and offers protection by cladding. The diameter of the core depends on the application used. Due to internal reflection, the light traveling within the core reflects from the core, the cladding boundary. The core cross-section needs to be a circular one for most of the applications.

Cladding

Cladding is an outer optical material that protects the core. The main function of the cladding is that it reflects the light back into the core. When light enters through the core (dense material) into the cladding(less dense material), it changes its angle, and then reflects back to the core.

Buffer

The main function of the buffer is to protect the fiber from damage and thousands of optical fibers arranged in hundreds of optical cables. These bundles are protected by the cable’s outer covering which is called a jacket.

JACKET

Fiber optic cable jackets are available in different colors that can easily make us recognize the exact color of the cable we are dealing with. The color yellow clearly signifies a single-mode cable, and the orange color indicates multimode.

2 Types of Optical Fibers

Single-Mode Fibers: Single-mode fibers are used to transmit one signal per fiber; these fibers are used in telephone and television sets. Single-mode fibers have small cores.

Multi-Mode Fibers: Multimode fibers are used to transmit many signals per fiber; these signals are used in computer and local area networks that have larger cores.

Photo Detectors

The purpose of photodetectors is to convert the light signal back to an electrical signal. Two types of photodetectors are mainly used for optical receivers in optical communication systems: PN photodiode and avalanche photodiode. Depending on the application’s wavelengths, the material composition of these devices vary. These materials include silicon, germanium, InGaAs, etc.

Why Light is used Instead of Electricity?

In fiber-optic communication, laser light is used for transmission because this light source has a single wavelength. As compared to other light sources like bulb light or sunlight have several light wavelengths. Thus, if another light source like sunlight is used for this communication then they will generate a less powerful sunbeam whereas the laser light generates a more powerful beam. So, laser light source is the best option for communication because of the low dispersion, generating a number of signals in less time.

What is Dispersion in Optical Fiber Communication?

Dispersion can be defined as the transmitting of the light signals once they transmit in a fiber. So, this occurrence is mainly because of the light speed that depends on its wavelength as well as propagation mode. When the light travels for long distances then small differences within speed can be build up, so bit errors will happen.

Similar to attenuation, this dispersion will reduce the distance that signal moves within optic fibers. Not like attenuation, it does not decline the signal, however, it blurs. For instance, at the transmitter, the signal of 1ns will be transmitted to 10 ns at the receiver. Therefore, signals are not correctly received & decoded.

Dispersions are classified into four types like model dispersion, material dispersion, waveguide & polarization mode.

• In modern dispersion, dissimilar modes will propagate at dissimilar group velocities
• In material dispersion, the refraction index of the medium will change through wavelength
• In waveguide dispersion, the refractive index will alter across the waveguide which means that dissimilar wavelengths will include different delays
• In polarization mode dispersion, the waveguide includes two different refractive indices.

Characteristics

The main characteristics of fiber optic communication mainly include the following. In this communication, the light signal can be used as a signal to transmit within the optical cable.

Bandwidth

The dispersion of single laser light is a good quantity of signal which can be transmitted for every second which results in high BW for long distances.

Smaller Diameter

The Optical fiber cable diameter is approximately 300 micrometers.

Less Weight

The cable used in fiber optic communication is less weight as compared to the copper type cable.

Signal Transmission for Long-distance

As the laser light doesn’t dissolve, then it is simply transmitted over lengthy distances.

Less Attenuation

The fiber optic cable is designed with glass & a laser light travels throughout it, then the signal loss while transmitting has simply 0.2 dB/km.

Security of Transmission

The data over optical fiber cable can be secured through optical encryption as well as no occurrence of the electromagnetic signal.

Optical Fiber Impact on IoT

The impact of IoT on Fiber Optics Communication is high due to the following reasons.

• Quick Transmission Media
• Data Security
• There is no loss of data because of interference

Fiber Optic Vs Satellite Communication

At present, the leading technologies like Optic fiber as well as satellite communications are revolutionizing the telecommunication world. So these technologies have their benefits as well as limitations to use in a specific type of applications.

Both the communications like Fiber optic as well as satellites have quite opposite properties so their usage changes. The main differences between these communications can be done depending on the following areas which include the following.

Fiber  Optic Communication	Satellite Communication
Fiber-optic communication is used in urban areas including the best infrastructure, wherever it is suitable to arrange communication lines.	Satellite communication is best suitable for uneven terrains, badly connected regions, and areas where it is hard to lay wires.
The bandwidth of Fiber optic is very high including small electromagnetic interference.	Satellites include less bandwidth & are prone to interferences.
This kind of communication works with the light signals like a medium of propagation.	This kind of communication utilizes electromagnetic signals like a medium for propagation.
In optical communication, the communication can be done through a fiber optic cable	In satellite communication, the communication can be done through a relay station
Antennas are not required in this communication	This communication uses special antennas
In this communication, the transmission medium is fiber.	In this communication, the air is the transmission medium.
Optical communication is suitable for point-point less distance communication.	Satellite communication is suitable for long-distance communication.
In fiber optics, the data rates are high including less propagation delays.	In satellite, the data rates are very low. So, the distance from the ground to the satellites setups unintended delays within the transfer.
Fiber optic cables use a lot of BW.	Satellites are mainly designed for broadcasting. The messages transmitted through a satellite can be obtained by ground stations concurrently.
Installation cost is less	Installation cost is high
Fiber optics is stationary through design & their utilization is incomplete in set locations.	This kind of communication facilitates mobile communications.
Fiber-optic communication is more dependable	Satellite communication is low prone to errors.
The cost of this cable mainly depends on the distance among the links & the number of points.	The price of satellites is independent of distance among the stations, i.e. the price will be similar for 5km as well as 5000km. The recurring cost of this communication is high as compared to fibers.

The fewer delays within communications will make the fiber optic cable use in real-time communications. These are mainly used for permanent, point-to-point positions which need high bandwidth. These are also mainly used in Gigabit LANs, landlines, Internet communications, cable TV networks, etc.

Satellite communications are suitable for broadcasting. Thus, they are utilized for the services of radio & TV. These communications are also appropriate for communication within terrains wherever it is not possible to lay communication lines.

LED in Fiber Optic Communication

In a fiber-optic communication system, LED is an essential element. The main function of this component is to change the signal from electrical to an equivalent light signal which is injected into the fiber optic. The LED characteristics frequently influence the performance.

Light-emitting diodes are complex semiconductors used to change the current from electrical to light. So, this conversion procedure is quite efficient to generate less heat as compared to incandescent lights. So, LEDs are used in fiber optic communication due to the following characteristics.

• Small in size
• They have a high radiance
• The emitting region is small, similar to the dimensions of the optical fiber.
• Offers high reliability
• They can be changed at high speeds.

Advantages

The advantages of optical fiber communication include the following.

• Communication is secured
• Speed
• Electromagnetic compatibility
• Distance
• Bandwidth
• No Power loss
• Interference
• Size
• Less Weight
• Security

Applications

The applications of fiber optic communication include the following.

• Medical Industry
• Mechanical Inspections
• Communication
• Lighting and Decorations
• Defense
• Broadcasting
• Industries
• Defense/Government
• Data Storage
• Used for data transmission
• Telecommunications
• Networking
• Industrial/Commercial
• Broadcast/CATV
• Audio communication using fiber optic cable can be done to transmit your voice from one location to another using fiber optic cable.

Thus, Fiber optical communications have changed the telecommunication industry by becoming the major choice for different services like high-speed internet, Ethernet backbone infrastructure & general data networking. At present, fiber optic communication has to turn into very common in business networks because of the IP-based devices demand like IP cameras, video conferencing units, VoIP phones, which need an increase in BW to carry IP communications. Because of these capabilities, this communication can support BW intensive devices with no problem.

This is all about the basic elements of the fiber optic communication system. For additional information, and for any kind of assistance, please write to us as we encourage and appreciate your suggestions, feedback, queries, and comments. Please share your ideas, suggestions, and comments in the comment section given below.

Photo Credits

• Fiber optic communication by mrb
• Working of Fiber optic communication by expertsmind
• LED vs Laser Diodes by fiberoptics4sale