What is Fiber Optic?

Fiber optic is a fragile transparent glass material widely used in data networks through which light representing the data to be transmitted is sent.

Fiber Optic Definition, Features and Types

What is Fiber Optic Cable, and Where is it Used?

The light signal propagates through the core of the fiber with a reflection angle above the total reflection limit angle as a function of Snell’s law. Also, the light source can be laser or LED.

Fiber optics are widely used in telecommunications because they allow large amounts of data to be sent over a long distance with speeds similar to radio or wired network structures.

The transmission medium and power are excellent as they are not immune to electromagnetic interference. They are also used for local networks where it is necessary to take advantage of other transmission media.


The history of fiber optic communication dates back to the beginning of its production in England, a few years after a test system was installed.

In 1959, as a result of physics studies focusing on optics, a new use of light called laser signaling was discovered, which was applied to telecommunications to transmit messages at extraordinary speeds and over long distances.

However, it was minimal due to the lack of suitable pipelines and channels to move the electromagnetic waves caused by the shower of photons from the source called lasers.

At that time, scientists specializing in optics led them to the production of a pipe or channel known today as fiber optics.

Later, in 1966, a proposal to use an optical guide for communication emerged.

This use of light as a carrier of information is an electromagnetic wave of the exact nature as radio waves, except that the length of the waves is on the order of micrometers rather than meters or centimeters.

The concept of lightwave communication has been known for many years. However, the results of the theoretical study were not published until the mid-1970s.

He showed that it was possible to impregnate a light signal into a transparent fiber and thus electronically provide an optical analog of the wire signal.

The technical problem that had to be solved for the advancement of optical fiber in fibers was that the fibers absorbed light, which made the process difficult.

For practical communication, the optical fiber must be capable of transmitting light signals for many kilometers.

New, very pure glasses have been developed that are much more transparent than ordinary glass since ordinary glass has a light beam of several meters.

These glasses began to be produced in the early 1970s, and this innovation gave impetus to the fiber industry.

Lasers or light-emitting diodes are used as light sources in fiber cables.

Both have been further scaled down for fiberoptic system components that require significant research and development efforts.

Lasers produce coherent light in an extremely narrow path. Diodes, on the other hand, emit inconsistent light.

Fiber Optic Features

Fiber optic cable is a dielectric waveguide that operates at optical frequencies. Each filament consists of a central plastic or glass core of high refractive index, surrounded by a layer of material similar to some refractive index.

When light reaches a surface bounded by a lower indication of refraction, it is primarily reflected. As the difference in indices grows and the angle of incidence increases, total internal reflection occurs.

By projecting light onto walls at vast angles so that it practically travels along its center, light signals can be directed losslessly over long distances.

Stronger Coverage

The fiber’s coating material contains 25% more material than conventional products.

Dual Use Area

Resistance to water and ultraviolet emissions, resistant coater, and extended environmental performance contribute to excellent reliability throughout the life of the fiber.

More Protection in Humid Locations

The ingress of moisture into the fiber optic combined with multiple layers of protection around the fiber ensures a longer lifespan and reliability in wet locations.

High-Density Packaging

With the maximum number of fibers in the most minor possible diameter, it is faster and easier to bend the cable into sharp bends and tight spaces.

A cable with a super-dense structure of 72 fibers, whose diameter is less than that of conventional cables, was obtained.

Fiber Optic Components


The core consists of silica, fused quartz, or plastic. Optical waves pass through it, and a diameter of 50 or 62.5 um is used for the multimode type and 9 um for the single mode type.

Optical Sheath

It generally consists of the same materials as the core but has additives that limit the optical waves in the core.

Protective Coating

The protective coating is usually made of plastic and provides mechanical protection of the fiber.

Fiber Optic Types

1) Single-Mode Fiber

Single-mode fiber optic is the fiber that offers the most extraordinary capacity for information transfer. It has a bandwidth of 100 GHz/km, and the highest streams are achieved with this type.

It can transmit signals with a path that follows the axis of the fiber, hence the name single mode.

They are fibers whose core diameter is the same size as the wavelength of the optical signals they transmit, that is, approximately 5 to 8 mm.

High data transfers are the main advantage of single-mode fibers, but they are difficult to use and connect sensitively due to their small size.

2) Gradient Multimode Fiber

Multimode fibers have a data band going up to 500 MHz/km. It is based on the decrease in the refractive index within the core as it moves into the shell.

Fibers allow for reducing the dispersion between different propagation modes from its core.

Multimode fiber optic with graduated gradient index size 62.5/125m is average. However, multimode types with graduated index multimode 100/140 mm and gradual gradient index 50/125 mm can be found.

3) Multimode Staggered Fiber

Multimode-graded index fibers are made of glass with 30 dB/km attenuation or plastic with 100 dB/km attenuation and have a data band going up to 40 MHz/km.

In these fibers, the core is made of a material whose refractive index is clearly higher than that of the surrounding shell.

Fiber Connector Types

Whether transmitting or receiving, these connector types are responsible for connecting fiber optic lines. There are a wide variety of connector types available, but some of them include:

  • FC Connector

FC connector is used in data transmission and telecommunications.

  • FDDI Connector

FDDI connector is used for fiber networks.

  • LC and MT-Array Connector

LC and MT-Array connectors are used for high data-density transmissions.

  • SC and SC-Duplex Connector

SC and SC-Duplex connectors are used for data transmission.

  • ST/BFOC Connector

ST or BFOC is used to build networks and security systems.

Light Beam Emitters

These devices are responsible for converting the electrical signal into a light signal, emitting the light signal that allows data transmission. So, these emitters are divided into LEDs and Lasers.

1. LEDs

They use 50 to 100 mA current. The speed is slow. It can only be used on multimode fibers. However, it is easy to use and economical, and it has a very long life.

2. Lasers

This type of transmitter uses 5 to 40 mA current. It is swift and can be used with both single-mode and multi-mode types. However, on the contrary, it isn’t easy to use, and its lifespan is long but short.

Electric Light Current Converters

This type of device converts optical light signals into electrical signals.

They are limited to obtaining a current from the defect-modulated light, and this current is proportional to the received power and, hence, the waveform of the modulation signal.

It is based on the reverse phenomenon of recombination, that is the creation of electron-hole pairs from photons.

The simplest detector type corresponds to a P-N semiconductor junction.

For a photodetector to fulfill its use in the field of communications, the reverse current must be tiny to detect feeble optical signals and fast response, and the noise level produced by the device itself must be minimal.

There are two types of detectors: PIN photodiode and Avalanche photodiode.

1. PIN Photodiode

PIN photodiode consists of a P-N port. Between this connection point, there is a new internal material (I) region, which increases the efficiency of the detector.

It is generally used in systems that allow easy discrimination between possible light levels and short distances.

2. Avalanche Photodiode

The Avalanche photodiode applies a high reverse voltage. They are photodiodes that exhibit an internal effect of current gain due to pulse ionization.

The job of these photodiodes is to shoot an electron at high speed against an atom so that it can attract another electron.

These detectors are of two types: silicon and germanium.

  • Silicon

They have a low noise level and up to 90% performance. They also require high supply voltage (200-300 V).

  • Germanium

It is suitable for operation at wavelengths between 1000 and 1300 nm and with 70% performance.

How Does Fiber Optic Work?

In the fiber optic transmission system, there is a transmitter responsible for converting electromagnetic waves into optical or light energy. That is why it is considered the active component of this process.

When tiny fibers transmit the light signal, there is a third component at the third end of the circuit, called an optical detector or receiver, whose job is to convert the light signal into electromagnetic energy similar to the original signal.

The primary transmission system consists of this row of the input signal, amplifier, light source, optical corrector, line, insert, optical corrector, receiver, amplifier, and output signal.

In summary, in this communication process, optical fiber works as a medium to carry the light signal produced by LEDs and laser transmitters.

LED and laser diodes are suitable sources for conduction as their output can be quickly controlled by bias current. Additionally, their small size, brightness, wavelength, and low voltage required to process them are attractive properties.

Fiber Cable Internal Components

The main blocks of the communication link are the transmitter, receiver, and fiber optic cable guide. The transmitter has an analog or digital interface, a voltage-to-current converter, a light source, and a light source-to-light adapter.

Also, the guide is an ultra-pure glass or plastic cable.

The receiver includes a fiber-to-light detector connector device, a photodetector, a current-to-voltage converter, a voltage amplifier, and an analog or digital interface.

In a transmitter, the light source can be modulated with an analog signal or digital, but combining impedances and the amplitude of the signal or digital pulses are limited.

The current converter voltage acts as an electrical interface between the input circuits and the light source.

The light source can be an LED or an ILD laser injection diode. So, the amount of light emitted is proportional to the excitation current.

Therefore, the voltage to the current converter converts the input signal voltage into a current used to drive the light source.

The connection socket is a mechanical interface whose function is to connect the light source to the cable.

It consists of a fiberglass or plastic core, a jacket, and a protective layer. The detector’s coupling device is also a mechanical coupler.

The light detector is usually a PIN diode or an APD.

Both convert light energy into current. As a result, a current-to-voltage converter is required that converts changes in the detector current into voltage changes in the output signal.

Fiber Cable Advantages

  1. It has a vast bandwidth, allowing very high data transfers.
  2. Small in size, therefore, it takes up little space.
  3. Excellent flexibility, the radius of curvature can be less than 1cm, which significantly facilitates the installation.
  4. It is very light; the weight is a few grams per kilometer, which is approximately nine times less than that of a conventional cable.
  5. It is solid against electromagnetic disturbances, which means it has excellent transmission quality.
  6. Entry into an optical fiber can be easily detected by the attenuation of light energy upon reception, making it useful for applications that require a high level of confidentiality.
  7. It is insensitive to interference, a feature used predominantly in disruptive industrial environments.
  8. It allows identical cables of non-metallic optical cables to coexist with electrical power cables.
  9. The minimal attenuation is independent of frequency, making it possible to bridge significant distances without intermediate active elements.
  10. It is resistant to heat, cold, and corrosion.
  11. Thanks to a telemetry-based process, it is easy to locate cuts, which simplifies maintenance by allowing us to find and then repair the fault quickly.

Fiber Cable Disadvantages

These cables present a number of disadvantages compared to other transmission media, the most important of which are:

  1. The fibers have high brittleness.
  2. Requires more expensive transmitters and receivers.
  3. Connections between fibers are complex to make, especially in the field, making repairs difficult if the cable breaks.
  4. You cannot transmit power to intermediate repeaters.
  5. In many cases, electrical-optical conversion operations are required.
  6. This cable cannot transmit high power.

The cost of these cables can only be high when large bandwidth capacity and low attenuation are required. For low bandwidth, copper can be a much more expensive solution than the conductor.

Optical fiber cable does not transmit electrical energy, which requires the receiving terminal to be powered from a power line, and separate conductors must supply the power.

Hydrogen molecules can penetrate silicone fibers and cause changes in attenuation. As water erodes the glass surface, the lifespan of the cables may be reduced.

There are international regulations regarding some aspects of transmission quality and testing.

Where is the Fiber Connection Used?

These cables can be used for digital communications, sensors, and decorative designs such as Christmas trees, night lights, and other similar elements.

It is mainly used in single fiber optic applications and submarine and intercity network connections.

1) Internet Area

It is the most significant element that provides high data transfer and reliability in internet connection services.

To navigate the global network of networks, the Internet, you need not only a computer, modem, and some programs but also a large structure.

The user may spend several minutes waiting for a page to load or several hours trying to download a program from the Internet to their computer.

This is due to the various tools that millions of users use to connect to the Internet.

It makes it possible to surf the Internet at a speed of two million bps compared to the traditional system, where the majority of users connect at 28,000 or 33,600 bps.

2) Computer Networks Field

Optical cable is increasingly used in computer networks because light signals have a high frequency. The ability of a signal to carry information increases with frequency. Additionally, laser systems are used in communication networks.

Many optical cables for long-distance communication operate in computer networks today. That is, it offers intercontinental and transoceanic connections.

An advantage of these systems is the considerable distance a signal can travel before needing a repeater to recover intensity.

Optical cable repeaters are spaced approximately 100 km apart, compared to approximately 1.5 km for electrical systems.

Amplifiers can extend this distance even further, and another increasingly common application is local area networks.

Unlike long-distance communication, these systems connect a series of computers or printers to central equipment.

This system improves equipment performance. This allows new users to join the network quickly.

The development of new electro-optical and integrated optical components will further increase the capability of these systems.

Distances of up to several kilometers separate computers on a local network and are typically used in offices or university campuses.

LAN enables fast and efficient information transfer within a group of users and reduces operating costs. Other connected computing resources are Wide Area Networks (WAN) or Private PBXs.

WANs are similar to LANs but connect computers separated by greater distances located in different parts of a country or other countries.

PBXs provide persistent computer connections for private data transfer, such as telephone transmissions. Still, they are not suitable for emitting and receiving the short-lived bursts of data used by most computer applications.

3) Telephone Networks Area

Due to the standardization of available interfaces, transmission systems for public telecommunications network levels are available in wide applications but differ from subscriber network systems.

It is entirely sufficient for a telephone connection with existing copper conductors.

With the introduction of broadband services such as video conferencing and videotelephony, the use of fiber optics will become necessary.

Extensive experience has been gathered on this subject with BIGFON (Integrated Urban Fiber-Optic Broadband Telecommunications Network).

According to the developed strategy, broadband services will subsequently be expanded with radio and television distribution services in an integrated broadband telecommunications network (IBFN).

4) Sensor Area

Optical fibers can be used as sensors to measure tension, temperature, pressure, and other parameters.

Small size and no electric current flowing through it provide some advantages over the electrical sensor.

They are used as hydrophones for earthquake or sonar applications. Hydroponic systems with more than 100 sensors have been developed using optical cables.

The oil industry and the navies of some countries use hydrophones.

These sensors can operate at higher temperatures than semiconductor sensors.

Another use as a sensor is in the optical gyroscope and hydrogen microsensors used by the Boeing 767.

5) Lighting Area

Another use is to illuminate any space. Due to the advantages this type of lighting represents in recent years, it has become widely used.

Due to the absence of electricity and heat, the fiber is only capable of transmitting light signals, and the lamp illuminating the fiber does not come into direct contact with it.

You can change the color of the lighting without having to replace the lamp. This is because the fiber can carry a light beam of any color, regardless of its color.

You can provide wider illumination with a lamp via fiber optics. This is because you can illuminate several fibers with one light and place them in different places.

It can be used as a waveguide in medical or industrial applications where a beam of light must be directed to a target that is not in the line of sight.

These cables can be used as sensors to measure stress, temperature, pressure, and other parameters.

Patch cords can be used with lenses to make long, thin imaging devices called endoscopes.

Endoscopes are used in medicine to visualize objects through a small hole.

Industrial endoscopes are used for similar purposes, such as inspecting the insides of turbines.

Optical fibers have also been used for decorative uses, including lighting and Christmas trees.

It is also used to trick the sensory taxi system, causing the taximeter not to mark the actual cost of the trip.

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