Optical fiber cables, how do they work? | ICT #3

Summary

This educational video explores the fascinating world of optical fiber cables, which enable the rapid transmission of data across the globe. It explains how light, guided by the principle of total internal reflection, travels through these thin strands, revolutionizing communication. The video delves into the construction of optical fibers, the role of refractive index, and the importance of attenuation and signal boosters. It also contrasts fiber optics with traditional copper cables, highlighting the former's superior speed, bandwidth, and security. The script concludes by noting the initial use of optical fibers in endoscopy before their widespread adoption in telecommunications.

Takeaways

• 🌐 Global communication is facilitated by a network of optical fiber cables laid under the ground and beneath the ocean.
• 💡 Optical fiber cables transmit data using light, which is faster and more efficient than traditional copper cables.
• 🔬 The core principle behind optical fibers is total internal reflection, where light is reflected within the cable without loss.
• 🌟 The refractive index, which can be manipulated with dopants, determines how light bends and is crucial for total internal reflection.
• 📶 Information such as phone calls and internet data are converted into binary code and transmitted as light pulses through optical fibers.
• 🌊 Submarine optical fiber cables are protected by a mechanical structure and use a copper shell to carry electric power for amplifiers.
• 🔋 Amplifiers are necessary to boost signal strength over long distances due to attenuation caused by absorption and scattering.
• 🛡️ Optical fiber cables offer high data security as external light signals have minimal chance of being transmitted along the cable.
• 🏅 Optical fibers provide superior performance over copper cables in terms of bandwidth, speed, and resistance to electromagnetic interference.
• 🏥 The technology was first used in endoscopy before its widespread adoption in telecommunications for transmitting both digital and analog signals.

Q & A

What is the primary function of optical fiber cables?

Optical fiber cables are used to transmit data in the form of light over long distances, revolutionizing communication by enabling the rapid exchange of information globally.

How are optical fiber cables different from traditional copper cables?

Optical fiber cables use light to transmit data, providing larger bandwidth and higher speeds than copper cables. They also offer better resistance to electromagnetic interference and higher data security.

What is the basic material used in the construction of optical fibers?

Both the core and the cladding of optical fibers use silica as their base material, with different types of dopants added to achieve the desired refractive index.

What phenomenon allows light to be transmitted over long distances within an optical fiber?

Total internal reflection is the key phenomenon that allows light to be transmitted over long distances within an optical fiber, as it confines the light within the fiber core.

Why is a protective coating necessary for optical fibers?

A protective coating is necessary to prevent the total internal reflection phenomenon from being disrupted by the introduction of a protective material, which would otherwise replace the low refractive index air and cease the reflection.

What causes signal attenuation in optical fiber cables?

Signal attenuation in optical fibers is caused by absorption and scattering, which are the main reasons for the loss of signal strength over distance.

How are amplifiers used in optical fiber communication?

Amplifiers are used to boost the signal strength in optical fiber communication, allowing signals to be transmitted over long distances. They are powered by nearby sources or, in the case of undersea cables, by a thin copper shell inside the cable.

How is information encoded and transmitted through optical fibers?

Information is encoded into binary code, represented as a sequence of zeros and ones, which are then transmitted as electromagnetic waves. These are converted into light pulses by cell towers and transmitted through optical fibers.

Who are some of the global players that own and maintain the submarine cable network?

AT&T, Orange, and Verizon are among the global players that own and maintain the submarine cable network, which is crucial for global communication.

What is the significance of the mechanical structure in an undersea cable?

The mechanical structure in an undersea cable serves to protect and provide strength to the cable, with only a small portion of the cable dedicated to holding the optical fibers.

How was optical fiber first used before its application in telecommunications?

Optical fiber was first used in endoscopy for transmitting visual signals in an analog form, before its widespread adoption in telecommunications for digital pulse transmission.

Outlines

00:00

🌐 Understanding Optical Fiber Cables

This paragraph introduces the concept of optical fiber cables, which are essential for global communication. It explains how these cables, made of thin strands of glass, transmit data using light. The narrator discusses the fundamental principles of light, including refraction and total internal reflection, which are crucial for the functioning of optical fibers. The process of total internal reflection is described in detail, highlighting how light can be guided along the cable with minimal loss. The paragraph also touches on the challenges of signal attenuation and how amplifiers are used to boost signals over long distances. The importance of a protective coating for the fragile glass fibers is mentioned, along with the materials and methods used to create the refractive index difference necessary for total internal reflection.

05:03

📡 The Global Network of Optical Fiber Cables

The second paragraph delves into the global infrastructure of optical fiber cables, which form the backbone of modern communication networks. It describes how these cables are laid under the ground and across the ocean, connecting different parts of the world. The paragraph mentions major service providers like AT&T, Orange, and Verizon, who are responsible for maintaining these vital links. A cross-sectional view of an undersea cable is provided to illustrate its protective mechanical structure. The unique method of powering amplifiers deep underwater using a copper shell within the cable is explained. The paragraph concludes by contrasting the advantages of optical fiber cables with traditional copper cables, emphasizing the superior bandwidth, speed, and security offered by fiber optics. It also briefly mentions the historical use of optical fibers in endoscopy before their widespread adoption in telecommunications.

Keywords

💡Optical fiber cables

Optical fiber cables are strands of glass or plastic that transmit data in the form of light pulses. They are central to the video's theme as they revolutionize global communication by enabling the rapid transfer of information. The video explains that these cables are thinner than a human hair and are used for transmitting data over long distances under the ground and oceans, highlighting their crucial role in our interconnected world.

💡Refractive index

The refractive index is a measure of how much the speed of light slows down when it passes through a medium. In the context of the video, the refractive index is key to understanding how light behaves within optical fibers. It's mentioned that the change in the refractive index at the interface between two media causes light to bend, which is a fundamental principle behind the operation of optical fibers.

💡Refraction

Refraction is the bending of light as it passes from one medium to another with a different refractive index. The video uses the example of a pencil appearing bent in a glass of water to illustrate refraction. This concept is essential for understanding how light is guided within optical fibers, as the light bends and stays within the fiber due to differences in refractive indices.

💡Total internal reflection

Total internal reflection occurs when light traveling within a medium hits the boundary with another medium at an angle greater than the critical angle, causing the light to be completely reflected back into the original medium. The video explains that this phenomenon is harnessed in optical fibers to transmit light over long distances without loss, as the light is confined within the fiber by the high refractive index core and the lower refractive index cladding.

💡Attenuation

Attenuation refers to the loss of signal strength as it travels along a medium, such as an optical fiber cable. The video mentions that absorption and scattering are the main causes of signal attenuation in optical fibers. To counteract this, amplifiers are used to boost the signal strength, allowing for long-distance transmission of data.

💡Cladding

Cladding is the outer layer of an optical fiber that has a lower refractive index than the core. Its purpose, as explained in the video, is to ensure that total internal reflection occurs, keeping the light signals within the core of the fiber. The cladding also provides a protective barrier, allowing for the application of a protective coating over the fiber.

💡Dopants

Dopants are substances added to a material to alter its properties, such as its refractive index. In the context of the video, dopants are used in the manufacturing of optical fibers to create the necessary difference in refractive index between the core and the cladding. This allows for the effective guidance of light within the fiber.

💡Binary code

Binary code is a system of representing information using only two symbols, typically zeros and ones. The video explains that all information, such as phone calls or internet signals, is converted into binary code before being transmitted through optical fibers. This digital representation is essential for the efficient transmission and processing of data.

💡Electromagnetic waves

Electromagnetic waves are waves of the electromagnetic field, which include radio waves, microwaves, and visible light. The video describes how mobile phones convert binary data into electromagnetic waves, which are then picked up by cell towers and converted into light pulses for transmission through optical fibers.

💡Submarine cable network

Submarine cable networks are the systems of undersea optical fiber cables that connect different parts of the world, facilitating global communication. The video highlights the importance of these networks, mentioning that companies like AT&T, Orange, and Verizon own and maintain them. These cables are crucial for the global exchange of data, as they span across oceans to connect continents.

💡Data security

Data security in the context of the video refers to the protection of information transmitted through optical fibers from unauthorized access or interference. The video points out that optical fibers provide high data security because any light signal entering from the side has a minimal chance of traveling along the cable, making it difficult for external signals to interfere or tap into the data.

Highlights

Optical fiber cables enable rapid global communication by transmitting data through light.

Optical fibers are used not only for communication but also in medical equipment.

A single fiber strand in an optical fiber cable is as thin as a human hair.

Light's speed changes when passing through different media, a concept known as refractive index.

Refraction is demonstrated by light bending as it passes through a prism.

Total internal reflection is a key principle used in optical fibers to keep light confined.

Optical fibers consist of a core with high refractive index and a cladding with low refractive index.

The protective coating of optical fibers is crucial for their durability.

Signal attenuation in optical fibers is caused by absorption and scattering.

Amplifiers are used to boost signal strength over long distances in optical fiber networks.

Information such as phone calls or internet signals is transmitted as binary code through optical fibers.

The global network of optical fiber cables is maintained by mobile service providers like AT&T, Orange, and Verizon.

Undersea cables have a mechanical structure for protection and a thin copper shell for power supply.

Optical fiber cables provide larger bandwidth and higher data transmission speeds compared to copper cables.

Optical fibers offer high data security as external signals have minimal chance of interaction.

Optical fiber was first used in endoscopy before its widespread use in telecommunications.

The video concludes with a call for support on Patreon to continue educational services.

Transcripts

- [Narrator] Have you ever thought about how you get emails

or any other information from any corner of the world

within a blink of an eye?

This has been made possible by a network of cables

which are laid under the ground and below the ocean.

The cables which carry most of the world's data

are optical fiber cables.

They are also used in medical equipment.

(upbeat music)

Let's learn how optical fiber cables work

and how they have revolutionized the world around us.

Optical fiber cable is made up of thousands

of fiber strands.

And a single fiber strand is as thin as a human hair.

Optical fibers carry information in the form of light.

Let's first learn some fundamental behaviors of light

to understand the workings of optical fibers.

The speed of light changes when it passes through a medium.

And this change in speed is expressed

by the refractive index.

This variation and the speed of the light

leads to another interesting phenomenon.

Refraction, to understand what it is,

let us carry out an interesting experiment.

In this experiment, light passes through a prism.

You can see that at the interface

the light gets bent instead of going straight.

This phenomenon is known as refraction.

Refraction occurs when light passes from a medium

with a one refractive index

to one with another refractive index.

The light bends towards the interface

when it goes from a medium of high

to one of low refractive indices.

Refraction is the reason why a pencil looks bent

in a glass of water.

This simple refraction technique

is effectively used in optical fibers.

Now, let's make this experiment a hypothetical one.

Using some dopants we are able to increase

the refractive index of the glass in real time.

As we increase the refractive index,

the light will bend more and more towards the surface.

After a time you can see that,

the light will pass through the surface of the glass.

If we increase the refractive index further,

the light will suddenly come back to the first medium

as a pure reflection.

This is called total internal reflection.

The total internal reflection is possible

if we increase the incident angle

rather than increasing the refractive index.

In this case at a certain angle called the critical angle,

the light will come back to the first medium.

This phenomenon of total internal reflection

is used in optical fiber cables to transmit the light.

The simplest form of optical fiber cable is shown here.

Cylindrical glass with a high refractive index.

If the laser strikes the interface

at an angle greater than the critical angle,

total internal reflection will happen

and the light will reach the other end.

This means that light can be confined

in the optical fiber over a long distance.

No matter what complex shape the fiber forms.

Remember, total internal reflection happens

between the high refractive index glass

and the low refractive index air.

However, optical fibers need a protective coating.

A protective coating is not possible

with this configuration.

The introduction of protective material

will replace the position of the air

and cease the total internal reflection phenomenon.

An easy way to overcome this issue

is to introduce a low refractive index glass

above the core glass known as cladding.

This way total internal reflection will happen

and we'll be able to use a protective layer.

Both the core and the cladding use silica

as their base material.

The difference in the refractive index

can be achieved by adding different types of dopants.

The optical fiber we have just constructed

won't be able to carry signals for more than 100 kilometers.

This is due to various losses that happen in the cable.

This loss of signal strength

is generally called attenuation.

Absorption and scattering are the main reasons

for signal attenuation.

This is why you see amplifiers and cables

after a certain distance.

They boost the signal strength and allow signals

to be transmitted over a long distance.

The power required for the amplifier

is drawn from nearby sources.

Now, back to the main topic,

how does the optical fiber transmit information

such as phone calls or internet signals?

Any information can be represented

in the form of zeros and ones.

Assume you want to send a hello text message

through your mobile.

First this word will be converted

into an equivalent binary code

as a sequence of zeros and ones.

After the conversion your mobile phone will transmit

these zeros and ones in the form of electromagnetic waves.

One is transmitted as a high frequency

and zero as low frequency wave.

Your local cell tower picks up these electromagnetic waves.

At the tower, if the electromagnetic wave

is of high frequency, a light pulse is generated.

Otherwise, no pulse is generated.

Now these light pulses can easily be transmitted

through optical fiber cables.

The light pulses which carry the information

have to travel through a complicated network of cables

to reach their destination.

For this purpose, the entire globe is covered

with optical fiber cables.

These cables are laid under the ground and below the ocean.

It is mainly the mobile service providers

that maintain these underground cables.

AT&T, Orange and Verizon are some of the few global players

who own and maintain the submarine cable network.

A detailed cross section view of an undersea cable

is shown here.

You can see that only a small portion of the cable

is used for holding the optical fiber.

The remaining area of the cable is a mechanical structure

for protection and strength.

Now the question is, where does the amplifier get power

from under these deep oceans?

Well, for this a thin copper shell is used inside the cable.

Which carries electric power along the cable

so that the amplifiers can be powered.

This whole discussion simply means

that if optical fiber cables

do not reach a part of the globe,

that part will be isolated from the internet

or mobile communications.

If we compare optical fiber cable

to traditional copper cable, the optical fiber cable

is superior in almost every way.

Fiber optic cables provide larger bandwidth

and transmit data at much higher speeds than copper cables.

This is because the speed of light

is always greater than the speed of electrons.

The flow of electrons in a copper cable

generates a magnetic field even outside of the cable

that can cause electromagnetic interference.

On the other hand, the light which travels

through the optical cable is always confined

within the fiber.

Thus the chance of interaction with an external signal

does not exist.

One more interesting feature about optical fiber cables

is that any light signal which enters from the side

has a minimal chance of traveling along the cable.

Thus the optical fiber cables provide high data security.

You might be amazed to know that optical fiber

was first used in endoscopy

even before it was used in the telecommunications field.

In telecommunications, digital pulses are transferred

through the optical fiber cable.

However, in endoscopic cables,

visual signals which are on the analog form

are transmitted to the other end.

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