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Fiber Internet How It Works – Get A Quick Guide to Fiber Optic Internet

picture is a symbolic scheme of global internet connections that determines the path of communication to any point on the planet.
Posted on Jan 2, 2021

To get a profound understanding of Fiber Internet How It Works, it is better to explain a little about the Internet and the network. Many people across the globe have been using the World Wide Web.

Has it happened to you that while sending an email or making a video call with a friend, you think about the power of the internet? At first glance, the image below may look like a galaxy picture, but It is a symbolic scheme of global internet connections that determines the path of communication to any point on the planet.

At first, the Internet did not have the current universality, and only some specific users could access it using traditional and slower methods. Gradually, the internet network expanded to cover the entire world.
Dial-Up was the oldest method of accessing the internet when the volume of Internet use was low.

Dial-up modems transmitted data at a maximum speed of 56,000 bits per second. However, the inherent limitations of public telephone networks often decreased the speed to 33.0 kbps. The modems’ sound is still familiar to many of us and is somehow memorable as well.

A special and distinctive sound with a repetitive pattern helped us hear if the connection process was going well. Using these modems would occupy the telephone line.

After that, users experienced a change in internet speed by ADSL technology. This technology has gradually increased its speed. Simultaneously, various technologies like fiber optics and TD-LTE have provided users with fast and uninterrupted internet access.

Before answering the question of fiber internet how it works, you should have information about the fiber-optic network structures, OLT-ODN-ONU, their differences, and other network equipment used in optical fiber internet.

How Does Internet Fiber Work

optical fibers are significant parts of the telecommunication system. Its high bandwidth capabilities, low interference, and attenuation properties have made them the best choice for gigabit scale transmission.

Understanding fiber optic internet and answering the question “fiber broadband how it works” needs to know more about fibers’ mechanism.

One of the significant strengths of fiber optics internet over DSL standards is the symmetrical structure that leads to equal upload and download speeds.

Besides, unlike ADSL and VDSL that are so sensitive to the user’s distance from the service center, fiber optics can be applied at long distances without worrying about severe speed deceleration or excessive delay.

Unlike conventional metal cables, which are severely affected by noise, fiber optics are protected from noise and interference. Long life and low depreciation are other advantages of fiber optics over a copper or telephone network.
With these important advantages, you must know some of the disadvantages as well.

Internet fiber also requires different cabling and installation of new equipment, and this issue imposes a relatively higher cost on the end-user or the provider company.

Fiber Optic Cables Types

Fiber optic cables contain thin strands of glass. They can carry light pulses with low attenuation. There are two optical fiber cables with different usages and characteristics:

Fiber optic cables types - single mode and multi mode
  1. Singlemode: They pass light directly and without Light refraction. The light source of single-mode cables is the laser with high light intensity. These cables’ core diameter very small (approximately equal to 9 micrometers (µm)). The small fiber core of the SM cable makes the light pass directly with minimum reflection and attenuation. Single-mode cables have two categories: OS1 and OS2. The difference is the wavelength, and the core light propagates.
  2. Multimode: The core diameters are much larger than 50 or 62.5 (up to 100) micrometers that the principal issue in investigating how fiber optic internet works is that they are significantly larger than single-mode fiber optic cables. The light source of these cables is LED. They emit light in different beams with different wavelengths, depending on the type of cable, and have different shapes of emissions along the cable. Multi-mode cables have five categories: OM1, OM2, OM3, OM4, OM5.
    In OM1 and OM2 cables, the light is refracted when it hits the clad wall and travels the cable’s length. The technology of these cables’ core construction is called the step-index. In OM3, OM4, the cable core is produced with Graded-index technology. After several refractions, when the light hits the cable clad cover, it will be emitted with a small refractive index and deviation along the cable.
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Fiber Internet How Does It Work: Network Architecture

The principal issue in investigating fiber optic internet how it works is that ISPs implement it in a variety of network architectures. For example, the internet can be provided from the source to the subscriber, entirely based on fiber optics or sometimes the last-mile on the copper cable basis.

The implementation methods of FTTX are various. FTTX or Fiber to the X refers to fiber optics’ signal transmission structures (along with copper cable).

the picture depicts fiber optic internet provided to users' homes in Ftth architecture and shows fiber internet how it works


Fiber Internet How It Works: FTTN stands for Fiber to The Neighborhood or Fiber to The Node. In this method, the internet reaches the telecommunication cabinets in the neighborhoods through fiber optics. This place may be a few miles away from the user.

From this point, coaxial copper cables take the signal in the rest of the path to the user. FTTN architecture is not a good option because it slows down the internet speed severely due to the user’s long distance from the fiber optic location.


FTTC stands for Fiber to The Cabinet. Optical fiber is delivered to the nearest telecommunication cabinet to the user (maximum distance of 328 Yards), and finally, the user connects to the network through one of the DSL technologies.

FTTB – Fiber Broadband How It Works

FTTB  Fiber Broadband internet stands for Fiber to The Building. The fiber optic cable reaches the building, and the service is delivered to users by copper cable inside the building. (usually VDSL- Very high bit-rate digital subscriber line).

FTTH Fiber Internet How It Works

FTTH stands for Fiber to The Home. Another name of this network architecture is FTTP, which stands for Fiber to The Premises. FTTH was first introduced in 1999, and Japan was the first country to implement a significant FTTH project.

This method provides the best quality and fast connection. Fiber optic cabling is delivered from the central point to the user’s home.

a comparison beetween ADSL and FTTH (fiber to the home)

Ftth Pros And Cons

  1. Bandwidth: FTTH can provide very high bandwidth, and it is not so expensive.
  2. Connection speed and FTTH transmission capacity: FTTH can provide faster connection speeds and greater transfer capacity than twisted-pair cables. To understand the difference between the two, consider that a pair of copper conductors can only transmit six phone calls. In comparison, a single fiber pair can transmit more than 2.5 million phone calls simultaneously. Countless companies from various fields of business are installing it in thousands of places around the world. FTTH is a perfect choice for gamers due to its low ping. Simply ping is the delay between your computer and a server. It specifies the time for a data packet to be transferred and returned from your computer to the server.
  3. A step towards the future: FTTH is the only technology that can respond to high-quality 3D “holographic” TV. Achieving the goal of 20 to 30 Gbps is not possible without fiber optic technologies.
    Besides the pros, Ftth has some cons, like being expensive to install and a higher monthly cost for the end-user. Also, fiber optic cables can’t carry power like copper cables.

Fiber Optic Internet How Does It Work: Equipment

What equipment is needed to implement these fiber optic architectures?

OLT(Optic line Terminal)/ Fiber Internet How It Works

OLT is a fiber optic telecommunications hub. Suppose an OLT device is supposed to provide 2000 fiber-optic service subscribers. OLT is a device similar to a switch; each port has a fiber optic string as output that goes to a device called a splitter

. From an OLT line, we can get 128 outputs, for example. The splitter has one input and several outputs. OLT’s main task is to manage data between the central switch and dozens of ONT modem devices.
A general category of OLT devices is as follows. It is useful for understanding “fiber internet how it works”

OLT(Optic line Terminal)/ fiber internet how it works

GPON (Gigabit Passive Optical Networks)

To answer this article’s main question: “fiber internet, how it works?” and getting acquainted with fiber optic internet, we will discuss GPON in this section.GPON is one of the PON technologies, which stands for Passive Optical Network. It is an efficient method of delivering fiber to the home.
GPON is the fiber optic access network between the operator and the home or office subscriber with no active equipment (like repeaters and amplifiers). That is why its name is a passive network.

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Passive equipment (like splitters and combiners) only transmits the signals produced by active equipment.
GPON technology is a Point-to-Multipoint access mechanism.

It uses passive splitters in fiber-optic distribution networks, which means only one fiber from the provider centers will be delivered to several consumers, including homes and small businesses.
GPON sharing speed in downstream capacity (data transfer from server to client-download) is 2.488Gbps, and in Upstream capacity (data transfer from client to server-upload) is 1.244Gbps. you can see TDM PON standards up and downstream capacity in this table:

Downstream Bitrat [Gb/s]≤1.251.25102.5≤1040
Upstream Bitrat [Gb/s]≤0.6251.2511.251010

The important thing about this technology is that GPON is a new technology generation and introduced after EPON. The latest version of GPON is a 10GB version called XGPON or 10G-PON.

G-EPON (Ethernet Passive Optical Network)

EPON technology is a version of Ethernet-based PON that provides network access with lower installation costs. It goes well with other Ethernet standards. It is a major advantage in that there is no need for conversion or encapsulation in Ethernet networks.

Wireless networks such as LTE and WiMAX can benefit from this technology.
In another classification, OLTs have three categories in terms of appearance:

  • One-unit OLT
  • Dual-unit OLT
  • Chassis-based OLT

What Is The EPON And GPON Difference?

EPON and GPON are both standard versions of fiber optic network structures. These networks use fiber optic cables to connect various devices to the World Wide Web. The main use of this network is in VoIP systems or sending audio and video on digital TVs.

The main two differences between EPON and GPON are their protocols (Each protocol has specific upstream and downstream speeds) and the ONU units’ number.
Other differences between EPON and GPON are as follows:

  1. Wider bandwidth in the GPON structure: GPON offers a bandwidth of 1.25 to 2.5 GB/s and EPON about 1 GB /s.
  2. Structure: The GPON has a point-to-point structure, while EPON indirectly uses Ethernet.
  3. Encryption process: The GPON system’s encryption is usually performed on the downstream structure, and in the EPON, it is done in both the upstream and downstream sections.

ONU or ONT/ Fiber Internet How It Works

Another device called ONU (Optical network units) or ONT is installed in the user’s home. Something like a modem where the fiber optic line from the splitter goes to its input fiber port. ONU or ONT has several outputs; one is Ethernet, which is for connecting to the Internet. ONU also has other ports, such as telephones.

passive optical network - what is ONU or ONT equipment? / fiber internet how it works

ODN/ Fiber Internet How It Works

ODN or optical distribution network place between the OLT and ONU. As we said in the previous section, each OLT port has an output fiber optic string that goes to a splitter. ODN splits and distributes the signal traveling along the passive optical network.

What is a fiber optic modem, fiber internet how does it work?

Computers need a communication channel like copper wire, optical cables, or wireless RF waves. In the first years of the internet advent, telephone lines were used to establish this connection.

Computers and telephone lines do not speak in the same language. Computer language is Binary codes, and the phone signal is analog. Modems solve this problem as a professional real-time translator. When a person at computer A writes for computer B: -Hello, how are you?

it will turn in to binary 0-1 code.

fiber optic modem

The modem converts this digital signal into a comprehensible analog signal to telephone lines, the name of this process is Modulation. This message reaches computer B but is not readable. As you might guess, translator B must do the opposite and reconvert the received analog signal to 0 and 1. This process name is Demodulation.

By doing this, user B only can read his friend’s message. He wants to reply to it, but he can only read with the current system. So, both parties should have a modulator and demodulator. The word MODEM is a combination of modulator and demodulator in signal processing.

In general, Optical modems convert and reconvert computer’s electronic signals into optical signals for transmission. In other words, it is a device that modulates Ethernet digital signals to optical fibers. A Fiber optic modem sends and receives incoming computer signals through a network cable and connects to the optical network by fiber optic.

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It is often referred to an ONU (Optical network units) that connects to the router with an ethernet cable or LAN cable because it cannot directly connect to the router. First, an optic cable is connected to the modem’s port, and then an Ethernet cable connects the modem’s LAN port with the router’s WAN port.

FAQ: How Does Internet Fiber Work

What Is The Difference Between GPON and FTTH?

FTTH is the physical connection of fiber to homes, and the GPON is a technology that provides services such as telephones, television, Internet through fiber optics.

What Are Fiber Optic Cable Types?

There are two types of optical fiber:

  • Multi-mode: Single-mode cables have two categories: OS1, OS2.
  • Single-mode: Multi-mode cables have five categories: OM1, OM2, OM3, OM4, OM5.

Briefly, multi-mode fibers can transmit multiple beams of light simultaneously and have a bigger core diameter than the single-mode. Due to the bigger core, they have higher attenuation

What Is The Shape of The Waveform of The Optical Signal?

To get an overview of “fiber broadband how it works.” It is helpful to know the optical signal in the fiber optic transmission system is a digital square wave. Digital zero-one data turn into the on-off square signal in a light source.

What are the different parts of fiber optic cable?

Despite ordinary cables which have two parts, including core and sheath, optical fibers have five main components:

OPTICAL FIBER - fiber broadband how it works
  1. Core: it is the thin, glass inner layer that carries the data.
  2. Cladding: the outer part of the fiber optic layer which reflects the light into the fiber core. The Cladding’s reflection coefficient is lower than the core and causes complete refraction of the light reflected in the core.
  3. Coating: it has a significant role in fiber optic cables’ strength, attenuation, and decay. It also protects the fibers against abrasion and the external environment. Due to fiber optic vulnerability, it has several coating layers.
  4. Strength member: it helps cables to preserve integrity. Strength members are from Aramid yarn (five times more strength than steel), fiberglass epoxy rods (FGE), and steel wire.
  5. Outer jacket: This coating protects the optical fiber against the destructive effects of the environment.

What Are The Difference Between Plastic And Glass Fiber Optics?

Plastic optical fibers like glass ones deliver data signals from one point to another point. (There is no significant difference in how does internet fiber work matter). Due to plastic elasticity, it can stand more weight and pressure than glass.

However, due to the lack of 100% plastic transparency, the signal attenuation is greater than glass optical fiber, but it has little effect on short distances, so it can be a good alternative. Glass fiber cores are much more expensive than plastic ones.

Young man hand pointing with fiber optic light trail connection.  fiber internet how it works

Disadvantages of Fiber Optics?

If you compare the fiber-optic advantages over their disadvantages, you will understand why engineers utilize these cables. These are the disadvantages:

  • It is costly for small networks.
  • Its installation requires specialized staff, while the copper cable is so easy to install.
  • fiber optic requires precise calculations, Because the amplifiers are expensive, and if engineers install them at a long distance, the network will have a high signal attenuation level.
  • It needs different cabling and installation and new equipment.
  • It can have a higher cost for the end-user and the service provider company(read more in: Do You Know How Much The Fiber Internet Costs?)

Factors Affecting Fiber Optic Cable Attenuation?

Since the mirror coating layer around the core does not absorb any light, the light wave can travel long distances. But some light waves are attenuated while traveling along with the fiber, which is because of glass impurities.

Signal attenuation depends on the purity of the glass used inside the fiber as well as the wavelength of light traveling through the fiber. Manufacturers usually report the loss amount in decibel or decibel per kilometer.

Fiber Optic Internet How Does It Work – Three Main Factors That Can Affect Light Transmission

There are three main factors affecting light transmission through optical fibers which have a significant effect on “fiber internet how it works” as follows:

  1. Attenuation: As the light signal passes through the fiber, it will be attenuated due to absorption, scattering, and glass impurities. The signal level may become too weak, so we need amplifiers to compensate for this loss.
  2. Bandwidth: the fiber will limit the highest and lowest frequencies and will restrict the bandwidth.
  3. Dispersion: the light pulses will spread and limit the information capacity at very high bit rates in long distances.



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