Optical Fibre Cable: Construction & Working

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We discuss the following topics in this blog:

  1. Significance and Origin of Optical Fibres.
  2. Choosing Optical Fibre Cable Over Copper Cables
  3. How Exactly Does Light Travel Inside the Strand of a Glass?
  4. How is Optical Fibre Cable Made?
  5. Single-mode and Multi mode fibres

In addition to these topics, we shall also be answering the following FAQs:

  1. What is WiFi?
  2. What is 5G NR?
Optical Fibre Cable

Optical fibre is at the heart of the communication networks. It took over from copper cables in the 70s and revolutionized communications. Today Optical fibres run through millions of kilometres over land and on sea beds connecting every corner of the world. In 2019 alone there was enough fibre to us to pull ourselves to the moon and back a good 430 times!!

So How did Optical Fibres Come to be?

Well since the invention of telegraphs and telephones, copper cables have been connecting the world. However, they carried information in the form of electric forces which resulted in heat generation and high losses. This required installation of repeaters at short distances to regenerate the last electrical signal. with the rapid expansion of communication networks. There was a need for a more efficient mode of transmission. So by the early seventies, engineers have developed flexible strands of pure glass as thin as the human hair called optical fibres

What made the World Choose Optical Fibre Cable Over Copper Cables?

These fibres had higher bandwidth capacity. Could help carry signals over longer distances faster and at much lower signal loss. They were thus most space and cost-efficient. One optical fibre today carries multiple signals of different wavelengths in the same time in the form of light each representing separate data channels. Hundreds and thousands of these optical fibres have been bundled to form an optical fibre cable.

How Exactly Does Light Travel Inside the Strand of a Glass?

As light moves from one medium to another. It bends a little if the light hits the surface of a particular angle while moving from a denser medium to a rare medium, complete reflection of light takes place. This phenomenon is called internal reflection and it’s the principle by which optical fibres work.

How is Optical Fibre Cable Made?

Optical fibre is made up of the core and two the cladding which surrounds the core. Glass used in the core has a higher refractive index than the glass used in the cladding making the core denser than cladding using the principles of total internal reflection, light is trapped inside the core as is guided along the length of the optical fibre. However, while travelling through the core, it is also expressed through a slightly larger area including the inner edge of the cladding. This effective area is the fibres mode field diameter or MFD. There can be two types of optical fibres, single mode fibres, and multi mode fibres.

Single mode fibres:

This is the most widely used fibre. Having a very narrow core of around nine microns. It is ideal for long haul signal transmission applications such as across campuses, underseas or in remote offices. Currently, single mode fibres are optimized to operate as 1310 and 1550 nm in 1625 nm wavelengths.

Multi mode fibres:

These have higher light gathering ability but due to a larger core diameter of 15 or 62.5 microns. They simply connect the applications like data centres about a certain wavelength noses cut off for events. A fibre supports only a single mode. Multi mode fibres operates at 1850 and 1300 nanometers.

Does That Mean Optical Fibres can Carry Signals Without any Losses?

No, any mode of signal transmission would have losses, but digression of signals inside an optical fibre is much lower over long distances in comparison to electrical and radio signals. The optical fibre major causes of losses would be attenuation, which happens due to absorption and scattering of light inside the core or micro bends with some axial distortions and core cladding interface caused majorly by the local mechanical stress placed in the cable to a manufacturing or packaging or largely due to macro bends. Macro Bend is the result of light leaking due to cable bends beyond the specified bend radius during installation.


What is WiFi?

Put simply, WiFi is a technology that uses radio waves to create a wireless network through which devices like mobile phones, computers, printers, etc., connect to the internet. A wireless router is needed to establish a WiFi hotspot that people in its vicinity may use to access internet services. You’re sure to have encountered such a WiFi hotspot in houses, offices, restaurants, etc.

To get a little more technical, WiFi works by enabling a Wireless Local Area Network or WLAN that allows devices connected to it to exchange signals with the internet via a router. The frequencies of these signals are either 2.4 GHz or 5 GHz bandwidths. These frequencies are much higher than those transmitted to or by radios, mobile phones, and televisions since WiFi signals need to carry significantly higher amounts of data. The networking standards are variants of 802.11, of which there are several (802.11a, 802.11b, 801.11g, etc.).

What is 5G NR?

5G typically refers to the fifth generation of wireless technology. NR, commonly known as New Radio, is a standard developed by the 3GPP Group (Release 15 being the first version introduced back in 2018) outlining the technology required to harness the newly-available millimeter-wave frequencies. The two frequency bands in which 5GNR operates are Frequency Range 1, i.e., Sub 6GHz band (410 MHz to 7125 MHz), and Frequency Range 2, i.e., millimeter-wave (24.25 to 52.6 GHz). Over 4G LTE, 5G NR provides better spectrum utilization, faster data rates, hardware efficiency, and improved signal processing.

From a deployment standpoint, we have Non-Standalone Mode(NSA), Dynamic Spectrum Sharing(DSS), and Standalone Mode (SA). The initial deployments of 5G NR are based on NSA standards, meaning the existing 4G LTE network will operate on the control plane, and 5G NR will be introduced to the user plane.

This particular standard was introduced by 3GPP, keeping in mind the industry’s push to faster 5G services rollout while utilizing the existing 4G LTE infrastructure currently in place. On the other hand, operators are also implementing Dynamic Spectrum Sharing (DSS) to accelerate the deployment cycle, reducing costs and improving spectrum utilization. In this standard, the same spectrum is shared between the 5G NR and 4G LTE, multiplexing over time per user demands. Lastly, we have the Standalone Mode (SA), which moves towards a complete 5G based network where both signaling and the information transfer are driven by a 5G cell.

In the future, 5G will enable new services, connect new industries and devices, empower new experiences, and much more, providing mission-critical services, enhanced mobile broadband, and various other things.

a) Enhanced mobile broadband (eMBB) Applications: High device connectivity, High mobile data rates, and Mobile AR & VR applications
b) Ultra-reliable, low-latency communications (uRLLC)Applications: Autonomous vehicles, Drones, Data monitoring, Smart mfg.
c) Massive machine-type communications (mMTC)Applications: Healthcare, Industry 4.0, Logistics, Environmental monitoring, Smart farming, Smart grids

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