Fibre optics: what is it and how does it work?

Fibre optics, optical fibre and optical networking are all ways to describe the science of transmitting data traffic as pulses of light through glass fibre strands inside an insulated casing. In this blog post we’ll explore fibre optics and the role of fibre optic networks in communications and connectivity. We’ll answer questions around how fibre optics works, the types of fibre optic cables available, and what fibre optics is used for, as well as addressing the pros and cons of optical network fibre for business.

What is fibre optics?

Fibre optics is a way of sending information through a transparent optical fibre in the form of a pulsed beam of light. The light travels through the core of the fibre, the inner transmitting cylinder, surrounded by a reflective cladding to prevent any light from escaping. These optical fibres can be manufactured from plastic, but more often than not are made from silica glass, with each one less than a tenth of the thickness of a human hair.

Typically, the light-transmitting core of the optical fibre only accounts for around 3.5% of its total diameter, with the cladding and coating layer forming the bulk of the fibre’s volume.

When glass cladded with a refractive material was originally introduced in the 1950s, impurities in the glass restricted optical fibre applications to medical use for endoscopies. It wasn’t until 1975 that the first non-experimental fibre optic link was installed in the UK by Dorset Police. Two years later, the first live telephone transmission through fibre optics took place in California. The science of fibre optics has come a long way since those early days, and optical networks are now sending light signals across distances in excess of 50 miles.

What is an optical network?

An optical network is the fastest way to transmit and receive data, allowing reliable electronic communications to take place over long distances.

An optical network consists of:

• A laser or LED light source, to create and transmit the signal
• Optical fibre, to carry the signal
• A multiplexer, so multiple pieces of data can be sent over the same wire
• A photodiode receiver, to capture the signal at the end of its journey

When compared with copper, an optical network is far less prone to external inference and signal loss over distance, and can achieve substantially higher speeds.

How do fibre optics work?

Using the components of an optical network, fibre optics work by converting electronic binary data, the zeros and ones of computer code, into a series of light pulses. These ‘light off’ and ‘light on’ states are created by sending photons bouncing down the fibre optic core through a process known as total internal refraction. That means no light leaks out of the fibre tube as it progresses along its journey.

The light travels down the fibre optic cable in a process known as modes. These modes are just ways to describe the path taken by the light beam. One mode is to fire the light beam directly down the centre of the fibre, another is to bounce it off the wall at a shallow angle.

These modes can also be categorised as single-mode or multi-mode. These definitions depend on whether all light beams travel straight down the middle (single-mode), or as multiple light beams transmitted simultaneously, each at a marginally different reflection angle.

To increase the bandwidth, optical wavelengths can be exploited, allowing data to be transferred across up to 88 bandwidth channels at once.

Different types of optical fibres and their uses

Single-mode optical fibre is the most common type of optical fibre. It is a single glass fibre strand used to transmit a single mode or ray of light. Single-mode, as the name suggests, features only one transmission mode and is used to send data over long distances, meaning it can form the foundations of Dark Fibre networks.

Examples of single-mode optical fibre use are:

• Internet
• Cable television
• Telephony

Multi-mode optical fibre cable carries multiple light beams, all travelling through the core together, following different paths so that they don’t interfere with one another. That means higher bandwidth and faster data transfer is available.

Multi-mode cables are used for computer networking and send information over relatively short distances.

Fibre optic gastroscopes are another type of fibre optic cable. They consist of a tube of even thicker optical fibres and are used primarily for medical purposes to detect digestive system disorders, allowing doctors to view the lining of the stomach and intestines. An industrial version of the gastroscope, called a fibrescope, is used to examine inaccessible pieces of machinery in manufacturing, automotive and aeronautical sectors.

What types of optical networks are available?

Fibre optic networks can come in different varieties, for different purposes, such as protection for energy infrastructure or for a company transmitting data between sites. Each uses fibre optic cables to carry signals between sites or from a network hub to a point in close proximity to its final destination. The latter is how company and consumer internet services are sold and are commonly known as FTTx architectures, or Fibre To The X which can be an office or a point on a road.

As the name suggests, in Fibre To The Home (FTTH) and Fibre To The Premise (FTTP) installations, optical fibres carry the signal all the way to the home or office. This is the fastest type of connection available.

Fibre To The Cabinet (FTTC) is a partial optical fibre connection, where the cables run to the nearest street cabinet, and copper cable is used to carry the signal the rest of the way. Similarly, Fibre To The Building (FTTB) terminates at a point on a shared property, and then other cabling types provide the connection to individual offices, residential properties and spaces.

What are the pros and cons of optical network fibre for business?

We’ve covered a lot of ground, from ‘what is optical fibre?’ to ‘what are the types of optical network?’, now let’s explore some of the advantages and disadvantages of the technology as a whole.

The advantages of optical network fibre for business are:

• Speed with faster data transfer than copper cable can achieve
• Quality because there’s no electromagnetic interference between adjacent optical fibres
• Scalability as it’s easy to install new equipment using original fibre, and wavelengths can be turned on or off as required
• Security because data is transmitted as light, which makes it much harder for hackers to intercept
• Long-term savings as there’s no signal loss over the fibre’s lifetime, which makes fibre networks simpler and cheaper to operate and maintain

But it’s not all good news, there are some downsides to consider. The challenges of optical network fibre for business are:

• Threat of physical damage with optical fibres being thinner and lighter than metallic wiring, they can be cut accidentally
• Immediate costs as test equipment and specialist installers are required to lay a precision fibre optic network
• Fibre fuse when too much light meets with an imperfection in the fibre, this can destroy long lengths of cable very quickly

Why is fibre optics the best method for transmitting data over long distances?

Fibre optic networks can carry data for distances of tens of miles, without suffering from any signal attenuation. They provide route security, reliability and low latency, while future scalability will not be an issue. Often, cables are provisioned to handle traffic demands for ten years or more.

If making an investment in a fibre optic network seems like it could be the right decision for your business, take a look at our optical connectivity service. Or you may wish to contact one of our experts to explore the advantages of optical fibre in more detail and discover what it can do for you.