Fiber optics and requirements in 5G infrastructure

Fiber optic networks improve upon legacy copper systems in terms of reliability, cost speed, security and bandwidth. It’s fiber optics that make high-speed wireline networks possible. It’s used in long-haul networks due to its high performance over long distances.

In fact, fiber can transmit up to 40 miles and still retain its signal strength. This is why fiber optics is the preferred option over copper, which can only carry a gigabit signal up to 250, 300 feet at most.

There are both advantages and disadvantages of fiber optics:

Advantages

• Higher transmission bandwidth than metal cables
• High data transmission
• Very low power loss for superior long-distance transmissions
• High security – cannot be tapped
• Most secure way for data transmission
• Immune to electromagnetic interference
• Unaffected by electrical noise
• Higher capacity than copper wire cables, without increasing size of cables
• Takes up less space
• Lighter than the copper
• Cables are di-electric – no spark hazards
• More corrosion resistant than copper cables
• More flexible than copper cables – bends easily
• The raw material for manufacturing fiber optic cables is glass -- much cheaper than copper
• Longer lifespan than copper cables

Disadvantages

• Higher installation cost
• The number of repeaters increase with distance
• More protection needed – fragile if not enclosed in a plastic sheath

How fiber optics work

Copper wire-based transmission depends on electrical signals passing through the cable. Fiber optics transmit signals in the form of light from one point to the other. The transmitter circuitry converts the input data, in the form of electrical signals, into a light signal with the aid of a light source.

This is an LED source. For efficient transmission, its amplitude, frequency and phases must be stable. There can be no fluctuations. A fiber optic cable carries the LED source to the circuitry, where the information is then sent back to the electrical signal by a receiver circuit.

The Receiver circuit comprises of a photodetector and an electronic circuit, which measures the magnitude, frequency, and phase of the optic field. Communication relies on the wavelengths near the infrared band above the visible range.

How much data can a fiber optic cable carry?

Let’s use the International Telecommunication Union (ITU) standard 50 GHz dense wavelength division multiplexing (DWDM) grid. DWDM combines multiple signals on the same fiber. It’s quite easy to use 80 x 10 Gbps channels in one fiber pair – and modulation technology has advanced that capacity ten times more.

The data transmission system used depends on the application. P2P, or point-to-point links in optical fiber communication, consists of:

• Optical transmitter to transmit data
• Optical fiber as the medium
• Optical receiver
• Optical amplifiers

Point-to-point fiber connection involves splicing points in between the fiber optic link system, as seen below. These splicing points occur between connectors at transmitter and receiver points. Note, fiber bandwidth capacity is generous, supporting speeds of up to 2,000 Mbps, compared to cable, which supports speeds of up to 1,000 Mbps.

Does 5G need fiber optics?

5G connectivity operates either using wireless or fiber backhaul connections.

4G macro cell towers use radio frequency spectrums, which travel long distances. Fewer towers are therefore needed to serve an area. The problem is, 4G can’t meet the demands for speed, latency and bandwidth demanded these days. Adding more towers is not a simple fix, never mind the expense. Enter 5G.

5G wavelengths are different than what 4G utilizes. 5G wireless networks use higher frequency millimeter waves, known as mmWaves. This spectrum provides much higher bandwidth without latency. However, mmWaves transmit at short distances – typically around 250 feet – although distances are being improved.

To make 5G a reality, telecom companies will have to move from large cell towers to cheaper small-cell sites, or nano-masts, to transmit and receive signals from within their small coverage area. As small cells cost less than macro cell towers, while using less power, this will enable more cells on streetlamps and buildings – up to 60 per square mile is possible. Using this model depends on a deep fiber backhaul, which will enable use of higher frequency waves while improving the end-user experience on wireless devices. Eight miles of fiber optic cable would be needed to connect these cells.

Another point that makes fiber optics essential to 5G network connections: higher frequencies can’t penetrate buildings, trees or double glazing, making 5G connected to fiber even more necessary. More fiber optic cables are needed to connect nano-masts so that 5G can operate at maximum speeds. 5G speed vs fiber is no contest. Without fiber optics, 5G will deliver limited performance.

To understand the importance of fiber optics in 5G, a comparison between the two when acting without the other is necessary.

5G vs. fiber

By itself, 5G uses radio waves for sending and receiving data. Fiber optics relies on light to transmit data through fiber-optic cables.

Criteria	5G	Fiber optics
Speed	20 Gbps downlink to 10 Gbps uplink	Up to 100 Gbps, although in theory, up to 1 petabit per second
Reach	Up to 300 meters	Up to 43.5 miles
Response time	Slower than fiber optics	Faster than 5G
Cost for end user	Cheaper than fiber optics	More expensive than 5G
Installation cost	Lower than fiber optics	More expensive than 5G; involves manhours and cost of cables
Operational cost	Up to five times that of fiber optics	Lower than 5G

Is 5G better than fiber optics? By itself, no. But put the two together to create a 5G fiber optic network and you can realise a fantastic leap in speed, among other things.

More 5g fiber optic cables needed

The problem is, not enough fiber optic has been laid. For 5G to realize its potential, we need a more dense, high-capacity fiber-based network infrastructure. Fiber fronthaul cable is also important to connect the dense mesh of 5G’s small cells. It’s perhaps with some irony that 5G wireless solutions include fiber optic cables. The performance of the wireless network will depend on the wireline network – meaning fiber – and its ability to carry traffic to and from the 5G small cells.

Policy makers and service providers will have to work together to ensure investment in laying more 5G fiber optic cables. Networks of fibers often include underground or aerial fiber optic cable that’s not being used, called dark fiber. These can easily be activated with an optical signal. Laying additional fiber at the onset of a job is easier and cheaper in the long run than coming back and doing an overlay.

Before taking any steps in your design, read What is 5G base station architecture?

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