Plastic Optical Fibre

TECHNOLOGY

Although relatively common in a variety of short reach, low bandwidth industrial and automotive applications, plastic optical fibre technology has never really caught on amongst Telecoms operators and broadband service providers. However, Spanish incumbent Telefonica's trial of plastic optical fibre in home networks may signal a resurgence of interest in the technology.

There are a few benefits to using Plastic optical fibre (POF), also referred to as Polymer optical fibre. For one thing, it is highly resistant to bending and stretching and maintains a high refractive index difference between the cable core and cladding. The fibre cables, optical links, connectors, and installation are all relatively inexpensive and, as with all fibre networks, the signal can’t be tapped in to. The core area is typically around 1 mm, which is larger than glass fibre. This makes coupling and handling fast and easy, without the need for specialised skills and tools. Like glass fibre, POF is immune to electromagnetic interference. Unlike copper cabling, it can run alongside power cables or near electrical equipment, which can make installation easier.

Historically, POF hasn’t offered the same reach and capacity as glass fibre, but a new IEEE Ethernet specification is now providing support for gigabit transmission. The IEEE 802.3bv standard, ratified in 2017, comprises specifications for three applications: home, industrial, and automotive networks. The 1000BASE-RHA home network specification defines 1 Gb/s using over 50 m of duplex POF via red light (at approximately 650 nm). We see the main application of this standard in premises networks for entertainment, home automation devices and wireless access points.

Plastic optical fibre provides unique capabilities for these applications where long link lengths aren’t required and simplicity of connectivity is a requirement

In November 2017, Telefónica completed a project using POF for a Gigabit-speed home network. 30 homes were equipped with a combined POF backbone with a 60GHz Wi-Fi ‘WiGig’ network. 60GHz Wi-Fi enables bandwidth with a theoretical maximum of 4600 Mb/s. In the test, four wall outlets provided gigabit-speed, wireless coverage throughout each home. In effect, POF makes it possible to bring the wireline network close to the wireless network, thereby reducing the impact that Wi-Fi’s limitations might have on performance - thick walls can severely impede wireless signals. However, the advantage of this technology versus 1000GBASE-T running over copper cable which offers 100m reach, easy connectivity and deployment is not obvious. The use of POF in automotive and industrial applications where space is limited, electromagnetic interference is high or both, is more obvious than in home networks.