Simplex vs. Duplex Fibre Optic Cable: What’s the Difference?

What’s the Difference between Simplex and Duplex Fibre Optic Cable?

Simplex and duplex are two options for the cables in your fibre optic network. Whether you choose full-duplex vs. half-duplex vs. simplex depends on your application and budget. Learn the differences between simplex and duplex fibre optic cables, their various applications and the advantages of each.

Simplex vs. Duplex Fibre Structure

Simplex and duplex fibre optic cables are both tight-buffered and jacketed with Kevlar strength members. Simplex fibre optic cables, also known as single-strand, have only one fibre. On one end is the transmitter, and the other end has the receiver. These are not reversible.

Duplex fibre optic cables used to have two fibres joined together by a thin web or “zipcord” construction. One strand transmitted from point A to point B and the other from B to A. Both ends had a transmitter and a receiver. The emergence of single-strand fibre transmission has changed the situation. It seemed to be a better alternative for network managers, providing an increased network capacity, higher reliability due to fewer connections and overall cost savings. Single-strand duplex fibre transmission uses a single fibre to send data in both directions, namely bidirectional or BiDi transmission. This technology is based on two wavelengths traveling in opposite directions and is achieved by combining and separating data transmitted over a single fibre based on the wavelengths of the lights (typically around 850, 1300 and 1550 nm). Only some equipment manufacturers are using or moving to a single-strand cable for their connectivity, as the equipment becomes very expensive. It exists for certain applications, but it is not the norm.

Duplex fibre optic cables can be half-duplex or full-duplex. Half-duplex means that data can be transmitted in two directions but not simultaneously. Full-duplex indicates that data transfer can occur in both directions at once.

Simplex vs. Duplex Fibre Applications

Fibre optic simplex offers one-way data transfer. It’s a good choice for an application such as an interstate trucking scale that sends weight readings back to a monitoring station. Another example is an oil line monitor that sends data about oil flow back to a central location.

Fibre optic duplex enables bidirectional data transfer. It’s a good choice for applications such as telecommunications as well as workstations, Ethernet switches, fibre switches and servers, and backbone ports. Simplex multimode fibre optic cables can also be used for bidirectional data transfer if a multiplex data signal is used.

Simplex vs. Duplex Single-Mode and Multimode Fibre

Both simplex and duplex fibre optic cables come in single-mode or multimode. Single-mode is often better for long distance applications because it carries one ray of light at a time. Multimode has a larger core and can transmit more data at a given time. However, it is better for shorter distances due to high dispersion and attenuation rates. Read more about the differences between multimode and single-mode in our Multimode vs. Single-Mode Fibre Optic Cable article.

Simplex vs. Duplex Fibre Advantages

As simplex and half-duplex fibre optic cables use only one fibre to communicate, they are often less expensive than full-duplex fibre optic cables. They also allow for more incoming data at higher speeds. The primary advantage of a full-duplex fibre optic cable is the capacity for simultaneous bidirectional communication. One potential disadvantage to fibre optic full-duplex is that it only permits two devices to communicate at once, which means you will need enhanced connections to accommodate additional devices.

Need help deciding whether full-duplex vs. half-duplex vs. simplex is right for your network? Contact Black Box for expert advice on your cabling infrastructure.