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Simplex vs. Duplex Fiber Patch Cable

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

Simplex and duplex are two options for the cables in your fiber 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 fiber optic cables, their various applications and the advantages of each.

Simplex vs. Duplex Fiber Structure

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

Duplex fiber optic cables used to have two fibers 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 fiber 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 fiber transmission uses a single fiber 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 fiber 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 fiber 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 Fiber Applications

Fiber optic simplex offers a 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.

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

Simplex vs. Duplex Single-Mode and Multimode Fiber

Both simplex and duplex fiber 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 Fiber Optic Cable article.

Simplex vs. Duplex Fiber Advantages

As simplex and half-duplex fiber optic cables use only one fiber to communicate, they are often less expensive than full-duplex fiber optic cables. They also allow for more incoming data at higher speeds. The primary advantage of a full-duplex fiber optic cable is the capacity for simultaneous bidirectional communication. One potential disadvantage to fiber 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.

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