Understanding Simplex & duplex fibre patch cable

we are all aware that fiber optic cable is made of glass or plastic,  Fiber optic cable can be divided into many types according to different classification principles, such as source, mode, usage. Duplex and simplex fiber patch cables offer a variety of uses. Before discussing simplex vs. duplex fiber optic cables, is necessary  to get a clear and deep knowledge  of simplex vs. duplex. Simplex and duplex are different forms of communication medium in telecommunications and computer networking, which provide channels  to convey information. According to the ITU-T definition, a simplex circuit is one where signals can flow only in one direction at a time. One end is the transmitter, while the other is the receiver and that is not reversible. On the other hand, the full duplex system uses two fibers to communicate. This allows one fiber to transmit from point A to point B while the other fiber transmits from B to A. Therefore, both ends of a full-duplex system have both transmitters and receivers. Unlike simplex, duplex can be divided into half duplex and full duplex. Half duplex means a communication channel that data can be transmitted in both directions on a signal carrier but not simultaneously. One end is the transmitter, while the other end is the receiver and may be reversible (this is the opposite of simplex). This makes it similar to a two-way radio. In addition, full duplex is two-way communication achieved over a physical link that has the ability to communicate in both directions simultaneously.

Simplex Fiber Optic Cables

Simplex fiber optic cables provide the strength and flexibility required for today’s fiber interconnect applications. simplex fiber optic cable is composed of a single strand fiber with a tight-buffered (coated with a 900 micron buffer over the primary buffer coating) with Kevlar (aramid fiber) strength members and jacketed for indoor use, and is used mostly for patch cord and backplane applications. Simplex fiber is most often used for applications that only require one way data transfer. Simplex fiber is most often used where only a single transmit and receive line is required between devices or when a multiplex data signal is used (bi-directional communication over a single fiber). Simplex fiber is available in single-mode (SM) and multimode (MM). Single mode simplex fiber patch cable is an ideal option for setting up a cable network that will require data to travel in one direction over long distances. Since this simplex optical fibre cable only carries one ray of light at a time, it’s better for long-distance transmissions. for instance, Simplex fiber optic patch cable is ideal for use in office LAN connections, patch cords, pigtails and internal point-to-point links where frequent handling is likely (e.g. data cabinets, equipment rooms, user outlets). Utilising 600 µm or 900 µm buffered fiber, the cable is suitable for use with industry standard connectors and can be easily made into a patch cords. They are designed for production termination where consistency and uniformity are vital for fast and efficient operation. Moreover, simplex multimode fiber has a larger diameter core that effectively allows multiple modes of lights to propagate. The number of light reflection is created due to a larger diameter. The core of a single mode simplex optic patch cord is 8 to 10 microns, while a multimode simplex optic patch cord is either 50 or 62.5 microns. more data passes through the multimode fiber at a given point in time. The quality of the signal is reduced over long distances due to high dispersion and attenuation rate with this type of fiber. multimode fiber is used for short distance data transmission purposes.

Duplex Fiber Optic Cables

Duplex fiber optic cable consists of two strand fibers of glass or plastic it can be referred as two simplex cables. This duplex fiber cable is carefully structured in a zip-cord arrangement i.e (side-by-side) construction format by a thin connection between the two jackets. A duplex communication system is a point-to-point system composed of two connected parties or devices that can communicate with one another in both directions, simultaneously. Duplex fiber is available in singlemode and multimode. Use multimode duplex fiber optic cable or single mode duplex fiber for applications that require simultaneous, bi-directional data transfer. Workstations, fiber switches and servers, fiber modems, and similar hardware require duplex fiber cable.

Duplex fibers types:

  • Half-duplex: Data may only be transmitted in one direction at a time.
  • Full-duplex: Data is transferred in two directions simultaneously.

Half Duplex Fiber Optic Cables

Half duplex fiber optic cable is capable of sending the signal in both directions but in only one direction at a time. Some transmission network uses half duplex cables but it is necessary to specify this requirement for all the nodes in the network. For instance, half duplex fiber optic can be used in police car radio phones to allow only one person to talk at each time.

Full Duplex Fiber Optic Cables

In the full duplex fiber optic cables, the data is transferred in two different directions simultaneously on a single carrier at the same time. An example is a telephone IP service where people at both ends of a call can speak and be heard by each other at the same time because there are two communication paths between them, thus using the full duplex mode can increase the efficiency of communication.


Simplex fiber optic cable and duplex fiber optic cable both have single-mode and multimode cable type. They are different from source, transmission direction and cost. If you need a fiber optic cable for one-way transmission, and then simplex fiber optic cable is a good choice. When you are looking for a bi-directional fiber optic cable, duplex fiber optic cable is highly recommended.

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