What Are Simplex and Duplex Fiber Optic Patch Cords?

Fiber optic patch cord, also known as fiber optic patch cable or fiber jumper, is a fiber optic cable terminated with fiber optic connectors on its both ends. According to fiber cable structures, fiber optic patch cords can be divided into simplex and duplex fiber jumpers. What are simplex and duplex fiber optic patch cords? And what are their differences? This post will give answers to these two questions.

Simplex Fiber Optic Patch Cord

Simplex fiber patch cord has one fiber and one connector on each end. Both single mode and multi-mode simplex optic patch cords have only one single strand of fiber. The core of a single mode simplex optic patch cord is 8 to 10 microns. Light travels toward the center of the core in a single wavelength in single mode patch cables. The core of a multi-mode simplex optic patch cord is either 50 or 62.5 microns. The core of the latter gathers more light compared to the former, and allows more signals to be transmitted.

Duplex Fiber Optic Patch Cord

Duplex fiber optic patch cable has two fibers and two connectors on each end. There are single mode and multi-mode duplex optic patch cords. A single mode duplex optic patch cord is constructed of two identical strands of single mode fiber. A multi-mode duplex optic patch cord is constructed of two identical strands of multi-mode fiber. For example, a duplex 9/125 single mode fiber patch cable has two strands of 9/125 micron single mode fiber, featuring a 9µm core and 125µm cladding; a duplex 62.5/125 multi-mode fiber patch cable has two strands of 62.5/125 micron multi-mode fiber, featuring a 62.5µm core and 125µm cladding. One fiber transmits data in one direction and the other one transmits data in the reverse direction. Each fiber is marked “A” or “B” or different colored connector boots are used to mark polarity. Every connector can only be connected to the corresponding port, same as the simplex situation. The following picture shows simplex and duplex fiber optic patch cords.

Simplex & Duplex Fiber Patch Cable

What Are Their Differences?

Simplex and duplex fiber patch cords have their respective features and applications. There is only one single strand of glass or plastic fiber in a simplex fiber patch cord. Simplex optic patch cords can be used for applications that only require one-way data transfer. It is just like that water only flows in one direction—downwards. So one end of a simplex fiber patch cord is a fixed transmission end, and the other is a fixed receiving end. A duplex fiber patch cord consists of two strands of glass or plastic fiber which are typically found in a tight-buffered and jacketed “zipcord” construction format. The duplex fiber is most often used for duplex communication between devices where a simultaneous and bi-directional transmit and receive are required, such as backbone ports, workstations, Ethernet switches, fiber switches and servers.

Other than simplex and duplex, with different connectors or cable constructions, there can also be different categories of fiber optic patch cords, like LC-LC fiber patch cord, or ST-LC fiber patch cable. These fiber patch cables can be with custom length. If you want to choose a fiber optic patch cord, you need to take all these things into consideration, simplex or duplex, single mode or multi-mode, connectors, etc.


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