Types of Joints in Optical Fiber

Optical fiber is a technology through which data passes in the form of light at high speed. It is a thin transparent cable type that is flexible and can be bent easily Fiber optics cable can be joined many times in one installation using joints. Joints are used to transfer light from one fiber optic cable to another fiber optic cable and are made up of plastic or glass material. In this article, we will explore the various types of Joints in Optical Fiber.

Types of joints in optical fiber

Unlike the normal joints, these are the special joints used for fiber optic cables only and can be classified based on their characteristics as follows −

  • Splice

    • Mechanical splice

    • Fusion splice

  • Connector

    • DNP connector (Dry No Polish)

    • SMA connector (Sub Miniature type A)

  • Coupler

    • T-coupler

    • Star

    • Three ports coupler


Splice joints are used to connect the two ends of fiber optic cables permanently. It is used when two cables (for example 45- fiber cable and 22-fiber cable) are connected using a splice joint to form one long cable. This method is commonly used for signal transmission over a long distance.

Splice is of two types

  • Mechanical splice

    This joint uses a technique designed to hold two fiber ends in a position such that light passes through two fiber cables.

  • Fusion splice

    A fusion splice is considered the most reliable joint between two cables. This joint uses an electric arc to pass a high-voltage signal so that the maximum output is received at the end.

Difference between mechanical splicing and fusion splicing


Mechanical splicing

Fusion splicing


Mechanical splicing does not use any other thing to connect two cables.

Fusion splicing uses heat or an electric arc to join two cables.


Mechanical splicing holds two cables together using its own assembly.

Fusion splicing fuses two cables into one single cable


It is comparatively less expensive.

It’s more expensive than mechanical splicing.


Average signal loss is more because of variability in the type of connector used.

Average signal loss is less because they offer very high-quality signal transmission.


Fiber optics connectors are joints that are reusable, and easy to attach and detach at any point in time.

The connector is of two types −

  • DNP connector

    Dry No Polish connectors are pre-assembled connectors that do not require field polishing and assembling.

  • SMA connector

    It is a Sub Miniature type A coaxial connector that is used for high-frequency devices like a microwave, mobile signal antennae, wifi antennae, etc.

Difference between DNP and SMA connectors


DNP connector

SMA connector


DNP is Dry No Polish connector.

SMA is Sub Miniature type A connector.


It is a pre-assembled design.

It is a screw-type coupling design.


Installation is fast.

Installation is slower than the DNP connector.


It is a device that divides one input signal into two output signals. Coupler can also be used for dividing two inputs into one output. In such cases, it is called a Combiner.

Different types of couplers are

  • T-Coupler

    The T-coupler is used split one incoming signal into two output signals using a grin lens and beam splitter.

  • Star Coupler

    The start coupler is used to split one incoming signal into many output signals.

  • Three ports coupler

    The three ports coupler splits one input signal into two output signals without using grin lens and beam splitter.

Difference between T-Coupler and Star coupler



Star coupler


T-Coupler has one input and two outputs

A Star coupler has one input and many outputs.


The output power of the two ports is not evenly distributed.

The output power is equally distributed


It is used in bus types of networks and small networks.

It is used in large networks.


If anyone coupler in the network gets disconnected, all other terminals will also get disconnected.

If any one-star coupler terminal gets disconnected, it won’t impact other terminals in that network.


Multiple types of Joints have been discussed in this article. The type of fiber optic joints to be used to connect two or more fiber optics cables depends on the following factors the joint should cause minimum power loss, it should be easy to install, it should be strong, and have less weight.

Updated on: 28-Mar-2023

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