What is an OADM (Optical Add/Drop Multiplexer)?

Fiber optic communication networks are becoming increasingly popular day by day. All of the corporate networks as well as service provider networks make use of the fiber optic communication technology to efficiently serve their end users. Fiber optic communications are also making inroads into the houses of the end users. With the advent of FTT-X networks, the usage of fiber optic cables has increased exponentially. It is not possible to have a dedicated fiber cable pair for each link as it would take a lot of space and the links would still be under-utilized.

 

To make fiber optic communications more effective and efficient, engineers developed a technique called multiplexing which allowed different signals to travel on a single fiber optic cable without interference. Multiplexing is widely used in its various forms across all the communication methods that are currently in use today.

 

OADM

 

An optical add-drop multiplexer (OADM) is a critical device that is used in the wavelength-division multiplexing systems for multiplexing and routing different channels of light into or out of a singlemode fiber (SMF). It is one of the fundamental constructional blocks of the modern day telecommunications networks.

 

Components of OADM

 

Traditionally, an OADM has three major components which are responsible to carry out the task assigned to an OADM. These three components are given below:

 

Optical Demultiplexer

An Optical Demultiplexer separates the multiple of wavelengths in a fiber and directs them to many fibers

Optical Multiplexer

The optical multiplexer is used to couple two or more wavelengths into the same fiber

A set of ports for adding and dropping signals

Types of OADM

 

There are two main types of OADM that are widely used in communication networks, namely, Fixed OADM (FOADM) and Reconfigurable OADM (ROADM). An OADM with remotely reconfigurable optical switches in the middle stage is called a reconfigurable OADM (ROADM). Ones without this feature are known as fixed OADMs. Fixed OAMDs are used to drop or add data singles on dedicated channels, and reconfigurable OADMs have the ability to electronically alter the selected channel routing through the optical network. While the term OADM applies to both types, it is often used interchangeably with ROADM.

 

Fixed Optical Add-Drop Multiplexer (FOADM)

 

FOADMs use fixed filters that add/drop a selected wavelength and pass the rest of the wavelengths through the node. Static wavelength-filtering technology eliminates the cost and attenuation to demultiplex all DWDM signals in a signal path. The solution is called FOADM because the wavelengths added and dropped are fixed at the time of add/drop filter installation on the optical path through a node.

 

Reconfigurable Optical Add-Drop Multiplexers (ROADM)

 

Reconfigurable Optical Add Drop Multiplexers (ROADMs) are used to provide flexibility in rerouting optical streams, bypassing faulty connections, allowing minimal service disruption and the ability to adapt or upgrade the optical network to different WDM technologies my electronically configuring the OADM to achieve the required functionality.