ROADM - Reconfigurable Optical Add-Drop Multiplexer
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ROADM – Reconfigurable Optical Add-Drop Multiplexer

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Definition

ROADM, short for reconfigurable optical add-drop multiplexer, is a form of optical add-drop multiplexer that adds the ability to remotely switch traffic from a wavelength-division multiplexing (WDM) system at the wavelength layer. In the fiber optic network which uses wavelength division multiplexing (WDM), reconfigurable optical add-drop multiplexer (ROADM) is used to remotely add, block, pass or redirect modulated light emissions-infrared and visible-within a range of wavelengths. With ROADM devices, signal switching doesn’t need optical-to-electric and electric-to-optical conversions. Instead, outgoing light beams can be generated, incoming beams could be terminated or beams could be passed through the device unmodified. This is achieved through wavelength-selective switch (WSS) components within the device.

Advantages

There are several advantages of ROADM, they are:

  • ROADM allows for remote configuration and reconfiguration.
  • Bandwidth could be assigned when needed and without interrupting concurrent traffic, and power balancing is automatic.
  • Most ROADM devices use technologies according to first-generation, wavelength blocking (WB) or second generation, planar light-wave circuit (PLC) technology.
  • Whenever a wavelength change is required inside a specific channel, these technologies filter light emissions, extract data and impress data onto another emission.
Applications

The different switching technologies in ROADM devices include microelectronic mirrors, live view screen, thermo-optic and beam-steering switches in planar waveguide circuits, and tunable optical filters.

ROADM devices were initially used in long-haul DWDM equipment. By 2005, metropolitan networks began using ROADMs in reaction to increased interest in Ethernet, as well as high-speed data, audio and video services. Within the ensuing years, ROADM devices have brought bandwidth flexibility and operational efficiency to networks. ROADM-based networks are enabling an automated optical layer with dynamic multipoint connectivity, independent wavelength add-drop, remote bandwidth allocation that has been enhanced power management capabilities.

Common Testing-related Challenges

Combined with the benefits of ROADM comes the inevitable need for fiber optic testing that safeguards function and helps to make sure performance. Here are common testing-related challenges to consider in ROADM-based networks.

  • Increases both in insertion loss per node and insertion loss per channel
  • The need to measure optical loss per channel for multiple ROADM configurations
  • The necessity to measure optical signal-to-noise ratios utilizing a precise and repeatable method
  • The impact of possible bandwidth thinning, other changes to bandwidth, and dispersion, that is of particular concern in multiple cascaded devices and 40 Gbit/s systems
  • Compliance using the optical transport network (OTN) standard-ITU-T G.709 standard

Unlike the optical add-drop multiplexer, Capabilities of ROADM test equipment should encompass optical spectrum analysis (OSA), and OTN performance qualifiers for newly commissioned links, along with the transport layer and all ROADM-supported interfaces.

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