Passive WDM Multiplexer Glossary


Point-to-Point applications combine 4 or more WDM channels onto a fiber pair. These applications consist of a Mux/Demux on each end of the connection. WDM transceivers connect to the appropriate Tx and Rx port on each passive device.

  • Mux: Short for Multiplexer. This is the optical component that combines the Transmit portion of the fiber link on to a fiber. “Mux” is also loosely referred to as device that supports both Multiplexing and Demultiplexing function.
  • DeMux: Short for De-Multiplexer. This is the optical component that separates the Receive portion of the fiber link from a fiber to individual channels.
  • Mux/Demux: A passive WDM device that includes both Mux and Demux components.
  • OADM: Optical Add/Drop Mux – OADMs come in two flavors, a Add or Drop mux and a Add/Drop Mux. The Add or Drop mux adds or drops a single WDM wavelength on to a link. The Add/Drop mux support East/West functionality to both add and drop WDM wavelengths on/off a link.
  • Form Factor: The physical package that passive WDM components are presented to the network. Many form factors exist, each with advantages and disadvantages for each network. Form factors vary from non-modular rack mount units to modular systems designed to offer cable management or extreme density.
  • LGX® - LGX® is a registered trade market of Lucent-FITEL and refers to specific optical form factor. An industry standard LGX cassette or module is 5” high, 1.2” wide, and 6” deep, with optical connectors on the front plate. Other non-industry standard LGX variants are available in the market to address density and depth requirements.

Port Labels

  • COM: Short for common port. This is the ‘uplink’ port for the passive mux/demux.
  • EXP: Express port, also referred to as Pass or Upgrade port. Offers ability to add/drop or pass through additional WDM channels. On CWDM, it can be any CWDM wavelength not locally muxed or demuxed. For DWDM, this port is for CWDM channels.
  • MON: This port provides a test access port to monitor the WDM signal, usually at 1% of the optical power level.
  • 1310: Pass-through port of wideband 1310 or “gray” optic circuit. The passive device requires wide-WDM filters to separate the narrow CWDM channels from the gray circuits.
  • PASS: See EXP
  • UPG: See as EXP
  • WDM: See COM

Key Specifications

  • ITU 100GHz grid: Most common DWDM passive mux/demux type. DWDM frequencies are assigned wavelengths and channel numbers in the ITU grid. These channel numbers label each port in a DWDM passive mux/demux. Transceivers using 50GHz ITU channels can use standard 100Ghz DWDM mux/demux components.
  • C-Band: The C-Band spectral window for DWDM traffic is between 1525nm and 1565nm. 100GHz DWDM channels are spaced at 0.8nm across the C-Band, offering approximately 42 channels.
  • Center Wavelength: The specification for the individual channel in the passive WDM. Example, CWDM 1471, DWDM 1530.33 or channel 59.
  • Channel Spacing: CWDM mux/demux channels are spaced 20nm from the center wavelength. DWDM mux/demux channels are spaced 0.8nm from the center wavelength.
  • Pass Band: The Pass band is the usable bandwidth within the WDM mux port. The pass band is the range that WDM laser can drift from the center wavelength. Should the WDM laser drift outside the pass band, the pass band will block the transmission. For CWDM, the pass band is +/-6.5nm, DWDM +/-0.1nm from the center wavelength.
  • Channel Bandwidth: See Pass Band
  • Channel Isolation: Measures the ability of the WDM pass band filter to prevent light from passing through the channel pass band of the device. Isolation is measured in dB against Adjacent and Non-Adjacent channels.
  • Insertion Loss: The loss introduced by the passive WDM component. As a rule, the more WDM ports, the greater the loss.
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