Optical: Passive Multiplexers (Mux, Muxes, Filters)

Table of Contents

Overview 

• Passive muxes, as the name implies, are unpowered, unmonitored devices
• Sometimes called filters
• Passive muxes allow you to combine and split apart many frequencies of light on one fiber pair

Details

• Filtering technology
  • Inside of a mux one of these three technologies is used to filter frequencies of light
    • Fiber Bragg Grating

    • Thin Film Filter

    • Arrayed Waveguide Grating

• Channels - CWDM vs DWDM
  • ITU
    • Standards for channel width and numbering for each frequency
    • In the c-band (DWDM, diagram here Optical: Dense Wavelength-Division Multiplexing (DWDM) Channels) this is typically 100GHz spacing for passive filters
  • See Optical: Coarse Wavelength-Division Multiplexing (CWDM) Channels
  • See Optical: Dense Wavelength-Division Multiplexing (DWDM) Channels

CWDM Example

• Example diagram:

Add/Drop Design Example

• Example diagram
• In this example each location on the add/drop path has two circuits - one east and one west (color coded)
• Each lateral is folded, so keep in mind that
  • A fiber cut on a lateral would take down the location served by the lateral AND all other locations served on the add/drop path would see one of their two paths go down