Datasheet

31
Illustrated: CCM-1600 Chassis connected to a CR-8MD1-E Standalone
Multiplexer
Coarse Wavelength Division Multiplexing
Optical Insertion Losses
The following definitions and explanations are used in estimating
accumulated Optical Insertion Losses.
1. Multiplexer/De-Multiplexer stages: where multiple channel
wavelengths (four, eight or twelve) are initially combined and
coupled to a single-mode fiber cable or de-coupled and separated
into individual channels - typically at fiber cable end-points i.e. at
Origin CWDM launch-points and at (Remote) CWDM channel
end-points.
2. Drop-Point - an OADM function: where one or more wavelengths
(user channels) are de-coupled from the fiber cable at an
intermediate location along the cable span i.e. a branching point.
3. Add-Point – an OADM function: an intermediate location where one or more wavelengths (user channels) are re-inserted (coupled) onto
the fiber cable for the Return-path trip (back) to the CWDM Origin.
4. Pass-Thru – an OADM function: Forwarding or “Passing” through the OADM, that fraction of channel wavelengths that are
not being de-
coupled at that intermediate point. The forwarded wavelengths continuing along the fiber-cable towards the next intermediate OADM
‘Drop’-point or to the Remote site CWDM end-point.
5. The Optical Insertion Losses through each device are treated as equivalent for all wavelengths for calculation purposes.
6. Insertion Loss can be estimated (calculated) in a “forward” direction i.e. from Origin to Remote End-point or from any OADM user-channel
“Add/Drop” point forward to the Remote End-point.
7. Total insertion Loss should also be estimated for the Return-path i.e. from the Remote End-point to the Origin, or from any OADM “Add/
Drop” point to the Origin.
8. In some cases, calculation results accumulated in a “forward” direction may be equal to the Return-path calculation results, suggesting a
symmetrical relationship. This should not be assumed to be always true. In order to identify critical network power-budget constraints,
accumulated device Optical Insertion Losses should be independently calculated for each path direction and for each starting point i.e. “Add-
Point” (stage) where an optical signal is inserted into the fiber cable.
9. The results of CWDM device Optical Insertion Loss calculations must be factored into other typical network Optical Budget calculations in
order to get an accurate estimate of the total fiber optic Power Budget available to the network designer.