Recommendation G.957 (06/99)
29
APPENDIX IV
Upgradability examples
Two examples for accomplishing upgradability are described below:
IV.1 Example
1
To realize low-cost designs optimized for a particular hierarchical level
by using current, widely
available
optical components, the following maximum attenuation ranges may be adopted for the
long-haul applications:
– STM-1
28
dB;
– STM-4
24
dB;
– STM-16
24
dB.
For upgrading from one hierarchical level to a higher one when it is desired to maintain regenerator
spacings for the
original and upgraded system, the following options are available:
i)
The original system design may be based on the smallest attenuation (i.e. highest hierarchical
level) expected for the upgraded long-haul system.
ii)
If the original system operates in the 1310 nm region on G.652 fibre, then the upgraded
system may be chosen to operate in the 1550 nm region to obtain lower cable attenuation,
although with increased dispersion penalty.
iii)
Relatively high-loss components (e.g. connectors) may be
replaced with lower-loss
components for the upgraded system.
iv)
Statistical design approaches may be employed to provide enhanced cable sections for the
upgraded system.
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