Page 240 - Optical Communications Essentials

Constructing the WDM Network Puzzle

230 Chapter Thirteen

Original Gigabit Ethernet link
Single-wavelength fiber link
GigE GigE
GigE
GigE
TX1 RX
TX1
RX
Upgraded link with CWDM
GigE GigE
GigE
GigE
TX1 RX1
RX1
TX1
GigE GigE
GigE
GigE
TX2 8-λ RX2
RX2
TX2
• fiber link •
• •
• •
ATM ATM
ATM
ATM
TX7 RX7
RX7
TX7
FC FC
FC
FC
TX8 RX8
RX8
TX8
8-channel 8-channel
CWDM CWDM
mux demux
Figure 13.12. Implementing a major capacity
upgrade of telecommunication campus links by
means of CWDM.
Hub N
Central
office (hub)
Bidirectional
Metro access ring
Hub 3
Users
8-channel
CWDM
Hub 2 8-channel
CWDM
Users
Figure 13.13. A hub-and-spoke LAN and metro network
configuration.

13.4. Performance Monitoring Needs
To ensure that information is sent reliably, electric networks monitor signal
integrity at strategic points in the transmission path. Traditionally this is done
by monitoring the bit error rate (BER) of the data. Although BER testing can
be done on an end-to-end basis in a WDM network, a different mechanism

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