User's Manual

Confidential & Proprietary 42/139
Figure 4.18 – MDBU Outer Look
2) Expansion Wavelength Division Multiplexer(EWDM)
EWDM module makes optical-electronic conversion of TX signals and makes electronic-optical
conversion of RX signals. With an FSK modem in it, this multiplexer communicates with BIU. It
also has ATT for optical compensation to compensate for optical cable loss between ODUs.
Furthermore, it has internal WDM, and so, it needs only one optical cable to work with ROU.
Figure 4.19 – EWDM Outer Look
3) Expansion Central Processor Unit(ECPU)
ECPU can inquire and control state of modules to be installed into OEU. This unit
communicates with upper BIU while communicating with lower ROU. It also acts as
communication bridge between BIU and ROU.
In addition, the unit has RS-232C port for serial communication, which enables inquiry and
control of devices thorugh PC. At the front panel, communication LED indicator indicates
communication state with upper BIU and lower ROU. It also has ALM LED indicator to show if a