Installation & Operation Manual Chapter 2

Chapter 2. Theory of Operation FibeAir 1500 Installation & Operation Manual
2-2 In Door Unit (IDU) Revision 2.0
2.2. In Door Unit (IDU)
The IDU is a compact, 17” wide, 1U-high unit, mount compatible for both
ETSI and ANSI standard racks. The IDU modulates/demodulates the
155Mbps Sonet/SDH payloads, manages local and remote units, provides
I/O line alarms, and provides interfaces for 1.544/2.048 Mbps Wayside
channel, 64Kbps User channel and 64Kbps Order Wire channel.
The IDU also interfaces a Local Maintenance Terminal or Network
Management System. In addition, status alarms and indicators are provided
on the front panel.
The IDU major modules:
n Multiplexer
n Modem
n Manager Card
n Cable Interface
n Power Supply
2.2.1. Multiplexer
The Mux module functions as a Sonet/SDH Regenerator. On the line side it
interfaces the OC-3/STM-1 stream, and on the radio side the Modem
module.
As a regenerator, the MUX either terminates or regenerates the
OC-3/STM-1 RSOH. In one direction, the OC-3/STM-1 stream, interfacing
through the MUX’s Rx line input terminates and the resulting stream is
transmitted to the Modulator in the Modem module.
In the opposite direction, the stream coming from the Modem’s
Demodulator, undergoes OC-3/STM-1 Regeneration in the MUX, and
transmitted through the MUX’s Tx line output.
In addition, the MUX module uses the OC-3/STM-1 SOH bytes to support
other services: 1.544/2.048 Mbps Wayside channel and management, 64
Kbps User Channel and Order Wire channel.
The MUX module may be configured via software for transparency of most
of the SOH bytes for maximum system transparency and non-intervention,
at the cost of reduced functionality and services.
The multiplexer module enables to integrate different interfaces and
services into the SDH payload to converge Datacom and Telecom
applications.