User Manual

Users Guide - Andrew InCell™ Fiber Optic Distributed Antenna System
5-2
The InCell™ family is designed to minimize maintenance and monitoring costs. Provisions are
made for both local and remote monitoring of small and large systems. The InCell™ system
continuously monitors and reports status of the system hardware, by a combination of indicators
available at the central hub (CDU) and at each remote antenna and alarms for remote monitoring
that aid in system fault detection and fault isolation down to a circuit board or cable.
The wideband, single mode fiber cable allows a low frequency RF test signal to be continuously
passed over the downlink and uplink signal paths with the multiple RF wireless signals. For
example, in a dual band system, the pilot test signal, the 800 MHz cellular service, and the 1900
MHz PCS service signals simultaneously pass through the downlink and uplink paths.
Pilot Tone Generation
The CDU generates a continuous pilot tone for system level fault detection and isolation and
distributes that signal to each of the CDU ports. This low frequency RF tone is combined with
the downlink RF signal and transmitted over the fiber optic cable to the ERAU where it is
received and filtered from the downlink RF signal. In the ERAU, the pilot tone is separated,
amplified and combined with the RF uplink signal to be sent over the optical uplink path back to
the CDU. Within the ERAU, the pilot tone is detected by a threshold detector to indicate the
presence of the pilot tone at a minimum signal level. The pilot threshold detector drives an LED
on the ERAU that indicates that the downlink optical signal path to the ERAU is connected.
The return path pilot tone from the ERAU is also filtered, amplified and detected. The detected
pilot signal is passed to a threshold detector to indicate the tone presence at a minimum signal
level. The pilot threshold detector in turn drives an LED at each port of the CDU indicating that
both the downlink to the ERAU and the uplink back to the CDU are connected and that power is
properly functioning at the ERAU.
ERAU Front Panel Indicators
The POWER indicator on the ERAU shows that DC power from the composite cable is present
at the ERAU. If the POWER indicator is green, DC power is present in the ERAU.
The LINK indicator on the ERAU shows that the pilot tone from the CDU is present over the
downlink. When the LINK indicator is off on the ERAU, the downlink optical path between the
CDU and the ERAU is installed correctly and DC power is present in the ERAU. If the LINK
indicator is red, there may be a problem with the downlink optical path between the CDU and
ERAU or a problem with the ERAU power. The ERAU indicators allow system installers and
maintainers to easily determine the ERAU functional status, the power supply status, and the
downlink optical path status.