Operation Manual

Fiber Distributed Antenna System (Fiber DAS)
15
Fiber Optic Interface (FOI) unit
The FOI converts the RF signals in the downlink to fiber-optical laser output that is transmitted on the fiber to the
remote unit. It also receives the laser light transmitted by the Remote Unit and converts it back to RF signals that
are then routed to the ICU and/or BIU.
Figure 11
Base
Station
Base Station
Interface
Interconnect
Unit
Fiber-Optic
Interface Units
Fiber-Optic
Cables
to
Remote
Units
(Antenna)
Master Frame Unit
FOI
FOI
FOI
FOI
ICU
BIU
FOI Signal Flow
The FOI is powered from the MFU backplane and communicates via Ethernet with the BGW.
Figure 12 Fiber Optic Interface (FOI) Unit
WARNING
Avoid looking into connected fibers and receptacles.
The laser used in this system is a Class 3b laser that produces invisible infra-red coherent light. Not safe to view
with optical instruments. Always put the protection caps on unused fibers and receptacles.
This interface is designed to work with SC-APC connectors (angled physical connector) and single mode fibers only.
All connectors between the master unit and the remote unit must be APC, otherwise problems with reflections will
arise, which could cause severe problems in the system.
The Ethernet communication between the Headend and the Remote Units takes place on two sub-carriers in the
FOI where the Ethernet signals are superimposed on the RF signals. The Ethernet sub-carriers are on frequencies
not used by the RF traffic so they do not cause any system performance degradation.
As shown in Table 10 , Bird offers several FOI cards. The "DOI300 Series FOI" on page 16 , the "DOI380X FOI" on
page 19 , and the "DOI401 FOI" on page 20 .
Table 10 FOI Variants
Parameter Fiber Ports Wavelength
DOI 301 2 1310 nm (RX), 1550nm (TX)
DOI 302 (WDM) 1 1310 nm (RX), 1550nm (TX)
DOI 380x 1 Various wavelengths available
DOI401 4 1310 nm (RX), 1550nm (TX)