Handbook

Axell Wireless Limited
Technical Literature
WMATA CRCS Redundant Antenna System
General Overview
Document Number 60-228701HBK Issue No. 3 Date 28/05/2010 Page 73 of 114
5.11 Dual Fiber Optic Unit 60-228703 (Gallery Place Station)
Dual Fiber Optic Unit 60-228703 is built into a 2U, 19” rack-mount case.
The Primary Downlink optical signal from the Jackson Graham Building CRAS System enters the Dual Fiber
Optic Unit via the SC/APC optical port 1 RX” (annotated “A” in section 5.11.4.) and passes into a Fiber
Optic Receiver Module 20-005501 which demodulates the Downlink optical signal to RF and the Downlink
RF signal then passes through a 20dB Directional Coupler 90-852420 which couples off a small portion of
the signal and feeds it to the N type port labeled “MON -20dB RX 1” (annotated “C” in section 5.11.4.) which
provides a 20dB test/monitor port for the Primary Downlink output. The Primary Downlink path then exits the
Dual Fiber Optic Unit for the RF Failover Switch Unit 60-228905 via the N type port labeled “RX 1”
(annotated “B” in section 5.11.4.)
The Redundant Downlink optical signal from the Carmen Turner Facility CRAS System enters the Dual
Fiber Optic Unit via the SC/APC optical port 2 “RX” (annotated “G” in section 5.11.4.) and passes into a
Fiber Optic Receiver Module 20-005501 which demodulates the Downlink signal to RF and the Downlink RF
signal then passes through a 20dB Directional Coupler 90-852420 which couples off a small portion of the
signal and feeds it to the N type port labeled “MON -20dB RX 2” (annotated I” in section 5.11.4.) which
provides a 20dB test/monitor port for the Redundant Downlink output. The Redundant Downlink path then
exits the Dual Fiber Optic Unit for the RF Failover Switch Unit 60-228905 via the N type port labeled “RX 2”
(annotated “H” in section 5.11.4.)
The Primary RF Uplink from the RF Failover Switch Unit 60-228905 enters the Dual Fiber Optic Unit via the
N type port labeled “TX1” (annotated “D” in section 5.11.4.) and passes through a 20dB Directional Coupler
90-852420 which couples off a small portion of the signal and feeds it to the N type port labeled “MON -
20dB TX 1” (annotated “E” in section 5.11.4.) which provides a 20dB test/monitor port for the Primary Uplink
input.
The Primary Uplink path then passes into a Fiber Optic Transmitter Module 20-005401 where the RF signal
is modulated onto a laser and the optical signal thus produced then exits the Dual Fiber Optic Unit via the
SC/APC optical port 1 “TX” (annotated “F” in section 5.11.4.) and is transmitted to the Jackson Graham
Building CRAS System via a fiber optic cable link.
The Redundant RF Uplink from the RF Failover Switch Unit 60-228905 enters the Dual Fiber Optic Unit via
the N type port labeled “TX2” (annotated “J” in section 5.11.4.) and passes through a 20dB Directional
Coupler 90-852420 which couples off a small portion of the signal and feeds it to the N type port labeled
“MON -20dB TX 2” (annotated “K” in section 5.11.4.) which provides a 20dB test/monitor port for the
Redundant Uplink input.
The Redundant Uplink path then passes into a Fiber Optic Transmitter Module 20-005401 where the RF
signal is modulated onto a laser and the optical signal thus produced then exits the Dual Fiber Optic Unit via
the SC/APC optical port 2 “TX” (annotated “L” in section 5.11.4.) and is transmitted to the Carmen Turner
Facility CRAS System via a fiber optic cable link.
Dual Fiber Optic Unit 60-228703 is powered by a 24V DC supply from one of the PSU Modules 96-300091
in PSU Housing Shelf 96-300090, The 24V DC supply powers two on-board DC/DC converters 96-200024
arranged in a parallel dual redundant configuration, the outputs of which are combined by power diodes to
provide a 12V DC supply for the fiber optic modules within the unit
An alarm system is fitted to Dual Fiber Optic Unit 60-228703, each of the fiber optic modules carries its own
voltage-free contact alarm relay output which are summed at the 15 way “D” panel plug labeled “ALARM”
(annotated “EE” in section 5.11.4.)