206/2006Release of single-band and dual-band remote units that support 800 and 1900 MHz operation and inclu-
309/2006Non-technical changes for agency approvals.
sion of the RLM feature in the 800 and 1900 MHz remote units.
LIST OF CHANGES
The technical changes incorporated into this issue are listed below.
PAGEIDENTIFIERDESCRIPTION OF CHANGE
ixStandards Added FCC Part 15.5 statement.
2-25Table 2-7Deleted references to 1900 MHz Band G
TRADEMARK INFORMATION
ADC and Digivance are registered trademarks of ADC Telecommunications, Inc.
OptiTap is a trademark of Corning Incorporated.
Stargazer is a registered trademark of ADC DSL Systems, Inc.
Procomm Plus is a registered trademark of Quarterdeck Corporation.
Acrobat and Adobe are registered trademarks of Adobe Systems, Inc.
DISCLAIMER OF LIABILITY
Contents herein are current as of the date of publication. ADC reserves the right to change the contents without prior notice. In no
event shall ADC be liable for any damages resulting from loss of data, loss of use, or loss of profits and ADC further
disclaims any and all liability for indirect, incidental, special, consequential or other similar damages. This disclaimer of
liability applies to all products, publications and services during and after the warranty period.
This publication may be verified at any time by contacting ADC’s Technical Assistance Center at 1-800-366-3891, extension 73476
(in U.S.A. or Canada) or 952-917-3476 (outside U.S.A. and Canada), or by e-mail to wireless.tac@adc.com
Page ii
ADC Telecommunications, Inc.
P.O. Box 1101, Minneapolis, Minnesota 55440-1101
In U.S.A. and Canada: 1-800-366-3891
Outside U.S.A. and Canada: (952) 938-8080
Fax: (952) 917-1717
This operation and maintenance manual provides the following information:
• An overview of the Digivance Street-Level Coverage Solution (SCS) system.
• A basic description of the system components including the Host Unit (HU), Remote Unit
(RU), and Digivance Element Management System (EMS).
• Procedures for turning-up the system and verifying that the system is functioning properly.
• Procedures for maintaining the system including scheduled maintenance tasks and fault
isolation and troubleshooting procedures.
• Product warranty, repair, return, and replacement information.
The procedures for installing the host unit, remote unit, and for installing and using the EMS
software are provided in other publications which are referenced in the Related Publications
section and at appropriate points within this manual.
RELATED PUBLICATIONS
Listed below are related manuals, their content, and their publication numbers. Copies of these
publications can be ordered by contacting the Technical Assistance Center at 1-800-366-3891,
extension 73476 (in U.S.A. or Canada) or 952-917-3476 (outside U.S.A. and Canada).
ADCP-75-187 • Issue 3 • September 2006 • Preface
Title/DescriptionADCP Number
Digivance LRCS and SCS Systems 800/900 MHz SMR Rear Access
Host Unit Installation and Maintenance Manual75-180
Provides instructions for mounting the rear access host unit in an equipment
rack, installing and connecting the various cables, and replacing the cooling fans.
Digivance SCS System Interim Single-Band Remote Unit Installation Manual75-190
Provides instructions for mounting the interim single-band remote unit and for
installing and connecting the various cables.
Digivance SCS System Single-Band Remote Unit Installation Manual75-188
Provides instructions for mounting the single-band remote unit and for
installing and connecting the various cables.
Digivance SCS System Dual-Band Remote Unit Installation and
Maintenance Manual75-189
Provides instructions for mounting the dual-band remote unit and for installing
and connecting the various cables.
Digivance Element Management System Version 7.0 User Manual75-201
Provides instructions for installing the Digivance Element Management System
(EMS) software and for using both the Graphical User Interface (GUI) and the
Network Operations Center (NOC) versions of the software.
Digivance SNMP Agent Software Version 7.1 User Manual 75-202
Describes how to install, configure, and use the LRCS SNMP Proxy Agent.
Important safety admonishments are used throughout this manual to warn of possible hazards to
persons or equipment. An admonishment identifies a possible hazard and then explains what
may happen if the hazard is not avoided. The admonishments — in the form of Dangers,
Warnings, and Cautions — must be followed at all times. These warnings are flagged by use of
the triangular alert icon (seen below), and are listed in descending order of severity of injury or
damage and likelihood of occurrence.
Danger: Danger is used to indicate the presence of a hazard that will cause severe personal
injury, death, or substantial property damage if the hazard is not avoided.
Warn ing: Warning is used to indicate the presence of a hazard that can cause severe personal
injury, death, or substantial property damage if the hazard is not avoided.
Caution: Caution is used to indicate the presence of a hazard that will or can cause minor
personal injury or property damage if the hazard is not avoided.
GENERAL SAFETY PRECAUTIONS
Danger: This equipment uses a Class 1 Laser according to FDA/CDRH rules. Laser radiation
can seriously damage the retina of the eye. Do not look into the ends of any optical fiber. Do not
look directly into the optical transceiver of any digital unit or exposure to laser radiation may
result. An optical power meter should be used to verify active fibers. A protective cap or hood
MUST be immediately placed over any radiating transceiver or optical fiber connector to avoid
the potential of dangerous amounts of radiation exposure. This practice also prevents dirt
particles from entering the adapter or connector.
Danger: Do not look into the ends of any optical fiber. Exposure to laser radiation may result.
Do not assume laser power is turned-off or the fiber is disconnected at the other end.
Danger: Wet conditions increase the potential for receiving an electrical shock when installing
or using electrically-powered equipment. To prevent electrical shock, never install or use
electrical equipment in a wet location or during a lightning storm.
Warn ing: The HU is powered by 48 VDC power which is supplied over customer-provided
wiring. To prevent electrical shock when installing or modifying the HU power wiring,
disconnect the wiring at the power source before working with uninsulated wires or terminals.
Caution: Always allow sufficient fiber length to permit routing of patch cords and pigtails
without severe bends. Fiber optic patch cords or pigtails may be permanently damaged if bent
or curved to a radius of less than 2 inches (50 mm).
Each respective SMR, Cellular, and PCS system in the SCS platform is FCC and IC approved.
Information in this manual explains applicable portions of these systems.
FCC: The Digivance SCS system complies with the applicable sections of Title 47 CFR Parts
22, 24, and 90. Installation requirements the licensee needs to follow are listed in Title 47 CFR
90.635. This document may be found at the following website: http://www.access.gpo.gov/nara/
cfr/waisidx_03/47cfr90_03.html.
Caution: Modifications not expressly approved by the party responsible for compliance
could void the user’s authority to operate the equipment.
Part 15.5 General conditions of operation:
a. Persons operating intentional or unintentional radiators shall not be deemed to have
any vested or recognizable right to continue use of any given frequency by virtue of
prior registration or certificate of equipment.
b. Operation of an intentional, unintentional, or incidental radiator is subject to the
conditions that no harmful interference is caused and that interference must be
accepted that may be caused by the operation of an authorized radio station, by
another intentional or unintentional radiator, by industrial, scientific and medical
(ISM) equipment, or by an incidental operator.
ADCP-75-187 • Issue 3 • September 2006 • Preface
c. The operator of a radio frequency device shall be required to cease operating the
device upon notification by a Commission representative that the device is causing
harmful interference. Operation shall not resume until the condition causing the
harmful interference has been corrected.
UL/CUL: The Host Unit complies with UL and CUL 60950 Standard for Safety for
Information Technology Equipment including Electrical Business Equipment.
The Remote Unit complies with NEMA Type 6, UL and CUL 50, Standard for Enclosures for
Electrical Equipment.
The Remote Unit provides the degree of protection specified by IP67 as defined in IEC
(International Electrotechnical Commission) Publication 60529.
The Remote Unit complies with UL and CUL 60950 and UL 50 as Communication Service
Equipment under the DUZO category.
FDA/CDRH: This equipment uses a Class 1 LASER according to FDA/CDRH Rules. This
product conforms to all applicable standards of 21 CFR Part 1040.
IC: This equipment complies with the applicable sections of RSS-131. The term “IC:” before the
radio certification number only signifies that Industry Canada Technical Specifications were met.
This section provides basic description, application, and configuration information about the
Digivance SCS system. Throughout this publication, all items referenced as “accessory items”
are not furnished with the basic product and must be purchased separately.
2SCS SYSTEM OVERVIEW
The Digivance Long Range Coverage Solution (LRCS) system is an RF signal transport system
that provides long-range RF coverage to areas where it is impractical to place an Enhanced Base
Transceiver Station (EBTS) at the antenna site. High real estate costs and community
restrictions on tower and equipment locations often make it difficult to install the EBTS at the
same location as the antenna. The LRCS system overcomes equipment placement problems by
hubbing base stations at a central location and placing antennas at remote locations with
minimal real estate requirements. The LRCS system transports RF signals to remote locations to
expand coverage into areas not receiving service or to extend coverage into difficult to reach
areas such as canyons, tunnels, or underground roadways.
The SCS system provides the same functionality as the LRCS system but incorporates a low
profile, low power, low cost remote unit. The SCS system remote unit complements the high
power remote unit used with LRCS systems. The primary application includes urban areas
where multiple, strategically placed, low power remote units provide better coverage than high
power remote units.
2.1Basic SCS System Components
The basic components of a typical Digivance SCS system and their function are shown in
Figure 1-1. A basic SCS system consists of a Host Unit (HU) and a Remote Unit (RU). The HU
consists of a rack-mountable chassis that is designed for use in an indoor environment. The RU
consists of a sealed enclosure that is designed for use in an outdoor environment. Control and
monitoring functions are provided by the Digivance Element Management System (EMS).
The HU is interfaced with an EBTS over coaxial cables as shown in Figure 1-2. The EBTS
provides the RF channel inputs and outputs for a designated sector. In the forward path, the HU
receives two RF inputs from the EBTS. The HU digitizes the RF spectrum and then converts it
to digital optical signals for transport to the RU. In the reverse path, the HU receives digital
optical signals from the RU. The HU converts the digital optical signals back to two RF outputs
which are supplied to the EBTS over the coaxial cable interface.
The RU interfaces with the subscriber units (cell phones) through an antenna. In the reverse
path, the RU receives RF spectrum from each subscriber unit (see Figure 1-1). The RU digitizes
the RF spectrum and then converts it to digital optical signals for transport to the HU over the
optical fiber link. In the forward path, the RU receives digital optical signals from the HU. The
RU converts the optical signals to RF spectrum for transmission to the subscriber units. The RU
is connected to an antenna (not provided) which transmits and receives the subscriber unit RF
spectrum.
2.4Local Management Interface
Communications with an individual Digivance system is supported through a local management
interface capability as shown in Figure 1-3. A local management interface requires a PC-type
computer loaded with the Digivance Element Management System (EMS) software. EMS
provides the various control and monitoring functions required to locally manage a Digivance
system. The EMS computer connects directly to the HU through the computer’s RS-232 port.
Operation is implemented through the EMS Graphical User Interface (GUI). The GUI consists
of a series of screens from which the user selects the desired option or function. An RS-232
service port is provided on the HU for connecting the EMS computer.
Figure 1-3. Local Management of a Single Digivance System
An EMS computer may be used to locally manage a networked group of multiple Digivance
systems as shown in Figure 1-4. A Controller Area Network (CAN) port is provided on each
HU. Up to twenty-four HU’s may be linked together through the CAN interface and controlled
by the same EMS computer. All the networked HU’s and the associated RU’s may be managed
by connecting the EMS computer to one HU. The EMS computer provides an RS-232 port (#1)
to support the interface with the networked HU’s.
HOST UNIT
REMOTE
UNIT
CAN
HOST UNIT
NOTE: THE SUM MAXIMUM
LENGTH FOR THE CAN BUS
CABLES IS 75 FEET
NOTE: THE MAXIMUM LENGTH
FOR THE RS-232 CABLE IS 75 FEET
CD-ROM WITH DIGIVANCE
ELEMENT MANAGEMENT
SYSTEM (EMS) SOFTWARE
Figure 1-4. Local Management of Networked Digivance Systems
20857-A
2.5Network Operations Center Interface
Communications between a Network Operations Center (NOC) and a networked group of
multiple Digivance systems is supported by a NOC interface capability as shown in Figure 1-5.
To support the NOC interface, a PC-type computer loaded with the Digivance Element
Management System (EMS) software is required. EMS provides the various control and
monitoring functions required to remotely manage multiple Digivance systems through the
NOC interface.
A Controller Area Network (CAN) port is provided on each HU. Up to twenty-four HU’s may
be linked together through the CAN interface and controlled by the same EMS computer. All
the networked HU’s and the associated RU’s may be managed by connecting the EMS computer
to one HU. The EMS computer provides an RS-232 port (#1) to support the interface with the
networked HU’s.
The NOC can be linked to the EMS computer through a T1 system, DS0 with RS232
conversion, or some other medium. The EMS computer provides an RS-232 ASCII interface
port (#2) to support the interface with the NOC.
At the NOC, control and monitoring of the networked Digivance systems is implemented
through a Network Element Manager (NEM) interface which requires only a VT100 terminal/
emulator for operation. The NEM interface language consists of simple ASCII text strings. All
communications are input as either SET or GET commands which result in ASCII text string
responses from the specified system or systems.
Communications between an external Simple Network Management Protocol (SNMP) Manager
and a networked group of multiple Digivance systems is supported by an SNMP interface
capability as shown in Figure 1-6. To support the SNMP interface, a PC-type computer loaded
with both the Digivance Element Management System (EMS) software and the SNMP Proxy
Agent software is required. The EMS and SNMP Proxy Agent software plus the associated
Management Information Base (MIB) provide the various control (Set) monitoring (Get) and
trap functions required to remotely manage multiple Digivance systems using an SNMP
Manager.
A Controller Area Network (CAN) port is provided on each HU. Up to twenty-four HU’s may
be linked together through the CAN interface and controlled by the same EMS computer. All
the networked HU’s and the associated RU’s may be managed by connecting the EMS computer
to one HU. The EMS computer provides an RS-232 port (#1) to support the interface with the
networked HU’s.
The SNMP Manager may be linked with the EMS computer through a Local Area Network
(LAN). The EMS computer provides an Ethernet port to support the interface with the LAN.
The SNMP Proxy Agent supports two versions of the SNMP protocol: SNMPv1 and SNMPv2c.
A facility to Register/Unregister an SNMP Manager for receiving traps is also supported by the
SNMP Proxy Agent. The SNMP Manager is an option and must be ordered separately from
the EMS software.
NETWORK
SNMP
MANAGER
ETHERNET
LOCAL
AREA
NETWORK
HOST UNIT
CAN
HOST UNIT
CAN
HOST UNIT
RS-232
REMOTE
UNIT
REMOTE
UNIT
REMOTE
UNIT
CD-ROM WITH EMS
SOFTWARE
Figure 1-6. Remote Management of Networked Digivance Systems Through SNMP Manager
This section describes various system level functions and features of the Digivance system.
3.1Fiber Optic Transport
In a typical Digivance LRCS system, the HU is connected to the RU over two single-mode
optical fibers. One fiber is used to transport the forward path optical signal. The other fiber is
used to transport the reverse path optical signal. Because the optical signal is digital, the input
and output RF signal levels at the HU or the RU are not dependent on the level of the optical
signal or the length of the optical fiber. A diagram of the fiber optic transport system for a
typical Digivance LRCS system is shown in Figure 1-7.
Figure 1-7. LRCS System Fiber Optic Transport - Typical
The maximum length of the optical links is dependent on the loss specifications of the optical
fiber, the losses imposed by the various connectors and splices, and the RF modulation protocol
response timing limitations. The basic system provides an optical budget of 25 dB (typical)
when used with 9/125 single-mode fiber.
In SCS applications, the forward path and reverse path optical signals from an HU/RU pair are
combined onto a single optical fiber. This is accomplished by using a passive bi-directional
Wavelength Division Multiplexer (WDM) system. The optical wavelengths used in the
Digivance system are 1550 nm for the forward path and 1310 nm for the reverse path. Because
different wavelengths are used for the forward and reverse paths, both signals can be combined
on a single optical fiber. A WDM module (accessory) is installed with the HU at the host site
The SCS RU, which is equipped with an internally mounted WDM, is installed at the remote
site as shown in Figure 1-8.
FIBER OPTIC LINK
HOST UNIT
WDM
FORWARD AND
REVERSE PATH
WDM
REMOTE
UNIT
20721-A
Figure 1-8. SCS System Fiber Optic Transport with Wavelength Division Multiplexer
The EMS software and the SNMP Proxy Agent software provide control and monitoring
functions for the Digivance system through the local, NOC, and SNMP interfaces. The EMS
software package supports the local and NOC interfaces but does not include the SNMP Proxy
Agent software which must be ordered separately. Both the EMS and the SNMP Proxy Agent
software are required to support the SNMP interface. All software files are provided on CDROM’s. Software installation consists of copying the software files from the CD-ROM’s to a
designated directory on the hard-drive of the EMS computer.
The EMS software provides the capability to provision and configure the Digivance system for
operation. This includes selecting a site name, setting alarm thresholds, and setting forward and
reverse path RF gain adjustments. The EMS software also provides the capability to get alarm
messages (individual or summary), obtain data measurements, and to upgrade the HU/RU
system software. All control and monitor functions (except software upgrade which is not
supported by the NOC/NEM and SNMP interfaces and HU/RU pair site number assignment
which is not supported by the SNMP interface) may be implemented using the NOC/NEM
interface, the SNMP interface, or the EMS software GUI.
3.3Fault Detection and Alarm Reporting
LED indicators are provided on the front panel of the HU and on the underside of the RU to
indicate if the system is normal or if a fault is detected. In addition, normally open and normally
closed alarm contacts (for both major and minor alarms) are provided at the HU for connection
to a customer-provided external alarm system. All alarms can also be accessed through the
NOC/NEM interface, SNMP manager, or the EMS software GUI.
3.4Powering
The HU is powered by ±24 or ±48 VDC and must be hard-wired to a local DC power source
through a fuse panel. A screw-down terminal strip is provided on the rear side of the HU for the
power connections.
The RU is powered by 90 to 265 VAC (nominal 120 or 240 VAC), 47 to 63 Hz power. On an
optional basis, the RU may be powered by 60 to 89 VAC, 47 to 63 Hz power. A connector is
provided on the underside of the RU for the AC power connections. A 3-wire AC power cable
rated for outdoor use is included with the RU. The stub end of the cable must be hard-wired to
the AC power source.
3.5Equipment Mounting and Location
The HU consists of a rack-mountable chassis assembly that is designed for mounting in a noncondensing indoor environment such as inside a wiring closet or within an environmentally-
controlled cabinet. The HU is usually installed within 20 feet of the EBTS and may be mounted
in either a 19- or 23-inch, WECO or EIA, equipment rack.
The RU consists of a sealed aluminum enclosure designed for mounting in either an indoor oroutdoor environment. The RU may be mounted from a pole or the exterior side of a building
with the standard mounting bracket or from a strand with an accessory bracket.
Sections 1 through 3 described the functions and features of a typical SCS system equipped with
one HU and the single-band RU. Each single-band RU is equipped with the electronics to
support one frequency band. If it is necessary to support two frequency bands (such as 800/900
MHz SMR and 1900 MHz) at the same remote location, a dual-band RU can be deployed. A
dual-band RU provides the electronic and optical functionality of two single-band RU’s except
that all the electronic and optical components are housed within a single enclosure.
A dual-band SCS system consists of two standard host units and a dual-band RU that are linked
together over two optical fibers. At the hub site, each HU is connected to a separate EBTS
facility. The dual-band RU supports the frequency bands (such as 800/900 MHz SMR and 1900
MHz) associated with the two connected HU’s. Each HU and the corresponding RU electronics
function independently of each other and may be managed separately using the same element
management system (EMS). Figure 1-9 shows a typical SCS system equipped with a dual-band
RU. One fiber is used to transport the forward/reverse path optical signals for one SCS system.
The other fiber is used to transport the forward/reverse path optical signals for the other SCS
system.
This section describes the basic components of a typical Digivance SCS system including the
Host Unit (HU), Remote Unit (RU), element management system, and accessories. The system
specifications are provided in a table at the end of this section.
2HOST UNIT
Two versions of the HU are available. The rear access HU, shown in Figure 2-1, is used with
800/900 MHz SMR systems. The front access HU, also shown in Figure 2-1, is used with 800
and 1900 MHz systems. Connection points for the RF, optical, and alarm cables are provided on
the rear side of the rear access HU and on the front side of the front access HU. Both HU
versions provide the following basic functions:
• Provides a limited adjustable RF interface with the BTS.
• Provides a fiber optic interface with the RU.
• Digitizes the two forward path composite RF signals.
• Converts the two digitized forward path RF signals to a digital optical signal.
• Converts the digitized reverse path optical signal to two digitized RF signals.
• Converts the two digitized reverse path RF signals to two composite RF signals.
• Sends alarm information to an external alarm system through relay contact closures
• Provides an RS-232 interface for connecting the EMS computer.
• Provides a CAN interface for networking multiple HUs.
2.1Primary Components
The HU consists of an electronic circuit board assembly and a fan assembly that are mounted
within a powder-paint coated sheet metal enclosure. The enclosure provides a mounting point
for the circuit board and fan assemblies and controls RF emissions. The only user-replaceable
component is the fan assembly. The HU is designed for use within a non-condensing indoor
environment such as inside a wiring closet or cabinet. The front access HU is also equipped
with a front cable management tray and vertical cable guides.
2.2Mounting
The HU is intended for rack-mount applications. A pair of reversible mounting brackets is
provided that allow the HU to be mounted in either a 19-inch or 23-inch EIA or WECO
equipment rack. When the rear access HU is installed, the front panel of the HU is flush with the
front of the rack. When the front access HU is installed, the front panel of the HU is flush with
the front of the rack and the cable management tray extends 3.9 inches (99 mm) beyond the
front panel. Screws are provided for securing the HU to the equipment rack.
Figure 2-1. Front View of Front and Rear Access Host Units
2.3Fault Detection and Alarm Reporting
The HU detects and reports various internal and external faults including host unit fault, optical
fault, power fault, temperature fault, and RF fault. Various front panel Light Emitting Diode
(LED) indicators turn from green to red or yellow if a fault is detected. A set of alarm contacts
(normally open and normally closed) are provided for reporting an alarm to an external alarm
system when a fault is detected. Both major alarm (system operation seriously affected) and
minor alarm (system operation not affected or only slightly degraded) contacts are provided.
17.2 INCHES
(437 mm)
FRONT ACCESS HOST UNIT
FRONT PANEL
CABLE MANAGEMENT
TRAY
MOUNTING
BRACKET
(BOTH SIDES)
20666-A
Fault and alarm information may also be accessed locally through the EMS software GUI or
remotely through the NOC/NEM interface or SNMP interface. An alarm history file is
maintained by the EMS software so that a record is kept of all alarms as they occur. This is
useful when an alarm is reported and cleared before the reason for the alarm can be determined.
The status of the HU, the alarm state (major or minor), and other alarm information is
summarized and reported over the service interface, the CAN interface, and the optical interface
to the RU. In addition, the status of the RU is transmitted to the HU over the optical interface
and reported over the service interface and the CAN interface.
The RF signal connections between the rear access HU and the EBTS are supported through
four N-type female connectors. Two connectors are used for the forward path RF signals and
two connectors are used for the reverse path RF signals.
The RF signal connections between the front access HU and the EBTS are supported through
two N-type female connectors. One connector is used for the forward path RF signal and the
other connector is used for the reverse path RF signal.
In most installations, it is usually necessary to install external attenuators to support the RF
interface between the HU and the EBTS. The HU should be as close as possible to the EBTS to
minimize coaxial cable losses.
2.5RF Signal Level Adjustments
The HU is equipped with several attenuators for adjusting the signal levels of the forward and
reverse path RF signals. The attenuators provide an attenuation adjustment range of 0 to 31 dB
and can be set in 1 dB increments. The attenuators are software controlled and are adjusted
through the EMS software GUI, NOC/NEM interface, or SNMP interface.
The host forward path attenuators adjust the level of the input RF signal(s) to the HU. Using
the forward path attenuator, an input signal with a nominal composite signal level of –9 dBm to
–40 dBm can be adjusted to produce maximum power output. Additional external attenuation
is required if the input signal level is greater than –9 dBm.
Note: The optimum composite RF input signal level for 800/900 MHz SMR systems is
–20 dBm.
The hostreverse path attenuators adjust the level of the output RF signal(s) from the HU and
will add from –1 dB of gain (attenuator set to 31 dB) to +30 dB of gain (attenuator set to 0 dB)
to the RF output signal(s) at the HU.
2.6Propagation Delay
The HU forward and reverse path propagation delays may be adjusted in 0.1 μsec increments
within a range of 0 to 63 μs. The propagation delay is software controlled and may be adjusted
through the EMS software GUI, NOC/NEM interface, or SNMP interface.
2.7Optical Connection
Optical connections between the HU and the RU are supported through two optical ports
equipped with UPC/SC (flat) connectors. One port is used for the forward path optical signal
connection and the other port is used for the reverse path optical signal connection.