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A.4.5 Test, Measurement, and Diagnostic Equipment (TMDE)
The use of Test, Measurement, and Diagnostic Equipment OXIDE) with Intelligent
Transportation Systems (ITS) Animal installation, acceptance testing, and long term operational
maintenance should not deter jurisdictions from deploying private networks. Modem system
designs and state-of-the-art hardware allow He use of software diagnostic tools to provide
communicators link status and error reporting to Be network manager at a dedicated
workstation terminal. Network management software is capable of identifying real-time
communications errors, the malfunctioning communications unit, the geographic location, and
shelf location of the failed unit. Deployment of Metropolitan Area Network (MAN), broadband
communications backbones win network manageable elements, allows Me reduction of ~iDE
by performing communications unit and module-level communications error reporting. Modern
communications equipment design typically provides front panel indicators in addition to the
network management reporting to facilitate Mean-Time-to-Repa~r ~), and vendor
equipment service agreements provide replacement and depot-level repair of failed units, Printed
Circuit Boards (PCBs), and modules. A minimum compliment of TMDE is therefore required
for jurisdictional maintenance operations to provide the installation and test, and the long term
maintenance to operate advanced systems within scheduled downtime parameters. Junsdictional
maintenance should be involved with system and subsystem testing to the following levels:
· Functional unit, and
· Board module.
Equipment testing to the component level is not regarded as necessary for jurisdictional
maintenance activities when modern system architectures are used.
Selection of TMDE should be based on the junsdiction's maintenance activity level of repair.
Typically, TMDE used in laboratory/electronic repair shops should provide a level of accuracy or
readout resolution of four (4) times greater Man the Unit Under Test (OUT). Laboratory and
electronic shop TMDE equipment should be manufactured in accordance with Belicore reliability
specifications and be directly traceable to meteorological standards provided by Be National
Institute of Standards and Technology (LIST) to ensure quality measurements, testing reliability,
and repeatability. TMDE bench standards require periodic calibration services to check the
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amount of elTor for each operational function and range of the equipment and to realign/repair
equipment which fails to meet operating parametric levels defined by the manufacturer. Product
selection should consider environmental conditions under which MADE is to be operated (shop
or field equipments, this will ensure quality measurements without errors induced by ambient
operating conditions.
The following discussions pertain to specific commun~cations-related TILDE common to
advanced system deployment. HE required for modern communications system installation
and long tenn maintenance pertains to the following major categories:
Fiber optic cable,
Modem communications over twisted wire pair CrwP),
Local area networks,
· Microwave communications,
Direct sequence, digital spread spectrum radio,
Synchronous optical network (SONNET,
American digital hierarchy (ADH), and
Video communications.
For each category, a description of a minimum compliment of test equipment is provided. The
equipment described should provide adequate system installation and long tenn maintenance
support for the application area described, but is not considered to be a comprehensive list to
provide testing functionality at all repair echelons. Equipment lists have been provided which
support jurisdictional maintenance activity levels in addition to network management and
equipment depot repair services.
A.4.5.1 Fiber Optic Cables
In general, optical fiber cables and optical fiber cable systems are extremely reliable with very
little maintenance required. Many systems can and have been used in the field for more Man 20
years win little or no maintenance. System maintenance falls into two categones:
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Basic Cable Maintenance
Some key elements for basic system maintenance are as-built system documents, spare
connectors, jumpers, and test equipment such as Optical Time Domain Reflectometers
(OTDR's) and power meters. In addition, the draftsperson should have the capability for
element troubleshooting. Applicable test equipment includes:
Optical time domain reflectometer (OTDR), and
Optical source and power meter.
Emergency Restoration
The more urgent category of maintenance is emergency restoration. Fiber optic cables can carry
an extremely large number of circuits on each fiber. In the event of a partial or catastrophic
outage, it is essential to: I) Achieve rapid temporary restoration; and 2) Transition to a final
permanent repair without disturbing any fibers over Han the ones being repaired.
Some key elements for emergency restoration are a restoration lcit, test equipment, mechanical
splices, as-built system documents, and access to expert consultation via phone. Commercially
available kits include spare cable, two splice closures, two tool kits, and aR items required for
bypassing a damaged section. In most cases, these restoration kits are field-ready for instant
response. Equipment which should be on site include OTDRs, power meters, and two-way
communication devices. Finally, housed with Be restoration equipment should be Me as-built
documents of the systems. These documents are vital in isolating problems, and should be
accurate and readily available for restoration crews.
Personnel should be trained on emergency restoration prior to this type of maintenance. Tidal
training should include safety, use of cable system-designated splice methods and hardware,
proper use of the OTDR to test and document Be system, operation of an optical power meter,
handing and installation of fiber optic cables and connectors, knowledge of system
documentation, troubleshooting, and restoration mesons. Personnel should have practiced these
skins completely and expeditiously prior to Be advent of an emergency.
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Applicable test eaninment includes
-~r
· Op~cal dme domain reflectometer (OTDR),
· Optical source and power meter, and
Two-way communication devices.
For emergency restoration or long term cable maintenance, equnpment should include:
.
Mechanical stripping tool,
· Fining compound remover,
Tissues,
Hook blade knife,
Sheath npper,
Cable cutters,
Scissors,
Cleaver,
Buffer tube shippers (fiber access tools),
Closurefs),
Mechanucal splices (for temporary restoration) or fusion splicer (for permanent restoration),
Isopropyl alcohol, and
Safety equipment.
Private Modem and [eased Line Service
Over Twisted Wire Pairs (TWP) Opera fing al Subrafe Communications Levels
Copper u ire communications, provided by Public Switched Telephone Networks (PSTNs) or by
dedicated point-to-point private communications link services, are the most commonly used
medium of providing field traffic controller connectivity with Traffic Operations Centers
(TOCs). The use of copper as a communications medium presents specific deployment
considerations and requires awareness of test procedures involved with installation and
operational maintenance. Maintenance personnel should understand basic and advanced
troubleshooting techniques and should understand cause-and-effect relationships pertinent to Me
effects of Electro-magnedc Interference (E~)lRadio Frequency Interference (1~), impulse
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noise, and distortion with respect to the transmitted signal's power, Frequency, and phase
characteristics. Knowledge of analog and digital troubleshooting techniques is required. The
experienced field technician should be able to accurately monitor and diagnose warplane
communications failures with a minimum complement of TMDE.
Applicable test equipment includes:
· Built-in test for Channel Service UnitsIData Service Units (CSU/DSU) including:
· Loop-back testing, Data Term~nabon Equipment (DTE), DTE with test pattern
DTE/LOOP, and test pattern;
· Portable digital meter with the following built-in functions:
.
Oscilloscope, volt-ohm-milliammeter (VOM), frequency counter, and power meter (in
dBm);
Bit Error Rate Tester (BERT) with built-in signal polling, and answer back functions;
Modem, compatible with manufacturer and model deployed in field;
Handset (2 way communications);
Senal communications exerciser/analyzer, providing bit trap and generator functions; and
Breakout box with light emitting diodes (LEDs) providing communication pin activation.
The serial communications exerciser/analyzer is typically not required for most problems
experienced wig TWP communications, but is listed as a requirement for applications where
protocol examination may provide indications as to possible link failures.
tonal Area Network (LAND Communications
Local Area Network ~AN) communications are becoming prevalent in modern system
architecture design and deployment. Communications mediums provided for access to shared
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resources vary wad deployment schemes. LANs are evolving from the predominant market of
copper-based infrastructures to both wireless and fiber optic communications. Specifications for
LAN communications are defined by standards developed by the Institute of Electncal and
Electronics Engineers (EKE) and American National Standards Institute (ANSO committees on
networking technologies. Specifications pertaining to the maximum operating distances and
number of terminals need to be observed to maintain proper operational performance of the
LAN.
LANs currently offer network management software which provide, but are not limited to, the
following diagnostic capabilities:
Monitonng of network traffic for individual network elements, or composite network
analysis,
,
Setting of network alarms - typically implies that some action is performed upon alarm
activation such as providing a log of conditions which precipitated He alarm, i.e., network
saturation;
Setting of workstation options;
Enabling/Disabling of logging of maintained information;
Generation of reports; and
Compilation of run-time statistics such as frame counts, frame size distribution, network
utilization, bytes per second, and frames per second.
IbIDE associated win copper based LANs includes:
Protocol Analyzer;
Hand held digital meter wad oscilloscope, VOM, and power meter; and
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Time Domain Reflectometer CADRE.
TMDE associated with fiber optic communications requires equipment similar to Mat for
backbone plant ~nstaRation and maintenance, with the following addidons:
Visible light fiber fault finder; and
Protocol analyzer.
Wireless LAN communications are a relatively new technology. It is recommended Hat wireless
communications elements be serviced under a depot repair agreement. The technology deployed
is typically direct sequence, digital spread spectrum communications.
Most maintenance operations for aR types of LANs do not require the use of protocol analyzers,
except In extreme circumstances. These devices may be procured under lease agreements for
"short-tenn" maintenance activities. They are typically very costly and deployment should be
provided as a single unit for an organization.
Analog and Digifal Microwave Communications
Microwave communications links typically have very exact testing requirements to provide
compliance win Federal Communications Commission (FCC) certification regulations.
Microwave installation acceptance and certification testing requires highly specialized diagnostic
troubleshooting skins and the operation of sophisticated TMDE. It is recommended Mat
contractual agreements be made to support jurisdictions win this process unless the capability
already exists within Be jurisdictional maintenance support personnel.
Modem systems are providing more built-in communications maintenance functionality Mat
includes software diagnostic tools. The system software provides the capability to run
preliminary diagnostics, checking system alignment, and proper operation of interconnected
system devices.
Test equipment required in support of preliminary microwave systems includes:
· Digital muldmeter;
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Power meter; and
Frequency counter.
The following tools are required:
· SMA wrench;
Small (1J4") slotted screwdriver;
Small Phillips screwdriver; and
Static-free workstation.
A more complete list of TMDE for the long term operational maintenance should include:
Spectrum analyzer;
Test antenna kit (antennae, antenna correction factors, cables, cable adapters, and tripod);
Frequency counter,
Signal generator;
dB meter;
· BERT;
· Voltage Standing Wave Reflectometer (VSWR) meter;
Signal-to-noise and distortion (STEAD) measuring device; and
Dummy loads.
Functionality from several of the above listed TMDE have been consolidated to one piece of
specialized microwave test equipment, and are available from a variety of manufacturers.
Direef Sequence Digifa/ Spread Speefrum Radio Communications
Direct sequence spread spectrum radios providing digital packet network communications have
been recently introduced to the Intelligent Transportation System ~S) marketplace. The radios
provide communications resiliency by establishing alternate communications routing in the event
Me primary channel fails. These radios have been constructed so that sensitive electronics are
contained in a positive pressurized environmental housing to protect against ambient
env~ronrnental conditions associated with traffic control instaNadon sites. Manufacturers
L;\NCHRP\Phase2.rph N~3-51 · P~2F~Re~n A4-33
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l
recommend a depot-level maintenance service agreement be provided to jurisdictional users at
the functional unit level.
The following TIDE should be considered for initial deployment and Tong term maintenance:
BERT;
Spectrum analyzer, and
Antennae (directional and omnidirectional), cable adapters, cables, antenna correction
factors, and tnpod.
Synchronous Optical Network (SONET)
Synchronous Optical Network (SONET) communications equipment provides communications
as described by Bellcore standards for fiber optic and ANSI standards for electrical interfaces.
SONET uses Graphical User interface (GUM network management, providing extensive
perfo~ance mon~tonng to include network alarm summaries, fault isolation, alarm history logs,
provisioning, adm~nisundon, protection switch ac~vadon, configurations, etc. Network
management is typically supported via laptop computer or dedicated workstation terminals.
Network management allows local and remote fault isolation doom to He module level to provide
maintenance personnel web advance ~ndicabon of He spare modules required to perform repairs.
The following TMDE is required:
Digital multimeter;
Optical power meter;
Fiber optic test set;
Fiber optic attenuator; and
Transmission analyzer.
American Digifa/ Hierarchy (ADH) DS-O, DS-', and DS-3 Communications
The Amencan Digital Hierarchy (ADH), comprised of digital data communications transfer rates
at DS-0 (56/64 Kbps), DS-1 (~.544 Mbps), and DS-3 (44.736 Mbps), is defined by Bellcore and
~:WCHRP`Phasc~rpr\ NCHRP 3-51 · Phase 2 final Report A4-34
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ANST specifications. Communications testing of these circuit interfaces is similar in nature to
some of He subrate copper-based communications. Bit Error Rate Tests (BERT) to detemune
He amount of errored communications seconds is still applicable, as well as He use of frequency
counters. Special test equipment has evolved capable of testing broadband communications
protocols per DS-! and DS-3. The analyzers are typically expensive, but provide a number of
functional tests to determine He health of ADH communications links. Maintenance personnel
performing tests on such circuits are required to have strong troubleshooting skins which include
advanced test equipment operation and knowledge of He operational protocols used.
HE used in testing and evaluating ADH circuits includes:
· BERT;
· Frequency counter, and
· Protocol analyzer.
E/A 770A Video Communications Testing
Video communications networks deployed In modem systems typically can consist of bow
analog and digit distribution systems. End-to~nd video communications quality is required to
conform with Electronics Industries Association (ELA) specification ElA 250C, medium haul,
when measured as fiercest remote source to He point of termination (display). Medium haul,
when tested as an isolated component, should conform to ETA 250C short haul specifications.
The ELA 170 signal is encoded with color burst information as defined by the National
Television Standards Committee (NTSC). Typically, a test pattern generator with multiburst
and color bars should be rack mounted at the nearest add/drop location to the source and at He
point of termination (TOC for example). A vectorscope or waveform monitor should be used.
This signal analysis and generation equipment should be provided with the ability to be remotely
operated upon command at the TOC. Perhaps the easiest way to test to satisfy EIA 250C, is
Trough the use of an automatic test signal generator. Hand-held test pattern generators are also
resell for testing video systems.
Video compressors/decompressors (CODECs) are used to optimize bandwidth over digital
communications links. Once in digital format, video is typically tested at He electrical output
L:\NCHRP\Phase;~.rptY NCHRP3-51 · P~2F~Re~n
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Representative terms from entire chapter:
test equipment
