Because it categorizes each individual event,
OTDRs tend to be used more as troubleshooting tools
than as certification tools unless they are required by
specifications. For an MPO-based system, with all the
complexity and connectivity discussed, there is excessive
loss on a fiber. An MPO-based OTDR will show where the
problem lies so that the technician does not have to start
disconnecting things.
OTDRs are simplex devices; to use one an MPO
switch is needed and the pinned/unpinned nature of the
system must be considered. Figure 13 is an example of
an OTDR with switches built in as a module. There is a
simplex fiber connecting the simplex OTDR to the switch
module. Connect up to the fiber using a launch and
receive cable, and press the button on the OTDR, which
controls the switch. Automatically, it goes on to fiber #1,
does the acquisition, and accomplishes the traces on two
wavelengths. It then switches the next fiber until it has
worked through all 12 fibers in an automated fashion,
eliminating the need for manual switching. In this case,
the OTDR shows results of all 12 fibers.
In conclusion, MPO-based systems represent the best
way to support high data rate, high speed systems in the
data center. Evolving standards will continue to support
the guidance outlined in this article — namely, that
CONVEYING THE CABLES
THAT MAKE LIFE BETTER!
50 I ICT TODAY
Inspect all fibers in a multi-fiber
connector and both sides of
every connection. Dirty fiber
end faces are the #1 cause of
problems in fiber systems.
meticulous cleaning and proper handling will be even
more important to ensure that systems perform reliably
and within loss budgets. It is also strongly recommended
that network designers and end users navigate the myriad
options for designing MPO-based systems with an eye
toward testing and verification.
AUTHOR BIOGRAPHIES: Rodney Casteel is a senior
field application engineer for CommScope and is a 14-year
BICSI member who holds the designations of Registered
Communications Distribution Designer (RCDD), Network
Transport Specialist (NTS) and Outside Plant Specialist (OSP).
He is a frequent speaker at industry conferences and seminars,
a contributor to many industry trade publications and an author
of industry technical papers. Email: rcasteel@commscope.com
Ed Gastle is a product line manager at VIAVI
Solutions who has worked in the ICT industry
for more than 30 years, focusing on the test and
measurement of all types of infrastructure and
networks. Ed speaks frequently at industry
events and is the author of numerous articles
and white papers. Email:
Ed.Gastle@viavisolutions.com
This article was written on behalf of the TIA’s
Fiber Optic Technology Consortium, which
represents technology leaders committed to
providing the most current, reliable and vendor
neutral information about fiber optics and
related technologies for advancing new and
better communications solutions.
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