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EuroWire – March 2011
119
technical article
Soak times of three hours are required for
all temperature extremes and for the final
23˚C temperature. All test fibres are to
be measured at room temperature at the
1,550nm wavelength prior to temperature
cycling. This is the reference measurement.
The test fibres are then measured at the
1,550nm wavelength in the last cycle at
the temperature extremes and at the final
23˚C temperature. Attenuation increases
are calculated and evaluated against an
upper specification limit.
The tubes, cable and assemblies are also to
be inspected at the final room temperature
for any visual damage.
FOTP-244
The FOTP-244 test method requires two
complete cycles and a final 23˚C tem-
perature soak. It requires 14 hours of soak
for the first 70˚C temperature extreme.
This extended soak time is intended to
help release shrink-back stresses that
may have been locked into the tubes
during processing. All other soak times are
required to be a minimum of one hour.
All test fibres are measured at room
temperature at the wavelength of 1,550nm
before temperature cycling. This is the
reference measurement.
The test fibre attenuations are then
measured at the 1,550nm wavelength at
the last temperature cycle extremes and
the end of the test, at room temperature.
The tubes, cable and assemblies are also to
be inspected at the final room temperature
for any visual damage.
A comparison of the two test methods is
outlined in
Table1
.
During the course of the testing it was
found that the only significant attenua-
tion increases occurred at the –40˚C
temperature extremes.
Attenuation increases at 70˚C and at the
final 23˚C were not significant. For this
reason, the attenuation increases that are
presented in this paper are all measured at
the –40˚C temperature extremes.
Multiple fibres were tested in each
cable sample. The average attenuation
increase was calculated and the maximum
individual measurement was identified.
These are the values reported in this paper.
Each cable sample was inspected for cable
damage at the completion of the mid-span
test. There was no physical damage found
on any of the cable samples.
3 Acceptance criteria
comparison
There are also two sets of acceptance
criteria that are associated with these two
test methods. These two specifications
are through the PE-90 document and the
GR-20 document. Each specification is
outlined below.
The PE-90 specification and acceptance
criteria is as follows:
a) Mid-span opening for installation of
loose tube single mode optical cable in
pedestal shall be 6.096m (20ft)
b) No greater than 0.1 dB attenuation
increase (at 1,550nm) on any individual
fibre and no greater than 0.05 dB
attenuation increase average (at
1,550nm) on all of the fibres, during
the last cycle at –40˚C and 70˚C
c) No greater than 0.05 dB attenuation
increase (at 1,550nm) on any individual
fibre at the final 23˚C temperature
Maximum attenuation increase (dB) at 1,550nm and –40ºC
PE-90 Cycle
Cable 1
Cable 2
Cable 3
Cable 4
1
0.02
0.02
0.007
0.02
2
1.34
0.02
0.417
0.87
3
1.11
0.03
0.653
0.70
4
1.73
0.02
0.577
0.74
5
1.25
0.02
0.575
1.01
20-ft PE-90 final
cycle maximum
1.25
0.02
0.575
1.01
14-ft FOTP-244
maximum
0.59
0.01
0.311
0.31
Attenuation requirements at 1,550nm
PE-90 GR-20
Expressed tube length
20ft
14ft
Maximum attenuation increase at last temperature extremes
0.1 dB
-
Average attenuation increase at last temperature extremes
0.05 dB 0.15 dB
Maximum attenuation increase at final 23˚C temperature
0.05 dB
-
Average attenuation increase at final 23˚C temperature
-
0.15 dB
Table 2
▲
▲
:
PE-90 and GR-20 mid-span test attenuation requirements comparison
Table 3
▲
▲
:
20 ft PE-90 & 14 ft draft FOTP-244 midspan test comparison at –40˚C
Average attenuation increase (dB)
Cable 1 Cable 2 Cable 3 Cable 4 Cable 5 Cable 6
Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 20ft draft FOTP-244
Figure 1
▼
▼
:
20-ft PE-90 and 20-ft draft FOTP-244 midspan test comparison – average attenuation increase