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heat, local temperatures exceeding 70℃ can also cause diameter of 1.85 mm and nominal wall thickness of 0.30
serious thermal deformation. By modifying the equipment mm). It can be seen that the tensile strength, yield strength,
and reducing the processing temperature, the cooling rate and lateral pressure resistance of PET sleeves are superior
of the sheath is increased to ensure that the PET sheath to those of PBT sleeves; The bending performance of
in the optical cable does not experience serious thermal PET tubing meets the standard requirements and has good
deformation and tie marks. In addition, when encountering compatibility with fillers; The elongation at break and
severe tie marks on the sheath, the production speed is longitudinal thermal shrinkage performance of PET sleeves
further controlled to ensure rapid cooling of the sheath, in meet the requirements for optical cable laying and daily
order to reduce the depth of the tie marks or eliminate the use. In summary, PET sleeve optical cables produced using
problem. After implementing corresponding solutions, the PET as the secondary coating material for optical fibers can
thermal deformation and tie marks of PET sleeves in the be fully put into practical use.
sheath process were severe, and the excessive attenuation
of optical fibers was significantly improved. In addition, 4. Summary
during the process testing research, it was found that the
degree of cable tie marks produced by PET sleeves with PET, as a secondary coating material for optical fibers
different outer diameters and wall thicknesses also varies. in optical cables, faces many process difficulties in
The larger the outer diameter of the PET sleeve and the the production of PET sleeve optical cables. Through
thicker the wall thickness, the better the ability to resist exploration of material modification and process
thermal deformation and tie marks caused by the heat improvement, multiple specifications of PET sleeve optical
conduction of the sheath during the cooling process of the cable products have been successfully trial produced.
sheath. At present, for PET sleeve optical cable products with a
diameter of Φ1.85 and above (sleeve outer diameter ≥1.8
3.6 PET sleeve performance test mm, wall thickness ≥0.3 mm), although the problems of
After solving multiple technical difficulties, we successfully thermal deformation and tie marks in the PET sleeve after
trial produced multiple specifications of PET sleeve optical cable formation cannot be completely eliminated, they have
cables. According to the standard GB/T 7424.23-2021 been greatly improved, and the product performance index
"General specification for optical cables - Part 23: Basic test results meet the acceptance standard requirements;
test methods for optical cables - Test methods for optical However, for PET sleeve optical cable products with
cable components", clauses G7 and G11A, and YD/T specifications below Φ1.85 (sleeve outer diameter <1.8
1118.1-2019 "Secondary coating materials for optical fibers mm, wall thickness <0.3 mm), there are still serious
- Part 1: Polybutylene terephthalate", the performance of thermal deformation and tie marks in the PET sleeve after
the PET and PBT sleeves of the same specification were cable formation, which affects the normal use of the optical
tested. Table 6 shows the performance test results of PET cable. Therefore, the thermal deformation and tie marks of
and PBT sleeves with a diameter of φ1.85 (nominal outer PET sleeves have become key factors restricting the mass
application of PET as a secondary coating material for
Table.6 Performance indicators of PET and PBT sleeves with optical fibers in small-sized sleeve optical cable products,
a diameter of Φ1.85 and must be improved. This will be a key research area in
the future.
5. Reference
[1] Chen bingyan Design and Manufacturing of Fiber Optic
Cables[M]. Hangzhou: Zhejiang University Press,2011.
[2] Zhang yulong. Handbook of Plastic Varieties and
Properties[M]. Beijing: Chemical Industry Press,2012.
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