Page 51 - Market Analysis Report of Optical Communications Field in China & Global market 2024

FTiagbulree.45O. Crthaobgleoncarlbteosnt froeostupltrsinot fisPiEmTprsoleveevdewfliethxibreildityucimedprdoivaemmeetenrt of the fiber length should be achieved during the production
o(epltoicnaglafitbioenr at break and bending diameter) of PET sleeves by reducing the number of main traction
loops or increasing the temperature of the hot water tank.

FTiagbulree.55A. CnalbylseiscaorfbRoannfgoeotpforirnPt iEsTimSpleroevveedFwleitxhibrielidtyucImedprdoivaemmeetenrt 3.4 Improvement of PET sleeve deformation and tie
oOprttihcaolgfoibnearl Experiment Results (Fracture Elongation, ε and Bending marks in the cabling process
Diameter, db) After a period of tracking and statistical analysis of the
cable laying process, it was found that the main process
3.3 Reasonable control of excess length of PET sleeve problems were deformation of the PET sleeve, the presence
optical fiber of tie marks on the surface of the sleeve, and increased
PET is a crystalline polymer that crystallizes at temperatures fiber attenuation. Regarding this, a root cause analysis and
between its melting point and glass transition temperature. corresponding solutions were implemented: a. In response
Once the temperature is below its glass transition to issues such as PET sleeve deformation and increased
temperature, PET stops crystallizing, and the main chain fiber attenuation, a reasonable twisting pitch was designed
and most of the branches of the molecule stop stably and to ensure the stability of the twisting equipment operation.
orderly arranging and moving. Compared to PBT used for b. In response to the problem of tie marks on the surface of
secondary coating of optical fibers, PET used for secondary PET sleeves, the tension of the tie yarn is adjusted to control
coating of optical fibers has higher molecular chain rigidity, the stability of the tie yarn machine tension. Polyester tie
slower crystallization rate, and higher glass transition yarn with higher line density and smaller thermal shrinkage
temperature (80℃). Therefore, if the conventional PBT is selected. At the same time, it is necessary to combine the
sleeve extrusion cooling process is used (i.e., the hot water processing temperature and cooling method of the sheath
tank temperature is set to 35-45℃), the PET sleeve will process to choose the optimal combination method to solve
undergo crystallization and shaping after passing through the problem of tie marks on PET sleeves in finished optical
the hot water tank and cold water tank, resulting in the cables. After implementing corresponding solutions, the
remaining length of optical fibers in the PET sleeve being deformation and tie marks of PET sleeves in the cabling
smaller than that in the PBT sleeve after being taken off the process, as well as the attenuation of optical fibers, have
machine (the difference between the two is 0.01%~0.03%), significantly improved.
and the post shrinkage of the PET sleeve is also very small.
The 168 hour monitoring results of the changes in the 3.5 Sheath process: Improvement of PET sleeve ther-
remaining length of the optical fiber in the PET sleeve after mal deformation and tie marks
removal also confirmed this phenomenon, that is, due to After a period of tracking and statistical analysis of the
the small shrinkage of the PET sleeve after removal, the sheath process test, it was found that the main process
remaining length of the optical fiber was basically the same problems encountered were thermal deformation and
as when removed after 168 hours. Therefore, in order to severe tie marks on the surface of the PET sleeve, as well
obtain the same fiber length as PBT sleeves, precise control as excessive fiber attenuation (the internal space of the
PET sleeve becomes smaller after severe deformation, and
the fiber bends slightly after being compressed, resulting
in excessive fiber attenuation). A root cause analysis and
corresponding solutions were implemented for this issue:
In response to the serious deformation and tie marks of
PET sleeves at high temperatures (above 80℃), the reason
was analyzed to be that the cooling of the optical cable
sheath was too slow during high-speed production, and
the heat that was not dissipated by the sheath was quickly
transferred to the metal strip, which was then transmitted to
the sleeve and polyester tie yarn. After absorbing heat, the
tie yarn contracted, causing local deformation of the sleeve
and tie marks. In addition, after the PET sleeve absorbs

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