Optical loss stability of a fiber cable under lateral force and optimum design of the coated fiber structure.
Optical loss increase characteristics under lateral force were investigated to determine the load limit for coated fiber. Plastic deformation of the coating was analyzed, and the loss increase was found to occur in the large deformation region beyond a limit theoretically determined using structural dimensions (diameter and thickness) and the material constant of the coating. The optimum coating structure for preventing loss increase has been designed by introducing the result of the lateral deformation limit as well as fiber stress induced by the lateral force and fiber strain at low temperature. The nylon outer and silicone layer diameters are 0.9 and 0.4 mm, respectively.
Optical loss measurement in graded-index fiber using a dummy fiber.
The utility of an auxiliary fiber, called a dummy fiber, is investigated for optical fiber loss measurements. The dummy fiber is spliced and used to excite the test fiber. Excess loss caused by undesirable modes is found to be reduced to less than 0.05 dB by using a 500-m dummy fiber and choosing the test fiber cut length to be 2 m for reference. Loss linearity to the fiber length is examined on 6-km spliced fibers, and satisfactory agreement is obtained between the total loss and the sum of the individual fiber and splice losses.
EFFECT OF SAMPLE PREPARATION ON WATER TREE RESISTANCE OF XLPE/SEBS BLENDS
The effects of an aromatic polymer, such as poly[styrene-b-(ethylene-co-butylene)b-styrene] (SEBS), and its preparation processes on water tree resistance, morphology, crystallinity, dielectric constant and dielectric loss tangent of crosslinked polyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA) blends were investigated. The XLPE/SEBS samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, dielectric spectral analysis and the accelerated water treeing experiment. The results clearly showed that although SEBS was partially compatible with LDPE and it was dispersed evenly in XLPE matrix, the blends demonstrated excellent dielectric performances, such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBS blends was decreased with increase in SEBS content and it was further decreased with the addition of EVA. SEBS could effectively improve the water-tree resistance of XLPE and both SEBS and EVA were found to improve the water tree resistance of XLPE synergistically as expected. The differences in sample preparation processes could change the phase morphology and dielectric performance of the blends, and could also influence the dispersion of SEBS in XLPE matrix as well as the crystallinity of the blends. Different preparation processes led to different water tree resistance behaviours of the samples. The improvement of SEBS dispersion in XLPE matrix helped to improve the water tree resistance of XLPE.