由熔体拉制的硼硅酸钠玻璃纤维采用“在线”塑料被复来保持纤维强度。由于在涂布器中采用了锥形管咀,可以在光纤周围形成同心的被复层,并且发现40μm 的同心被复层足以使光纤经受和缓的磨损试验而强度不致下降。在室温下作的强度测量表明,光纤具有均匀的4％的断裂伸长率。相同纤维在液氮温度下测量,则有14％的断裂伸长率,即使经过广泛的作业以后也是如此,这已接近玻璃的理论内聚强度 The sodium borosilicate glass fibers drawn from the melt are “plasticized” using an “in-line” plastic to retain fiber strength. Due to the use of conical nozzles in the applicator concentric layers of cladding can be formed around the optical fiber and a 40 μm concentric cladding layer was found sufficient to subject the optical fiber to a gentle wear test without degradation in strength. Strength measurements at room temperature showed that the fiber had a uniform elongation at break of 4%. The same fibers, measured at liquid nitrogen temperatures, have a 14% elongation at break, even after extensive work, which is close to the theoretical cohesive strength of the glass