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Because the external environment and internal quality of the optical cable are greatly different in the actual use process, the cable product life problem is more complicated. At present, the industry has proposed three technical points that affect the life of optical cables.

First, fiber coating material selection and drawing process

The reasons for the increase of fiber loss mainly include hydrogen loss, fiber cracking, and fiber stress. It has been found through actual testing that the optical properties of the fiber optic cable have not changed substantially after being used for many years, such as geometrical characteristics, mechanical properties, continuation characteristics, and optical properties. Scanning electron microscopy and other methods have found that the fiber has no obvious microcracks and other anomalies. However, the fiber coating condition is significantly different. The fiber with high modulus, tight coating and high peeling force has a significant increase in attenuation at 1550 nm and 1310 nm.

Second, the grease filling design

The fiber paste is an oily substance that is in close contact with the optical fiber. It is a mixture based on mineral oil or synthetic oil. It is used to isolate water vapor and lubricate the fiber. The performance of the fiber paste is evaluated by visual observation of the morphology and the oxidation induction period of the test ointment. The increase of acid value after oxidation of the ointment can lead to an increase in hydrogen evolution. At the same time, the oxidation of the ointment affects the stability of the cable structure, resulting in a decrease in yield stress, so that the fiber is affected by vibration, impact, bending, temperature difference, topographical geological changes, etc. It will be stressed and weaken the buffering effect of the fiber paste on the fiber, thus reducing the reliability of the cable. The direct contact of the fiber paste with the fiber is the most important indirect cause of the deterioration of the fiber performance. Through the actual detection of the in-use optical cable produced in different periods, it was found that the cellulose paste slowly denatured with time. It is usually first assembled into small particles, which are then gradually volatilized, decomposed, and dried. For direct buried or pipeline cables in Central China, the typical time for the fiber pulp to begin to undergo significant denaturation is 18 years.

Third, the size of the loose tube

The influence of the size of the loose tube on the life of the cable is more reflected in the comprehensive stress. When the size is too small, under the variation of temperature, mechanical stress, interaction between the filler and the fiber, the stress on the fiber is not relieved, and the attenuation of the fiber is increased, resulting in aging.

The above are the three technical points that affect the life of optical cable products. I hope that everyone can pay attention and improve them to produce better cable products.