Fig.4 Increase in loss due to laying of single-mode fiber cable

Increase in loss due to laying of single-mode fiber cable

Copyright © Institute of Electronics, Information and Communication Engineers (IEICE) 2006, All Rights Reserved.

The laying of optical cable increases optical loss. The main factor behind this phenomenon is microbending loss. Taking cable-laying tension, temperature variation, and other practical requirements and conditions into account, a unit-type single-mode optical-cable structure was designed that could decrease microbending loss and prevent fiber cracks. Many experiments confirmed the low-loss and wide-bandwidth characteristics of this structure as well as its robustness to long-distance laying and its exceptional reliability.

Microbending loss depends on correlation length W of the microbending distribution, number of microbends N per unit length, and radius of curvature R of the microbend. The figure shows measured values of loss increase due to laying and theoretical values of loss increase versus relative index difference. The results of actual measurements reveal an average W of 0.49 mm and an average N/(R*R) of 3/(m*m). Loss increase due to laying can be sufficiently suppressed even in the 1.55 μm band if relative index difference is kept above 0.3%.

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