Fig.1 Relationship between optical loss and parameter A (= outer diameter/core diameter) for graded-index multimode optical fiber

Relationship between optical loss and parameter A (= outer diameter/core diameter) for graded-index multimode optical fiber

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    Extensive experimental and theoretical studies were undertaken to determine the optimum fiber parameters for practical use. Graded-index fiber with a 125 μm outer diameter, a 50 μm core diameter, and a 1% relative refractive-index difference was utilized. The relative refractive-index difference Δ was studied taking account of the bending loss including the micro-bending loss and baseband frequency response, and the relative refractive-index difference of 1 % was found to be the optimum value. Moreover, 2b was also investigated taking account of fiber handling, mechanical fiber strength and fiber cost, and an outer diameter of 125 μm was adopted as the optimum value. Thus, 2a was a 50 μm core diameter, because the optimum ratio A (=b/a) was 2.5 for 2b=125 μm, to minimize the total loss.

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