| Objectives | Background | Approach |
We will perform a design of experiments study on fusion
spliced optical fiber patch cords to determine the effect of
proof testing coupled with temperature, humidity or bending
stress on (1) optical return loss at the fusion splice and (2)
ultimate pull strength of the fiber cord.
Fusion splices are an effective means of providing seamless interconnections between fiber cables or between various fiber optic components within an optical system. Unlike the bulk fiber optic connector, the fusion splice is permanent and requires no additional real estate on the optical breadboard. One important effect associated with the use of fusion splices is the reduction of the fiber mechanical strength. The use of fusion splices can reduce the fiber strength by 60% on average. As well, the splice (like any interconnect component) will introduce additional loss to the optical signal. However, the return loss is generally much lower than that of a bulk connector when appropriately matched fibers are used.
Efforts aimed at estimating the overall reliability of an optical system should address any effects associated with the fusion splice. As well, long term influences of environmental factors should also be addressed. This includes the effects of temperature, moisture, and bending stresses due to fiber routing on the optical breadboard. Moreover, it has been shown that screening tests such as the fiber proof test can weaken the ultimate strength of the fiber. For example, it is known that appropriate loading and unload rates, as well as appropriate static load time and strength should be determined to minimize the impact on the ultimate fiber strength. Because the fusion splice actually creates a fiber joint that may be thought of as a welded joint, it may be prudent to perform proof testing after the splice has been formed, even if the fibers were proof tested prior to the splice procedure. Therefore, the same effects that proof testing is known to produce in unspliced fibers, may also be anticipated in spliced fibers.
The design of experiments (DOE) technique is a systematic method that may be used to determine the effects of a given stress parameter on a performance outcome. Interaction effects between stress parameters may also be determined when the DOE study is completed. While the DOE study can identify the important stress parameters contributing to the performance outcome, analytical models of degradation based in Physics-of-Failure theory is coupled to stress testing and failure analysis. We propose development of a DOE matrix to determine the effect of proof testing coupled with exposure to temperature, moisture and bending stress on two important parameters associated with fusion splice reliability. The performance parameters include optical return loss at the fusion splice and fiber pull strength.