Fusion splicing is the act of joining two optical fibers end-to-end using heat. The goal is to fuse the two fibers together in such a way that light passing through the fibers is not scattered or reflected back by the splice, and so that the optical loss is nearly zero (B). However, when splicing two different fibers to each other, higher losses can occur when the refraction index or the diameter of the cores of both fibers are different. This is for example the case when splicing DTG-LBL-1550 fiber with a core of approximately 6µm to a standard single mode fiber, which has a typical core diameter of 9 µm. The figure below shows the splice loss of a DTG-LBL-1550 fiber to a SMF-28 fiber. The splice loss has been measured for different arc cycles (heating cycles). As can be oberserved, the typical loss one way (single pass) amounts to about 0.8 dB. Furthermore it can be observed that the splice loss tends to decrease with multiple arc cycles.