The three basic fiber interconnection methods are: de-matable fiber-optic connectors, mechanical splices
and fusion splices. De-matable connectors are used in applications where periodic mating and de-mating is
required for maintenance, testing, repairs or reconfiguration of a system.
The penalty for this flexibility is the larger physical size and higher cost, as well as higher losses of optical
power (typically 0.2 to 1 dB) at the connector interface. Mechanical splices are available for both multimode
and single-mode fiber types and can be either temporary or permanent.
Typical mechanical splices for multimode fiber are easy to install and require few specialized installation
tools. Insertion loss, defined as the loss in optical power at a joint between identical fibers, typically is 0.2 dB
for mechanical multimode splices. Since single-mode fibers have small optical cores and hence small mode-
field diameters (MFD), they are less tolerant of misalignment at a joint. Consequently, mechanical splices
capable of achieving acceptable performance within a single- mode system loss budget are somewhat more
expensive to purchase, more time consuming to install, and may require capital equipment outlays on par with
fusion splicing. Typical insertion losses for single-mode mechanical splices range from 0.05 to 0.2 dB.
Single fiber fusion splicing is one of the most widely used permanent methods for joining optical fibers.
Obtaining good fusion splices is much easier today, due to continued improvements to the fusion splice
equipment, procedures and practices, in addition to the evolutionary improvements in controlling optical fiber
As a result, losses typically are in the range of 0.05 to 0.10 dB for both single-mode and multimode
fibers. Although the economics associated with any particular fiber splicing technology vary with splicing
environment, loss budgets, craft skill level and other system parameters, fusion splicing remains the most
widely used technique: either single or mass and with active or passive alignment techniques.
The following sections of this application note specifically address the single fiber fusion
splicing method. However, many of the areas discussed below - for example, loss factors,
fiber preparation, fiber alignment and testing - are common both to mechanical and to
fusion splicing techniques.