Describe the steps involved in performing a fusion splice on a single-mode fiber, including preparation, alignment, and verification.

Performing a fusion splice on a single-mode fiber involves several steps to ensure a low-loss and reliable connection. The process includes fiber preparation, alignment, splicing, and verification. First, the fiber must be prepared. This begins with stripping the protective coating from the ends of the fibers to be spliced. A fiber stripper is used to carefully remove the outer jacket, strength members, and buffer coating, exposing the bare glass fiber. Next, the exposed fiber is cleaned using isopropyl alcohol and lint-free wipes to remove any contaminants such as dust, dirt, or oil. After cleaning, the fiber is cleaved using a precision cleaver. This tool creates a perfectly flat and perpendicular end-face on the fiber, which is essential for a low-loss splice. The cleave angle should be as close to 0 degrees as possible. Once both fibers are prepared, they are placed into the fusion splicer. The splicer uses a precise alignment system to align the two fiber end-faces. This alignment can be done manually or automatically, depending on the type of splicer. The splicer uses a core alignment or clad alignment system. Core alignment is more precise. After alignment, the fusion splicer applies a controlled electric arc to melt the ends of the fibers together. The splicer carefully pushes the fibers together during the arc, creating a permanent fusion splice. Once the splicing process is complete, the splicer estimates the splice loss based on the fiber alignment and the arc parameters. This estimated loss is typically displayed on the splicer's screen. Finally, the splice is verified. The bare fiber splice is very fragile and must be protected. A heat shrink sleeve is slid over the splice area and then heated using a heat shrink oven. This shrinks the sleeve, providing mechanical protection and strain relief for the splice. The splice loss should be verified using an OTDR (Optical Time Domain Reflectometer) to confirm that the splice meets the required performance specifications. A typical acceptable splice loss for a single-mode fiber is 0.1 dB or less. For example, a fusion splice with an estimated loss of 0.05 dB from the splicer and a verified loss of 0.07 dB from the OTDR is considered a good splice. If the splice loss is too high, the splicing process must be repeated.