something about optic fiber Splicing

A splice is a device to connect one fiber optic cable to another permanently. It is the attribute of permanence that distinguishes a splice from connectors. Nonetheless, some vendors offer splices that can be disconnected that are not permanent so that they can be disconnected for repairs or rearrangements. The terminology can get confusing.

Fiber optic cables may have to be spliced together for any of a number of reasons. 

One reason is to realize a link of a particular length. The network installer may have in his inventory several fiber optic cables but, none long enough to satisfy the required link length. This may easily arise since cable manufacturers offer cables in limited lengths - usually 1 to 6 km. If a link of 10 km has to be installed this can be done by splicing several together. The installer may then satisfy the distance requirement and not have to buy a new fiber optic cable.

Splices may be required at building entrances, wiring closets, couplers and literally any intermediary point between Transmitter and Receiver. 

At first glance you may think that splicing two fiber optic cables together is like connecting two wires. To the contrary, the requirements for a fiber-optic connection and a wire connection are very different. 

Two copper connectors can be joined by solder or by connectors that have been crimped or soldered to the wires. The purpose is to create an intimate contact between the mated halves in order to have a low resistance path across a junction. On the other hand, connecting two fiber optic cables requires precise alignment of the mated fiber cores or spots in a single-mode fiber optic cable. This is demanded so that nearly all of the light is coupled from one fiber optic cable across a junction to the other fiber optic cable. Actual contact between the fiber optic cables is not even mandatory. The need for precise alignment creates a challenge to a designer of a splice.

There are two principal types of splices: fusion and mechanical.

Fusion splices - uses an electric arc to weld two fiber optic cables together. The splices offer sophisticated, computer controlled alignment of fiber optic cables to achieve losses as low as 0.05 dB. This comes at a high cost.

Mechanical-splices all share common elements. They are easily applied in the field, require little or no tooling and offer losses of about 0.2 dB.