Fiber splicing basics

Fiber splicing is an increasingly common skill requirement for cabling technicians. The emergence of optical fiber splicing technology is because it can connect two optical fibers together by a fixed or movable method. Fiber optic cables need to be spliced ​​for a variety of reasons - such as to establish a link of a specific length, or to repair a damaged fiber optic cable or connection. Since the factory specifications of optical cables are usually about 5km, if a 10km optical cable is required, it is necessary to connect two optical cables together.

Fiber splicing

Classification of optical fiber splicing technology

Mechanical connection

Mechanical splicing is often used where fast and easy splicing is required. Although the optical loss level of the mechanical splice is around 10%, it can complete the splice operation in 5 minutes. But this level of loss is much better than a mechanical connection. Some mechanically spliced ​​connectors, advertised, are detachable devices. Therefore, mechanical splice can be used in applications where active splice is required.

fusion splice

This splicing method joins the fibers together by fusing the end faces of the fibers. This method splices two optical fibers by arc discharge, and requires special equipment to operate. The loss caused by welding is low, but it has high stability. However, this technique requires the use of expensive fusion splicing equipment.

The Mechanism of Optical Fiber Connectors

When connecting optical fibers, the cores of the optical fibers must be properly docked. Optical fiber splice loss usually occurs in the following situations:

Axial misalignment

The axial misalignment of the splice fiber will cause splice loss. In general-purpose single-mode fiber, the rough calculation formula of splice loss is: (axial misalignment value) 2*0.2. (For example, if the wavelength of the light source is 1310nm, each 1µm of axial misalignment will cause a loss of about 0.2 dB)

axis tilt

If the axis of the spliced ​​fiber is not in a horizontal plane, it will cause splicing loss. For example, when cutting the optical fiber before fusion splicing, it is necessary to avoid the appearance of the inclination angle of the end face of the optical fiber, because the inclination angle will cause the optical fiber to have a phenomenon of axial inclination after fusion splicing.

face separation

A gap between the end faces of the spliced ​​fiber will cause splice loss. For example, in mechanical splicing, if the end face of the optical fiber is not butted, it will cause splicing loss.

reflection

The gap between the fiber end faces can cause a return loss of up to 0.6 dB due to the change in the refractive index of the fiber to air. In addition, the fiber end face should be thoroughly cleaned, because the loss of the fiber end face will also occur if the fiber end face is not clean.

Classification and principle of fusion splicing

There are two methods for fusion splicing:

Fiber core docking

After the fiber cores are butted by microscope imaging, the cores are fused together by arc discharge. The optical fiber fusion splicer has a lens, which can observe and position the fiber core from two directions.

Fixed V-groove butt

This fusion splicing method uses a high-precision V-groove for positioning and butt joints of the optical fibers, and the splicing (cladding butt splicing) is achieved by the surface tension of the optical fibers after melting. The low loss caused by splicing achieved by this method is due to the recent development of optical fiber production technology that improves the dimensional accuracy of the fiber core, making the splicing easier. This method is mainly used for one-time splicing of multi-core optical cables.

Tips for a better connection

1. Clean your splice tool thoroughly and frequently. When splicing fibers, paying attention to particles that cannot be seen with the naked eye can cause huge problems. "Excessive" cleaning of your fibers and tools will save you time and costs that may be incurred in the future.

Properly maintain and operate your cutter. The cleaver is the most important tool in the fiber splicing process. In a mechanical splice, you need the right angle to ensure a usable end face is cut, otherwise a lot of light will escape through the gap between the two fibers. Although the matching fluid can solve most of the light escape problems, it cannot overcome the degradation of communication quality caused by improper cutting.

3.The welding parameters must be adjusted in small amounts in an orderly manner (only for welding and splicing), otherwise you may not get the desired settings. Whether the equipment is clean should be the first step you should check, and then continue to adjust the parameters. Discharge time and discharge current are two key elements of continuity. Different variants of these two elements can produce the same continuation effect. Long periods of low current can produce the same results as short periods of high current. Make sure to change only one variable at a time and keep checking until you find the right splice parameters for your fiber type.