Tag Archives: Mechanical Splicing

Causes of Mechanical Splice Termination Failures

FTTH (fiber to the home) has become increasingly popular in optical communication industry. Fiber optic termination, as one of the topics which have never been out of fashion in this field, has naturally become a focus of FTTH network deployment, especially the indoor termination. In FTTH network, mechanical splice connectors are usually used in FTTH indoor termination with the advantages of flexibility, fast-installation and cost-effective. Currently manufactures can provide various types of mechanical splice connectors of high quality which have low insertion loss and high performance. However, no matter how excellent the mechanical splicing technology is, there are still fiber optic termination failures and bad fiber optic termination due to improper operation. To avoid it, this post is to offer the causes of mechanical splice termination failures.

The Basic of Mechanical splicing

Before finding the cause of mechanical splice failure, the basic of mechanical splicing should be introduced. To finish a mechanical splice, the buffer coatings of fiber optic should be removed mechanically with sharp blades or calibrated stripping tools. In any type of mechanical stripping, the key is to avoid nicking the fiber. Then the fibers will be cleaved. Two fiber ends are then held closely in retaining and aligning a mechanical splice connector with some index matching gel between them. The gel are used to form a continuous optical path between fibers and reduce reflecting losses.

mechanical splicing

Causes of Mechanical Splice Termination Failures

Mechanical splice connector is sensitive to many factors. There are also a large number of factors to cause failures. However, most of the factors are located at the end face of fiber optic. The following is to describe them in details.


When facing mechanical splice failures, there would be no argument that contamination is the first thing to think about. There are many ways that contamination can be carried into the fiber termination splices. Generally, there are the following possible causes of splice contamination:

  • Using a dirty cleave tool: as the fiber should be cleave before inserted in the connector, a fiber optic cleaves would be used. If a dirty cleave is used, the contamination would be attached on the end face of the fiber optic and be embedded in the connector. Thus, do remember to clean the surfaces thoroughly with alcohol wipes;
  • Wiping the fiber after cleaving;
  • Setting the connector or fiber down on a dusty surface;
  • Heavy airborne dust environment;
  • Glass fragments from insertion broken fibers, or applying excessive force;
  • Polluted index matching gel.


Please note that once the contamination is carried inside the mechanical splice connector, especially with the index matching gel, there would be little possibility to clean them out, which means the connector may be scrapped.

Glass Fragmentation

Improper operation like overexertion when inserting the fiber optic into the mechanical splice connector might break the fiber optic and produce glass fragmentation which will cause air gap and optical failure. Or if a broken fiber if inserted, there will also be optical failure. If the glass fragments are embedded in the connector, they cannot be cleaned out and the connector would be scrapped. Thus, be gentle and carefully when splicing the fiber ends.


Bad Cleave

Cleaving the fiber optic is an important step during fiber optic mechanical splicing. The quality of the cleave can decide the quality of the optical splice transmission to some degree. It is not easy to inspect the cleave quality in the field. There are several possibilities there might cause the bad cleaves:

  • Dull or chipped cleave tool blade
  • The bent tongue on the cleave tool concentrated too much bend stress on the fiber
  • Bending the fiber too much or too tight of a radius
  • Applying no tension or insufficient tension to the fiber while cleaving.

bad cleave

Excessive Fiber Gap

Fiber gap is another factor that might cause the fiber optic termination failure. The fiber optic transmission is very sensitive to the gap between two fiber ends in the mechanical splice connector. Improper operations that might cause the excessive fiber gap are listed as following:

  • Cleaving the fiber without enough lengths;
  • The fiber is not fully inserted, or pulled back during termination;
  • The fiber was not held steady during termination and was pushed back into the fan-out tubing when terminating outdoor cable.

These faults can be corrected one time.

fiber gap

Excessive Cleave Angle

During fiber cleaving, cleave angle can be produced easily and is difficult to be inspected in field. These angles are typically ranging from 1 to 3 degree. Even with precision tool, there might still be cleave angle ranging from 0.5 to 1 degree. The angle is generally produced by bent tongue, fiber bending or insufficient fiber tension.


However the cleave angles can be corrected by fine tuning with a VFL (visual fault locator). Rotating the fiber while using a VFL and terminate the connector at the position (as shown in the following picture).



Fiber optic mechanical splicing gives quick and high quality result at a low price for fiber optic termination. Choosing the right fiber optic mechanical splice connector and fiber optic cleaver of high quality is not enough. Acknowledge the possible causes to fiber optic termination failures and use the right tools with skills can reduce the risk of termination failure effectively.

Source: http://www.fs.com/blog/causes-of-mechanical-splice-termination-failures.html

Fiber Optic Splicing Tutorial

A few days ago, I have been a bit of interest in the fiber optic splicing work after I communicating with some fiber optic splicing engineers. Happen to have an product learning opportunity to learn the Fusion Splicer in these two days, I have read some references about it and today I am going to share some knowledge about fiber optic splicing in this paper. If you are just beginning to do the fiber splicing work, this paper may give some information to chose which technique best fits your economic and performance objectives for your long-term goals in this field.

What Is Fiber Optic Splicing
The most intuitive understanding of fiber optic splicing is joining two fiber optic cables together using a technology. Compared to connectorization, fiber optic cable fusion splicing provides the lowest-loss connection so that it always the preferred method when the cable runs are too long for a single length of fiber or when joining two different types of fiber cable together. In addition, fiber optic splicing is also used to restore fiber optic cables when a buried cable is accidentally severed.

fiber optic splicing

There are two optical fiber splicing methods which are available for permanent joining of two optical fibers:
Fusion splicing – Insertion loss < 0.1dB
Mechanical splicing – Insertion loss <0.3 – 0.5dB
By looking at the data above, we can know that both fiber optic splicing methods could provide much lower insertion loss compared to fiber connectors or terminators.

Mechanical Splicing Method vs Fusion Splicing Method
Mechanical Splice
Mechanical splice is a device for fiber optic cable splicing. It is designed to hold the two fiber ends in a precisely aligned position and reduce loss and reflection with a transparent gel or optical adhesive between the fibers that matches the optical properties of the glass.

mechanical splice

Fusion Splice
Fusion splice uses an electric arc or heat to weld two fiber-optic cables together which can produce a continuous connection between the fibers enabling very low loss light transmission.


Which is better?
In general, the initial investment of a mechanical splice seems much lower than a fusion splice. But the splice component itself, which includes a precision alignment mechanism, is more expensive than the simple protection sleeve needed by a fusion splice. For the performance, mechanical splice generally has higher loss and greater reflectance than fusion splice. Additionally, fusion splice is used primarily with single mode fiber while mechanical splice works with both single and multi-mode fiber.

Nowadays, many companies in this industry, such as the telecom or CCTV, invest in fusion splicers for their long distance singlemode networks, but have still use mechanical splicer for shorter, local cable runs. But as signal loss and reflection are minor concerns for most LAN applications, LAN industry has the choice of either method. Therefore, what the best is the suitable, you should choose a best suitable splicer according to your item.

Fiber Optic Splicing Procedure(Fusion Splicing)
The splicing process begins by preparing each fiber end for fusion. We should firstly strip the outer jackets, polymer coating and so on to leave only bare fiber. And then a thorough cleaning of cable is needed. After cleaning, cables should be precisely cleaved to form smooth, perpendicular end faces. When everything was ready, you could place the fiber into the guides in the fusion splicing machine and clamp it in place. Repeat the above steps for the other fiber to be spliced. Here, we begin to run the splicer. Choose the proper program for fusion splicing, the fiber types being spliced. And then uses an electrical arc or heat to melt the fibers, permanently welding the two fiber ends together. The detail splicing processes could see the following video.

Warm Tips

  • Thoroughly and frequently clean your splicing tools
  • Properly maintain and operate your cleaver
  • Fusion parameters must be adjusted minimally and methodically (fusion splicing only)