Category Archives: Fiber optic termination

What Leads to Mechanical Splice Failure in Fiber Optic Termination?

Mechanical splice connectors are popularly used in FTTH (fiber to the home) fiber optic termination, since they are flexible, cost-effective and quick for field installation. As the FTTH network gradually becomes more widely implemented, fiber optic termination, especially indoor termination, has well become a focus of FTTH network deployment. Though current vendors can provide various types of pre-polished ferrule connectors of high quality which have low insertion loss and high performance, it is still very hard to make a perfect fiber optic termination even with advanced mechanical splicing technology. Because of inappropriate handling, fiber optic termination failures or bad fiber optic termination can occur in mechanical splice. In order to get a good termination, this article will introduce the most common factors that can lead to mechanical splice termination failures and some tips to avoid them.

Brief Introduction to Mechanical Splicing Steps

Before going to the reasons for mechanical splice termination faults, let’s briefly review the steps for mechanical splicing. Firstly, the buffer coatings of fiber optic cable should be mechanically removed, by using sharp blades or calibrated stripping tools. It is important not to damage the fiber surface in any type of mechanical stripping. Then the fibers will be cleaved. After the two fiber ends are held closely and optimally aligned in a mechanical splice connector, some index gel is used between them to form a continuous optical path between fibers and reduce reflecting loss.


Mechanical Splice Termination Defects

Mechanical splice connector is sensitive equipment. And there are many factors that can cause mechanical splice termination failures. However, most of the factors are located at the end face of optical fiber, which may include contamination, glass fragmentation, bad cleave and excessive fiber gap.

Contaminants Between Fiber Ends

Contamination is the usually the first thing to think about when mechanical splice termination failure occurs. There are many ways that contamination can be carried into the fiber termination splices. Generally, the following incorrect operation can cause splice contamination:

1. Use a dirty cleave tool: s 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;
2. Wipe the fiber after cleaving;
3. Set the connector or fiber down on a dusty surface;
4. Splice in a heavy airborne dust environment;
5. Cause glass fragments from insertion broken fibers, or applying excessive force;
6. Use 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 that might cause bad cleaves:

1. Use dull or chipped cleave tool blade
2. The bent tongue on the cleave tool concentrated too much bend stress on the fiber
3. Bend the fiber too much or too tight of a radius
4. Apply no tension or insufficient tension to the fiber while cleaving.


During fiber cleaving, excessive 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.


Luckily, 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 right position.


Excessive Fiber Gap

Fiber gap is another factor that might cause the fiber optic termination failure. Improper operations that might cause the excessive fiber gap are listed as following:

1. Cleave the fiber without enough lengths;
2. The fiber is not fully inserted, or pulled back during termination;
3. 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 on time.



This article has introduced some factors that will lead to mechanical splice failures in fiber optic termination, and some tips are also included to ensure good splice transmission. After knowing these factors we can see that it is not enough to choose good mechanical splice connector and high quality fiber optic cleaver. Concentrating on proper operations and using right tools for mechanical splice are key to avoid bad results in mechanical splice termination.

Considerations for Fiber Optic Termination

Fiber optic cables and connectors are necessary components of current telecommunication systems which are transmitting greater information at faster speeds. As we all know, when appropriate optical cables have been selected for a system, connectors and termination method also should be taken into account to meet the system requirements. This article mainly explores several considerations for fiber optic termination and how different optical termination methods impact the performance of telecommunication systems.

fiber optic termination

Important Factors to Be Considered
Insertion Loss of Fiber Optic System

Fiber optic cabling systems support various communications technologies like Gigabit Ethernet, local area networking (LAN) and CATV (community access television). No matter what types of networks it supports, the communication devices have a limitation for maximum channel insertion loss measured in units of decibels (dB). Optical fiber channel insertion loss usually occurs when an active transmitter is linked to an active receiver via terminated fiber optic cables, splicing points and fiber optic connectors. The quality of fiber optical links’ terminations has an impact on the channel insertion loss. Poor quality terminations often cause more loss than high-performance terminations. An optical system will fail due to excessive insertion loss.

Return Loss of Optical System

Return loss is the power of the optical signal that returns towards the optical source against the direction of signal propagation, which is mainly caused by Fresnel reflections and Rayleigh back scattering. Communication systems can be impaired by an excessive amount of reflected optical power, which could alter the transmitted signal to an extent that is not the power level received by the receiver. Generally, components like connectors and mechanical splices are specified as reflectance, and system sensitivity is specified as return loss.

Fiber Optic Termination Methods

Nowadays various fiber optic connectors are available such as LC, SC and MTP connector, so are termination methods existing for different connector types. Common termination methods include no-epoxy-no-polish (NENP) connector, epoxy-and-polish (EP) and splicing.

No-epoxy/no-polish Connector

NENP connector is a type of connector that does not require the use of epoxy or polishing in the field, because those processes have been finished when the connector is made. This type of field termination is the fastest and simplest for a new installer to master. Compared with those connectors terminated in the field, the termination process (polishing the fiber end-face) of NENP connector is accomplished in advance in a manufacturing environment, which provides insurance for the fiber optic termination quality.


Epoxy-and-polish Connector

Another common termination method is to use epoxy and polish connectors. EP fiber termination includes the following steps: injecting the connector ferrule with epoxy, curing, scribing the protruding fiber from the ferrule, and polishing the ferrule end-face. During this termination process, two situations may affect the termination quality. One is the bubbles that occur in the epoxy. Another is the debris that may appear in the ferrule. Besides, the quality of the polished end-face also can directly impact both the insertion loss and reflectance.

Pigtail Splicing

Pigtail splicing is another method used to terminate an optical fiber. This method is achieved by fusing the field fiber to a factory-made pigtail in a splicing tray. The person who has some experience of pigtail splicing must know pigtails should be cleaned and cleaved before they are spliced, and the cleave precision significantly impacts splice quality.



Different fiber optic termination methods vary amounts of insertion loss and reflectance. The epoxy injection and subsequent polishing process are the most critical steps during optical terminations that determines the magnitude of air gap at a connector interface. Factory-controlled manufacturing processes ensure consistent optical performance. Field epoxy and polish procedures produce connector end-face conditions that vary among installation techniques. However, no epoxy-no-polish connectors and pigtails are not only manufactured with precise and repeatable polishing process, but insertion loss and reflectance are measured for every connector.

To ensure that epoxy and polish connectors meet specified optical performance established by industry standards, both insertion loss and reflectance must be measured after fiber is terminated. In a word, the proper optical fiber termination method should be chosen to ensure easy system installation as well as meet required insertion loss and reflectance values prescribed by either industry standards or link loss budget, or both.

Related article: Brief Introduction to Fiber Optic Termination

Brief Introduction to Fiber Optic Termination

When it comes to install a fiber optic network, undoubtedly, fiber optic termination is one of the extremely important procedures. Since an unreliable network will cause many problems and may not perform correctly. Therefore, much attention is paid to this area today, and numerous related products are appearing on the market to make fiber optic termination easier and more accurate than before.

What Is Fiber Optic Termination?

Fiber optic termination is the connection of fiber or wire to a device such as a wall outlet or equipment, which allows for connecting the cable to other cables or devices. It is an essential step for installing a fiber optic network. Since any mistakes can lead to the system functioning unreliably, this step must be operated correctly.


Methods of Fiber Optic Termination

Generally, there are two methods of fiber optic termination. One is to use connectors to create a temporary joint or to connect the fiber to a piece of network gear. Another is to create a permanent joint between two fibers with splicing. Here is a brief overview of this two methods.


Fiber optic connectors are unique. They transmit pulses of light rather than electric signals, so the terminations must be more precise. Instead of merely making metal to metal contact, fiber optic connectors must align precisely so that signals can run through successfully. Although there are various types of connectors on the market, they share the same structures. And there are three major components of a fiber optic connector: the ferrule, the connector body and the coupling mechanism.

  • Ferrule—This is a thin structure (often cylindrical) that holds the glass fiber. It has a hollowed-out center that forms a tight grip on the fiber. Ferrules are usually made from ceramic, metal, or high-quality plastic, and typically will hold one strand of fiber.
  • Connector body—this is a plastic or metal structure that holds the ferrule and attaches to the jacket and strengthens members of the fiber cable itself.
  • Coupling mechanism—this is a part of the connector body that holds the connector in place when it gets attached to another device (a switch, NIC, bulkhead coupler, etc.). It may be a latch clip, a bayonet-style nut, or similar device.

There are various types of connectors available on the market such as SC, LC, FC, MPO, MTRJ, etc. When install a network, problems about the connector type should be considered. For example, whether the connector is compatible with this systems planned to utilize the fiber optic cable plant and whether the connector is accepted by the customers.



Fiber optic splicing is needed when the cable runs are too long or a numbers of different types of cables are needed to be mixed. As mentioned above, splicing is to connect two fibers permanently. Splicing also has two types. One is mechanical splicing and another is fusion splicing. Fusion splicing is most widely used as it provides the lowest loss and least reflectance as well as the most reliable joint. While mechanical splicing is like connectors which only combine fibers temporarily.

How to choose splicing types depends on the installation locations or cost. Most splicing is on long haul outside plant single-mode cables, not multimode LANs (Local Area Networks). So if you do outside plant single-mode jobs, you will want to learn how to do fusion splice.


Fiber Optic Termination Loss Mechanisms

We have known the methods of fiber optic termination, and what we should make sense is that, no matter which methods we adopt, the loss is unavoidable. And now I’d like to talk about the loss mechanisms caused by connectors and splicing.

Connector and splice loss is caused by a number of factors. As we all known, when the two fiber cores are identical and perfectly aligned, the loss is minimized. And only the light that is coupled into the receiving fiber’s core will be transmitted. The rest of the light becomes the loss. Here are some common causes that appear in fiber optic termination, which can result in loss.

End Gaps

End gaps can result in two problems—insertion loss and reflectance. When light runs in the end gaps, it will become cone shape and spill over the core of the receiving fiber and be lost. Besides, the air gap in the joint also causes a reflection. Because when the light runs from the glass fiber to the air in the gap, the different refractive index can lead to loss.


Core Diameters

Different core diameters connected together also can cause light loss. And the loss amount is determined by the transmission direction. When light transmits from a fiber with a larger core diameter to a small one, the loss will be higher than the reverse. So when terminating two fibers, it’s important to make the core diameter of them identical.


Improper Fiber Ends

Improper fiber ends can cause loss, too. Therefore, the end finish of the fiber must be properly polished to cut loss. A round surface will scatter light, and dirt also can scatter light. Since the fiber is so small that a little dirt can be a major source of loss. Whenever connectors are not used, they should be covered to keep the ferrule from dirt.


In summary, this article introduces some basic information about fiber optic terminations. And the fiber optic termination process has become much simpler today with readily available termination products. Fiberstore provides all kinds of fiber optic connectors and splicing equipment for you to make your fiber optic terminations easier and more convenient.