Tag Archives: splicing

Lower FTTH Cost and Increase Reliability With Tight Buffer Indoor/Outdoor Cable

FTTH (Fiber to the Home) network connects a large number of end users to a central point known as an access node to provide the application and services of high speed. The links between end users and access node are achieved largely by fiber optic cables. Loose buffer cables and tight buffer cables are commonly used to transmit signals with high speed, which are capable of surviving outdoor environment or indoor environment. However, to accomplish the whole transmission link, loose buffer cables for outdoor application should be connected with the tight buffer cables for indoor application. The splicing and termination of these fiber optic cables come as one of the largest link items in a FTTH system installation budget.

Is There A Better FTTH Cable Solution?

Is there a cost-effective and time-saving solution by using a single type of cable that can survive both indoor and outdoor environment in FTTH network? The answer is YES. Tight buffer indoor/outdoor cable is such a cable. It is a specially designed tight buffer cable which can answer the market call for a single type cable surviving both indoor and outdoor environment. To understand why it is a better choice for FTTH installation, the construction and comparison of loose tube cable and tight buffer cable will be introduced firstly.

Loose Buffer VS Tight Buffer

The “buffer” previously mentioned in “loose buffered” and “tight buffer” is actually a basic component of fiber optic cable and the first layer used to define the type of cable construction. A typical fiber optic cable consists of the optical fiber, buffer, strength members and an outer protective jacket (as showed in the following picture). The buffer literally is used to provide protection and some tensile strength, which are useful when pulling the cable to install it or when it must hang between two suspension points.

cable structure

Loose buffer cable consists of a buffer layer that has an inner diameter much larger than the diameter of the fiber (showed in the following picture). Thus, the cable will be subject to temperature extremes that cause expansion or contraction. That’s why loose buffered cable are usually used outdoor. The loose buffer cables designed for FTTH outdoor application are usually loose-tube gel-filled cables (LTGF cable). This type of cable is filled with a gel that displaces or blocks water and prevents it from penetrating or getting into the cable.

loose buffer cable

Tight buffer cable using a buffer attached to the fiber coating is generally smaller in diameter than loose buffer cable (showed in the following picture). The minimum bend radius of a tight buffer cable is typically smaller than a comparable loose buffer cable. Thus tight buffer cable is usually used in indoor application.

tight buffer

Tight buffered indoor/outdoor cable with properly designed and manufactured can meet both indoor and outdoor application requirements. It?combines the design requirements of traditional indoor cable and adds moisture protection and sunlight-resistant function to meet the standards for outdoor use. Tight buffered indoor/outdoor cable?also meets one or more of the code requirements for flame-spread resistance and smoke generation.

A Better Choice for FTTH Cable Solution

The structure and performance advantages of tight buffer indoor/outdoor cable have been introduced above. How about the other advantages? The following will explain why tight buffered indoor/outdoor cable is a better FTTH cable solution from the aspects of cost and reliability.


Using the traditional choice of LTGF cables as the outdoor cable, there would be a conversion from one fiber type from another type, which includes prep work on the fiber, the need for splice tray, the routing of fibers in the tray, and other similar detail. Before termination and splicing, the gel of LTGF cable must be cleaned and the breakout point of the main cable must be blocked by some method to prevent oozing of the cable gel. In addition, this cable type must normally be terminated or spliced close to the cable entryway of a building to switch to indoor cable, as it generally incompatible with indoor fiber codes. This time consuming and labor intensive process adds hidden costs to install the LTGF cables.

However, using only tight buffer indoor/outdoor cable for FTTH is much more convenient and cost-effective. A tight-buffered indoor/outdoor cable can be used throughout the link, requiring no transitions at the building entryway. Tight buffer indoor/outdoor cable requires less care to avoid damaging fibers when stripping back the cable. The termination and splicing of these cables are easier than that of LTGF cables.


An important reason why choose tight-buffered indoor/outdoor cable for FTTH cable installation is the reliability of the overall system. Splicing are the weakest point in a FTTH network. With splicing, the bare fiber ends are open to dust, dirt, water, vapor, and handing which might reduce the fiber strength and increase brittleness. Choosing loose tube outdoor cable for FTTH, there will be splices after the conversion from one cable type to another type. The splices inside a building may be held in a cabinet that is open to the air, which might decrease the reliability of the FTTH network. Using the tight buffer indoor/outdoor cable could eliminate splicing and improve the installation reliability greatly.


In conclusion, the benefits of tight buffer indoor/outdoor cable are clear. The installer can run a single cable type and remove a transition point between the outside plant and the inside plant, which decrease FTTH installation cost and time effectively. At the same time, the reliability of the overall FTTH network can be increased greatly.

Source: http://www.fs.com/blog/lower-ftth-cost-and-increase-reliability-with-tight-buffer-indooroutdoor-cable.html

Introduction of Fiber Optic Cleaving

As we know, in most cases, when a fiber is used or spliced, it is essential to prepare clean ends. Stripping, cleaving, polishing are the basic steps to ensure fiber ends clean and smooth. Since we have discussed fiber optic splicing and polishing in the last several weeks, we must know more about them. Cleaving, an essential step of making fiber ends clean, though it’s a simple mean, but it works surprisingly well, at least for standard glass fibers. Thus, I want to share something about the cleaving in this paper today.

Understanding Of Cleaving

Cleaving is one of the processes for termination or splicing. Simple to understand, it “cut” an optical fiber or makes it precisely broken, just like cutting glass plate. But it is different from the general concept “cut”, or perhaps, we may define it as a professional “cut technique” because fiber is cut by scoring or scratching the surface and applying stress so that the glass breaks in a smooth manner along the stress lines created by the scratch. With a properly well done cleaving, the fiber will cleave with a clean surface perpendicular to the length of the fiber, with no protruding glass on either end.

Cleaving Tool

cleaverCleaver – If you have more experiences in the cleaving and splicing, you must know that a right cleaver helps cut out costly mistakes. The working principle of cleaver is very easy to understand. It first holds the fiber under low tension, scores the surface at the proper location and then applies greater tension until the fiber breaks. Automatic cleavers now are widely used because they can produce consistent results, irrespective of the operator. It is easy to use and does not need training. Users just need to clamp the fiber into the cleaver and operate its controls. In addition, there are some cleavers less automated. This kind of cleavers are more dependent on operator technique and less predictable as they require operators to exert force manually for breaking the fiber.

scribeScribe – Except the cleaver, there is another tool for cleaving which is typically used to remove excess fiber from the end of a connector before polishing. Scribe is a simple hand tool with a hard, sharp tip (generally made of carbide or diamond), that is used to scratch the fiber manually (some scribes are with pen-style shapes). Then the operator pulls the fiber to break it. However, it is less predictable than a cleaver because both the scribing and breaking process are under manual control. Nonetheless, scribe can produce adequate results for polishing so that it is still used today.


Why Is Proper Cleaving So Important?

To get good fiber optic splices or terminations, especially when using the pre-polished connectors with internal splices, it is extremely important to cleave the fiber properly. As we know, fiber splicing requires mating two fiber ends. Any defect of the ends would impact the performance of fiber splicing. For example, if the fiber ends are not precisely cleaved, the ends will not mate properly. Or if the cleaved ends are at an angle, there will be a gap between the fibers that will cause loss in a mechanical splice or uneven fusion splicing. In addition, if there is a protrusion, or lip, on one of the fibers, the two fibers will not butt up against each other and if there are hackle or mist, the ends will reflect or diffuse light, also causing loss.


Warm Tips: A good cleaver is a little expensive but it’s easy to use and do not need much techniques and can help cut out costly mistakes. Of course, inexpensive cleaver provided in most termination kits is common used. If you decide to use such inexpensive cleaver, the point you may remember is that you must learn how to use it properly. Follow directions, but also do what comes naturally to you when using the device, as they are sensitive to individual technique.