What you need to know about Optical Fiber Splicing

Optical Fiber Networks have become very common, and form the backbone of many enterprise networks. In fact, even your home might soon get a direct optical fiber link through FTTH. So, it is important to have an idea about two of the common methods used to join optical fiber cables – Mechanical Splicing & Fusion Splicing.

What is Fiber Splicing?

Optical Fiber Cables are not as simple as Cat6/telephone cables(to deal with). But there are a number of advantages of using Optical Fiber Cables, especially to connect the backbone of a Local Area Network (Inter switch/ Inter-departmental connections that run more than hundred meters). And  Fiber Splicing refers to the method used to join two optical fiber cables together. An OFC cable might have various cores (6/12/24), and two cores are required to make one connection. Each of these cores needs to be spliced individually.

Why is Fiber Splicing required?

Optical fiber Splicing is required for number of reasons. When you want to lay a long fiber cable, the manufacturer might supply it as two or three short pieces – So, you to splice to join these cables together and make a single communication link. Sometimes, optical fiber links might be cut off, so you need splicing to join them together.

You need splicing to terminate the optical fiber cables to network switches/ fiber switches/ fiber patch panels (You can’t just terminate an optical fiber cable directly to a switch. You need to first terminate it to a fiber patch panel which has pigtail connectors, then use fiber patch cords of the right type (SC/LC etc) to connect the fiber patch panel and the network/ fiber switch. On newer switches LC-SC patch cords are used : LC at the switch side; SC at the fiber patch panel side – but this depends on manufacturer, so check with specs).

There are two types of Fiber Splicing that are commonly used: Mechanical Splicing & Fusion Splicing.

Mechanical Splicing (OFC):

Mechanical Splicing joins two fibers together mechanically by holding the ends together wrapped inside a kind of sleeve/ joint. This is used for both temporary fiber connections, as well as permanent fiber connections.

While this method might have a slightly higher optical loss / reflection than Fusion based splicing (which is still acceptable in optical fiber networks), the initial capital costs required for purchasing the mechanical splicer is lesser. The cost per splice is higher, when mechanical splicing units are used to join optical fiber cables/ cores.

A video describing the mechanical splicing method can be accessed from this Youtube link.

Fusion Splicing (OFC):

With Fusion Splicing, two fiber cores are welded/ fused together using heat/ electric arc. The equipment used for fusion splicing is relatively high tech and costs higher than a mechanical splicer. But the operating costs (per splice) is lesser and the optical losses are also lesser. So, fusion splicing is a more accurate method for joining two fibers. Fusion splicing is better for permanent connection between two fibers that are not going to be disturbed in the short run.

In some fusion splicers, splice time and temperature can be customized. Some fusion splicers can magnify and display the splice connection. Fusion Splicers even indicate the estimated amount of fiber losses (in dB) after two cores have been joined together by fusion splicing.

A video showing the Fusion Splicing method can be accessed from this Youtube link.

How can the Fiber Splicing connectivity be checked?

One can use the OTDR (Optical Time Domain Reflectometer) to check the optical fiber cable connectivity – Continuity and fiber losses, all along the link that was joined by using fiber splicing. It is however recommended to take the OTDR measurements from both ends (bidirectional measurement) in order to get an accurate analysis.

Generally, in enterprise networks, a splice loss of 0.25 to 0.3 dB could be tolerated. But however, if fusion splicing is used, the losses can be as minimum as 0.1 dB or lesser.

What are some factors that could affect the good performance of Optical Fiber Splicing?

Cleaving is a very important step before Fusion Splicing. Its important to cleave the fibers with with a good quality cleaver. The cleanliness of the splicing equipment is equally important as dust can affect the performance of splicing. It may be better to clean the fibers with isopropyl alcohol. Also, joining two optical fiber cables of different makes may not give the best splice results.

In an enterprise company, where there are limited number of optical fiber cables, it may be prudent to rent the splicers/ technicians for fiber splicing. But in this case, the downtime that might be incurred while waiting for the equipment/ technicians to arrive, is an important factor to consider.

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