Basic of Optical Distribution Frame (ODF)

Driven by requirements for high-speed data rate, the deployment of fiber optic has been growing. As the growth of installed fiber optic, the management of optical transmission networks becomes more difficult. Many factors should be considered during fiber optic cabling, like flexibility, future viability, cost of the deployment and management, etc. To handle large amounts of fiber optic with lower cost and higher flexibility, various optical distribution frames (ODF) are being widely used to connector and schedule optical fiber. Choosing right fiber optic distribution frames is the key to successful cable management.

What Is ODF?

An optical distribution frame (ODF) is a frame used to provide cable interconnections between communication facilities, which can integrate fiber splicing, fiber termination, fiber optic adapters & connectors and cable connections together in a single unit. It can also work as a protective device to protect fiber optic connections from damage. The basic functions of ODFs provided by today's vendors are almost the same. However, they come into different shapes and specifications. To choose the right ODF is not an easy thing.

Types of ODF

According to the structure, ODFs can mainly be divided into three types, namely wall mount ODF, floor mount ODF and rack mount ODF.

Wall mount ODF (shown in the following picture) usually uses design like a small box which can be installed on the wall and is suitable for fiber distribution with small counts. Floor mount ODF adopts closed structure. It is usually designed with relatively fixed fiber capacity and nice appearance.

Rack mount ODF (shown in the following picture) is usually modularity in design with firm structure. It can be installed on the rack with more flexibility according to the fiber optic cable counts and specifications. This kind of optical distribution system is more convenient and can provide more possibilities to the future variations. Most of the rack mount ODF is 19'', which ensures that they can be perfectly installed on to the commonly used standard transmission rack.

ODF Selection Guide

The selection of the ODF is not limited to the structure, many factors like applications should be considered. Some of the most important are introduced as following.

Fiber Counts: with the number of fiber connections in places like data center increase, the need for high density ODF become the trend. And it is very common to find ODF with 24 ports, 48 ports or even 144 ports for fiber optic cables in the market now. Meanwhile, many vendors can provide the customized ODFs according to the customers' requirement.

Manageability: High-density is the good but management is not easy. ODF should provide an easy management environment for technicians. The basic requirement is ODF should allow for easy access to the connectors on the front and rear of those ports for insertion and removal. This requires that ODF should reserve enough space. In addition, the color of adapters installed on the ODF should be remain consistent with the color code of fiber optic connectors to avoid wrong connections.

Flexibility: as mentioned rack mount ODF is relatively flexible during applications with the modular design. However, anther aspect which can increase the ODF’s flexibility effectively is the port size for adapters on the ODF. For example, an ODF with ports of duplex LC adapter size can be installed with duplex LC, SC or MRTJ adapters. An ODF with ports of ST adapter size can be installed with both ST adapters and FC adapters.

Protection: optical distribution frames integrate fiber connections in it. The fiber connections like splicing joint, fiber optic connectors are actually really sensitive in the whole transmission network and is directly related to the stability and reliability of the network. Thus, a good ODF should have protection device to prevent fiber optic connections from damages produced by dust or stress.

Conclusion

The ODF is the most popular and comprehensive fiber optic distribution frame which can reduce the cost and increase the reliability and flexibility of fiber optic network during both deployment and maintenance. The high density ODF is the trend in telecommunication industry. Selecting an ODF is important and complex which requires full consideration including applications and management. The factors like structure, fiber counts and protection are just the basic elements. The ODF which can meet the current requirements and the challenge of future growing and easing of expansion without sacrificing cable management or density can only be selected with repeated comparison and full consideration.

Source: http://www.fiber-optic-tutorial.com/basic-of-optical-distribution-frame-odf.html

Fiber Patch Cable Management

Deploying more fiber optic cable is just the first step to meet the high-bandwidth requirements, strong management over the fiber optic cable is a basic requirement for a successful fiber optic network infrastructure. Fiber patch cable might be the weakest link in optical network infrastructures. To deliver and guarantee and optimal network performance, patch cable management is critical. In addition, well management of fiber patch cable can lower operation cost & time and increases the reliability and flexibility of network operation and maintenance. This post will offer the critical elements that should be noted during patch cable management, as well as tips for fiber patch cable management.

Elements That Affects Patch Cable Management

To get a flexible and well organized patch cable management, the factors that affect the performance of the fiber optic patch cable should be introduced first. Here are four key elements that should be considered during patch cable management.

Bend Radius

Unlike copper, fiber optic made of glass is much fragile and need more protection and attention during the operation and management. Thus, the fiber’s bend radius will impact its reliability and performance. If a fiber cable is bent excessively, the optical signal within the cable may refract and escape through the fiber cladding which will cause a loss of signal strength and is known as bend loss. What’s more, bending, especially during the installation and pulling of fiber optic patch cable might also cause micro cracks and damage the fiber permanently. Generally, there are two basic types of bends in fiber, which are microbends and macrobends as shown in the following picture. The macrobends are larger than microbends.

What should be noted is that bend radius might not be seen during the initial installation of fiber patch cable. This is because the number of patch cables routed to the optical distribution ODF is usually small. However, when more patch cords are added on the top of installed patch cables in the future the problems will come across (shown in the following picture). A fiber patch cable that working fine for years might suddenly have an increased level of attenuation, as well as a potentially shorter service life.

Path of Patch Cable

Patch cable path is an aspect closely related to bend radius that can affect the performance and maintenance of the patch cable. The path of the patch cable should be clearly defined and easy to follow. Improper cable routing can cause increased congestion in the termination panel, increasing the possibility of bend radius violations and long-term failure. However, the well managed patch cable path ensures that bend radius requirements are maintained at all points and makes accessing individual patch cable easier, quicker and safer. What should be mentioned is that the well organized fiber patch cords can help to decrease operating costs and the time required to turn-up or restore service.

Accessibility of Patch Cable

The third aspect is accessibility of the installed patch cable. If the installed patch cable is easy to be accessed, the maintenance and operation would be quick without inducing a macrobend on an adjacent fiber, and it can also offer proper bend radius protection. Accessibility is critical during network reconfiguration operations and directly impacts operation costs and network reliability.

Physical Protection

Patch cables routed between pieces of equipment can largely affect network reliability. Without proper protection, they would be easy to be damaged by technicians and equipment accidentally. Thus, physical protection of the installed patch cords is very important.

Tips for Fiber Patch Cable Management

According to the mentioned aspects that can affect the performance and maintenance of the fiber optic patch cable, here offers several tips that can help to increase the performance of patch cords, as well as the reliability and flexibility of patch cable management.

Tip 1: Pay attention to the bend radius of the patch cable. Generally, for 1.6mm and 3.0mm cords the minimum un-loaded bend radius is 3.5 cm, and the minimum bend radius of MPO patch cable is ten times the cord diameter.

Tip 2: Never pull or stress the patch cords (shown in the following figure). During the patching process, excessive force can stress fiber patch cables and connectors attached to them, thus reducing their performance. There might be something wrong if you need to use force in pulling a cord.

Tip 3: Routing cords through cable pathways. If the existing cord is the right length, it may be possible to re-use it. If this is the case, remove the cord completely and re-run it in through the cable pathways. This is the only sure way to ensure there are no tangles, kinks or strains in the cord. For efficient routing, find the best path between the ports to be connected. Avoid routing cords through troughs and guides that are already congested.

Tip 4: Bundling and tying cords gives the panel a neat appearance but tight bundling increases the risk of pinching (shown in the following figure). Do not tighten cable ties beyond the point where individual cords can rotate freely.

Tip 5: Labeling is necessary. Labeling is the most important part of a System Administrator’s responsibilities. At any administration point in a cabling infrastructure, including patching panels, accurate labels are essential. These will identify pair modularity and tell technicians where the other end of the cable is terminated.

Tip 6: Inspect fiber cords for physical damage including stress marks from sharp bends on the sheath, or damage to connectors as shown in the following figure.

Conclusion

A strong and successful patch cable management which can increase the reliability and flexibility and decrease the cost of network operation and maintenance should provide bend radius protection, reasonable patch cable path, easy accessibility of patch cable and physical protection. When the four mentioned aspects are satisfied, there is already half the success to strong patch cable management.

Source: http://www.fiber-optic-tutorial.com/fiber-patch-cable-management.html

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.

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.

Contamination

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.

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.

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).

Conclusion

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.fiber-optic-tutorial.com/causes-of-mechanical-splice-termination-failures.html