It is essential to follow correct procedures in administration of fiber optic patch cords to achieve optimum performance and reliability. The principles of good management for fiber optic cords are similar to those for twisted pair cabling; however, there are special considerations with optical fiber and extra care is needed in some areas. Applying best practices at every stage will also minimize costs related to moves, adds and changes (MACs).
Best practices in fiber patch cord management can be divided into four parts:
Administration activities (i.e., MACs) are initiated with a change request. The change request must contain all necessary information to begin the planning process. Once a request form is received, search the records to be sure of the circuit path.
Any changes or additions made since your cabling infrastructure was installed should also be documented. If the records are stored in a database, such as an Automated Infrastructure Management (AIM) system, a different screen can be displayed for each user. This screen should supply you with the information you need, including the riser and horizontal fiber pairs serving the particular area and the locations of available fiber.
Check Design Guidelines and Match Cords
Make sure you know the specifications and design of your fiber cabling. Ensure you have patch cords matched to the installed cabling, since optical fiber cords of different types should not be mixed.
The first step in choosing a cord of the correct length is to determine the best route between its points of connection. Having established the best route for the cord, find the required length by adding the horizontal and vertical distances.
When selecting a cord to make a cross connection, avoid excessive slack and provide a neat appearance. Tight or stretched cords will pull on connectors, and too much slack complicates cord management making the panel more difficult to work on.
Ensure you have cords of the right length available and that panels are fitted with correct cable management accessories. At the optical patch panel, route patch cords equally toward both sides of the vertical cable management channels to prevent overloading one side.
Take care not to mix up cords of different optical core diameters. Additionally, cords must be of the same or higher bandwidth as the behind-the-wall cabling. System performance regarding distances cannot be guaranteed if lower rated patch cords are used. Color-coding of connectors for different fiber standards make it easy to avoid confusion.
Fiber patch cords must use the same core diameter as the trunk cable. A large attenuation penalty will occur when using a 62.5-μm patch cord with a 50-μm trunk fiber cable or vice versa. Single mode fiber patch cords should use fiber with the same Mode Field Diameter as the trunk cable fiber.
Factory-terminated vs. Field-polished
Factory-terminated cords guarantee fiber patches with optimum performance. Field polished cords are likely to deliver lower performance and variable quality.
Fiber Safety Precautions and Responsibilities
The lasers that carry information through fiber cables may cause irreparable damage to the retina. Always avoid looking directly into an energized optical fiber, and never attach a microscope or other magnifying device to an energized optical fiber. Always wear appropriate eye protection and ensure that unused ports are covered.
To minimize disconnect time, do as much preparation as possible before performing administrative activities. Locate the ports that must be connected or reconnected. Ensure technicians have clear information on what they need to do, including labeling information for the ports involved.
It is essential to ensure cords are of the right type and quality, and that they are clean and in good condition.
Fiber patch cords should be inspected for physical damage including:
- Stress marks from bending on the sheath
- Pull-out of fibers from the connector
- Cracks or scratches on fiber end in the connector using a fiber examination microscope
Cleanliness is vital in fiber optic connections so special care is needed with connector ends on:
- Patch cords
- Network equipment
Once work on a panel is started, it should be completed without delay using best practice at each stage. Kinks, snags, pinches and poor contacts can dramatically reduce the performance of a fiber patch cord. The following factors are important in avoiding these problems.
The minimum bend radius for optical fiber patch cords varies with cord diameter and should be verified before use. Exceeding the bend radius can result in significant additional loss and adverse impact on channel performance.
Cord Pulling and Stress
Be careful not to use excessive force during the patching process. This can stress cords and connectors, reducing their performance. If you need to use force in pulling a cord, something is wrong. Find the problem and fix it before proceeding.
Bundling and tying cords gives the panel a neat appearance but tight bundling increases the risk of pinching. Do not tighten ties beyond the point where individual cords can rotate freely. Use only products manufactured for this purpose and consider the use of products that can be re-used without the use of tools such as “hook and loop” strapping.
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.
Final Visual Inspection and Panel Closure
Patching must be right first time since mistakes can cause costly disruption and re-work. The time taken to make a final visual check on connections is a good investment. When patch panels are mounted in enclosures, ensure these are securely closed and, where necessary, locked, making sure that cord slack is not snagged or pinched by the doors.
The final step is to update the documentation to the as-built configuration and close the work order associated with the completed change request. Using an AIM system will automate much of this activity and aid the patching process.
If you are looking for a free course, the CommScope Infrastructure Academy offers the Best Practice for Patch Cord Management (WR9301) course. It is a free instructional video that looks at the best practices and recommendations for planning, preparing connections in network infrastructure.
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