Spool (Reel) Testing - Why do we do it?

We have all been there, we installed a fiber cable we received from our favorite manufacture and when we test the cable (post installation) it fails because a strand, if you are lucky, is broken. Was it broken during the installation or did it come from the factory that way? That is where Pre-installation test would have helped you. 

I remember once, during the installation of some copper backbone at one of the largest law firms in Washington DC, as the spool was unwinding as we pulled the cable we found the spool was not 1,000 feet but two 500 foot pieces that was taped together in the middle. Lucky for us we found it during installation. It was still a nightmare pulling it back out and then dealing with the manufacture for replacement. It would have been ten times worse if we didn’t discover it until it was terminated and tested! A simple pre-installation test could have saved us earlier.

Pre installation testing is usually done on fiber cable installations, sometimes it is required by the customer in the contract language. You may hear it called “spool” or “reel” testing. Those customers who require this either have been affected by a cable that was broke during shipment, or if they are lucky they learned from someone else’s mistake. 

This test is done when the common carrier (trucking company) delivers the cable to your office. The trucking company is responsible for any damage that happens to the cable from the point they pick up from the shipper and until you sign the bill of lading. 

Dictionary.com defines bill of lading as “a detailed list of a shipment of goods in the form of a receipt given by the carrier to the person consigning the goods”. If the product is damaged, lost, or stolen they are financially responsible. Before you sign the bill of lading you will want to perform the pre-installation test. Don’t let the truck driver make you feel guilty because you are holding up their day, just do it. 

Another advantage of performing the pre-installation test is you can verify that the spool is the length you ordered and performs as it should. In the example I gave with our cable we would not have caught the defect just by a simple visual inspection of the spool and outer wraps of the cable. 

Pre-installation test will provide you protection from factory defects, damage that happened during shipping, and validate the factory test report. WIth the cost of cable today and shipping costs this will be critical. Pre-installation tests will come in a one, if not all, of the following types:

Visual Inspection:

Before the driver takes the spool out of the trailer, you will want to visually inspect it. Verify first that the spool is yours. Make sure it has your company name on the spool. Drivers sometime, in a hurry, will accidently give you a spool that was supposed to be delivered to someone else. Next, look at the label on the cable jacket and make sure that it is the right strand count and jacket type (plenum/riser). Then move on and look at the spool, the plastic wrap, and the exposed wraps of the cable. You will want to look for tears, rips, broken spools, anything that indicates the cable may be damaged. Even if you perform a VFL or OLTS test and accept the cable, document the damage on the bill of lading before you sign it. This will provide a foundation for a claim for any unseen damage that might reveal itself later. If there is damage to the spool and cable to the point you are concerned, refuse the shipment!

Testing with VFL:

The simplest of the tests is a continuity test. You want to make sure the strands will pass a light all the way through the cable. You can do this with a VFL or a optical flashlight. A VFL is a laser light source that emits visible light and plugs into a connector. An optical flash light is a flashlight you can also plug onto a fiber strand. There are even adapters you can purchase to put on the end of your flashlight.

To perform this test you possibly may have to unwrap the plastic shipping material to gain access to the end of the spool. The other end usually comes out the on the side of the spool. You may have to put on a connector to perform this test if using a VFL. A simple mechanical connector will work fine. Put your VFL or optical flashlight on the end of each strand and verify the light travels all the way through by looking at the ends of the strands on the other side of the cable. CAUTION: Make sure you use a light source that will not damage your eye if you look at it. 

Some technicians will use a laser pointer or other similar device. Those have the ability to cause an injury to your eyes and skin. DO NOT USE THESE DEVICES! If you are using a laser light source and you are not sure of the power level get one that you do. It is also good advice to purchase a pair of safety glasses that protect your eyes from lasers. YOU SHOULD though, just not use a light source that will not cause you an injury, 

Testing with OLTS:

An optical light souce (OLTS) is a tester that consist of a power meter and light source. It injects a signal down the cable and measures the attenuation of the signal. Some models of OLTS will also provide you the length. Verify your test results to factory test and your expectations. 

A simple mechanical connector of fiber pig tail will help you easily attach to the strands under test. 

Testing with OTDR:

The absolute best way to perform pre-installation test is to use an OTDR. OTDR stands for Optical Time Domain Reflectometer. This is an expensive fiber tester that will test for length, continuity, and attenuation. 

An OTDR will inject a series of light pulses down the strand under test. The light is reflected back (Rayleigh backscatter) to the tester. It then will plot that information on a fiber trace. You will be able so see how long and how much attenuation the fiber has. 

The process is the same as a OLTS to perform the test. 

Conclusion:

If it passes the visual test and any other tests you administer then sign the bill of lading and accept the shipment. Save the test result from your pre-installation test and make it part of the project file. Just be careful now not to damage the cable while you transport it to the job, storing or install the cable!