Fiber Optic Cable Test

To ensure proper performance when used in an optical transmission system, passive fiber-optic cable assemblies, patchcords, connectors and components are usually tested to verify their levels of insertion loss and reflection.

 Although these tests are relatively basic, they can become cumbersome when performed in high volumes as required in a manufacturing environment. This is where fast and accurate measurement solutions allowing automation can make a substantial difference.

The Production Floor - Where Performance Matters

In a manufacturing environment, the production throughput is critical in order to control the cost of the finished goods. Often times, final-product testing can be a source of inefficiency as it remains a very manual process. Simplifying or even automating these steps would save considerable time and money ─ turnkey systems, such as the EXFO IQS-12001B Cable Assembly Test System, do just that.

Test Solutions for Connector, Cable Assembly, Patchcord, Splitter and Coupler Manufacturing

Almost every singlemode patchcord used throughout the telecommunication network is tested for insertion loss and reflectance. Multimode assemblies (patchcords, pigtails and connectors) have always been tested to verify the insertion loss but, over the past few years, reflectance measurements have been gaining popularity mostly due to the Gigabit Ethernet applications and the use of VCSEL transmitters.

EXFO's IQS-12001B Cable Assembly Test System maximizes production throughput for insertion loss (IL) and mandrel-free reflection testing for all types of fiber-optic interconnect cables and for component assemblies such as planar arrays and PLC splitters used in FTTx systems.

Multimode Launch conditions and Encircled Flux

A multimode light source with controlled launch conditions ensures accuracy, reproducibility and consistent loss readings. The type of light source used for multimode fiber-link certification and the way it is coupled to the fiber greatly affects the launch conditions.

Generally, surface-emitting LED sources overfill the fiber, while edge-emitting light sources (EELS), including LED and laser sources, have a smaller spot size, numerical aperture and emission, which means they significantly underfill the fiber. Vertical-cavity surface-emitting lasers (VCSELs) are similar to laser light sources and also underfill the fiber.

Usually, certifying fiber links using a light source that underfills the fiber when testing multimode-fiber link attenuation could produce misleading and overly optimistic test results. Also, some types of connector problems could remain undetected; for example, a connector ferrule could be slightly misaligned.

On the other hand, using a light source that overfills fiber when testing attenuation of multimode links may produce unrepeatable and unreliable loss readings. Chances are that the loss reading obtained will be over-estimated, leading to loss values that will not correspond to reality due to the significant transient loss effect.

The latest multimode launch condition proposal is known as Encircled Flux (IEC 61280-4-1) and improves upon previous standards. This standard proposes a filled condition with upper and lower limits, which is optimal to get consistent, realistic and repeatable loss readings.

If you have ever measured the loss of a multimode fiber with a light source from different manufacturers and gotten different loss readings, this is for you. If you have ever measured the loss of multimode fiber links with a light source and power meter and then measured loss with an OTDR and gotten different loss readings, then this for you. The Encircled Flux proposal tries to establish a universal launch condition, which all manufactures will hopefully adhere to. This will impose a uniform multimode launch-condition standard. Regardless of which manufacturer you purchased your light source from, as long as the light source is Encircled Flux compliant and Encircled Flux-compliant reference grade jumpers (reference jumper connected to source can affect the launch conditions) are used, the loss measurements will be about the same (within 0.6 dB or ± 10%). The same applies to OTDRs. If the OTDR and reference jumper are Encircled Flux-compliant and the light source, and reference jumpers used with the power meter are Encircled Flux-compliant, the loss reads between the instruments will also be the same (within 0.6 dB or ± 10%).