Fibre patch cables, also known as patch cord or jumper cables, are fibre optic cables that are terminated with connectors on both ends. When the connector types on each end are different, the cable is aptly dubbed a HYBRID CABLE. These hybrid cables can serve to link otherwise incompatible infrastructure in existing fibre systems, such as those found in networks or data centres. They can be used to connect newer racks to legacy hardware, in distribution hubs to branch lines from high density panels to the nodes they serve, or to connect between devices from different manufacturers.

How Can You Accurately Test Performance of Hybrid Cables?
While the hybrid nature of these cables makes them ideal for these types of applications, it does present some challenges when evaluating the performance of the cables, whether during production or prior to installation. Like most other passive components that are added to networks or data centres, hybrid cables typically need to have both sides qualified for insertion loss (IL) and return loss (RL), along with interferometry and visual inspection.

The challenge comes from mating the different connectors of the hybrid cable to the reference cables and detectors used to measure IL and RL, which must be done since each side of the cable must be tested. This can be achieved by having twice as many reference cables and detectors, two of each in the case of a simplex cable.

Tailored Solution for a Challenging Problem
The OP940 IL and RL meter serves as the base for our simplex hybrid cable test system, built with two detectors to accommodate the different connectors. Introducing the OP725 optical switch allows us to use two reference cables by toggling which cable the light travels through.
This configuration provides both ease of use and flexibility. Having multiple reference cables connected at once allows the user to test both sides of the device under test without having to swap cables in and out. This particular example uses LC and SC cables, but testing different connector types is as simple as substituting different reference cables. A similar substitution can be done for the adapters on the detectors. In fact, if the different connectors have the same size ferrule (i.e. FC and SC), the configuration can be simplified to use one detector with a universal adapter.

A Note on Hybrid Mating Adapters:
While hybrid mating adapters can allow different connector types to be mated together, these types of adapters can cause issues for IL testing. LC to SC mating adapters in particular often induce extra loss into the measurements. The difference in ferrule size between the two connector types makes their connection within the hybrid mating adapter unreliable for IL testing. For this reason, the better approach is to use a different reference cable for each type of connector being tested.

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Lambda Photometrics is a leading UK Distributor of Characterisation, Measurement and Analysis solutions with particular expertise in Electronic/Scientific and Analytical Instrumentation, Laser and Light based products, Optics, Electro-optic Testing, Spectroscopy, Machine Vision, Optical Metrology, Fibre Optics and Microscopy.