As optical networks have started to spread from their use in trunk networks into the latest technologies such as FTTx and G-PON, new requirements for testing have evolved.

The major change in the requirement is new systems such a GPON use splitters that allow one fibre from the switch to be shared with many end customers. This creates a point to multi point situation that conventional testing cannot cope with.

Traditionally, Optical Time Domain Reflectometers (OTDRs) have been used for Point to Point testing between nodes and exchanges, but with the rollout of FTTx networks new methods of testing have had to be implemented. Various implementations of FTTC, FTTB and FTTH are currently being installed worldwide and verification and restoration of the network has become an issue.

In point to multi point scenario tests must be performed through the splitters which most equipment was not designed to do. As an added complication a fault in one fibre can affect multiple customers depending upon where the fault has occurred. Compounding the problem is that the faulty fibre may be carrying a mix of services some of which may be vital services such as connections to medical or banking facilities. It is thus imperative to be able to diagnose faults quickly, accurately and be able to despatch the right repair team to deal with the fault.

When the customer reports a problem it is usual practice to dispatch an OTDR-equipped engineer to the premises, where they will test the fibre back to the exchange with a view to finding any fault conditions. It is not unusual for the engineer to find there is no problem with the fibre but that the problem is with the subscriber's equipment. Truck rolls and wasted manpower results in an increase in OpEx.

A new method of testing has evolved to take into account the problems caused by the use of splitters in a G-PON network when testing from the Central Office (CO). UTEL have designed a fibre test system made up of two components, a CO based OTDR and an Optical Test Access Switch.

PON to MDU

Optical fibre lines can be tested prior to dispatching an engineer. If no fault is detected on the fibre the subscriber can be informed that the problem is with their equipment and that an engineer could attend to rectify the problem for a fee. This not only reduces OpEx but introduces a new revenue stream for the Communication Provider.

Because both the Optical Switch and OTDR are based in the Central Office, control of the equipment can be performed by the Communication Providers own OSS or UTEL's bespoke test management software. When a fault is reported the Operations Centre would connect to the Optical Switch and select the appropriate fibre which is then automatically connected to the OTDR. Tests would then be initiated and the results automatically returned to the Operator.

Various levels of presentation are available to the operator performing the test action. At a deskilled operator level it can be a simple "traffic lights" indicator or for a skilled engineer it can present detailed OTDR traces.

FTTC Monitoring and Management >>

FTTB Overview >>