The dramatic growth in PON deployments has exposed a new problem for telecom operators' field technicians. When the optical fiber goes through a distribution panel or a distribution cabinet, the technician must identify which fiber belongs to which optical port on the OLT to ensure that he or she is testing the right fiber. Among others, incorrect identification may result in service interruptions to customers who are connected to a different fiber port!!!
A typical fiber distribution panel or cabinet has hundreds or even thousands of connections and looks something like this:
So how can you tell which fiber is which?
The majority of the service providers have procedures in place to label fibers and by this allow their identification, but as time goes by labels tend to fall off and the writing on them tends to fade. Furthermore, this labeling is typically done manually and is thus subject to human errors.
In the days of telephone services that were delivered over copper this problem was addressed with the Caller ID function, which the technician could use while connecting a phone to the copper line to make sure it's the correct one. But with fiber this is no longer possible, and this brought up the need for a new solution enabling fiber identification in a similar way.
The standardization bodies have taken the challenge and addressed this in the standards for the new PON technologies – starting from XG-PON1 and continuing in NG-PON2 and later on also in XGS-PON. The solution that was defined is the PON-ID – a unique identifier for every PON port, which is included in the frames sent by the OLT.
A similar idea was applied later on in the legacy GPON technology as an amendment to the standard, but for the sake of backwards compatibility its implementation was different – it was based on a periodic message which is sent by the OLT, rather than sending the PON-ID as part of every frame. The PON-ID message in GPON is also used to distribute additional information about the PON port, such as the class of its optical transmission and its optical power level.
Many service providers have realized the benefits of PON-ID, but implementing this solution in live GPON deployments is still in its infancy phase. Even though some vendors already support PON-ID in their GPON equipment, there are many others who don't, and once the vendor does support it upgrading the equipment in the field is a long process. Bottom line, today it is not available yet in the majority of GPON deployments and it will very likely remain this way for a long time.
Once PON-ID becomes available, unique optical test equipment is needed to extract this information from the fiber and display it to the user. Some of the test equipment in the market that display the PON-ID actually rely on it for presenting additional information, such as the optical power levels, and are thus limited for use in selected deployments only.
In our GPON Tracer we took a different approach – when PON-ID exists the GPON Tracer presents its related information, but in addition it presents true measurements and indications which are independent on the PON-ID. This allows it to be used in all GPON deployments today while being future-ready to benefit from PON-ID once it becomes available.