CAPEX can be greatly diminished by introducing ONUs from different manufacturers. This requires that any OLT is capable to interact with any ONT regardless of its manufacturer. Intrinsic characteristics of GPON networks need to be addressed to ease the interoperability among manufacturers:

• Commercial implementations from different versions of the standard.
• Problems during the activation process. ONUs identified from a manufacturer different from the OLT not accepted.
• Misinterpretation of the standard.
• OMCI, a very broad standard. Especially concerning “Vendor Specific entities”.
• Heterogeneity among operators regarding “IP Services” provisioning.

Furthermore, the structure of a PON network is a fiber that is split over using optical power dividers or splitters. The degree of splitting indicates that the percentage of optical power arriving at an ONT. Attenuation is key to be kept under control to avoid that some of the network active elements operate under stress conditions.

All these factors imply a great challenge in the deployment of GPON networks.

GPON-Doctor™ 4500 analyzes traffic within an FTTH network according to the ITU-T standards. Moreover, its automatic calibration and built-in touch screen into a high-performance chassis make it possible to get a full capture and analysis of GPON network traffic in just one-click.

GPONDoctor™ 4500 has several captures modes, from a “Full capture” to get all control and management traffic for in-depth troubleshooting to “Real-Time” that allows captures over long time periods to identify deviations from expected behavior. The information captured can also be shared with other experts that can analyze it in their own computers using the  GPONDoctor™ software.

The analysis software interprets the captured information and translates it into a graphical and categorized format that can be easily used for in-depth analysis of XGS/GPON protocol compliance, interoperability evaluation, bandwidth assignments, and field deployment troubleshooting.

• GPON network topology: ONTs detected, ONTs and OLT operational status, data channels established,
• Entities created and the relationship among them,
• Bandwidth assignment graphics per ONT and TCONT,
• Degree of standard compliance, by applying an evaluation system for the ITU-T G.984.x, G.988, (ITU-T G.987.2 and G.989.3 with XGS upgrade) protocol based on contextualized dynamic rules.

GPON-Doctor™ 4500 allows clear-text user traffic extraction in real-time for both upstream and downstream. The traffic is extracted at the Ethernet layer.

This traffic can be further analyzed by upper-layer protocol analyzers, either external or by a software network protocol analyzer installed within the GPONDoctor™.

The combination of the GPONDoctor with a traffic generator and, an external or internal analyzer that incorporates GPONDoctor 4500, is a powerful setup to validate the correct transmission of “IP services” over the network.

This feature can be also used to regenerate IP services inside GPONDoctor™: IPTV channels, VoD flows, reproduce voice stream in realtime so as to analyze their QoS & QoE and identify “Services” degradations.

• GPON Doctor displays this message in the capture window when it expects an upstream burst according to downstream BWMaps (SSTART and SSTOP) and no optical signal is detected in the upstream direction. Please note that uLOSb and uLOFb are not messages exchanged by OLT and ONUs, but an indication generated by the GPON Doctor itself.
• The most common reason for this indication is that the addressed ONU is not connected in the same branch as the GPON Doctor. Other reasons for these notification is that the ONU is not working properly (it is not generating transmissions when indicated by the OLT) or that there are power issues.
• When GPON Doctor includes uLOSb indications in the capture window these are also reflected in the Errors Report as LOSB notifications. When 4 or more of these notifications happen consecutively for the same ONU this will be reported as an “ONU enters in LOSi” Warning.

• Once transmission errors are discarded (both OLT and ONUs are operating “correctly”) and many CRC errors are still reported by GPON Doctor, the most common reason for these indications is that GPON Doctor is not working in the optimal optical operation range. Either the optical power is under the sensitivity limit or over the saturation point. Please, check the optical power before the capture to ensure GPON Doctor receives adequate optical power.
• Furthermore, some power meters obtain the average measure. In downstream, the value is reliable because the OLT sends a continuous optical signal, but in the upstream, the traffic is based on bursts. Therefore, the optical meters can provide a wrong or tricky measure.

• GPON Doctor displays this message in the capture window when it expects an upstream burst according to downstream BWMaps (SSTART and SSTOP) and although a valid optical signal is received, the delimiter cannot be found. Please note that uLOSb and uLOFb are not messages exchanged by OLT and ONUs, but an indication generated by the GPON Doctor itself.
• Possible reasons for this indication are that the ONU is not working properly (it is not generating transmissions when indicated by the OLT) or that there are power issues.
• When GPON Doctor includes uLOFb indications in the capture window these are also reflected in the Errors Report as LOFB notifications. When 4 or more of these notifications happen consecutively for the same ONU this will be reported as an “ONU enters in LOFi” Warning.

You can optimize GPON Doctor’s processing time by choosing the right capture configuration settings, the appropriate capture method and the right settings for the analysis tool:

The amount of information that can be captured is limited by the memory available in the system. To run a capture for a long time you can limit what type of messages you want to capture. Also select either a Real Time capture or a Store and Display capture (not Full).

This alarm is generated by the OLT when it receives an ONU transmission between 4 and 8 bits before or after the expected arrival time. Currently, GPON Doctor is not able to detect this condition with the required precision. On the other hand, GPON Doctor OLT Emulator generates DOWi alarm according to the Standard.