• Fundamental tool for GPON network deployment and maintenance.
• Diagnosis and Analysis of events and deviations for already deployed GPON networks.
• Interoperability troubleshooting among different vendors equipment coexisting in a Telco access network.
• Triple play services assurance by user traffic Quality of Experience monitoring
• Broadband Forum ONUs conformance testing.
• GPON Auditing and Optimization.
• Real time supervision of the Network state and all its active elements (ONTs).

With the aim of widening ONTs offer, it is important that any OLT interoperates with all available ONUs in the market. However, GPON has a number of intrinsic characteristics that is currently making difficult to achieve the desired level of the interoperability:

• Coexistence of products with different standard versions.
• Problems during the activation process.
• Different ways of implementing the standards.
• OMCI, a very broad and with “vendor specific” options.
• Heterogeneity among operators.

Furthermore, the structure of a PON network is a fibre that is further divided using optical power splitters. The “degree of splitting”, defined as the number of divisions that the fibre goes through before reaching an ONT, determines the percentage of optical power arriving to that ONT. Attenuation in a GPON circuit can be very high due to the sum of fibre splitting, connectorization (Insertion loss), fusion splice, and distance in the fibre, and thus, some of the network active elements may be operating under stress conditions.

In order to reach the optimum performance state of a GPON network , during the deployment and maintenance, all causes of interference need to be debugged by tools like GPONDoctor 2000.

Once a Network is deployed, it is required that the usage of a test tool does not impact in its behaviour. Therefore, GPON-Doctor™ 2000 transparently sniffs traffic within a FTTH network. Moreover, its automatic calibration and stand alone configuration enables full capture of GPON network traffic without disturbing the communication between the OLT and ONTs.

The capture can be very long (e.g. 30 minutes) and allows captured data export to XML format for later analysis in desktop computers.

The smart analysis software interprets the captured data and translates it into a graphical and categorized format that can be easilyused for in-depth analysis of GPON protocol conformance, interoperability evaluation, bandwidth assignments and field deployment troubleshooting.

The results from the GPON Doctor™ analysis show:

• 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 conformance, by applying an evaluation smart engine, based on contextualized dynamic rules, against the ITU-T G.984.x protocol .

GPON-Doctor™ 2000 allows clear-text user traffic extraction in real-time for both upstream and downstream. The traffic is extracted at Ethernet layer.

This traffic can be further analysed by upper layer protocol analyzers, either external or by a software network protocol analyzer installed within the host PC/Laptop.

The combination of the GPON Doctor™ 2000 with a traffic generator and GPON OLT emulator, like GPON-Doctor™ OLT-e, is a powerful setup to verify the correct ONTs behaviour over a GPON network.

This feature can be also used to regenerate services inside GPON Doctor™: Play Multicast Video flows, hear sound of voice services in realtime, analyze QoS & QoE.

• 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.