FTTx/PON Service Activation and Troubleshooting
When the network is activated and full-fledged operation begins, it is critical to conduct thorough test procedures, as it is at this stage that quality of service must be tested and monitored in order to meet service-level agreements (SLAs) with subscribers.
Service Activation
During the service-activation phase, a technician will go to the
customer premises and perform the following tasks:
- Install the ONT
- Install the drop cable
- Measure all optical levels
- Power up the ONT
Up to three optical signals can simultaneously travel along a PON link at different wavelengths. Network operators need a simple means of detecting these signals, measuring them and verifying that they are within acceptable power ranges, according to the type of network and equipment used.
Figure 1: Testing signal level quality with a PON power meter at the customer premises
The PON power meter can measure the power of simultaneous wavelengths when conducting PON service-activation tests at customer premises. This instrument features a patented pass-through design allowing technicians to obtain a power measurement of the upstream burst signals emitted by optical network terminals at 1310 nm and the downstream signals at 1490 and 1550 nm.
Link Troubleshooting
When a problem is diagnosed (e.g., low signal or no signal), troubleshooting must be performed to locate the source of signal disruption. A PON power meter, combined with an OTDR optimized for live testing, are the tools of choice for such applications.
More on Optical Power Measurements
Using a PON power meter will provide the user with a power level reading for each individual wavelength. Depending on the optical levels measured, the user will know which service can be affected. By measuring the optical levels at different locations, the defective section may be identified.
Figure 2: PPM-350B PON power meters graphical user interface (from PON powermeter spec sheet:
More on Live PON Testing with the OTDR)
An OTDR optimized
for access networks is specifically designed for in-service PON
troubleshooting. It features an optional dedicated port (for testing at 1625
nm) incorporating a filter that rejects all unwanted signals (1310, 1490 and
1550 nm) that could contaminate the OTDR measurement. The filter only lets
through the 1625 nm OTDR signal, ensuring accurate OTDR measurements.
In-service OTDR troubleshooting of optical fiber does not interfere with the
normal operation and expected performance of the information channels. For
example, the AXS-100 Access OTDR
does not
interfere with the COs laser transmitters, as it uses an out-of-band wavelength,
as per the ITU-T L.41 recommendation, entitled Maintenance Wavelength on Fibers
Carrying Signals.
Fig 3.:
Testing live PONs with an access OTDR
Service Activation and Commissioning
When turning up services in the PON, thorough performance assessment, detailed frame analysis and accurate bit-error-rate testing provide the baseline to define and maintain competitive, customer-retaining service-level agreements (SLAs).
The industry has developed test methodologies to address Ethernet
performance verification at Layer 2 and Layer 3 in EPON. The RFC 2544 from
the Internet Engineering Task Force (IETF) specifies the procedures for
testing the following characteristics:
- Performance availability (throughput)
- Transmission delays (latency)
- Link burstability (back-to-back frames)
- Service integrity (frame loss)
Tests like these are usually conducted at the end of the
installation phase, and they can be performed
with Ethernet testers and similar instruments.
For more information on Ethernet applications and related
testing, please visit the
Ethernet application page.