ITU-T SERIES G SUPP 49 PDF

A passive optical network has a shared medium in the upstream direction, and the passive optical distribution network (ODN) combines all ONU outputs towards the optical line terminal (OLT). Therefore, an ONU that is not transmitting in a manner consistent with parameters specified in the standard can threaten all upstream transmissions on the passive optical network (PON), causing interference and disrupting communications of other ONUs on the PON. An ONU that has been designed, produced and deployed with an intent to be compliant with the standards, but as a result of a design flaw, a manufacturing error, hardware or software failure, environmental or other external impact, transmits optical power up the PON to the OLT in violation of the parameters of the standard is called a "rogue ONU".

This kind of rogue behaviour is not unique to PON systems, but may exist in any communication system that uses the same shared channel scheme, leading to the situations where a single rogue device may impact other devices or disrupt the operation of the entire system. Diagnosing and isolating the offending device can be difficult since the affected devices are not always the ones causing the disruption. In the context of PON systems, this Supplement raises awareness of rogue ONU behaviour, and provides system designers and implementers with techniques and tools to facilitate the prevention, detection, isolation and removal of the offending ONU to avert or minimize service interruptions to other ONUs on the PON.

This treatment distinguishes a rogue ONU from a unit that intentionally or maliciously transmits optical signals that are not in accordance with the standard. In the strictest sense, these devices or intentional jammers are not ONUs, since they do not follow the ITU-T Recommendations that describe ONUs. They are essentially illegal devices that intend to deny or steal service from the network. However, these devices may exhibit behaviour and use processes that are similar to rogue ONUs and, therefore, the techniques considered in this Supplement may facilitate their detection.

The remainder of this Supplement is structured as follows.

Clause 2 lists the acronyms and abbreviations used herein.

Clause 3 discusses potential causes of the rogue ONU behaviour and describes general rogue behaviour prevention techniques.

Clause 4 presents possible techniques for rogue ONU detection.

Clause 5 presents possible techniques for rogue ONU isolation and mitigation.

Clause 6 discusses the best operational practices and strategies in dealing with rogue ONUs and actual PON deployments.

In comparison with the original release of this Supplement (02/2011), the present release addresses:

– Spectral aspects of rogue ONU behaviour;

– Leveraging multi-wavelength capabilities of TWDM PON system for rogue ONU isolation and mitigation;

– Advances in rogue interference detection;

– Advances in rogue ONU isolation;

– Best operational practices in application of rogue ONU detection, isolation and mitigation techniques.