One of the challenges of the market of high-speed access is the price per subscriber. The economic advantages of PON type deployment have presented, but we must bear in mind another point: The cost of the ONT or terminal client.

With the aim of reducing the price of the ONT, it is important that any OLT is able to interact with any ONT regardless of manufacturer. However, GPON has a number of characteristics that may make the interoperability of manufacturers difficult for any of the following reasons:

· Commercial implementations from earlier versions of the standard: Although it is now in a very mature state, there is still no final version of the standard. This has led to “early adopters” manufacturers to have implemented versions of the standard that may differ greatly from the current one. 

· Temporal complexity of the negotiation process: The processes of detection and ranging are very sensitive. A delay or advancement of microseconds can cause both equipment not to trade. 

· Misinterpretation of the standard: GPON standard is complex and has undergone major changes. It is easy for different manufacturers to interpret the standard differently causing problems in negotiations. 

· OMCI, a very broad standard: OMC management layer is designed to remotely configure all the functionality of an ONT. In addition, the standard defines a very broad set of OMCI entities that can be combined in various ways to establish the same services. Two manufacturers may be able to offer the same services but using different GPON OMCI entities. 

· Heterogeneity among operators: Each carrier deploying a GPON solution selects a subset of OMCI to deploy their services; this means GPON custom hardware implementations of the specific OMCI layer for each operator.

As can be inferred, interoperability is an important requirement in any GPON network. When problems of interoperability appear, identification of the causes is a difficult diagnostic challenge that usually requires a source of information and analysis beyond the GPON hardware manufacturers affected.