The ONT is the customer premises equipment of a GPON FTTH network, converting the optical signal carried on the fibre into electrical signals for use by connected equipment, and vice versa. It is monitored and controlled via the optical line termination (OLT), the box sitting on the end of the fibre in the telephone exchange.
Although there have been attempts to standardise this ONT management and control interface (OMCI), the degree of variation has precluded interoperability. The result is that, at present, only Alcatel-Lucent supplied ONTs can be deployed on an Alcatel-Lucent GPON FTTH network, and the same is true for other vendors' products. This lack of interoperability results in reduced competition and smaller markets leading to higher prices.
Alcatel-Lucent says that, by publishing the specification of its OMCI, " Service providers will be able to benefit from a more competitive ONT environment and a huge choice of third-party ONT models working seamlessly with Alcatel-Lucent's flagship GPON product, the 7342 ISAM FTTU."
This, Alcatel-Lucent says, "will translate into faster time-to-market, fewer engineering constraints and a reduced need for interop events [where multiple vendors test their equipment against each others for interoperability]. For ONT vendors, this will mean new business opportunities and less OPEX by having less interoperability events."
According to Dave Geary, president of Alcatel-Lucent's wireline networks activities. "Alcatel-Lucent is taking a bold step by being the first GPON player to share its OMCI specifications with other vendors. Our goal is to encourage the adoption of fiber-to-the-home by breaking down interoperability barriers. Alcatel-Lucent will shortly be publishing its OMCI Version-1, and is even prepared to go a step further - by making its full OMCI available to its partners on a case-by-case basis."
According to a posting on Light Reading in June this year, despite multiple rounds of interoperability testing GPON interoperability had never been fully achieved and lack of OMCI interoperability remained the major stumbling block. "OMCI was one of the last pieces of the GPON standard to fall into place, in 2004. And no one's used it since," Light Reading said.
According to Alcatel-Lucent, GPON interoperability was initiated in 2006 by The Full Service Access Networks (FSAN) group but this group is focusing its efforts on defining interoperability first on the physical layer, then the transmission convergence layer, and finally the most complex, ONT Management Control Interface (OMCI).
"While physical and transmission control layer standards are clear and well defined, the OMCI-related standards have too many optional objects which have hampered interoperability. GPON vendors have a choice of which option to implement, which leads to different mutually-exclusive implementations of the same standard."
Consequently, the ITU-T has standardised best practices in terms of OMCI in an OMCI implementers guide version 1 to address data services and multicast (December, 2008). A version 2 is underway and is expected to be finalised by the end of this month, September 2009.