A vital component of GPON operations is an ONT Management Control Interface, also known as OMCI. This OMCI protocol lets service providers make applications and services that use a Passive Optical Network (PON) that include voice, video, and data. Things like the internet and video services are possible due to the relationship between GPON and the OMCI protocol.

Want to learn more about the details of GPON technology in fiber internet access? Continue reading our overview to find out more about everything related to OMCI, ONU, ONT, and OLT.


Modes of GTC:

The GTC (G-PON Transport Convergence) adopts two modes of data transportation.

  • Asynchronous transfer mode (ATM)
  • G-PON-encapsulation-mode (GEM)

Different service types are supported by different adoption methods. GEM mode can only be supported by encapsulated traffic. GTC, when combine with GEM provide bigger payload and thus it supports managing several protocols like Eth and TDM using low OH (overhead) bytes.

Types of PON Control Messages:

The ITU-PON defines two types of control messages.

  • OMCI: ONU Management Control Interface.
  • PLOAM: Physical Layer OAM.

Introduction to OMCI:

 ONU Management Control Interface commonly known as OMCI is basically a mechanism, used by OLTs to configure, manage & Monitor ONUs. In other words, the OLT controls the ONT using the OMCI. ONT is managed by OLT with the help of OMCI in the following traits:

  • Fault management: due to less OH, the OMCI fault management feature can support limited faults and managed them accordingly, such as failure indication in a live network. Operates like DCN as is of Optical transport network.
  • Configuration management: Data is collected using the configuration management feature and in addition, it supports identifying/controlling and sending data to ONT.
  • Security management: data is encrypted downstream and the admin can even switch on/off this encryption mode.
  • Performance management: Admin can Collect and requests performance data like historical service data & data traffic.

OMCI Main Objectives:

The OMCI protocol helps OLT to do the following tasks on ONTs:

  • Manage the User network interfaces.
  • Creates and deletes connections with ONTs.

The OMCI is an asynchronous protocol as it helps to identify OLT as Master controller and ONT and Salve controller. The OMCI protocol runs over a GEM connection which is created during ONT initialization between the ONT controller and the OLT controller. The same transport mechanism is used by the payload.


OMCI Protocol Bytes are carried over OMCC (ONU Management & Control Channel) which are managed via GEM. In a way OMCC play a pivotal role in communication between ONU & OLT.

Multiple ONTs can be managed by a single OLT using multi- OMCI protocol instances over various OMCC (ONU Management & Control Channel).

OMCI connection setup & registration Process:

Upon initialization, the ONU creates a virtual OMCI T-CONT, an OMCC structure that contains an OMCI queue, a placeholder for an Alloc-ID attribute, and going beyond the definition of an ordinary T-CONT, a placeholder for an OMCI port-ID attribute.

The OLT sends a PLOAM message to ONU during activation which contains/requests the ONU ID.

ONU sets Allocate ID of the T-CONT for carrying OMCI messages. This Allocation ID must always be the same as the ONU ID which is mandatory for establishing OMCC. In case, OLT assigns the default Alloc ID, ONU should acknowledge this message without taking any action. It should not be possible to de-allocate the default Alloc – ID with an assign _ Alloc-ID.

The OLT allocates a GEM port-ID to the ONU for OMCI Protocol after ONU activation completes as described by ITU-UT G.984. This is accomplished by a configure port-ID PLOAM message. The ONU populates the OMCI port-ID attribute of the OMCC structure based on that message and responds back to the OLT with an acknowledgment.

How does ORFA TECH GPON ONU work with the 3rd Party OLT platform by OMCI? 

ORFA TECH GPON ONU is working well with 3rd Party OLT platforms like HUAWEI MA5800 Series, MA5600 Series, ZTE C300, or ZTE C600. Customers can issue the configuration like WAN interface, WIFI, VOIP parameters through OMCI, which will definitely help the Internet services provider to improve the ONU management.