Hello everyone,
Today, I will continue to write about the PON system overview. Now, I will write about ONU (Optical Network Unit).
ONU is a device located at the customer. Its function is to convert optical signal to electrical signal and vice versa. This device provides services through various interfaces.
There are two typical functions: PON core functions and service functions. The PON core function module is similar to the OLT. Service functions include service multiplexing and demultiplexing functions. It is part of the service stream processing. The next figure shows these functions.
Figure 1. ONU function
There are several different terminal devices - ONU, ONT, MxU, and MDU, but very often they are all called the same ONU. Which term will be used for the ONU device depends on the FTTx scenario.
For FTTH and FTTO, the ONU device provides a small number of Ethernet (usually max 4 ports) and POTS ports (one or two POTS ports), as well as a max 1 RF port. When there are a small number of ports, as is the case here, the ONU device is called an ONT (Optical Network Terminal).
For FTTB and FTTC, ONU devices have double-digit ethernet and xDSL interfaces. In this scenario, ONU devices are called ONUs, MDUs, MTUs, and SBUs. One name MxU (Multi x Unit) can be used for MDU and MTU.
Figure 2. shows FTTx scenarios.
Figure 2. FTTx scenarios
The example for FTTC/B+DSL scenarios is SmartAX MA 5818. Chasis of this device has 4 slots for the service board, one slot for fan module, power board, control board, and vectoring centralized processing board. This device is used for FTTC and FTTB and mini DSLAM/ mini MSAN construction. It can be used for indoor or outdoor applications.
For FTTB+LAN and POL, it is MA/EA 5821. This device provides 8 GE ports and 24 GE ports. There are PoE models.
There are different models ONU for POL: P613E, P812E, P802E, EG8020P, etc.
I will continue to write about this topic in the next article >> PON system overview (6): ONT.
Thank you!
