Huawei EchoLife HG861 Manual page 55

EchoLife HG861 GPON Terminal
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Issue 01 (2009-07-30)
Upstream VLAN: Service 4 K (VLAN ID: 1-4093)
Reserved: 15 VLANs for the system (not be used for all) and the range is configurable (ID:
4079-4093)
Used for AOE/TOP/BTV/Stacking/DBGENT/VoIP/MPLS
Number of user VLANs: 4096 (VLAN ID: 1-4095). The specific number of VLANs is
determined by the ONT.
Q: How is the DBA implemented in the GPON?
A: Dynamic bandwidth allocation (DBA) is a mechanism used to dynamically allocate the
upstream bandwidth of ONTs of the GPON within microseconds or milliseconds. It can
increase the bandwidth usage of PON ports on the OLT in the upstream line in an office in
the GPON, and add more users to a PON port so that users can share services requiring
larger bandwidth, especially the services that have large bandwidth burst.
The DBA is implemented as follows: The embedded DBA module of the OLT continuously
collects DBA reports, performs related calculation, and then issues the calculation results
to ONTs through downstream frames in the form of BWMap. According to the BWMap
information, the ONTs send upstream data in the timeslots allocated to them, and occupy
the upstream bandwidth.
Q: How many T-CONTs are there in an MA5680T and What is the range of T-CONT IDs?
A: The number of T-CONTs and range of T-CONT IDs are as follows:
A: There are 256 T-CONTs in a single PON port. The maximum split ratio of a PON
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port is 1:64 and each ONT has four T-CONTs on average.
The range of T-CONT IDs is from 0 to 7. T-CONT 0 is reserved for OMCI. It must be
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configured with the bandwidth larger than 5 Mbit/s.
Each ONT can be allocated with three T-CONTs on average.
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Alloc_ID: 0-4095 (256*Tcont_ID + Ont_ID).
Q: What is the function of the burst optical/electrical technology used by the GPON optical
port?
A: The burst optical/electrical technology is used to enable or disable the laser of a PON
port at a burst so that optical signals cannot be mutually affected due to slow enabling or
disabling of the laser.
Q: What is the difference between the single-mode optical fiber and multi-mode optical
fiber?
A: The single-mode optical fiber is an optical fiber that can transmit only one optical signal
(with one type of wavelength) at a time. With the inner diameter of smaller than 10
microseconds, the single-mode optical fiber is used for long-distance transmission of
signals at a high speed.
The core of the multi-mode optical fiber has a longer circumference than the core of the
single-mode optical fiber. The multi-mode optical fiber can be used for multi-mode
transmission. It provides multiple transmission channels, which have transmission delay.
The stability of the transmission channels degrades with the transmission distance and the
bandwidth is limited. The multi-mode optical fiber can be used to transmit more than one
optical line, which has different refractive indexes. The diameter of the core of the multi-
mode optical fiber is longer than the wavelength of the light source.
Q: Why must the distance between two ONTs that are the furthest away from and nearest
to the OLT respectively be within 20 km?
A: The GPON protocol processes the upstream traffic in the TDM mode. The duration of
encapsulating a frame is 125 us. During the periodical ranging of ONTs connected to one
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