Hello!
ODN (Optical Distribution Network) optical distribution network. It is an FTTH optical cable network based on PON equipment, and its role is to provide an optical transmission channel between the OLT and the ONU. From the functional point of view, the ODN can be divided into two points and three sections from the central office to the user end, which are optical distribution points, user access points, feeder cables, distribution cables, and household cables.
The PON optical module needs to have specifications for transmitting optical power, receiving optical power, and receiving sensitivity. Exceeding the range will cause the ONT to fail to go online. The ODN link budget and optical power loss calculation need to be planned in advance.
ITU G.984.2 class B+/C+ standard
Types of | Class B+ | Class C+ |
Maximum optical link loss | 28 dB | 31 dB |
Minimum optical link loss | 13 dB | 11 dB |
Minimum average transmit power | 1.5 dBm | 3 dBm |
Maximum average transmit power | 5 dBm | 7 dBm |
Receiving sensitivity | -28 dBm | -30 dBm |
Examples of optical power links:
For example, the situation of a certain ODN is as follows:
Link attenuation = L x a + n1 x b + n2 x c + n3 x d + n4 x e + f + g (dB)
L x a: Link attenuation (a: fiber optic cable attenuation per kilometer,
L: fiber optic cable length-mountain = L1+L2+L3)
n1 x b: Splice loss (b: Splice loss, n1: splices number)
n2 x c: cold connector attenuation (c: cold connector attenuation, n2: cold connectors number)
n3 x d: active connector loss (d: active connector loss, n3: active connectors number)
n4 x e: fast connector attenuation (e: fast connector attenuation, n4: fast connector number)
f: optical splitter attenuation
g: redundancy
Distance ≤5 km, redundancy = 1 dB
Distance ≈5 km, redundancy = 2 dB
Distance ≥5 km, redundancy = 3 dB
Optical power loss in ODN
Optical power loss in ODN | ||||
Serial number | Name | Types of | Attenuation (dB) | Quantity |
1 | Optical cable (G.652D) | 1310 nm optical cable (dB/km) | 0.35 | 4.5 |
1490 nm optical cable (dB/km) | 0.23 | |||
Hot melt | 0.1 | 7 | ||
2 | Junction | active connection | 0.3 | 6 |
quick connection | 0.5 | 1 | ||
cold connection | 0.2 | 0 | ||
3 | 1:64 | 20.5 | 1 | |
4 | 1:32 | 17 | 0 | |
5 | Optical splitter | 1:16 | 13.8 | 0 |
6 | 1:8 | 10.6 | 0 | |
7 | 1:4 | 7.5 | 0 | |
8 | 1:2 | 3.8 | 0 | |
9 | Redundancy | Redundancy attenuation | 1 | 1 |
Substitute the aforementioned link loss calculation formula:
Loss = 4.5*0.35+7*0.1+6*0.3+1*0.5+1*20.5+1
= 25.075 dB
Received optical power = minimum average transmit power-link attenuation
=1.5-25.075
=—23.575 within the receiving sensitivity range
Link attenuation meets ITU G.984.2 class B+ standard
That's all for today, you are welcome to leave a message and exchange in the comment area.
Thank you!
