1. DASAN NETWORKS GPON Training
Chapter 2. GPON Network - basics

2. Table of contents www.dasannetworks.eu
1. Network elements 2. Used wavelengths 3. GPON – maximum reach 4. Optical characteristics 5. Theoretical power budget 6. Real power budget 7. Power budget for CATV Overlay (1550nm) 8. Using typical splitter except WDM Triplexer 9. Reach extenders 10. CWDM Overlay 11. How to connect

3. 1. Network elements www.dasannetworks.eu
GPON network active devices/elements:
GPON OLT (central device)
GPON ONT (end customer device)
GPON SFP C+
GPON passive elements:
Optical splitters
(e.g. symmetric 1:2,1:4,1:8, 1:16,
1:32,1:64)
Maximum optical split on one GPON PORT is 1:128 – so to one GPON port You can connect up to 128 ONTs (depends on power budget – see more on next part)

4. 2. Used wavelengths www.dasannetworks.eu IPTV RF Overlay
Downstream direction: nm (+/- 10nm)
Upstream direction: nm (+/- 20nm)
OPTIONAL: CATV Overlay (downstream): 1550nm ( nm)
RF Overlay
Video Headend
Optical Line Terminal
IGMP
GigE
1550 nm
Soft Switch n
GigE
IP Router
IPTV
GigE
Video Headend

5. 3. GPON – maximum reach www.dasannetworks.eu a b User Side
Limitation: maximum distance between „Nearest ONT” and „Outermost ONT” is 20km.
By DEFAULT – DASAN OLT is discovering ONTs on distance 0~20km (we can change this on OLT)
User Side
Outdoor Environment
Central Office
Outermost ONU
ONU 1 a b
a – b ≤ 20 km
20 km
Maximum differential
distance
60 km
Logical Reach
Maximum distance between OLT
and outermost ONU supported by GTC
OLT
ONU 2
Splitter
ONU N
Nearest ONU
20 km
Physical Reach
Typical maximum distance considering infrastructure losses

6. 4. Optical characteristics
Distance is defined by optical budget.
Based on below optical characteristics:
- ONT should receive optical signal (1490nm) from range: -28 ~ -8dBm
FIBRAIN SFP GPON C+
ONT (1490/1310nm)
VIDEO (1550nm)
Tx Power: +3 ~ +7 dBm
Receiver sensivity: -32 dBm
Receiver overload: -12 dBm
ONT
X km
Adapters and splice
O NT
Elements which decreases the optical signal:
Optical splitters:
1:2 – 3.7dBm
1:4 – 7.1dBm
1:8 – 10.5dBm
1:16 – 13.7dBm
1:32 – 17dBm
1:64 – 20.5dBm
1:128 ~ 23.5dBm
Adapters – 0.3dBm
Splices – 0.02dBm
Distance – 0,4dB for 1 km‏ (0.33dB for 1km 1310nm „Corning”)

7. 5. Theoretical power budget
Theoretical optical budget calculation (based on datasheets)
Fiber Adapter
1km
1:16
100m
1:4
5km
1:32
250m
12.25km x 0,4dB/1km = 4.9dBm
Splitter 1:4 = 7.1 dBm
Splitter 1:16 = 13.7 dBm
4 splices: 4x 0.1dBm = 0.4 dBm
7 fiber Adapters: 7x0,4dBm = 2.8 dBm
Attenuation of violet link: 28.9dBm
12km
1:16
250m
1.100km x 0,4dB/1km = 0.44dBm
Splitter 1:4 = 7.1 dBm
Splitter 1:16 = 13.7 dBm
1 splice: 1x 0.05dBm = 0.05dBm
7 fiber adapters: 7x0,4dBm = 2.8dBm
Attenuation of the red link: 24.09
5.250km x 0,4dB/1km = 2.1dBm
Splitter 1:4 = 7.1 dBm
Splitter 1:32 = 17 dBm
2 splices: 2x 0.05dBm = 0.1dBm
7 fiber adapters: 7x0,4dBm = 2.8dBm
Attenuation of grink link : dBm

8. 6. Real power budget (1) www.dasannetworks.eu
Real (typical) optical budget calculation
Fiber Adapter
1km
1:16
1:4
5km
1:32
250m
12.250km x 0.3dB/1km = 3.7dBm
Splitter 1:4 = 6.5 dBm
Splitter 1:16 = 13 dBm
4 splices : 4x 0.02dBm = 0.08dBm
7 fiber adapters: 7x0,3 dBm = 2.1dBm
Attenuation : 25.38dBm
12km
1:16
250m
1.100km x 0,35dB/1km = 0.39dBm
Splitter 1:4 = 6.5 dBm
Splitter 1:16 = 13 dBm
1 splice: 1x 0.02dBm = 0.02dBm
7 adapters: 7x0,3dBm = 2.1 dBm
Attenuation : dBm
5.250km x 0,35 dB/1km = 1.84dBm
Splitter 1:4 = 6.5 dBm
Splitter 1:32 = 16.5 dBm
2 splices: 2x 0.02dBm = 0.04 dBm
7 adapters: 7x0,3dBm = 2.1 dBm
Attenuation : dBm
ONT should receive optical signal (1490nm) from range: -28 ~ -8dBm

9. 6. Real power budget (2) – Received optical power
Fiber Adapter
1km
1:16
1:4
RX Optical power for this ONT is:
+4.5 – = -17,51dB
+4.5dB
5km
1:32
250m
RX Optical power for this ONT is:
+4.5 – = -22,48 dB
SFP GPON C+ is installed.
C+ typical output power is +4.5dB
12km
1:16
250m
Attenuation : dB
Attenuation : dB
Attenuation : 25.38dB
RX Optical power for this ONT is:
+4.5 – = -20,88 dB
ONT should receive optical signal (1490nm) from range: -28 ~ -8dB

10. 7. Power budget for CATV Overlay (1550nm)
+20– 22.94=-2.94
RX 1550 should be – 2.94dB
DASAN GPON OLT
Spliter 1:32
100m
1km
Spliter 1:2
Spliter 1:16
8km
WDM - Triplexer
250m
+20– 21.28=-1.28
RX 1550 should be – 1.28dB
Example: BKTel Fx-AOT8200:
CATV transmitter 1550nm
+ integrated EDFA
TX 1550nm : +20dB
8.250km x 0,25dB/1km = 2.06dB
Triplexer (WDM) = 0.8dB
Splitter 1:2 = 3.5 dB
Splitter 1:16 =13dB
Splices: 6x 0.02dBm = 0.12 dB
6 Adapters: 6x0,3dBm = 1.8 dB
Violet link attenuation for 1550nm: 21.28dB
1.100km x 0,25dB/1km = 0.275dB
Triplexer (WDM) = 0.8dB
Splitter 1:2 = 3.5 dB
Splitter 1:32 = 16.5 dB
Splices: 3x 0.02dBm = 0.06 dB
6 Adapters: 6x0,3dBm = 1.8 dB
Violet link attenuation for 1550nm: 22.94dB
ONT should receive optical signal (1550nm) from range: -8 ~ +2dB

11. 8. Using typical splitter except WDM Triplexer
DASAN GPON OLT
Spliter 2:2
1:16
100m
1km
1310nm
8km
1:16
1310nm
250m
1550nm
Example: BKTel Fx-AOT8200:
CATV transmitter 1550nm
+ integrated EDFA
No WDM is needed as 2x2 splitter can inject 1550nm into fiber in this scenario. We can save on that 1dB.
Disadvantages is that 1310nm is coming to EDFA but this does not make a trouble if proper EDFA is installed.
2xN spliter are also installed when GPON Protection is necessary.

12. 9. Reach extenders …… …… DASAN OLT 1310 nm 1490 nm 1310 nm 1490 nm
GPON allow to install O/E/O converter to amplify signal from the OLT and from ONT to the OLT. Reach Extenders can increase the split ratio or optical budget but require electricity in the field. RE are working in L1 (ISO/OSI) only.
GPON combiners:
Up to 8 GPON lines can be care by 1 fiber via CWDM technology and 2 active combiners. ……
Ch 1
Ch 1
Ch 2
1450, 1470, 1490, , 1550, 1570, 1590 nm
Ch 2
Ch 3
Ch 3
Ch 4
Ch 4
Ch A
Ch B
Ch 5
Ch 5
1450, 1470, 1490, , 1550, 1570, 1590 nm
DASAN ONT
Ch 6
Ch 6
Ch 7
Ch 7
Ch 8
Ch 8 ……
DASAN OLT
1310 nm
1490 nm
1310 nm
1490 nm

13. 10. CWDM Overlay www.dasannetworks.eu
In existing GPON network we can use also other wavelengths on the same optical link - wavelengths which are not affecting GPON/CATV Overlay communication. Thanks that we can connect some business clients.

14. 11. How to connect www.dasannetworks.eu Connectors:
- GPON SFP: SC/PC (blue connector)
- ONTs: SC/APC (green connector)
What will happened when ONT will not receive correct optical signal:
ONT may be NOT discovered on OLT
ONT may be discovered on OLT, but will activate/deactivate all the time
Problems with transmissions can be present (BER – Bit Error Rate) – will be visible on OLT syslog
Please do not connect ONT directly to the GPON PORT (without proper attenuation added) because You can then damage ONT receiver.
By default OLT is not discovering ONTs – You must enable it on OLT.
GPON port diode will shine only when at least one ACTIVE ONT is discovered

15. Thank You info@dasannetworks.eu support@dasannetworks.eu