C HAPTER 2. GPON N ETWORK - BASICS .

DASAN NETWORKSGPON TRAINING

CHAPTER 2. GPON NETWORK - BASICS

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


Table of contents


1. Network elements

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)


2. Used wavelengths

Used Wavelengths:- Downstream direction: 1490nm (+/- 10nm)- Upstream direction: 1310nm (+/- 20nm)- OPTIONAL: CATV Overlay (downstream): 1550nm (1550

-1560nm)

GigE

GigE

Optical Line Terminal

n

GigE

IP Router

Video Headend

Soft Switch

Video Headend

RF Overlay

1550 nmIGMP

IPTV


3. GPON – maximum reach

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)

ONU 2 Splitter

ONU N

ONU 1

OLT

Outermost ONU

Nearest ONU

60 km

Logical ReachMaximum distance between OLT and outermost ONU supported by GTC

20 km

Physical ReachTypical maximum distance considering infrastructure losses

a

b

a – b ≤ 20 km20 km

Maximum differential distance

User Side Outdoor Environment Central Office


4. Optical characteristics

ONT (1490/1310nm) VIDEO (1550nm)

Tx Power: +3 ~ +7 dBmReceiver sensivity: -32 dBmReceiver overload: -12 dBm

FIBRAIN SFP GPON C+

Distance is defined by optical budget.

Based on below optical characteristics:

- ONT should receive optical signal (1490nm) from range: -28 ~ -8dBm

ONT

X km

Adapters and splice

ONT

ONT

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”)

Theoretical optical budget calculation (based on datasheets)


5. Theoretical power budget

1:4 1km 1:16

5km

1:32

1:16

12km

250m

250m

100m Fiber Adapter

5.250km x 0,4dB/1km = 2.1dBmSplitter 1:4 = 7.1 dBmSplitter 1:32 = 17 dBm2 splices: 2x 0.05dBm = 0.1dBm7 fiber adapters: 7x0,4dBm = 2.8dBm

Attenuation of grink link : 29.1 dBm

12.25km x 0,4dB/1km = 4.9dBmSplitter 1:4 = 7.1 dBmSplitter 1:16 = 13.7 dBm4 splices: 4x 0.1dBm = 0.4 dBm7 fiber Adapters: 7x0,4dBm = 2.8 dBm

Attenuation of violet link: 28.9dBm

1.100km x 0,4dB/1km = 0.44dBmSplitter 1:4 = 7.1 dBmSplitter 1:16 = 13.7 dBm1 splice: 1x 0.05dBm = 0.05dBm7 fiber adapters: 7x0,4dBm = 2.8dBm

Attenuation of the red link: 24.09

Real (typical) optical budget calculation


6. Real power budget (1)

1:4 1km 1:16

5km

1:32

1:16

12km

250m

250m

12.250km x 0.3dB/1km = 3.7dBmSplitter 1:4 = 6.5 dBmSplitter 1:16 = 13 dBm4 splices : 4x 0.02dBm = 0.08dBm7 fiber adapters: 7x0,3 dBm = 2.1dBm

Attenuation : 25.38dBm

1.100km x 0,35dB/1km = 0.39dBmSplitter 1:4 = 6.5 dBmSplitter 1:16 = 13 dBm1 splice: 1x 0.02dBm = 0.02dBm7 adapters: 7x0,3dBm = 2.1 dBm

Attenuation : 22.01 dBm

5.250km x 0,35 dB/1km = 1.84dBmSplitter 1:4 = 6.5 dBmSplitter 1:32 = 16.5 dBm2 splices: 2x 0.02dBm = 0.04 dBm7 adapters: 7x0,3dBm = 2.1 dBm

Attenuation : 26.98 dBm

Fiber Adapter

ONT should receive optical signal (1490nm) from range: -28 ~ -8dBm


6. Real power budget (2) – Received optical power

1:4 1km 1:16

5km

1:32

1:16

12km

250m

250mAttenuation : 22.01 dBAttenuation : 26.98 dBAttenuation : 25.38dB

Fiber Adapter

ONT should receive optical signal (1490nm) from range: -28 ~ -8dB

SFP GPON C+ is installed.C+ typical output power is +4.5dB

+4.5dBRX Optical power for this ONT is: +4.5 – 22.01 = -17,51dB

RX Optical power for this ONT is: +4.5 – 26.98 = -22,48 dB

RX Optical power for this ONT is: +4.5 – 25.38 = -20,88 dB


7. Power budget for CATV Overlay (1550nm)

Spliter 1:2

1km

Spliter 1:32

8km

Spliter 1:16

250m

100m

DASAN GPON OLT

Example: BKTel Fx-AOT8200:CATV transmitter 1550nm + integrated EDFA

TX 1550nm : +20dB

WDM - Triplexer

1.100km x 0,25dB/1km = 0.275dBTriplexer (WDM) = 0.8dB

Splitter 1:2 = 3.5 dBSplitter 1:32 = 16.5 dB

Splices: 3x 0.02dBm = 0.06 dB6 Adapters: 6x0,3dBm = 1.8 dB

Violet link attenuation for 1550nm: 22.94dB

+20– 22.94=-2.94RX 1550 should be – 2.94dB

ONT should receive optical signal (1550nm) from range: -8 ~ +2dB

8.250km x 0,25dB/1km = 2.06dBTriplexer (WDM) = 0.8dB

Splitter 1:2 = 3.5 dBSplitter 1:16 =13dB

Splices: 6x 0.02dBm = 0.12 dB6 Adapters: 6x0,3dBm = 1.8 dB

Violet link attenuation for 1550nm: 21.28dB

+20– 21.28=-1.28RX 1550 should be – 1.28dB


8. Using typical splitter except WDM Triplexer

Spliter 2:21km

1:16

8km 1:16

250m

100mDASAN GPON OLT

1550nm

1310nm

1310nm

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.

Example: BKTel Fx-AOT8200:CATV transmitter 1550nm + integrated EDFA


9. Reach extenders

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.

1450, 1470, 1490, 15101530, 1550, 1570, 1590 nm

1450, 1470, 1490, 15101530, 1550, 1570, 1590 nm

……

……

Ch A Ch B

Ch 1

Ch 2

Ch 3

Ch 4

Ch 5

Ch 6

Ch 7

Ch 8

Ch 1

Ch 2

Ch 3

Ch 4

Ch 5

Ch 6

Ch 7

Ch 8

DASAN OLT

DASAN ONT

1310 nm1490 nm

1310 nm1490 nm


10. CWDM Overlay

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.


11. How to connect

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

THANK YOU


[email protected]@dasannetworks.eu

mailto:[email protected]

mailto:[email protected]

C HAPTER 2. GPON N ETWORK - BASICS .

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