EPON, GPON, 10G EPON, 10G GPON OLT: How do They Work?

The Basic Concept of OLT

OLT is optical line terminal. The PON network consists of OLT, ODN and ONU. OLT belongs to the service node side of the access network and is connected to the corresponding service node equipment through SNI interface to complete the service access of the access network.

In the PON technology application, OLT equipment is an important local-end device, which achieves the following functions.

1. connect with the front-end ( aggregation layer ) switch with network cable, convert into optical signal, and interconnect with the splitter at the user end with a single fiber.
2. realizing the control, management, ranging and other functions of the ONU of the subscriber side equipment.
3. OLT equipment is the same as ONU equipment, and is also an optical and optical integrated device.

OLT uplink local equipment, if the optical signal is too strong (sometimes because of the short distance optical signal loss is small) need to add attenuator.

OLT downlink ONU, before the two connected to the splitter.

To meet different application scenarios, the OLT works with various types of ONUs to realize FTTC/FTTB, FTTH, FTTO, FTTM, and D-CCAP for a variety of optical access networking applications.

The PON network carries services such as voice, Internet access, IPTV video and data leased lines.

Introduction of OLT Equipment 

In order to facilitate a clearer understanding, we provide examples of manufacturers’ equipment for a detailed explanation.

Huawei MA5680T series

SmartAX MA5680T/MA5683T/MA5608T equipment is a GPON/EPON integrated optical access product launched by Huawei. With ultra-high convergence switching capability, 3.2T backplane capacity, 960G switching capacity, 512K MAC address capacity.

It supports up to 44 channels of 10 GE or 768 GE accesses.

▲SmartAX MA5680T

▲SmartAXMA5683T

▲SmartAX MA5608T

ZTE ZXA10 C300

ZXA10 C300 is a high-capacity, high-density xPON convergence access platform that supports access convergence and management control of full services such as HSI, VoIP, TDM, IPTV, CATV, mobile 2G/3G, WiFi, etc. for next-generation networks, and provides carrier-grade QoS and security and reliability assurance.

Hardware Features

Product Structure

Comparison of ZXA10 C300 and C220 main indexes

Shanghai Bell 7360 ISAM FX

7360 ISAM FX series OLT is the third generation of OLT system with application enabling mechanism, its function is far stronger than the first generation of Internet access platform and the second generation of triple play access platform system, and is the best choice for “triple play” full service access.

The 7360 ISAM FX series OLTs can meet operators’ requirements for multi-service access, multiple FTTx deployment scenarios, and convergence of multiple PON access technologies. 7360 ISAM FX series OLTs can integrate EPON, 10G EPON, GPON, 10G GPON, P2P and VDSL2 accesses (point-to-multipoint, point-to-point, DSL) in the same platform.

The 7360 ISAM FX series is available in three models, depending on capacity:

7360 ISAM FX-16, providing 16 service slots

7360 ISAM FX-8, providing 8 service slots

7360 ISAM FX-4, providing 4 service slots

▲7360 ISAM FX-16

▲7360 ISAM FX-8

Fiberhome AN5516-01

Fiberhome AN5516 series carrier-grade 10G platform PON local equipment, using industry-leading technology, full front-plug board and front-out design, providing high-density xPON port tray, supporting GE/10GE/STM-1/E1 uplink interface, enabling GPON/EPON/10G PON/P2P mixed-plug, continuous evolution, and effective protection of network construction investment. Adopting high-performance chips, green and energy-saving, improving network reliability and reducing operation and maintenance costs.

• High-capacity, high-density carrier-grade multi-10 Gigabit platform. Single frame supports 256 PON ports with 4.384G switching capacity and 14.08T backplane bandwidth.
• Provide 10 Gigabit high-speed uplink boards: 1*10GE+ 4*GE ,2*10GE+ 2*GE, 6*GE (optical and electrical optional).
• Support STM-1/E1 leased line uplink interface, support maximum 16×16GE leased line downlink interface.
• 1:32/64/128 optical split ratio, support ultra-long transmission distance, support CLASS C+ optical module.

The Physical Composition of OLT

OLT usually consists of the following parts:

1. Control board (also called the main control board or super control unit) generally an OLT has a main board and a backup board.
2. DC power supply board (from the negative 48 volts of the switching power supply to the power supply) is also generally 2 boardsof themain and backup.
3. Fan unit (the main equipment cooling and environmental monitoring, etc.)
4. Subrack (or service subrack)
5. Uplink board: GE optical interface board (including buckle board), optical transceiver integration module, generally a board is a 2-way GE port (currently 10GE has been commercialized). The uplink board is connected to BRAS (Broadband Remote Access Server) and other convergence switches through transmission (OTN transmission) or directly connected to BRAS and other equipment and SR equipment, and if there is IPTV service, it also needs to access the corresponding BNG equipment. The transmission distance (without transmission in the middle) of the uplink board can reach 10-40KM depending on the optical module.

6. Downlink board (also called service board or PON board), generally OLT equipment with multi-port PON board (such as a board with 8 PON ports), each port down through the splitter (no more than 1:64) connected to the ONT terminal. Downlink board transmission distance and attenuation have their limitations because of factors such as distance measurement between ONT and OLT. Such as 8-port GPON OLT interface board (with pluggable ClassB + optical module) requires ODN attenuation within -28db, 8-port GPON OLT interface board (with pluggable ClassC + optical module) requires ODN transmission attenuation within -32db. However, taking into account the later maintenance factors and other comprehensive reasons, it is required to control the board of ClassB+ optical modules within -25db and ClassC+ optical modules within -29db in the initial project.

7. According to business needs OLT can also insert (all can be mixed) TDM service board, Ethernet service board, 16-way E1 service board and other boards.
8. When adding a new OLT device, it is important to consider the power consumption at full configuration (estimated at around 1400W) in order to determine the appropriate size of the power cables and circuit breakers required (two sets are needed, one primary and one backup). Based on past experience, a 63A circuit breaker is typically sufficient and multi-stranded copper core wire with a cross-sectional area of 16mm² (flame-retardant) should be used for the power cables. The grounding wire should be a 16mm² yellow-green striped copper core wire.
9. Please ensure that the uplink ports on the OLT are properly allocated to avoid issues during activation, and consider all necessary downlink port allocations. Also, be sure to accurately measure the length of the tail fiber (which is provided by the manufacturer) and take note of the connector types (SC for downstream and LC for upstream) on the patch cords at both ends (the OLT side and the ODF side). Finally, make sure to verify the flange type on the ODF side for the patch cord connectors.

Deployment of OLT application scenarios

In OLT deployment, different access strategies should be selected according to different service types, customer needs (long term goals) and regions, etc.

1. General Internet Group Client Scenario (FTTO)

2. Home Client Scenario(FTTB+LAN)

3. Home Client Scenario (FTTH)

4. WLAN Client Scenario (FTTB+LAN)

5. FTTB rural construction scenario A

6. FTTB rural construction scenario B

OLT Installation Specifications