Optical access network OAN; focuses on solving the effective access of narrowband services such as telephones, and also solves the problem of adjusting data services, multimedia images and other broadband access services; OAN generally refers to the feeder section, wiring section and lead-in line between the switch and the user. A system that is partly or entirely connected by fiber optics

Reference configuration: G.902 with UNI SNI Q3

Optical fiber access network consists of: central office optical line terminal OLT user-side optical network unit ONU optical distribution network ODN optical fiber

Features of optical access network: point-to-multipoint transmission system, medium sharing; downlink broadcast (time division multiplexing to transmit cell stream); uplink: various multiple access technologies

OLT: [Core functions] Digital cross-connect function, transmission multiplexing function (G.902 has no switching function!!!) and ODN interface; [Business function]: Service port function; [Public layer function]: Power supply and OAM function

ODN: Provides optical transmission media for the physical links of ONU and OLT

ONU: [Core functions] User and business multiplexing functions, transmission multiplexing functions, ODN interface functions [Business functions] Provide user port functions [Public layer functions] Power supply and OAM functions

[Transmission between OLT and ONU]: TDM/TDMA; [Downlink channel] Time Division Multiplexing [Uplink channel] TDMA

Key technologies of PON: ranging technology, fast bit transmission technology, burst signal transmission and reception, scrambling technology, medium access control (MAC) technology

Passive optical fiber network for ATM; supports multi-service, multi-bit access and broadband, transparent data transmission; standard specification: ITU-T G.983

G.983 basic features:

APON key technologies: ranging and fast bit synchronization technology

Downstream direction: Adopt point-to-multipoint broadcast mode; ATM cells from the ATM switch-->OLT-->OLT assemble them into frames-->broadcast mode, and send them to the downlink channel using the 1550 wavelength zone.. ....

Upstream direction: burst mode; the user data of the network terminal is adapted to the ATM format by the corresponding AAL --> ONU assembles the ATM cells into the APON format, passing the 1310nm wavelength at a rate of 155.520

Downlink: Continuous time slot stream consists of 155.520Mbit/s 56 ATM cells 2 PLIAM (Physical Layer Operations, Management and Maintenance) cells; 622Mbit/s 224 ATM cells 8 PLOAM cells

Uplink: using TDMA method 53 ATMs

The physical layer uses PON technology and the link layer uses Ethernet protocol; low cost, high bandwidth, strong scalability, flexible and fast service reorganization, compatibility with existing Ethernet, and convenient management

EPON basic indicators: single-mode fiber, at 1000Mbps rate, splitting ratio 1:32, transmission distance 10km; single-mode fiber, 1000Mbps rate, splitting ratio 1:16 20km; G.652 single-mode fiber; uplink: 1310nm, downlink: 1490nm

Basic features of EPON: The signal transmission between OLT and ONU is based on IEEE 802.3 Ethernet; the transmission line rate is 1250Mbit in both uplink and downlink; based on the MPCP mechanism of the MAC control sublayer; logical splitting ratio: 1:32 (1:64)

EPON transmits variable-length Ethernet frames (64~1518 bytes), and EPON frames are timed long frames (2ms)

Downstream: A continuous data stream of fixed-length frames (2ms) containing multiple Ethernet frames (time slots) of different lengths, header (OUN identifier and synchronization header) + check part

Uplink: TDMA technology, frame length 2ms

Downstream: broadcast mode

Uplink; TDMA mode

IEEE802.3av

Gigabit passive optical network; downlink: 2.488Gbps uplink: 1.244Gbps; adaptation protocol ITU-T G.7041; multi-service and multi-bearer; currently the most ideal broadband optical fiber access network technology

Why choose GPON

Performance parameters

Standard protocol: ITU-T G.984.1 G.984.2 G.984.3 G.984.4

WDM single fiber bidirectional (mandatory); upper: 1310nm lower: 1490nm

Two multiplexing methods are used to separate the incoming and outgoing signals of multiple users on the same optical fiber.

Reference model: Transmission convergence sublayer GTC: GTC framing sublayer, GTC adaptation sublayer; physical media layer (PM layer)

GPON packaging method

Basic protocol concepts

Physical layer: Both uplink and downlink are fixed-length TDM frames 125us

frame structure

Asymmetric: XG-PON1 up: 2.5Gbps (1270nm) down 10Gbps (1577nm)

Symmetry: CG-PON2 Up and down: 10Gbps