Dense Wavelength Division Multiplexing Theory

What we will cover WDM Overview Optical Fiber Transmission Characteristics Key technologies of DWDM Technical Specifications

Background WDM TDM SDM

PDH SDH DWDM 155M622M2.5G10G G.957G.691 G.692 PDH, SDH and DWDM

IP ATM SDH DWDM Physical Fiber DWDM Physical Fiber Open Optical Interface SDH ATM IP Other Relationship between DWDM and Other Services

WDM Definition WDM enables transmitting multiple optical carriers with information (analog or digital) on one fiber N 2 1 N 2 1 N 2 1 OMU ODU OA

DWDM Concept Dense wavelength division multiplexing (DWDM) Power ( dBm) nm λ(nm) wavelength interval ： 0.8 ～ 2nm

DWDM System OTU1 ┇ Input Ch 1 Ch N Ch 1 Ch N λ1λ1λ1λ1 λnλnλnλn OTUn OMU BA LA PA ODU λ1λ1λ1λ1 λnλnλnλn OTU1 ┇ OTUn λs λs λs λs OSC OSCOSC Output EMS Optical Transmitter OLA Optical Receiver

Common Network Elements in DWDM Optical Terminal Multiplexer (OTM) Optical Line Amplifier (OLA) Optical Add/Drop Multiplexer (OADM)

Optical Terminal Multiplexer (OTM) Client side Line side λ1λ1 λnλn λ1λ1 λnλn OTM At the transmitter end, the OTM: Multiplexes the STM-N signals of “N” wavelengths λ 1 ~λ N into a DWDM main optical channel Amplifies the optical power of the main channel via the multiplexer Adds an optical supervisory channel λ s At the receiving end, the OTM: Extracts the optical supervisory channel λ s DWDM main optical channel is amplified and de-multiplexed into STM- N signals of the N different wavelengths

Optical Line Amplifier (OLA) OLA is configured in each direction of the fiber link OLA extracts the optical supervisory channel (OSC) and processes it It then amplifies the main optical channel signals, multiplexes them with the optical supervisory channel and sends them onto the fiber Line side OLA

Optical Add/Drop Multiplexer (OADM) OADM performs add/drop of wavelengths Client side Line side λ1λ1 λnλn λ1λ1 λnλn OADM

Operational Wavelength Range O BandOriginal nm E BandExtended nm S BandShort nm C BandConventional nm L BandLong nm U BandUltralong nm

Division Of Low-Loss Window

Feature Comparison between Low-Loss Windows WindowIIIIIIIVV Mark (nm) (O band) 1550 (C band)1600 (L band) 1360 ~ 1530 (E + S bands) Wavelength range (nm) 600~ ~ ~ ~ ~1530 Fiber typeMMF MMF/G.652/ G.653 G.652/G.653/ G.655 Full-wave fiber Applications Short distance and low rate Long distance and high rate

Wavelength Allocation On C-Band No.Central Frequency (THz)Wavelength (nm) Channels / 100 GHz interval

Wavelength Allocation On C-Band 40 Channels / 100 GHz interval

TDM Electrical Regenerator for Single Wavelength DWDM Multi-wavelength on Single Fiber, for Optical Amplification DWDM vs. SDH T T R R 1 Electrical MultiplexElectrical Demultiplex TransmitterReceiver Electrical Regenerator N 2 1 N 2 1 N 2 1 Optical Multiplexer Optical Demultiplexer OA

DWDM Features Large transparent transmission capacity greatly saves fiber resources Each wavelength can carry different signal: SDH 2.5Gbps, 10 Gbps, ATM, IP DWDM technology provides multiple virtual fiber channels in one physical fiber channel SDHDWDM

DWDM Features Through super-long distance transmission technologies, the transmission cost is reduced SDH DWDM Electrical Regenerator Light Amplifier

DWDM Features 8*2.5G 32*2.5G 16*2.5G 32*10G

Key technologies of DWDM

DWDM System OTU1 ┇ Input Ch 1 Ch N Ch 1 Ch N λ1λ1λ1λ1 λnλnλnλn OTUn OMU BA LA PA ODU λ1λ1λ1λ1 λnλnλnλn OTU1 ┇ OTUn λs λs λs λs OSC OSCOSC Output EMS Optical Transmitter OLA Optical Receiver

Key Technologies Of DWDM Optical Source Optical Multiplexer And De-multiplexer Optical Amplifiers The Supervision Of WDM System

Optical Source Requirements of optical sources: Larger dispersion tolerance value Standard and stable wavelength Types of optical sources: Light Emitting Diode (LED) Laser Diode (LD)

Optical Multiplexing and De-multiplexing Technology

Optical Multiplexer and Demultiplexer Multiplexer Fiber Demultiplexer

Supervision System Technology

Supervision System Detection, control and management are basic requirements of all network operations To ensure secure operation of DWDM system, physically, the monitoring system is designed as an independent system separated from working channels and devices Used to transmit the NE management and supervision information related to DWDM system

Functions Fault alarm Fault location Quality parameter supervision in the operation Control over backup line upon line interruption EDFA supervision

Optical Supervision Control (OSC) OMUODU OBA OPA OBA ODUOMU OLA OSC

Optical Supervision Control (OSC) 1510nm Signal speed :2.048Mb/s Receiving sensitivity :-48dbm Transmission power :0 ~ -7 dbm

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