32 CHANNEL DWDM SYSTEM

ZTE

OPTICAL NETWORK ELEMENTS

TP

TP OA

OD

EM

UX

OM

UX

OADM OXC

TP (Transponder)OMUX (Multiplexer)ODEMUX (De-multiplexers)Optical amplifiersOADMOXC

Optical Multiplexer

Optical De-multiplexer

Optical Add/Drop Multiplexer(OADM)

Transponder

DWDM Componentsl1

l2

l3

l1

l2

l3

850/1310 15xx

l1

l2

l3

l1...n

l1...n

Optical Amplifier(EDFA)

Optical AttenuatorVariable Optical Attenuator

Dispersion Compensator (DCM / DCU)

More DWDM Components

Functional block diagram of the ZXWM M900

ZXWM M900

• Divided into the hardware system and NM software system, which are independent of each other and work coordinately.

• Working wavelength range and channel interval C-band (192.1THz ~ 195.2THz) at 100 GHz interval.

System composition

• OTM: Optical terminal equipment As shown in Fig. OTU stands for the optical transfer board, OMU and ODU for the OM board and the OD board.

• OBA and OPA for the optical amplifying boards.• OSCT for the supervisory board, and it is used

as the OSC terminal (OSCT) when using as the terminal.

• At the receiving end of the OTM, DCM should be added for dispersion compensation after long distance transmission. Wavelength interval transferred by OTU is 100 GHz.

OLA: It is an optical line amplifier

• OLA: It is an optical line amplifier, including OLA and OSCL. As shown in Fig. OLA stands for the optical amplifying board, OSCL for the supervisory board. When it is used for a line amplifier, there are two supervisory directions, indicated as line OSC (OSCL).

Erbium Doped Fiber Amplifier

Isolator Coupler IsolatorCoupler

Erbium-DopedFiber (10–50m)

PumpLaserPumpLaser

PumpLaserPumpLaser

Two basic types of amplifiers: Co-directional (pumping) and Counter-directional. Co-directional pumping results in good SNR performance (pre-amp), where as Counter-directional results in better gain performance (Post/Power amp). One amplifier does not necessary fit all applications!, especially in LH networks.

EDFA Schematic

• EDFAs amplify all ls in 1550 window simultaneously

• Key performance parameters include– Saturation output power, noise figure, gain flatness/passband

...

...

980PumpLaser

WDMCoupler

WDMCoupler

EDF

DCF

OpticalIsolator

1480PumpLaser

OpticalFilter

OpticalIsolator

EDF

Wayside Optical Add/Drop Multiplexer

TM TM WDM MUX

WDM DEMUX

2

15

16

1

1-4 5-8

OA

OA

Optical Add/Drop Multiplexing

l1 l1l2 l2 l2 l2

Configurable OADM :1 or 2

Configurable OADM :1 or 2

l1 l1l2 l2 l2 l2

l1 l1

fixed OADM:2

fixed OADM:2

OADM : Optical Add/Drop Multiplexer

Terminal Equipt Terminal EquiptIn-Line Amplifier

OADM Connectivity

29 express ch

32 chWDM

• Omnibus

• From terminal to OADM, or from OADM to OADM

OPTICAL ADD DROP MUX

COUPLER

D M

CIRCULATOR

OPTICAL ADD DROP MUX

• OADM: It is an optical add/drop multiplexer.

• OAD stands for the add/drop board, • OUT for the optical transfer board, • OSCL for the supervisory board. When it

is used as an OAM, there are two supervisory directions, indicated as line OSC (OSCL).

Equipment Cabinet

• Unified Cabinet for ZTE Transmission Equipment Cabinet Structure .

Table: Dimensions and Weight of the ZXWM M900 Structure(The weight refers to that of an empty cabinet )

DimensionsWeight

(kg)

2,000 mm (H) x 600 mm (W) x 300 mm (D) 70

2,200 mm (H) x 600 mm (W) x 300 mm (D) 80

2,600 mm (H) x 600 mm (W) x 300 mm (D) 90

Optical Terminal Equipment (OTM)

• The main rack is configured with a NCP and others are extension racks.

• The main rack consists of 1 power alarm subrack, multiple OTU subracks, 1 OA subrack (equipped with an NCP), 1 ODF plug-in box.

• An extension rack consists of 1 power alarm subrack, multiple OTU subracks, 1 ODF plug-in box

Optical Line Amplifier (OLA)

• Generally single-rack configuration. An OLA consists of 1 power alarm subrack, 1 OA subrack. Specific configuration depends on actual conditions.

Optical Add/Drop Multiplexer (OADM)

• Generally single-rack configuration. • An OADM consists of

1 power alarm subrack

1 or 2 OTU subracks

1 OA subrack

1 ODF plug-in box

Layout of Integrated Equipment

• 2.2m-/2.6m-high cabinet: 1 power alarm subrack, 3 subracks (2 OTU subracks and 1 OA subrack, or 3 OTU subrack), 1 ODF plug-in box.

• 2m-high cabinet: 1 power alarm subrack, 2 subracks (1 OTU subrack and 1 OA subrack, or 2 OTU subrack), 1 ODF plug-in box

OA Subrack Structure

• An OA subrack has simple mechanical structure and consists of front/rear aluminum beams, left/right side boards, and guide rail bar. The guide rail (Dimensions: 577 mm (H) * 482.6 mm (W) * 269.5 mm (D)) of a plug-in box is of section aluminum.

• Backplane: A backplane is the carrier connecting boards and provides the interface between the ZXWM M900 and external signals.

• At the upper part of the backplane providing • signal connection interfaces like the subrack

power socket, • network interface, • transparent user channel interface, • alarm input/output interface . • The lower part of the backplane • signal sockets and power sockets of various

slot boards. Signal sockets at various slots employs the differential data bus to receive/transmit data. They work in parallel to transmit & receive data to the public interface area.

Board insertion area

The board insertion area includes 14 groups of guide rail slots with 30 mm in between

Fan insertion area

• Telephone bracket; Located in the front of the backplane interface area and configured within an OA subrack alone to lay a orderwire phone.

• Air filter; At the lowest part of a subrack. The air filter, together with a fan plug-in box, forms a circulating system within subrack.

• Chute;Located at the lower part of a subrack and used to lay the fiber coming into and out of a board panel.

• Installation lug;Including left and right lugs, used to fix a subrack and a cabinet by means of captive screws.

Board Name Full Name EquipComponents

NCP Net Control Processor OA sub rack

OSC Optical Supervisory Channel

OHP Orderwire Overhead processor

LAC Line Attenuation Compensator

OA Optical Amplifier

OP Optical Protect Board

OPM Optical Performance Monitor

OTUF Optical Transponder Unit withFEC OA/OTU subrack

GEMF Two Gigabit Ethernet Mux Board with FEC

OAD Optical Add/Drop Board

OMU Optical Multiplexing Unit

ODU Optical De-Multiplexing Unit

PWB Power Board Power Alm subrack

PWSB Power Supervision Board

FCB Fan-Control Board Fan plug-in box

OTUF• Implements wavelength conversion of multiple

service signals at single-Double-channel 2.5Gbit/s or lower rate. Support double-channel wavelength conversion.

• The OTUF on the customer side supports multiple service signals like STM-1/4/16. Optical signals on the line side satisfy G692 requirements. A OTUF has the FEC function conformable to G709 specifications.

• A OTUF is capable of Bl, B2, and JO detection of SDH signals, and monitor OTU overhead like BiP-8,TTI,OTUl-LOF.

• An OTUF consists of the optical receiver module, optical transmitter module, FEC framer, and control & communication unit.

Multiplexer / Demultiplexer

Wavelengths Converted via Transponders

Wavelength Multiplexed Signals

DWDMMux DWDM

Demux

Wavelength Multiplexed Signals

Wavelengths separated into individual ITU Specific lambdas

Loss of power for each Lambda

OMU optical multiplexer

• OMU multiplexes optical signals with different wavelengths into a fiber. Before combined output, OMU sends some light to the optical power monitoring module, which provides an online monitoring interface and reports to the NMS the total optical power output by means of the control & communication unit.

ODUOptical De-Multiplexing Unit • ODU is capable of de-multiplexing and provides

an online monitoring interface for combined light.• By means of an optical demultiplexer, ODU

filters optical signals of various channels combined in a fiber and sends them to different receivers. Before they enter the optical demultiplexer, some light is sent to the optical power monitoring module, which provides an online monitoring interface and reports total optical power input to the NMS by means of the control & communication unit.

OAD Optical Add/Drop Board

• An OAD invariably adds/drops 4-channel signals (Specific wavelength of add/drop signals is customized as required by the user) with constant wavelength. Other wavelength signals and locally added signals are multiplexed and output. Monitor add/drop optical signal power. OAD consists of the OADM, power monitoring unit, and control & communication unit.

LAC Line Attenuation Compensator • According to line optical power detection, adjust

the Electrical Variable Optical Attenuator (EVOA) in LAC by means of the NMS to ensure the power points of various segments during the running. The receiving power and OSNR of the receiving end maintain their normal value.

• LAC includes 2 types: LACG and LACT.LACG has 2 EVOAs applicable to OLA, OADM, and back-to-back OTM site.LACT has 1 EVOA applicable to a single-end OTM site.

OA Optical Amplifier

• The OA uses EDFA to amplify optical signals. It substitutes the original electrical regenerator relay mode to save system costs and simplify the system. According to its functions and locations in the system, OA includes 3 types: Optical Booster Amplifier (OBA), Optical Line Amplifier (OLA), and Optical Pre Amplifier (OPA). The OA is capable of gain adjustment, gain locking, and power suppression & control, thus realizing power adjustment.

OA Optical Amplifier

• Capable of Automatic Power Shut Down (APSD)/Automatic Power Reduction (APR) and restarting. APSD, APR, and restart functions mean that when detecting any input no light (that is, fiber cut) in a link, the system is capable of shutting down or reducing the output optical power of an upstream amplifier or all amplifiers within a downstream regenerator section. When signals are recovered, the OA resumes its operation. This ensures that optical power levels satisfy safety requirements during line fiber correction

• A board is equipped with a 1510/1550 optical multiplexer and optical demultiplexer (OBA has an optical multiplexer alone and OPA has an optical monitoring module located at the input & output end provides an online monitoring interface without affecting any service.

• EDFA, EDFA drive circuits: EDFA amplifies 1550 nm optical signals and is controlled by an EDFA drive circuit. The EDFA drive circuit is capable of gain adjustment, power suppression, gain locking.

• Control & communication: Used to detect input/output optical power and report it to the NMS. Meanwhile, the control & communication receives the control commands sent from the NMS to a board. The adjustable range of gain adjustment commands is the gain nominal value of ±2 dB and the adjustment step length of 0.1 dB.

OA Optical Amplifier

Loss Management: LimitationsErbium Doped Fiber Amplifier

• Each amplifier adds noise, thus the optical SNR decreases gradually along the chain; we can have only have a finite number of amplifiers and spans and eventually electrical regeneration will be necessary

• Gain flatness is another key parameter mainly for long amplifier chains

Each EDFA at the Output Cuts at Least in a Half (3dB) the OSNR Received at the Input

Noise Figure > 3 dBTypically between 4 and 6

Noise Figure > 3 dBTypically between 4 and 6

Optical Signal-to Noise Ratio (OSNR)

• Depends on :

Optical Amplifier Noise Figure:

(OSNR)in = (OSNR)outNF

• Target : Large Value for X OSNR>25 dB

Signal Level

Noise Level

X dB

EDFA SchematicEDFA Schematic

(OSNR)out(OSNR)in

NFPin

OPM Optical Performance Monitor

• It monitors optical performance in optical channels. Besides, it measures the parameters of each optical channel, such as optical power, central wavelength, and OSNR, and reports relevant data to the NMS. Precision of the power measurement: ±1.0 dB. Precision of the central wavelength measurement: ±0.1 nm. Precision of the OSNR measurement: ±1.5 dB (OSNR>25 dB). Each OPM detects the performance of 4 optical interfaces.

• OPM is accessed to 4 optical interfaces. In the detection processing module, it measures the parameters of each optical channel and reports them to the NMS by means of the control & communication module. The NMS may also deliver query commands of optical channel parameters by means of the control & communication module.

ITU-T BAND ALLOCATION

Optical Supervisorychannel

1500 1520 1530 1542 1547 1560 1620

REDBAND

C BAND L BAND

BLUE

BAND

• C BAND PRODUCTS ARE COMMERCIALLY AVAILABLE.• ERBIUM DOPED FIBRE AMPLIFIERS SUITABLE FOR ‘C’ BAND.• GAIN IN RED BAND FLATTEST FOR EDFA.• SOME MANUFACTURERS PROVIDE 16 CHANNELS IN RED BAND ONLY. OTHERS USE BOTH RED & BLUE BANDS.

OSC Optical Supervision Channel

• OSC forwards the supervisory information carried in a supervision channel (1,510 nm) to an NCP and OHP. Meanwhile, it completes reverse conversion.

• According to different demands, OSC includes 2 types: Optical Supervision Channel of Terminal (OSCT) and Optical Supervision Channel of Line (OSCL).

• OSCT: Used to process supervisory signals of 2 directions, applicable to an OTM equipment.

• OSCL: Used to process supervision signals of 4 directions. It is applicable to both OLA equipment and OADM equipment.

OHP (Order-wire Overhead processor )

• Responsible for processing orderwire overhead of in a supervisory channel, and processing voice and signaling related to voice processing.

• Order wire liaison system in the following calling modes:Addressing calling mode. No. less than 99 sites are selected.Conference calling mode: 3 sites.Group address calling modeBroadcast calling mode

NCP Net Control Processor • NCP performs all the functions of an NE monitoring subsystem

which include:• NCP collects and processes the alarm and performance

inform...ion of an NE where NCP is located, and reports it to the NMS. Meanwhile, NCP forwards data from other NCPs and receives the control commands from the NMS.

• Capable of saving configuration data. NCP works independently of the-NMS as soon as initial configuration is completed.

• NCP needs to provide F, f, and Qx interfaces to an upper-layer management system, ECC route to communicate with other NEs, S interface to communicate with MCU of boards. The Qx interface and the F interface adopt 10/100M Ethernet electrical interface; the f interface adopts the RS-232 interface and conforms to the V.28 protocol.

Net Control Processor

• Capable of alarm input/output.• Alarm input function: Provides 4-channel alarm

input, including the open-door alarm, fire alarm, flood alarm, and temperature alarm.

• Alarm output function: Including the LED alarm and sound alarm.

• Provides multirack management function. An NCP manages 4 racks at most and can be flexibly configured according to the number of racks in an node.