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Page 1: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU
Page 2: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

DWDM 101 & Intro to OTN Switching

BRKOPT-2106

Rodger Nutt

High-End Routing and Optical BU

Technical Leader

Page 3: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Agenda

• Introduction – What is DWDM?

• Optical Fiber

• Linear Effects and Solutions

• Non-Linear Effects –PMD, FWM, SPM, XPM

• DWDM and Optical Components

• Intro to OTN Switching

• DWDM Software

3

Page 4: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

What is DWDM?

Page 5: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Wavelength Division Multiplexing

5

• DWDM systems use optical devices to combine the output of several optical transmitters

Optical

fiber pair

TX

Optical

transmitters Optical

receivers

TX

TX

TX

RX

RX

RX

RX

Transmission

DWDM devices

Page 6: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

ITU-T Grid

6

Frequency

(THz)

Wavelength

(nm)

1528.77 nm 1578.23 nm

0.4 nm spacing

1552.52 nm

(Center channel)

196.2 THz 190.1 THz 193.1 THz

(Center channel)

50 GHz spacing

ITU wavelengths = lambdas = channels center around 1550 nm (193 THz)

Page 7: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Dense vs. Coarse (CWDM vs. DWDM)

7

DWDM CWDM Application Long Haul Metro

Amplifiers Typically EDFAs Almost Never

# Channels Up to 80 Up to 8

Channel Spacing 0.4 nm 20nm

Distance Up to 3000km Up to 80km

Spectrum 1530nm to 1560nm 1270nm to 1610nm

Filter Technology Intelligent Passive

Page 8: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

Optical Fiber

Page 9: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Fiber Geometry and Dimensions

• The core carries the light signals

• The refractive index difference between core & cladding confines the light to the core

• The coating protects the glass

9

Coating

250 microns

Cladding

125 microns

Core

SMF 8 microns

Page 10: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Communication Wavelengths in the InfraRed

850 nm Multimode 1310 nm Singlemode C-band:1550 nm Singlemode L-band: 1625 nm Singlemode

UltraViolet InfraRed

850 nm 1310 nm 1550 nm 1625 nm

l

Wavelength: l (nanometers)

Frequency: (terahertz)

C = x l

Visible

Optical Spectrum

10

Page 11: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

The primary difference is in the Chromatic Dispersion Characteristics

Good for TDM at 1310 nm

OK for TDM at 1550 nm

OK for DWDM (With Dispersion Mgmt.

Good for CWDM (>8 wavelengths)

Extended Band

(G.652.C)

(suppressed attenuation in the

traditional water peak region)

OK for TDM at 1310 nm

Good for TDM at 1550 nm

Good for DWDM (C + L Bands)

NZDSF

(G.655)

OK for TDM at 1310 nm

Good for TDM at 1550 nm

Bad for DWDM (C-Band)

DSF

(G.653)

Good for TDM at 1310 nm

OK for TDM at 1550

OK for DWDM (With Dispersion Mgmt.)

SMF

(G.652)

Applications for the Different Fiber Types

11

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Linear Effects

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© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Transmission Impairments

• Attenuation – Loss of Signal Strength

• Chromatic Dispersion (CD) – Distortion of pulses

• Optical Signal to Noise Ratio (OSNR) – Effect of Noise in Transmission

800 900 1000 1100 1200 1300 1400 1500 1600

Wavelength (nm)

0.2

0.5

2.0

Loss (dB/km)

L-ba

nd:1

565–

1625

nm

C-b

and:

1530–1

565n

m

S-b

and:

1460–1

530n

m

800 900 1000 1100 1200 1300 1400 1500 1600

Wavelength (nm)

0.2

0.5

2.0

Loss (dB/km)

L-ba

nd:1

565–

1625

nm

C-b

and:

1530–1

565n

m

S-b

and:

1460–1

530n

m

Time Slot

10Gb/s

2.5Gb/s Fiber

Fiber

Time Slot

10Gb/s

2.5Gb/s Fiber

Fiber

S+N

N

S+N

N

13

Page 14: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Attenuation

14

• With enough attenuation, a light pulse may not be detected by an optical receiver

Insertion loss (dB)

Attenuation (dB)

Distance (km)

Optical device

Page 15: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Fiber Attenuation (Loss) Characteristic

15

800 900 1000 1100 1200 1300 1400 1500 1600

OH- Absorption Peaks in

Actual Fiber Attenuation Curve

Wavelength in Nanometers (nm)

0.2 dB/Km

0.5 dB/Km

2.0 dB/Km

Loss(dB)/km vs. Wavelength

S-band:1460–1530nm

L-band:1565–1625nm

C-band:1530–1565nm

OH: Hydroxyl ion absorption is the absorption in optical fibers of electromagnetic waves,

due to the presence of trapped hydroxyl ions remaining from water as a contaminant.

Page 16: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Laser Output Power and Receiver Sensitivity and dBm

• Fiber loss expressed in dB but transmitter/receiver power is expressed in dBm

• This is why both the transmitter output power and the receiver sensitivity is expressed in dBm:

PowerdBm=10log(PmW/1mW)

dB and dBm are additive, hence the simplification

Example:

• Powerdbm = 10log(2mW/1mW)=3dBm

• Powerdbm = 10log(1mW/1mW)=0dBm

16

Page 17: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Gain expressed by ratio: Pout/Pin

Gain measured conveniently in dB: 10 log10 Pout/Pin

If the power is doubled by an amplifier, this is +3 dB

Amp Pin Pout

Gain and Decibels (dB)

17

Page 18: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Attenuation: Optical Budget

18

Optical Budget is affected by: – Fiber attenuation

– Splices

– Patch Panels/Connectors

– Optical components (filters, amplifiers, etc.)

– Bends in fiber

– Contamination (dirt/oil on connectors)

Basic Optical Budget = Output Power – Input Sensitivity

Pout = +6 dBm R = -30 dBm

Budget = 36 dB

Page 19: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Signal

Input

980 or 1480 nm

Pump Laser

Erbium

Doped

Fiber

Amplified

Signal

Output

Isolator

WDM Coupler for

pump and signal

Isolator

Basic EDFA

configuration

Attenuation Solution: EDFA

• Erbium doped fiber amplifies optical signals through stimulated emission using 980nm and 1480nm pump lasers

19

Page 20: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Chromatic Dispersion (CD)

• Total dispersion is a function of the length of fiber and it’s dispersion factor

• Limits transmission distance for 10G and above wavelengths

• Can be compensated by using negative dispersion fiber or electronically through modulation schemes

20

Bit 1 Bit 2 Bit 1 Bit 2 Bit 1 Bit 2 Bit 1 Bit 2 Bit 1 Bit 2

The Optical Pulse tends to Spread as it propagates down the fiber

generating Inter-Symbol-Interference (ISI)

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© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

DCUs use fiber with chromatic dispersion of opposite sign/slope and of suitable length to bring the average dispersion of the link close to zero.

Solution: Dispersion Compensating Unit

21

Page 22: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Optical Signal-to-Noise Ratio (OSNR)

22

• OSNR is a measure of the ratio of signal level to the level of system noise

• As OSNR decreases, possible errors increase

• OSNR is measured in decibels (dB)

• EDFAs are the source of noise

Signal level dBm)

Noise level (dBm)

Signal level

OSNR = -----------------

Noise level

Page 23: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Optical Signal Detection

23

• Across a fiber span, optical signals encounter attenuation, dispersion and increased noise levels at amplifiers.

• Each of these factors causes bit detection errors at the receiver.

Distance (km) Transmitting

end

Receiving

end

Low attenuation

Low dispersion

High OSNR

High attenuation

High dispersion

Low OSNR

Page 24: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Example: Link Design with Line Amplifiers

24

10G Xenpak spec: Tx: +3 to -1dBm, Rx min: -21dBm (0ps/nm)

CD tolerance: +1600ps/nm @ 2dB penalty

OSNR min: 16dB (0.5nm resolution)

-1dBm +2dBm

0ps/nm

Time

Domain

Wavelength

Domain

OSNR: 18dB Rx:

-9dBm

Meets receiver minimum

OSNR and power

requirement

+2dBm/ch

TX RX

Tx: -1dBm min M

ux

Dem

ux

DCU

-1600

ps/nm 25dB 25dB

DCU

-1600

ps/nm

+2dBm/ch -23dBm/ch -23dBm/ch

OSNR= 21dB

Noise

OSNR= 18dB

Noise

OSNR= 35dB

Noise

-23dBm

1600ps/nm

+2dBm

0ps/nm

-23dBm

1600ps/nm

+2dBm

0ps/nm

Page 25: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

OSNR Solution #1 Raman Amplifier

25

• Stimulated Raman Scattering creates the Gain

• Reduces the effective span loss and increases noise performance

• Gain is highly dependent on quality of fiber

• Gain Spectrum ~ 40nm with a single pump

Page 26: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Lo

g

(BE

R)

4 5 6 7 8 9 10 11 12 13 14 15 –15

–14

–13

–12

–11

–10

–9

–8

–7

–6

–5

–4

–3

–2

–1

0

S/N (dB)

Uncoded

No FEC

G.709

RS(255,239)

Raw Channel BER=1.5e-3

EFEC=8.4 dB FEC=6.2 dB

OSNR Solution #2: Forward Error Correction

26

• FEC extends reach and design flexibility, at “silicon cost”

• G.709 (G.709 Annex A) standard improves OSNR tolerance by 6.2 dB (at 10–15

BER)

• Offers intrinsic performance monitoring (error statistics)

• Higher gains (8.4dB) possible by enhanced FEC (with same G.709 overhead – G.975.1 I.4)

• New SD-FEC provides 2dB more coding gain

Benefit: FEC/EFEC Extends Reach and Offers 10–15 BER

Page 27: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

Non-linear Effects

Page 28: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Non Linear Effects

• Polarization Mode Dispersion (PMD) – Caused by Non Linearity Of

Fiber Geometry

– Effective for Higher Bit rates (10G)

• Four Wave Mixing (FWM) – Effects multi-channel systems

– Effects higher bit rates

• Self/Cross Phase Modulation (SPM, XPM) – Effected by high channel power

– Effected by neighbor channels

28

Wavelength (nm)

-5

-10

-15

-20

-25

-30

-35

-40

1542 1543 1544 1545 1546 1547 1548

Pow

er (d

Bm

)

Wavelength (nm)

-5

-10

-15

-20

-25

-30

-35

-40

1542 1543 1544 1545 1546 1547 1548

Wavelength (nm)

-5

-10

-15

-20

-25

-30

-35

-40

1542 1543 1544 1545 1546 1547 1548

Pow

er (d

Bm

)

nx

nyEx

Ey

Pulse As it Enters the Fiber

Spreaded Pulse As

it Leaves the Fiber

nx

nyEx

Ey

Pulse As it Enters the Fiber

Spreaded Pulse As

it Leaves the Fiber

Power SP

M D

isto

rtio

n

Power SP

M D

isto

rtio

n

Page 29: DWDM 101 & Intro to OTN Switchingd2zmdbbm9feqrf.cloudfront.net/2014/usa/pdf/BRKOPT-2106.pdfDWDM 101 & Intro to OTN Switching BRKOPT-2106 Rodger Nutt High-End Routing and Optical BU

© 2014 Cisco and/or its affiliates. All rights reserved. BRKOPT-2106 Cisco Public

Polarization Mode Dispersion (PMD)

• It is Relevant at Bit Rates of 10Gb/s or More

• Pulse broadens as it travels down fiber

• Mainly a manufacturing/install issue with concentricity of fiber

29

nx

ny Ex

Ey

Pulse as It Enters the Fiber Spreaded Pulse as It Leaves the Fiber

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Laser

10Gb/s

QPSK1 Modulator

10Gb/s

40Gb/s = 10Gbaud 10Gb/s

QPSK2 Modulator

10Gb/s

PMD Solutions • Increase system robustness with FEC

• Leverage MLSE

• Use PMD Compensation (PMDC)

• Deploy PMD-optimized fibers

• Advanced Modulation Schemes

30

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Intro to OTN Switching

31

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OTN Drivers

• Sub-Lambda Aggregation/Switching – Adapt to DWDM

– Switch/Router Intfc Mismatch to DWDM

• Transparency – Timing

– Protocols (i.e. OSPF vs ISIS)

• Sub-Lambda Protection

• Unnecessary when client interface = DWDM Trunk

Source: Infonetics

OTN Only Packet

Aggregation OTN OTN / Packet

Optimized

Private Line

Private Line

Private Line

Private Line

Not yet needed

Money saved

λ2 λ1 λ2 λ1 λ2

deferred λ1

Private Line

Private Line

Private Line

Private Line

Private Line

Private Line

Private Line

Private Line

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Cisco Confidential 33 © 2010 Cisco and/or its affiliates. All rights reserved.

Three Architectural Options for OTN

Switched

G.709

(Digital OTN)

Static WDM

(Analog OTN)

Flexible

WDM

(Analog OTN)

Switched

G.709

(Digital OTN)

Dynamic

WDM

(Analog OTN)

Framed G.709

(Digital OTN)

A B C

G.709 provides all dynamic capabilities

WDM for capacity only

G.709 provides dynamic switching

WDM with reconfigurable connections

G.709 provides framing only

WDM for all dynamic capabilities

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OPU

ODU

OTU OTU OTU

How Does OTN Relate to DWDM? O

TN

D

WD

M OCh

OMS

OTS OTS OTS

34

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OTN – A Quick refresher

35

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OTU4 Clients and Mappings

• ITU simultaneously defined an ODU0 at 1.25 Gbps to carry GigE

• Supplants ODU1 (2.5 Gb/s) as the fundamental TS size

• ODU4 is divided into 80, 1.25 Gb/s Time Slots

• ITU defined the ODUflex container, ODU2e is the first

36

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DWDM Components

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Typical Components of DWDM Systems

38

• Optical transmitters and receivers

• DWDM mux/demux filters

• Optical add/drop multiplexers (OADMs)

• Reconfigurable OADM (ROADM)

• Optical amplifiers

• Transponders/Muxponders

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Optical Transmitter Block Diagram

39

Detects pulses of

electrical charge

• Power measured in watts (W)

• Amplitude measured in

volts (V)

Creates pulses of light

• Power measured in

decibel-milliwatts (dBm)

• Relative amplitude

measured in decibels (dB)

Electrical conductor

E-O

Optical fiber

1 1 1 0 1 1 1 0

Electrical-to-optical

(E-O)

conversion +

-

dB

+

-

V + -

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Optical Receiver Block Diagram

40

Detects pulses of light

• Power measured in

decibel-milliwatt (dBm)

• Relative amplitude

measured in decibels (dB)

Creates pulses of electrical charge

• Power measured in watts (W)

• Amplitude measured in volts (V)

Electrical conductor

O-E

Optical fiber

+ -

Optical-to-electrical (O-

E)

conversion 1 1 1 0 +

-

dB

1 1 1 0 +

-

V

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100G Technology – Coherent Detection

41

Direct Detection

• Must correct for impairments in the physical domain (insert DCU’s)

• Forced to live with non-correctable impairments via network design (limit distance, regenerate, adjust channel spacing)

• Dumb detection (OOK), no Digital Signal Processing, only FEC

Coherent Detection

• Moves impairment correction from the optical domain into the digital domain

• Allows for digital correction of impairments (powerful DSP) vs. physical correction of impairments (DCU’s). Adds advanced FEC.

• Massive performance improvements over Direct Detection.

DD

CD

DD

DCU DCU DCU

Regen

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DWDM Mux and Demux Filters Block Diagram

42

1

2

3

N

DWDM

fiber

N light pulses of different wavelengths

From N

transmitters To N

receivers

1

2

3

N

Composite

signal

Multiplexer Demultiplexer

1, 2, ….N

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OADM Block Diagram

43

New data stream,

same wavelength

Signsl 1 drop

OADM

one signal

Pass through path Original

composite signal

New composite

signal

Drop path Add path

DWDM

fiber

Signal 2 add

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ROADM Architecture

44

Add

Wavelengths Drop

Wavelengths

Pass-Through Wavelengths Splitter

Add

Wavelengths Software

Controlled

32 Ch. DeMux

Pass-Through Wavelengths Splitter

l1 Network

Element l3

Network

Element

Software Controlled Selectors – 32 Ch.

(Pass-through/Add/Block)

DWDM

Signal

Transponder

Module

West

East

DWDM

Signal

Drop

Wavelengths drop block block drop

drop block block drop

Software

Controlled

32 Ch. DeMux

Add

Pass

Add

Pass

Network

Element

Network

Element

Transponder

Module

Pass

Pass

Add

Add

Software Controlled Selectors – 32 Ch.

(Pass-through/Add/Block)

l1 l3

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Optical Amplifer Block Diagram

45

• Unidirectional operation

• Extends the reach of a DWDM span

OA

DWDM

fiber

Attenuated input

composite signal

Amplified output

composite signal

Powerin Powerout

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Transponder Block Diagram

46

Optical fiber

Non-ITU-T

compliant wavelength

ITU-T

compliant wavelength

O-E-O

wavelength conversion

850, 1310, 1550 nm 15xx.xx nm

Transponder

Tx

Rx G.709 Enabled

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Muxponder Block Diagram

47

Optical fibers

Multiple Non-ITU-T

Compliant Clients

ITU-T

compliant wavelength Multiplexing and O-E-O

wavelength conversion

850, 1310, 1550 nm 15xx.xx nm Tx

Rx

Muxponder

G.709 Enabled

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Pluggable Optics

10G

XENPAK, X2, XFP

and SFP+

Below 10G

GBIC and SFP

40G/100G

CFP and CXP

48

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DWDM System

49

OEO Tx Rx

Tx Rx

OADM OA OA

Rx Tx

Transponder interface

OEO Tx Rx

Tx Rx

Direct interface

To client devices

Client Client

Mux and

demux Mux and

demux

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DWDM Software

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Intelligent DWDM

• Modern systems compensate real-time for variations in the network

– Gain Equalization

– Amplifier Control

– Automatic Node Setup

– Automatic Power Control

– WSON Restoration

• Allows for less truck rolls and maintenance windows

51

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Why Per-Channel Optical Power Equalization

• For amplifiers to operate correctly, all channels must be equalized in power.

• If channel powers are not equal, more gain will go to the higher powered channels.

• Channel power is inherently unequal due to different insertion losses, different

paths (add path vs. express/pass-through), etc.

• Controlling the optical power of each channel in an optical network is required.

AMP

AMP

Optical Power Equalized Channels

Channels with Unequal Optical Power

OADM Without Power Equalization

Express Path

Add/Drop

Path

Why Per Channel Equalization

52

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OADM Without Power Equalization

Express Path

Add/Drop

Path

Example

53

AMP AMP

OADM With Power Equalization

Express Path

Add/Drop

Path

AMP AMP

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ANS Example

54

Express Path

Add/Drop Path

AMP AMP

T3

T Target Power

T2

T1

VOA

T4

ANS Target

Powers

Per Channel Power

T1 +2dBm

T2 -16dBm

T3 -9dBm

T4 +2dBm

Express Path VOA

Constant Attenuation L1

L2

L3

Loss dB

L1 (Express Drop) 2.5dB

L2 (Per Ch Add) 5.0dB

L3 (Express Add) 2.5dB

L4 (Per Ch Drop) 5.5dB

VOA dB

Express Path VOA 6dB

Add VOA N/A (depends upon laser

TX power

Drop VOA 12.5dB (Start point)

Add/Drop VOA

Constant Power

L4

• Target Power comes from design tool or Measured Span Loss Values from System

• Loss values are measured and stored in the OADM(s) / ROADM(s)

• Constant Attenuation VOA’s set via ANS software logic

• Constant Power VOA’s set to close loop Loss L

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Constant Power Mode

55

AMP

Initial condition – 2 channels

Total Output Power +2dBm

Per Channel

Power -1dBm

AMP

Adding 2 channels Amp set to Constant Power Mode

Total Output Power +2dBm

Per Channel

Power -4dBm

Add Channels Example

AMP

Initial condition – Gain 14dB

Total Output Power +2dBm

Per Channel

Power -1dBm

Per Channel

Power -15dBm

AMP

Initial condition – Gain 16dB

Total Output Power +2dBm

Per Channel

Power -1dBm

Per Channel

Power -17dBm

Span Loss Increase Example

Per Channel

Power -15dBm

Per Channel

Power -15dBm

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Constant Gain Mode

56

AMP

Initial condition – Gain 14dB

Total Output Power +2dBm

Per Channel

Power -1dBm

AMP

Gain Stays Constant – Gain 14dB

Total Output Power +5dBm

Per Channel

Power -1dBm

Add Channels Example

AMP

Initial condition – Gain 14dB

Total Output Power +2dBm

Per Channel

Power -1dBm

Per Channel

Power -15dBm

AMP

Gain stays the Same – Gain 14dB

Total Output Power -1dBm

Per Channel

Power -4dBm

Per Channel

Power -18dBm

Per Channel

Power -15dBm

Span Loss Increase Example

Per Channel

Power -15dBm

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Automatic Power Control

57

• Automatically corrects amplifier power/gain for capacity change, ageing effects, operating conditions

• Keep traffic working after network failires

• Prevent BER due to network degrade

• Keep constant either power or gain on each amplifier

• No truck rolls

• No troubleshooting required

• No operation complexity

APC

No Human Intervention Required

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Automatic Laser Shutdown (ALS) w/ Booster

58

• ALS is required to decrease the risk of laser damage to the human eye

• The complete sequence of events is completed within 1s as required by IEC 825-2

• This is not possible on passive dwdm systems

OSCM

OPT-BST Node B

East side

OPT-PRE

P

P

OSCM

OPT-BST

Node A

West side

OPT-PRE

Fiber cut

Amplifier Automatic

Lasers Shutdown

Payload (LOS-P) & OSC

(LOS-O) detected

1 1

Loss Of Signal (LOS) is

declared 1

Amplifier Automatic

Lasers Shutdown

P

P

Amplifier Automatic

Lasers Shutdown

Payload (LOS-P) & OSC

(LOS-O) detected 1

1

Loss Of Signal (LOS) is

declared 1

Amplifier Automatic

Lasers Shutdown

LOS-O is detected

OSCM Automatic

Laser Shutdown

LOS-O is detected

OSCM Automatic

Laser Shutdown

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Dynamic Optical Restoration Touchless Optical Layer + Embedded WSON Intelligence

ONS 15454

MSTP

Client

Colorless, Omni-Directional ROADM switches the path Service is brought back up with the same Client and Optical interfaces, zero touches

Embedded WSON intelligence locates and verifies a new path Edge Nodes instruct client to re-tune its wavelength

Fiber Cut!

animated slide

Client

IPoDWDM IPoDWDM

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Session Summary

• Dramatic increase in Bandwidth has led to the use of DWDM

• Fiber type effects the quality of transmission

• Linear Effects are predictable and can be compensated

• Non-Linear Effects are known but somewhat unpredictable

• OTN Switching is an emerging transport technology

• Modern DWDM systems are intelligent and simple to operate

• Good reference is: http://www.cisco.com/en/US/products/hw/optical/ps2011/products_technical_reference_chapter09186a00802342dd.html

60

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Glossary Arrayed Waveguide (AWG)

Automatic Node Setup (ANS)

Automatic Power Control (APC)

Chromatic Dispersion (CD)

Cross Phase Modulation (XPM)

Decibels (dB)

Decibels-milliwatt (dBm)

Dense Wavelength Division Multiplexing (DWDM)

Dispersion Compensation Unit (DCU)

Dispersion Shifted Fiber (DSF)

Erbium Doped Fiber Amplifier (EDFA)

Four-Wave Mixing (FWM)

61

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Glossary

International Telecommunications Union (ITU)

Non-Zero Dispersion Shifted Fiber (NZ-DSF)

Optical Add Drop Multiplexer (OADM)

Optical Signal to Noise Ratio (OSNR)

Optical Supervisory Channel (OSC)

Optical Supervisory Channel Module (OSCM)

Polarization Mode Dispersion (PMD)

Reconfigurable Optical Add Drop Multiplexer (ROADM)

Self Phase Modulation (SPM)

Single Mode Fiber (SMF)

Variable Optical Attenuator (VOA)

62

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Continue Your Education

• Demos in the Cisco Campus

• Walk-in Self-Paced Labs

• Table Topics

• Meet the Engineer 1:1 meetings

64

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