Dwdm Poster

DWDM building bandwidth for the future

DWDM impairments

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Linear effects

Optical Transport Networks (OTN)

Abbreviation

Description

AON APD

All optical network Avalanche photo diode

IL ITU ITU-T LAN MUX

Insertion loss

OTN OXC

Optical transport networks Optical cross connect

PDL

Polarization dependent loss

PMD

Polarization mode dispersion

Multiplexer

PoS

Milliwatt

RFA

Packet over SONET/SDH Raman fiber amplifier

Nanometer Network management system

SBS

Stimulated Brillouin scattering

SDH SMF

Synchronous digital hierarchy

SOA

Semiconductor optical amplifier

Amplified spontaneous emission

dB DCF

Decibel Dispersion compensating fiber

Noise

DCM

Dispersion compensating module

Distance

DEMUX Demultiplexer

NMS

DFB DSF

Distributed feedback Dispersion shifted fiber

NZDSF Non-zero dispersion shifted fiber Optical carrier OC

DWDM

Dense wavelength division multiplexing

O/E

Optical-to-electrical converter

E/O

Electrical-to-optical converter

OADM

Optical add/drop multiplexer

EDFA

Erbium-doped fiber

OCC

Optical connection controller

ER

OFA

Optical fiber amplifier

FB

Extinction ratio Fabry-Perot

FWHM FWM

Full width at half maximum Four wave mixing

OFE OQM

Optical front-end

ORL

Gbps

Gigabit per second

GigE

3. Optical window

PMD – the effect of the different polarization modes (horizontal and vertical) of a signal statistically traveling at different velocities due to fiber imperfections. Effects: decrease of peak power distortion of pulse shape and bit errors

Solutions: careful fiber laying (no stress), use of new fiber with low PMD values, exact fiber geometry

1550

l/nm

Noise – unwanted power resulting from system components or natural disturbances.

mW nm

Single-mode fiber

SONET Synchronous optical network Self phase modulation SPM SRS Tbps

Stimulated Raman scattering Time division multiplexing

Optical Q-factor meter

TDM TIA

Optical return loss

TP

Transponder

OSA

Optical spectrum analyzer

WAN

Gigabit Ethernet

OSC

Optical supervisory channel

WDM

Wide area network Wavelength division multiplexing

GVD

Group velocity dispersion

Optical signal-to-noise ratio

XPM

Cross phase modulation

IEC

International electrotechnical commission

OSNR OTDR

Solutions: use of shorter spans and purer fiber material

Effects: decrease of peak power and bit errors

International Telecommunication Union ITU Telecommunication Sector Local area network

Chromatic dispersion

Attenuation and noise Attenuation – loss of signal power caused by factors such as material absorption and impurities.

Description

ASE

Polarization mode dispersion (PMD)

1310

Abbreviation

CD

0.1 850

Description

Power conversion

Terabit per second Telecom Industry Association

Optical power conversions dBm = 10 log10 {P/1 mW} Power (W) Power (dBm) +40 dBm 31.6 W +35 dBm 3.16 W +30 dBm 1W +25 dBm 316 mW +20 dBm 100 mW +15 dBm 32 mW +10 dBm 10 mW +7 dBm 5 mW 0 dBm 1 mW -3 dBm 500 µW -10 dBm 100 µW

Optical time domain reflectometer

Optical eye pattern X

Positive chromatic dispersion Chromatic dispersion (CD)

CD – the phenomenon of the different wavelengths of an optical pulse traveling at different velocities along a fiber and arriving at different times in the receiver.

Fiber classification facts

Solutions: use of fibers or modules with reverse CD values (DCF/DCM)

Effects: decrease of peak power, pulse broadening and bit errors

Bandwidth conversions

Bandwidth conversions du = {c/l2} Dl GHz to nanometers at 1550 nm

CD coefficient in ps/(nm*km)

Dispersion compensation modules (DCM)

Non-linear effects

Power

Cross phase modulations (XPM)

Power

Scattering effects

Parametric effects

G.655 non zero disp. shifted fiber 0

G.653 dispersion shifted fiber -10

16 75

16 25

15 30 15 65

14 40 14 60

12 60

1300

1200

1400

1600

1700

Stimulated Brillouin scattering (SBS)

Optical fiber amplification

Solutions: spectral broadening of the light source

Effects: decrease of peak power and OSNR, optical crosstalk especially in bi-directional DWDM systems, bit errors

Basic configuration of the EDFA

DWDM signal

Four wave mixing (FWM)

DWDM DEMUX

f331

WDM coupler

Input

Output

EDFA gain

12

Er-doped fiber

l1

Pump LD

Optical safety procedure and requirements for optical transport systems

G.692

Optical interfaces for multi-channel systems with optical amplifiers (DWDM systems, channel spacing grids and reference test points)

G.709

Interfaces for the optical transport network (OTN) (2.7 Gb/s, 10.7 Gb/s, 43 Gb/s, FEC and digital wrapper)

G.957

Optical interfaces for equipment and systems relating to the synchronous digital hierarchie

TP

l2

GR-1221 8

GR-2854 6

l3

Crosstalk Crosstalk occurs in devices that filter and separate wavelengths. A proportion of optical power intended for a specific channel is found in an adjacent or different channel. Solutions: use appropriate optical channel spacing, for example 0.4 nm ® 10 Gb/s

Generic reliability assurance requirements for passive optical components Generic requirements for optical isolators and circulators

GR-2882

Generic requirements for fiber-optic dispersion compensators

GR-2918

DWDM systems with digital tributaries for use in metropolitan areas

4

Erbium-doped fiber amplifier (EDFA) EDFAs are the most common OFAs used. This piece of optical fiber is doped with Erbium ions (Er3+). Radiation from a pump laser outside the wavelength range is introduced into the fiber resulting in amplification of the data signal.

http://www.iec.ch

2

0 1500

TIA 1520

1540

1560

1580

1600

1620

Wavelength (nm) Raman amplification This optical amplification process takes place throughout the transmission fibers in optical networks. It is initiated by pump lasers and wavelength scattering from fiber atoms that alter the wavelength to that of the optical signal. The optical fiber is commonly pumped backwards with a 600 mW laser which is most efficient with a wavelength difference of 100 nm/13.2 THz to the signal.

Note: Specifications, terms and conditions are subject to change without notice.– © 2005 JDS Uniphase Corporation. All rights reserved. 10143228 500 1205 DWDM.PO.FOP.TM.AE

http://www.tiaonline.com

TIA/EIA-526-4A Optical eye pattern measurement procedure TIA/EIA-526-6

TIA/EIA 526-12

Optical signal to noise ratio measurement procedure for dense wavelength division multiplexed systems Q-factor measurement procedure for optical transmission systems

196.10 196.05 196.00 195.95 195.90 195.85 195.80 195.75 195.70 195.65 195.60 195.55 195.50 195.45 195.40 195.35 195.30 195.25 195.20 195.15 195.10 195.05 195.00 194.95 194.90 194.85 194.80 194.75 194.70 194.65 194.60 194.55 194.50 194.45 194.40 194.35 194.30 194.25 194.20 194.15 194.10

Nominal central frequencies (THz) for spacings of 100 GHz and above

G.664

Telcordia http://www.telcordia.com

Crosstalk

TP

Effects: generation of additional noise affecting optical signal to noise ratios (OSNR), leading to bit errors

Gain (dB)

f321 f231 f332

f221

f312 f223

f223

f132 f231 f112

f113

l1-ln

f/GHz

Solutions: use of fibers with CD, irregular channel spacing

Application related aspects of optical amplifier devices anbd subsystems (describes non-linear effects)

Basic specifications for optical test methods 61291-1 Optical fiber amplifiers

Raman gain

TP

Effects: power transfer to new signal frequencies (harmonics), channel crosstalk and bit errors

G.663

61290

10

Crosstalk

This interference phenomenon produces unwanted signals from three frequencies (fxyz = fx + fy - fz) known as ghost channels. As three channels automatically induce a fourth, the term four wave mixing is used. FWM is problematic in systems using DSF fibers. Wavelengths traveling at the same speed at a constant phase over long time periods increase the effect of FWM.

Generic characteristics of optical amplifier devices and subsystems

IEC

14

Original channels

Interference products

G.662

G.959.1 Optical transport networks with physical layer interfaces

Gain profiles

f3

Definitions and test methods for the relevant generic parameters of optical amplifier devices and subsystems

Wavelength (nm)

Further limitations f2

G.661

Nominal central frequencies (THz) for spacings of 50 GHz

U-band (Ultra long wavelength)

L-band (Long wavelength)

Blue-banbd, C-band, Red-band

1500

Optical isolator

f1

http://www.itu.int

196.10 — 196.00 — 195.90 — 195.80 — 195.70 — 195.60 — 195.50 — 195.40 — 195.30 — 195.20 — 195.10 — 195.00 — 194.90 — 194.80 — 194.70 — 194.60 — 194.50 — 194.40 — 194.30 — 194.20 — 194.10

Nominal central frequencies (THz) for spacings of 50 GHz

Effects: spectral broadening, initial pulse compression (in positive CD regime), accelerated pulse broadening (in negative CD regime) and channel crosstalk due to walk-of effect

Solutions: use of fibers with CD

ITU-T

0.1

This backscattering process causes loss of power. Signal lightwaves induce periodic changes in the fiber’s refractive index at high power.

With high signal intensities, light induces variable local changes in the fiber’s refractive index known as the Kerr effect that produces a varying phase in the same channel.

10 pW 1 pW

-80 dBm -90 dBm

FrequencIes

References

Nominal central wavelengths (nm)

Red shift

0.2

S-band (Short wavelength)

Solutions: careful power level design

Effects: decrease of peak power and OSNR, optical crosstalk especially in bi-directional DWDM systems, bit errors

0.3

S+-band

G.655 non-zero dispersion shifted fiber (NZDSF) reduces non-linear effects caused by multiple wavelength transmission and high-power laser by leaving a small amount of CD in the fiber.

0.4

E-band (Extended)

This effect transfers power from a signal at a shorter wavelength to one at a higher wavelength. Signal lightwaves interact with optical photons in the silica fiber and are scattered in all directions.

Self phase modulation (SPM)

100 GHz » 0.8 nm 50 GHz » 0.4 nm 25 GHz » 0.2 nm

0.5

O-band (Original)

Channels

Attenuation (dB/km)

Channels

0.6

13 60

1400 1500 1600 l/nm G.653 dispersion shifted fiber (DSF) G.652 or “standard” fibers containing zero dispersion at 1310 nm were for transmission in the region of lowest attenuation with zero CD. the first single-mode fibers to be Intended initially for standard use used in long-haul communications. with new installations, multiple They show slightly more attenuation channels and high transmission in the 1310 nm than in 1550 nm rates have led to non-linear effects window and have the highest CD in being exhibited in these fibers. comparison to other fibers. 1300

1200

Stimulated Raman scattering (SRS)

X

T = 402 ps T = 100.5 ps T = 25.5 ps

Optical bands

Solutions: use of fibers with CD

Blue shift

G.652 standard fiber 10

2.5 Gbps 10 Gbps 44 Gbps

DCMs remove CD effects accumulated during transmission by using an element to create reverse behavior of the velocity per wavelength. CD can be compensated by using: – Fiber Bragg grating – Dispersion compensating fibers (DCF) DCFs DCMs are often integrated into optical fiber amplifiers (OFA) and can sometimes be adjusted to react to temperature dependent changes of the CD value.

-20

The effect a signal in one channel has on another signal’s phase is called XPM. It is caused by the Kerr effect but arises only from the transmission of multiple channels on the same fiber. Effects: spectral broadening, initial pulse compression (in positive CD regime), accelerated pulse broadening (in negative CD regime), channel crosstalk due to walk-off effect and bit errors

20

100 nW 10 nW 1 nW 100 pW

-13 dBm -20 dBm -23 dBm -30 dBm -40 dBm -50 dBm -60 dBm -70 dBm

50 µW 10 µW 5 µW 1 µW

1528.77 1529.16 1529.55 1529.94 1530.33 1530.72 1531.12 1531.51 1531.90 1532.29 1532.68 1533.07 1533.47 1533.86 1534.25 1534.64 1535.04 1535.43 1535.82 1536.22 1536.61 1537.00 1537.40 1537.79 1538.19 1538.58 1538.98 1539.37 1539.77 1540.16 1540.56 1540.95 1541.35 1541.75 1542.14 1542.54 1542.94

194.05 194.00 193.95 193.90 193.85 193.80 193.75 193.70 193.65 193.60 193.55 193.50 193.45 193.40 193.35 193.30 193.25 193.20 193.15 163.10 163.05 163.00 192.95 192.90 192.85 192.80 192.75 192.70 192.65 192.60 192.55 192.50 192.45 192.40 192.35

1543.33 1543.73 1544.13 1544.53

192.30 192.25 192.20 192.15 192.10

— 194.00 — 193.90 — 193.80 — 193.70 — 193.60 — 193.50 — 193.40 — 193.30 — 193.20 — 193.10 — 163.00 — 192.90 — 192.80 — 192.70 — 192.60 — 192.50 — 192.40 — 192.30 — 192.20 — 192.10

Nominal central wavelengths (nm)

2. Optical window

1. Optical window

Attenuation in singlemode fibers dB/km

Signal

Abbreviation

Nominal central frequencies (THz) for spacings of 100 GHz and above

Power

Lt

1

Acterna Test & Measurement Solutions

Dispersion effects

Attenuation loss

10

Glossary

1544.92 1545.32 1545.72 1546.12 1546.52 1546.92 1547.32 1547.72 1548.11 1548.51 1548.91 1549.32 1549.72 1550.12 1550.52 1550.92 1551.32 1551.72 1552.12 1552.52 1552.93 1553.33 1553.73 1554.13 1554.54 1554.94 1555.34 1555.75 1556.15 1556.55 1556.96 1557.36 1557.77 1558.17 1558.58 1558.98 1559.39 1559.79 1560.20 1560.61