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Lilin Yi

Chapter 9 Modulation formats in high-

speed optical communication systems

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Outline

Background – why need different modulation formatsBackground – Frequently used modulation formats in commercial systemsBasic modulation formats introductionAdvanced modulation formats introduction

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System and Network Architecture

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Increased Capacity

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Modulation formats enable higher capacity

Capacity World Record (up to 2010)

NTTPDM-16-QAM171Gb/s * 432ch69.1Tb/s6.4b/s/Hz

Spectral efficiency World Record (up to 2010)

AT&TPDM-32-QAM107Gb/s * 640ch64Tb/s8b/s/Hz

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Modulation format

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Modulation format

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Modulation formats implemented in current systems

2.5Gb/s:Internal/direct modulation, NRZ

10Gb/s:External modulation-EAM, NRZExternal modulation-MZM, CRZ

40Gb/s: External modulation-MZM, Duobinary, DPSK, CRZ, RZ-DPSK,DQPSK

100Gb/s: External modulation-MZM, PM-DQPSK, OOFDM

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Terminal productsTransceiver (transmitter-receiver without mux/demux)SFF – Small form factor, not pluggable, low speedSFP – Small form pluggable, bigger than SFF, usually for 2.5Gb/sSFP+ – Enhanced small form pluggable, same size with SFP, upgraded to 10Gb/s, without Clock recoveryXFP – specially for 10Gb/s, bigger size than SFP+

Transponder (transmitter-receiver with mux/demux, not pluggable, bigger size)10G transponder – competed by XFP and SFP+, will gradually quit 10G market40G transponder – Will be the main trend of transponder since external modulator can not be packaged into XFP or SFP+ sizeTunable transponder – Will be the main trend of transponder since it can enhance the system flexibility and reduce the system cost100G transponder – in development, will be commercially used in the next several years

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Transponder vs. transceiver

SPI: Serial Peripheral Interface

SFI: Serdes-Framer Interface

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10G Evolution

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Directly modulated laser

Low cost – access network (2.5Gb/s, less than 100 km)AM, PM, FMLarge chirp, short distance

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External modulator - EAMLarge insertion lossDFB+EAM+SOA – EMLLess chirp than DML – Metro network (10Gb/s, ~300 km)

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External Modulator - MZM

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40 Gb/s NRZ transmitter

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Ideal 40 Gb/s RZ (50%) transmitter

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Setup for pulse carving

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RZ with different duty cycle

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40 Gb/s RZ(50%) transmitter

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40 Gb/s RZ(33%) transmitter

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40 Gb/s RZ(67%) transmitter

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40 Gb/s CSRZ

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40 Gb/s CRZ

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Duobinary

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MZM switching curve

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Compared with traditional OOK

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Duobinary encoding

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Duobinary encoding

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Duobinary NRZ transmitters

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40Gb/s NRZ duobinary (delay+add)

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40Gb/s NRZ Duobinary (low-pass filter)

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40Gb/s RZ (50%) Duobinary (delay+add)

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40Gb/s CSRZ Duobinary (delay+add)

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Duobinary transmission performance

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Phase-shifted-keying in optical system

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Phase-shifted-keying

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Differential Phase-shifted-keying

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DPSK precoder

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DPSK precoder example

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Why DPSK?

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Balanced DPSK receiver

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Balanced vs Single-ended detection

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Why RZ-DPSK

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Carving Pulse

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RZ-DPSK transmitter using PM

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RZ-DPSK transmitter using MZM

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PM vs MZM

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QPSK

＋ ﹦

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Coherent QPSK

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DQPSK

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DQPSK precoder

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DQPSK transmitter

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DQPSK transmitter analysis

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DPSK demodulator

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DQPSK demodulator

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Why DQPSK

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DQPSK characteristics

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107 Gb/s DQPSK transmitter

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107 Gb/s DQPSK receiver

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DP-QPSK

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PM-DQPSK transmission performance

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Comparison of 40Gbps modulation formats

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Thanks for your attention