fiber optic network design class 8 c. s. yan, x. wu, m. y. li dept. of opt. engr., zju 2013

Fiber Optic Network Design

Class 8Class 8

C. S. YanC. S. Yan, , X. Wu, M. Y. LiX. Wu, M. Y. Li

Dept. of Opt. Engr., ZJUDept. of Opt. Engr., ZJU

20132013

ContentIntroduction

Development of optical fiber communicationBottlenecks

Basic theory of COCAdvantages, Principles, Structures and typesDPSKDP-QPSK

Simulation of DPSK system by OptisystemPulse generationSequence decoderBalanced receiver

Exercise todayReference

• Higher Spectral Efficiency• Higher Data Rates• Higher Receiving Sensitivity

Introduction

Development process on optical transmission rate and transmission distance product for thirty

yearsMoore's Law

bottlenecksRevolution?

Introduction

Year Development1966 C. K. Kao: fiber as communication medium 1976 Fiber loss <0.47dB/km (1.2um)1976 44.7Mb/s, 10km (Atlanta, multi-mode fiber)1976-1978 34Mb/s (100Mb/s), 64km (Japan)1983 400Mb/s (1.6Gb/s), 3400km, (Japan’s

north-south route)1988 6400km, TAT-8 Atlantic submarine cable1989 13200km, TPC-3/HAW-4 Atlantic submarine

cable

Development of optical fiber communication in the earlier years

Introduction

1. Chromatic dispersion

What is the bottlenecks for DWDM

2. polarization mode dispersion

Introduction

Nonlinear effect BottlenecksStimulated Raman Scattering

SNR degradation as the number of channel increases

Four-wave mixing Limit the channel spacingCross phase modulation

Limit the number of channels

3. Nonlinear effect

4. Electronic rateWhen >30GHz ， limited by electronic circuit and ADC chip

What is the bottlenecks for DWDMIntroduction

How to break through the bottlenecks ——Optical Time Domain Multiplexing (OTDM)?

8

4x40Gb/sdelayed

1x 160Gb/s

Electronic signals Optical signals

Introduction

The advantages of OTDM

Characteristics Advantages

Single wavelength operation

No gain flatteningSimple dispersion managing

All-optical digital signal processing

Overcome the electronic bottleneckImprove network capacityNetwork signal stream all-optical regeneration

Reduces signal noise and crosstalk accumulationTruly transparent transmission of optical signals

Bandwidth on demand

Flexibility to provide emergency service access

Achieved through the slot allocation routing

Data format and protocol transparent transmission

Introduction

The Disadvantages of OTDM

High price

Ultra-narrow optical pulse laser

Optical clock extraction and de-

multiplexing

Severe nonlinear effects

Introduction

Combination of OTDM and WDM

Introduction

How to breakthrough? COC?

Amplitude Modulation WDM

OTDM

Phase Frequency Polarization Modulation

Coherent Optical

Communication

Basic theory of coherent optical communication

Opportunities come again COC

solve the problem of channel attenuationBut hard to large scale CommercialReplaced by EDFA in the 1990s

2004, M. G. Taylor, PTL, Proposed to restore the signal using DSP, Digital coherent receiver technology

2004, 20Gbit/s, QPSK system

2002, R. A. Griffin (UK), DQPSK


Advantages of COC

AdvantagesHigh sensitivity and long distance relay

Sufficiently close to the quantum limit by raising the power of the LO light.

Good wavelength selectivity and large communication capacityLarge dispersion and nonlinear toleration

linear system, The linear distortion owing to dispersion and PMD can be completely compensated.

Use DSP to restore the dataUse electronic devices for Dispersion compensation and Polarization equalization

Low cost, high reliability, Commercialization,

Support various modulation schemes

M-PSK, M-QAM , OFDM, with higher spectral efficiency


The principle of COC

)](exp[)( SSss tjEtE

)](exp[)( LLLL tjEtE



)cos()( LSIFLSLS tPPRPPRI 2

Detector Responsivity

Optical power

)cos()(

)cos()(

LsIFLs

LSLs

tPPRtI

PPRtI

2 :detection Heterodyne

2 :detection Homodyne

termDC a as filtered becan

, Because

)( LS

sL

PPR

PP



Homodyne detection

Heterodyne detection

Advantages:

Disadvantages:High frequency stabilityNarrow bandwidthFrequency tunable

Optical phase locked loop (PLL)

SNR is two times lower than homodyne

Lout PI

Cor 0 Ls


Structures and types of coherent receivers

OFDM ngmultiplexidivision frequency Optical

64QAM

16QAM

8QAM

amplitude) & (phase QAMon Based

NRZ

RZ

QPSK-DP

QPSK

DPSK

modulation phaseon Based

Receiver

Cohenent


(Quadrature Amplitude Modulation)

(Differential phase shift keying)

Signal Modulation of Differential phase shift keying (DPSK)


phase change between 0 and 1 code

Coherent demodulation process of DPSKBasic theory of coherent optical communication

Modulation formats comparison of coherent receivers

OSNR=0.2dB

100Gbit/s50GHz channel spacing


After 1600km transmission in standard single-mode fiber

Dispersion can be compensated by DSP. For the same dispersion, it has different requirement for the computing power of the DSP (serials)


Modulation formats comparison of coherent receivers

Coherent receiver of Dual-polarization quadrature phase shift keying (DP-QPSK)

Polarization separation

Demodulation

Phase intensity

Balanced receiverTIA: Trans-impedance amplifierOptical Electrical


Optical fiber type

Free space type

90 phase shift mixer of DP-QPSKBasic theory of coherent optical communication

LiNbO3 waveguide type

Si-based monolithic integration

Bell Lab 2010

90 phase shift mixer of DP-QPSKBasic theory of coherent optical communication

90 phase shift mixer of DP-QPSK

Furukawa

Si-based monolithic integration type

InP-based monolithic integration type

Bell Lab 2011



Major international manufacturers of 100Gbit / s coherent receiver



Physical map of InP based monolithically integrated coherent receiver by HHI and U2T


DPSK—pulse generation

Simulation of DPSK system by Optisystem software

MiI kiki ,,,cos 21

MiQ kiki ,,,sin 21

MiiMkki ,,, 2112

1

nM 2

Constellation diagram

M-ARY pulse generator and Threshold detector


input M-ary signal

linear gain parameter Bias

bit period duty cycle

pulse position

if the signal input has a value of -3.3, the output level will be -3, since -3.3 is between -3.5 and -1.5.

DPSK—pulse generation and decoding


DPSK sequence decoderSimulation of DPSK system by Optisystem software

MiiMkki ,,, 2112

1

nM 2

MiI kiki ,,,cos 21

MiQ kiki ,,,sin 21

k

k

I

Qarctan

1

21

M

i kk

The DPSK decoder will calculate the value of i from the phase difference between consecutive signals k and k-1:

DPSK sequence decoderSimulation of DPSK system by Optisystem software

Assuming ϕ=0, if bits per symbol (n) equals 2, and M=4, then the values for I and Q will be:

Assuming ϕ=0, if bits per symbol (n) equals 3, and M=8, then the values for I and Q will be:

Balanced receiverSimulation of DPSK system by Optisystem software

Balanced receiverSimulation of DPSK system by Optisystem software

IFIFLOsLOs tPPRPPRI cos2

1

IFIFLOsLOs tPPRPPRI cos2

1

IFIFLOs tPPRI cos2

Eliminate intensity noise, improve sensitivity

Exercise today

Set up and study the system

Reference

刘卫华 . 用于 100Gbit/s 相干通信的 90°相移光混合器研究 . 华中科技大学博士学位论文 . 2012

王甲琛 . 基于 FPGA 的 DPSK调制解调技术的设计与实现 . 西安电子科技大学硕士学位论文 . 2010

fiber optic network design class 8 c. s. yan, x. wu, m. y. li dept. of opt. engr., zju 2013

Documents

electronic circuit

dispersion compensation

electronic ratewhen

chromatic dispersion

fiber loss

datause electronic devices

communication medium

nonlinear effect4