Integrated optical devices/circuitsfor photonic network applications

先端超高速情報工学

留学生特別コース）

Advanced High-Speed Communication Engineering

Hirohito Yamada

Integrated optical devices/circuits for photonic network applications

Lecture on July 12,19 2018

Self-intoroduction

Hirohito Yamada

1987 Graduated from Dep. of Electronics, Graduate School of Eng.,Tohoku Univ.

Doctor Engineering in study of surface emitting laser diodes 1987 – 1997 Research Laboratories, NEC Corp.

Research and development of laser diodes for optical communications 1997 – 1998 Physical Sciences, NEC Research Institute, Inc., Princeton, NJ

Research of wavelength tunable lasers with photorefractive materials

1998 – 2006 Research Laboratories, NEC Corp.

Research of photonic crystal and Si waveguide devices 2006 – Graduate School of Engineering, Tohoku University

Education in Department of Communications Engineering Research of Si photonic devices for optical communications

Lecture contents

Purpose of this lecture:

- To understand background of requiring high-capacity networks - To study about current optical communication systems and future

photonic network systems

- To study about optical devices and integrated optical circuits Lecture contents:

- Background of requiring high-capacity optical network - Photonic network and photonic node

- Optical devices and integrated optical circuits for photonic network Lecture slide can be downloaded from:

http://www5a.biglobe.ne.jp/~babe Any questions:

E-mail: [email protected]

Background of requiring high-capacity networks

Optical fiber submarine networks

Cited from https://www.alcatel-lucent.com/solutions/submarine-networks

Cited from: http://premium.nikkeibp.co.jp/ftth/part2/top_f.html

Familiar optical fiber communication

Internet FTTH(Fiber To The Home)

ONU(Left) Router(Right

Digital input/output cable of AV equipment )

Digital input/output cables and connectors of AV equipment

Familiar optical fiber communication

In multi-family apartment buildings, VDSL systems are used.

The VDSL uses optical lines up to the shared part where converts from light into electric signals by ONU.

VDSL(Very high speed Digital Subscriber Line)Cited from NTT East HP

Optical fibers used in data communications

Storage Area Network(SAN) with Active Optical Cable(AOC)

Bus interface for the SONY VAIO Z Backplane of a server

Universal Bus Interface for PC Light Peak

Optical Tx/Rx module for data communications

10Gbps, 12ch(120Gbps) Parallel optical module

MicroPOD^TM made by Avago

IBM Power775 super computing component

System board of Power775

Board-to-board optical link

Automotive Optical Network

Car Area Network(CAN)

Optical interconnection between LSI chips

Optical communication is being studied between LSI chips Laser diode

Si substrate

Photo diode Optical waveguide

Optical modulator LSI chip

Cited from PETRA HP

On-chip optical interconnection for LSI

Global

interconnection

Local

interconnection Transistor layer

Advantages - High speed

- Low power consumption - Low noise

Optical interconnection

Cross-section of LSI chip (Intel) 130nm 6-layer cupper wire

Problems

- Clock frequency - Power consumption - EM noise

Emerging performance limit of LSI

Performance limit of electrical interconnection Many core architecture

Optical interconnection Electrical interconnection

Change in clock frequency of CPU

year

year Clock

Number of core

Spreading application range of optical communication

Rack to rack → Board to board → Chip to chip → On chip interconnection

Cited from: C. Gunn, “CMOS Photonics™ Technology Enabling Optical Interconnects” Luxtera, Inc.

Light Peak Infiniband

DDR(20Gbps)AWG24 Up to 20m

Active optical cable (AOC) Up to 100m

Growth of internet traffic in Japan

Total download traffic in Japan

Total upload traffic in Japan

Daily average value

year

Cited from: H29

年度版情報通信白書

Total download traffic reached 10Tbps at the end of 2016

Annual growth rate: 40%

Power consumption forecast of network equipments

Domestic internet traffic is increasing 40%/year

If increasing trend continue, by 2024, power consumption of ICT equipments will exceed total power generation at 2007

http://www.aist-victories.org/jp/about/outline.html

Annual power consumption of network equipments (×1011 Wh)

year

Total internet traffic (Tbps)

Network traffic Total power generation

at 2007

Power consumption

Data transmission capacity

Question:

How much information can be transmitted by a thin piece of optical fiber ?

- Apple Thunderbolt: 20G bps Hint:

- FTTH (au

ひかり ホーム

ギガ

B. 10T bps (1T = 10¹²) C. 1P bps (1P = 10¹⁵)

Multiplexing in telecommunications

t₁ t₂ t₃

Bandwidth of transmission line

f₁

Signal bandwidth

f₂ f₃ f₄

frequency t

t₁ t₂ t₃

1 msec Time-division multiplexing (TDM)

Frequency-division multiplexing (FDM) Single transmission line

Multiplexing in electrical communications

Osc. Mod. DeMod.

Electric cable

2.4 Gbps 2.4 Gbps

bps: bit per second

1Gbps

100 Mbps

64 kbps 64 kbps

100 Mbps 1Gbps

2.4 Gbps

TDM or FDM

Demultiplexer Multiplexer

Multiplexing by increasing the modulation speed (high bit rate) Carrier

Multiplexing in optical communications

Multiplexing in electrical domain

- Electrical time-division multiplexing (ETDM)

- Electrical frequency-division multiplexing (EFDM)

Up to 100G bps, limited by response speed of electronics

time (frequency)

Ch1 Ch2 Ch3

Light Source

Photo Detector/

Demodulator Optical

Modulator Optical fiber

40G bps bps: bit per second 40G bps

1G bps 100M bps

64k bps 64k bps

100M bps 1G bps

40G bps

ETDM or EFDM

Demultiplexer Multiplexer

Optical Electrical

Optical Modulation

Direct modulation of laser diode Optical modulator

- Electro-absorption (EA) optical modulator

- LiNbO₃ (LN) MZI optical modulator

L-I characteristics of laser diode

Optical signal

Electrical signal Current

40G bps EA modulator (OKI)

LN optical modulator (Sumitomo Osaka Cement)

Light output

Developing history of optical-link capacity

Developing history of optical-link capacity in Japan

F-32M F-100M

F-400M

1980 1985 1990 1995 2000 2005

0.01 0.1 1 10 100 1,000 10,000

FS-400M F-600M F-2.4G F-1.6G

F-1.8G

FA-10G

FA-2.4G FSA-2.4G

new F-600M

Year

Transmission capacity (Gbit/s)

With optical amplifier SDH System

With dispersion shifted optical fiber With DFB-LD

With single-mode fiber

Commercial system

ETDM

Laboratory

ETDM

1^st generation with ETDM, EFDM (Electrical method)

Multiplexing method of 1^st and 2^nd generations

Electrical multiplexing

- Electrical time-division multiplexing (ETDM)

- Electrical frequency-division multiplexing (EFDM)

Up to 100Gbps, limited by response speed of electronics Optical multiplexing

- Wavelength division multiplexing (WDM)

More than 10T bps transmission (40G bps×273 wave ＝ 10.9T bps, 117km) have been demonstrated in 2001

Using many different wavelength as different channel

λ₁ λ₂ λ₃ λ₄ λ₅ λ₆ λ₇

λ₁ λ₂ λ₃ λ₄ λ₅ λ₆ λ₇

WDM transmission (1^st generation)

(2^nd generation)

time (frequency)

Ch1 Ch2 Ch3

- Optical time-division multiplexing (OTDM)

Bandwidth of silica optical fiber C-band L-band

1460nm 1530nm 1565nm 1625nm

S-band

~21 THz

WDM transmission with single fiber

Laser PD

DEMOD 40G bps

MOD Laser

Laser MOD PD

PD DEMOD

DEMOD MOD

Wavelength Multiplexer

Wavelength Demultiplexer Single fiber

40G bps 40G bps

40G bps λ₁

λ₂ λ₃

λ₁ λ₂ λ₃ 120G bps

40G bps

40G bps 40G bps

40G bps

40G bps Electrical

Multiplexing

Electrical Demltiplexing

Developing history of optical-link capacity

Developing history of optical-link capacity in Japan

F-32M F-100M

F-400M

1980 1985 1990 1995 2000 2005

0.01 0.1 1 10 100 1,000 10,000

FS-400M F-600M F-2.4G F-1.6G

F-1.8G

FA-10G

FA-2.4G FSA-2.4G

new F-600M

Year

Transmission capacity (Gbit/s)

With optical amplifier SDH System

With dispersion shifted optical fiber With DFB-LD

With single-mode fiber

Commercial system

ETDM

Laboratory

ETDM

1^st generation with ETDM, EFDM (Electrical method)

2^nd generation using WDM and Optical Amp. (Optical method)

F-6M

WDM System WDM + ETDM

WDM + ETDM OTDM

WDM + OTDM

1.6T (40G×40)

3^rd

Multiplexing method of 3^rd generations

Coherent transmission ‥‥ modulating both amplitude and phase of lightwave Optical orthogonal detection, Optical heterodyne/homodyne detection Digital coherent optical transmission

Multilevel modulation ‥‥ QAM, DPSK/DQPSK/DP-QPSK etc.

Digital signal processing (DSP) ‥‥ Error correction code (FEC)

Electrical

Electrical Code-division multiplexing (CDM) (3^rd generation)

Increasing transmission capacity of optical link

1980 1990 2000 2010 2020

year 100T

10T 1T

100G 10G 1G 100M

1P

Transmission capacity per single fiber (bps)

Electrical Mux.(Laboratory) Electrical Mux.(Commercial)

Optical Mux.(Laboratory) Optical Mux.(Commercial) ETDM

EFDM

1^st Gen. 2^nd Gen. 3^rd Gen.

WDM OTDM

Multilevel Modulation Digital coherent

What technology drive next gen.

?

Multiplexing method of 4^th generations

1. SDM using an optical fiber with multi-core Space-division multiplexing (SDM)

1.01P bps (380G bps×222 wavelength×12 core) 52.4 km transmission with multi-core fiber (NTT, Fujikura Ltd, Hokkaido Univ. and Technical U niversity of Denmark reported in ECOC2012)

(4^th generation) Optical

Cross section of 19 core fiber (Furukawa Electric Co., Ltd)

core

Ch1

SDM transmission with a multi-core fiber

Ch2Ch3 Ch4

Ch1 Ch2Ch3 Ch4

core

125 μm

Conventional single-core fiber

125 μm core clad

Multiplexing method of 4^th generations

Space-division multiplexing (SDM) Optical (4^th generation) 2. SDM using spatial modes with a multi-mode fiber

Mode1 Mode2 Mode3 Mode4 Mode5

SDM transmission with a multi-mode fiber

Propagating modes in a multimode fiber

LP₀₁ mode LP₀₂ mode LP₁₁ mode LP₂₁ mode LP₃₁ mode

Each spatial mode transmit different signal as different channel

Multiplexing method of 4^th generations

3. Multi-input/multi-output (MIMO) transmission with a multi-mode fiber

Tx1 Tx2 Tx3

Rx1 Rx2 Rx3 MIMO transmission for wireless systems

“Space” is the final frontier of optical communication

Rx1 Rx2 Rx3 Tx1

Tx2 Tx3

Increasing transmission capacity of optical link

1980 1990 2000 2010 2020

year 100T

10T 1T

100G 10G 1G 100M

1P

(19 core)305T (7 core)109T

1.6T

Transmission capacity per single fiber (bps)

Electrical Mux.(Laboratory) Electrical Mux.(Commercial)

Optical Mux.(Laboratory) Optical Mux.(Commercial) ETDM

EFDM

1^st Gen. 2^nd Gen. 3^rd Gen. 4^th Gen.

WDM OTDM

Multilevel Modulation Digital coherent

Multicore fiber

(12 core)1P

Total network traffic in Japan

10T (2016)

+40%/year

Summary of last week’s lecture

Transmission capacity of optical link is high enough against the demand.

Is there no need for studying optical communication for a while ?

No

Total network traffic in Japan was 10 Tbps at the end of 2016. And the annual growth rate of network traffic is 40%.

Even assuming that the growth trend of network traffic will

continue, Japan's network traffic will remain at around 100 Tbps at 2030.

We have already attained more than 1Pbps link capacity with a milti- core optical fiber.

Packet switching network

One line is shared by all user

Packet switch Packet switch

Label Data

Recent networks are packet switching network

Node (router) in the packet switching networks are performing very complex processing

Each packet has a label which inform destination address of data Every data is divided by a unit of packet (IP packet)

Function and configuration of router

Routing control ‥‥ Producing routing table

Label processing ‥‥ Reading label information and deciding output port based on routing table

Switching ‥‥ Switching output port of packet

Packet Scheduling Controlling output timing to avoid packet collision‥ ‥ Buffering ‥‥ Keeping data waiting a while for the timing of output

Date Label

Routing

(Producing routing table)

Label processing (Deciding output port)

Switching

(Switching output port)

Scheduling

(Packet collision control)

Buffering

(waiting data output) Output Function

Router configuration Packet

These functions can not be realized optically

Current optical network

Photo diode

Optical signal Electrical signal Laser

diode Laser diode Header

analysys Optical devices

Electron devices

Optical modulator

Optical modulator

Laser diode

Optical modulator

Electronic switch

Label detection

Optical(O) – Electrical(E) – Optical(O)

Buffer memory

Optical link (optical fiber) node

(router)

node

node node

(router)

Configuration of optical router High speed

Slow ! Slow !

OE/EO conversion is inevitable for optical router

Processing speed bottleneck in each node

Optical link (optical fiber) node

(router)

node

node node

(router)

Tollgate Expressway

Link capacity: 10Tbps

(40Gbps × 256 wave WDM) Processing speed: 100Gbps

Traffic jam

Problems

Transmission capacity of each optical link is high enough

However, signal processing in each optical node becomes bottleneck

Therefore, we need to realize optical network without electronic circuits

Photonic network

the operation speed of the electronic circuit is limited to 100 Gbps Since the optical router is composed of an electronic circuit,

Next generation optical network without OE/EO conversion is called

Resolving bottleneck by photonic network

node

node node

(router)

ETC system Optical link

(optical fiber) node

(router)

Link capacity: 10Tbps

(40Gbps × 256 wave WDM) Processing speed: 100Gbps

Expressway

What is photonic network

Next generation network that routes optical signals without using

OE/EO conversion (OE/EO: optical → electrical / electrical → optical)

OPS router

Mesh-type NW

OPS router OPS router

OADM(Optical Add/Drop Multiplexer)

WDM ring NW

OADM

OADM OXC

WDM ring NW

OADM

OADM

OBS(Optical Burst Switching) OXC(Optical cross connect) WDM ring-type network

WDM mesh-type network

OPS(Optical Packet Switching)

Photonic MPLS(Multi-Protocol Label Switching)

Optical Add/Drop Multiplexer(OADM)

R-OADM (Reconfigurable OADM)

Certain wavelength signal can be dropped out or added in

₁ ‥‥ _n OADM

_i _i

WDM signal

Add/Drop wavelength can be settable

₁ ‥‥ _n OADM

_i _i

WDM signal

OADM

OADM

OADM

WDM ring NW OADM

OADM

OADM

OADM

WDM ring NW OADM

OADM

R-OADM made of Si-wire waveguide

1550 1552 1554 1556 1558 1560 1562 1564 -35

-30 -25 -20 -15

Transmissions (dB)

Wavelength (nm)

0 mA 20 mA 40 mA 45 mA 55 mA 65 mA

1546 1548 1550 1552 1554 1556 1558 -40

-35 -30 -25 -20 -15

Wavelength (nm)

Transmissions (dB)

- Wavelength tuning by T-O effect - Wavelength tuning range: 6.6 nm - Channel switching time: < 100 μsec

signal in

drop out add in

through 3-dB coupler

 d

Bragg grating electrodes

heater

700 m

=370 nm d=30 nm

3-dB coupler

500 m

Wavelength tuning characteristics Demultiplexing characteristics

T. Chu et al., IEEE Photon. Technol. Lett. 18, 1409 (2006)

Wavelength Router

₁

₂

₃

₄

₁

₂

₃

₄

₁

₂

₃

₄

₁

₂

₃

₄

DEMUX MUX

DEMUX

DEMUX

DEMUX Port 1

Port 2

Port 3

Port 4

Port 5

Port 6

Port 7

Port 8

Output port can be switched by changing wavelength

₁ ₁

₃

₃ MUX

MUX

MUX

Arrayed waveguide grating(AWG)

50 mm

Arrayed Waveguide Grating (AWG)

SiO₂ core SiO₂ clad

Si substrate

0.5 m 0.5 m

Made of silica waveguide

N×N wavelength router can be constructed by an N×N AWG

AWG made by Si-wire waveguide

50 m

Size 1/1000 λ₁, λ₂, λ₃, …, λ_N

λ₁, λ₂, λ₃, …, λ_N λ₁, λ₂, λ₃, …, λ_N λ₁, λ₂, λ₃, …, λ_N

λ₁, λ₂, λ₃, …, λ_N λ₂, λ₃, λ₄, …, λ₁ λ₃, λ₄, λ₅, …, λ₂ λ_N, λ₁, λ₂, …, λ_N-1 Extremely small AWG can be realized by Si-wire waveguide

Light sources

Laser Diode

Feature

• Compact (Chip size: 0.3×0.3×0.1mm)

• Low voltage (~2V), low power operation

• High speed (>Gbps) direct modulation

• Long life (>10⁶ h)

• Low Price

へき開面(鏡面)

Structure of LD chip

Tunable wavelength laser with ring resonator LD module

K. Nemoto et al., Appl. Phys. Express 5, 082701 (2012)

Wavelength conversion with four- wave mixing

Set-up of 40Gbps NRZ wavelength conversion

Y.-H. Kuo et al., Optics Express 14, 11721 (2006)

Conversion efficiency: -8.6dB Pump power: 450 mW

40 Gbps wavelength conversion with reverse biased 8cm SOI pin rib waveguide

Spectra of converted signal

40Gbps Eye Diagram Left: Input signal

Right: Converted signal

Thermo-optic switch with Si-wire waveguide

T. Chu et al., Optics Express 13, 10109 (2005)

Electrode

Microheaters

Si-wire waveguide

0 50 100 150 200

-40 -30 -20

Transmission (dB)

Heating power (mW) Port 1

Port 2

Switching characteristics

T. Chu et al., Proc. SPIE 6477 (2007)

Photograph of the 1×8 switch

Footprint size: 4 mm×2 mm

Port1 Port2

Port8

Optical label processing

Data Data Data t

Color label Color label

₁ ₄ ₃ ₂ ₂ ₁ ₃ ₄

₁

₄

₃

₂

Optical fiber grating

Data Data Data t

Matching of label and grating pattern Circulator

Missmatching

Optical Buffer

1. Based on Optical Delay Line and Optical Switch

2. Based on Slow Light

Electromagnetically Induced Transparency(EIT)

300,000km/s 　→　 28m/s 0.9μK(-273 ) Natrium (Na)℃

70 ～ 90K(-203 ～ -183℃) Rubidium (Rb)

300,000km/s 　→　 1km/s

optical switch optical switch optical switch optical delay line optical delay line optical delay line

|1>

|3>

|2>

coupling probe

probe frequency

absorption transmittance

Photonic integrated circuit (PIC)

49

Integrated Optical Circuit

Integrating various micro photonic devices

Photonic Network

Photonic node

Integrated optical circuit Optical switch

Si waveguide MUX/DEMUX

Micro photonic devices for optical network

Photonic network Resonator

Moore's Law

Predicted by Gordon Moore (One of founders of Intel corp.) in 1965 Observation based on the history of computing hardware,

the number of transistors on integrated circuits doubles every two years

(Performance of electronics doubles every 18 months)

Evolution of Intel CPU

Collapse of Moore’s Law

Core 2 Duo Core i7

52

Photonic integrated circuit

Silicon-based PIC (Si Photonics)

Compound semiconductor-based PIC

Silica-based PLC

Monolithic integration of LDs or PDs

Simple fabrication process Complex fabrication process

Impossible to form LD or PDs

Impossible to form LDs

CMOS compatible fabrication process

NTT Electronics COBLA Proj.

53

Si Photonics

High density integration with high-Δ waveguide CMOS compatible fabrication process

Si PIC formed on a 12-inch Si wafer

~ cm

Gradual bend

Weak optical confinement

1 m

Available sharp bend

Strong optical confinement

Silica based optical waveguide

High-Δ waveguide

Massive production on a large scale Si wafer Coexisting together with electric circuit

on same wafer

Micro photonic devices realized by Si photonics

54

Ring resonator T-O switch

Directional coupler

E-O modulator MMI coupler Grating coupler

λ = 1549 nm

λ = 1569 nm

parallel

cross

Integration with compound semiconductor chips

55

Wafer bonding

Flip-chip mounting

Si substrate

Si waveguide LD chip

electrode position marker

solder bump

pedestal

electrode pad position marker

Bonding of a Si wafer with passive waveguide devices and an InP wafer with active (LDs or PDs ) devices

Flip-chip mounting of LD or PD chips on a Si substrate with passive

waveguide devices

Tunable wavelength laser diode

Wavelength [a.u.] 56

semiconductor optical amplifier (SOA)

ring resonator 1 ring resonator 2

loop mirror reflector

Transmittance [a.u.]

with large FSR with small FSR

SOA gain wavelength region facet mirror

Lasing wavelength

laser output

Tunable wavelength laser with Si waveguide ring resonator filters

Using vernier effect

Wavelength tuning operation

57

1620 1610 1600 1590 1580

L as in g W av el en gt h nm ] 1570

40 30

20 10

Ring2 Heater Power [mW]

heating heating

501GHz FSR ring2 472GHz FSR ring1

Power consumption for wavelength tuning  1.0 nm/mW

SOA injection current:50 mA

1610 1600 1590 1580 1570 1560

W av el en gt h [n m ]

50 40

30 20

10

Ring1 Heater Power [mW]

Wavelength tuning operation

58

1.600

1.595 1.590 1.585 1.580 1.575 1.570

W av el en gt h [µ m ]

50 40

30 20

10 0

Ring2 Heater Power [mW]

Fine wavelength tuning by heating both ring resonators

-40 -30 -20 -10 0

F ib er C ou pl ed P ow er [ dB m ]

1620 1610

1600 1590

1580 1570

Wavelength [nm]

SOA injection current: 50 mA

heating

heating

Electronic and optical IC

10⁷

10³

2000 year

10⁵ 10⁹

2010 10⁴

10⁶ 10⁸

Moore's Law (double/1.5 year)

Now

1970 1980 1990

10²

2020

Electronic IC

Photonic IC

87mm

74mm

Intel4004 2,300 Trs

Pentium4 42 million Trs

Pentium

3.1 million Trs Intel286

134 thousand Trs

Silica-base PLC

Si-base PIC?

16 ch R-OADM

(AWG×4, TO-SW×64)

K. Okamoto et al., Electron. Lett.

32 1471 (1996)

Core i7 1 billion Trs

Number of integrated devices (transistors) Core2Duo

Conclusion

Photonic integration is inevitable to realize photonic networks and to reduce power consumption

Optical link have been already developed for over 1Pbps transmission However, slow signal processing in optical nodes is bottleneck

We need to realize photonic network without OE/EO conversion

Silicon technology creates a new trend to realize photonic integrated circuits (PIC).

We have demonstrated tunable wavelength laser with silicon waveguide

Reporting Assignment

Describe how future networks can be solved the problems of network traffic explosion in order to enjoy a

comfortable and environmentally friendly network life.

Format: Word or PDF File

Submission to [email protected] Deadline: 3^rd August