광통신기술

(1)

Department of Physics

나노 정보 바이오 물리

Young-Geun Han

Department of Physics

Hanyang University yghan@hanyang.ac.kr

광통신기술

(2)

Department of Physics Hanyang University

 광통신 개요 및 특징

 ^{광통신 기술}

 WDM 핵심 기술

 ^광섬유

 광통신 핵심 소자 기술

• 1976~1977 ---최초의 현장 적용시험 및 상업화 시도

• 1977 --- 2세대 광전송 시대의 개막:

1.3µm InGaAsP 레이저

• 1980 --- 0.2dB/km 광섬유 개발

• 1981 --- 1.5µm InGaAsP 레이저 개발

• 1988 --- 최초의 대서양 횡단 광케이블 1.55µm 양자우물레이저 개발

3세대 광전송의 연구 ( 1.55µm ,~10Gb/s )

• 현재 --- 4세대: 파장분할다중화(WDM)방식, 광증폭기, Soliton 연구(5세대)

광통신의 역사

(3)

광통신의 장점

• 전송용량의 증대

• 고신뢰성

• 무중계 거리의 확대

• 보안성의 증대

• 크기 및 무게의 감소

• 무한한 성장 가능성

• 저가의 시스템

광통신 전송 기술의 발전

(4)

광통신 전송링크 구성요소

전기 신호

입력 구동회로

광 전송기

광 원

광섬유 광 증폭기

광섬유

광 중계기

광 송신기 광 수신기

광 증폭기 수광 소자 신호 복원기

광 수신기

전기 신호 출력

전기 신호 광 신호

광통신 방식 I - OTDM

(5)

광통신 방식 II - WDM

WDM 핵심기술

•Source types

•Laser  control

•Laser aging

•Standard 

•Channel spacing

•Gain flattening

•Dynamic gain control

•Gain bandwidth •Demultiplexer

•Demux control

•Bandwidth

•Crosstalk

•Dispersion compensation

•Nonlinearities

Operation, Administration, Maintenance Issues...

...

... ...

...

(6)

• 1세대 WDM

– 1310 nm와 1550nm 파장대의 다중화

• 2세대 WDM

– 1550nm 파장대역에서 2~4개의 파장의 다중화 – 400 GHz 파장 간격

• 현재의 WDM - DWDM (Dense WDM)

– 16, 32, 40개의 파장의 다중화 (1550nm 파장대역) – 100 GHz 파장 간격

• 차세대 WDM

– 40~80개의 파장의 다중화 (1550nm 파장대역) – 50 또는100 GHz 파장 간격

– 1300 ~ 1600 nm 대 모두 이용

WDM 발전 동향

1Tbps급 대용량 전송 방법

(7)

광통신 핵심 소자

• 단일 모드 광섬유 (SMF: Single Mode Fiber)

• 광원 (DFB-LD)

• Photodiode (PIN, APD)

• 광 증폭기 (EDFA 등)

• 광 변조기 (LiNbO

₃

)

• 광 스위치, OXC, Optical Router …

• 다중모드 광섬유(MMF) – 코어 직경은 50mm – 모드간 분산에 의해

전송거리 제한

• 단일모드 광섬유(SMF) – 코어 직경은 9mm – 색분산에 의해 전송

거리 제한

광섬유 종류

(8)

20

10

0

-10

-20

단일모드 광섬유 종류

Optical fiber and its parameter

(9)

Single mode (SM) and multimode (MM) fibers

Cutoff condition (SM)

Dispersion shifted fiber

Cutoff condition

Yamauchi et al., J. Lightwave Technol., vol. 4, 1986

(10)

Dispersion shifted fiber

Non-zero dispersion shifted fiber

(11)

Dispersion compensated fiber

Y. Akasaka et al., OFC 96. pp. 201 – 202, 1996

A. Goel et al., IEEE Photon. Technol. Lett., vol. 8, pp. 1668 –1671, 1996

Plastic optical fiber

Y. Koike, ECOC 96. Mob3-1, 1996

(12)

Erbium doped fiber

Specialty optical fibers

(13)

What is a photonic crystal fiber ?

• A solid core surrounded by a cladding which is defined by a fine array of air holes

– Made of a single material, usually pure silica

– Critical design parameters: hole diameter (d) and pitch ( = hole to hol e spacing) on the scale of the wavelength of light.

d

L n₁

n₂



Localized region of high refractive index forms fibre “core”

Main properties of photonic crystal fibers

• Physical differences between HFs and conventional types

– The large index contrast between glass and air and the small structure dimensions co mbine to make the effective cladding index a strong function of wavelength in HF

• Single mode operation regardless of operating wavelength

– fibres with a low air fill fraction (d/ < 0.4) [T. A. Birks et al., Optics Lett., p.961 (1997)]

– Particularly significant for broadband or short wavelength applications

• Tailorable effective area by changing d, , d/

– Effective fundamental mode area at 1.55 m can be varied over three orders of magni tude from ~ 1 m2 to 1000 m2 [T. M. Monro et al., J. Lightwave Technol., p.1093 (1 999)]

– Very high nonlinearity (  , d/ > 0.8) – Very low nonlinearity (  10-15 m, d/  <0.3)

• Tailorable dispersion properties

– Anomalous at  < 1.27 m : Solitons at short wavelengths [J. K. Ranka et al., Optics L ett., p.25 (2000)]

– Highly normal at  = 1550 nm : Dispersion compensators [T. A. Birks et al., IEEE Pho ton. Technol. Lett, p.674 (1999)]

– Flat over a large wavelength range : broadband nonlinear switching and wavelength c onversion [T. M. Monro et al., J. Lightwave Technol., p.1093 (1999)]

• Polarization maintaining property

(14)

Fabrication of photonic crystal fibers

< Capillary Drawing >

< Stacking >

< Drawing >

< Stack & Draw Procedure >

– Preform Diameter : 20mm – Preform Length : 80cm

(15)

 Optical Properties

• Transmission spectrum vs. bending radius

– Experimental set-up

• White light source : Ando AQ4303B

• OSA : Ando AQ6315B

• Fiber Length : 10m

400 600 800 1000 1200 1400 1600

-90 -80 -70 -60

Transmission [dB]

W avelength [nm]

No bending 15mm bending 10mm bending 7.5mm bending 5mm bending 2.5mm bending 1.5mm bending

Fabrication of photonic crystal fibers with

small core size

(16)

Physical Property

(1) Diameter of large hole (d₁) : 2.7μm (2) Diameter of small hole (d₂) : 1.7μm (3) Diameter of core : 3.72μm / 4.78μm (4) Hole-to-hole spacing (Λ) : 3.41μm (5) d₂/ Λ = 0.499

Fabrication of PM-PCF

■Cross section of the PM-PBGF

Physical Property

(1) Diameter of holey region : 62.94μm (2) Diameter of Core : 10.75μm / 15.06μm (3) Diameter of air hole : 2.98μm (4) Pitch (Λ) : 3.04μm

(5) d/ Λ : 0.98

Fabrication of PM-PBGF

(17)

Optical fiber gratings

Principle of fiber Bragg gratings

• Coupling between forward and backward propagating core mode

• Phase matching condition: =2 n

₁



• Reflection filter

1554 1555 1556

-60 -55 -50 -45 -40

Reflection [dBm]

Wavelength [nm]

1.540 1.542 1.544 1.546 1.548 1.550 -30

-25 -20 -15 -10 -5 0

Transimission (dB)

W avelength (m)

(18)

1200 1300 1400 1500 1600

-15 -12 -9 -6 -3 0

HE16 HE15

HE14 HE13 HE12 HE11

Transmission [dB]

Wavelength [nm]

• Coupling between core and cladding modes

• Phase matching condition: =(n

₁

-n

_2,m

)

• Transmission loss filter

Principle of long-period fiber gratings

Multiwavelength Raman fiber lasers

1366 1368 1370 1372 -50

-40 -30 -20

(a) (b)

Output Power [dBm / 0.05 nm]

Wavelength [nm]

D=55cm

1366 1368 1370 1372 -50

-40 -30 -20

D=110 cm

•0.66and 0.33 nm

• Number of channel : 9and 19 ( ER > 20 dB) Gain fibers

(1064 nm Yb-doped fiber laser)

WDM

Output Pump Pump WDM

Gain fiber : high nonlinear fiber (HNLF^TM) : 4 km Dispersion-shifted fiber (DSF) : 4 km Pump power : 5 W

Cont’

Y. G. Han et al., IEEE Photon. Technol. Lett., vol. 15, no. 3, pp. 383 – 385, 2003

(19)

Multiwavelength Er-doped fiber lasers

1544 1548 1552 1556 1560 1564

-60 -55 -50 -45 -40 -35 -30 -25 -20 -15

Output Power [dBm]

Wavelength [nm]

Output Coupler

980 nm Pump LD

WDM

EDF

Isolator

Liquid Nitrogen Polarization

Controller Output Coupler

980 nm Pump LD

WDM

EDF

Cascaded LPFGs Isolator

Liquid Nitrogen Polarization

Controller

OSA

Dense Channel Spacing (~0.56nm) More than 26lasing wavelengths Gain fiber : EDF : 10 m

Pump power : 60 mW

Cont’

Y. G. Han et al., IEEE Photon. Technol. Lett., vol. 15, no. 3, pp. 383 – 385, 2003

Introduction

Introduction – Imaging Technology Imaging Technology

 Large volume scan

 Impossible to detect tumors in their early state

 Submilimter spartial resolution

 High cost

 Ability to detect biological compounds

 High cost

 Quick & Low cost

 Low resolution

○X-ray Computed Tomography (CT)

○Magnetic Resonance Imaging (MRI)

○Positron Emission Tomography (PET)

○Ultra-Sound Tomography Imaging (UTI)

○Optical Coherence Tomography (OCT)

 compactness, low cost, safety

 in vivo, in real-time high resolution imaging

CT MRI

PET UTI

OCT

(20)

0 100 200 300 400 500 600 700 Cover glass 2 Cover glass 1

Air gap

Scan distance [m]

Reference Arm Sample Arm

3dB coupler

Cover glass 1

(t = 200 m) Cover glass 2

( t = 200 m)

Principle

Principle of OCT – Reflectometry + Scanning Probe

Optical Source SLD

λ

1480 nm Pump 1480/1550nm

WDM Isolator

5m EDF 16.7dB/m@1530nm

HNL-DSF

Output 980/1550nm

Isolator WDM 5m EDF 6dB/m@1530nm

Isolator

5m EDF 6dB/m@1530nm

980/1550nm

WDM 80:20

Coupler Isolator Bandpass

Filter

Bandpass Filter

5m EDF 6dB/m@1530nm

Isolator 980/1550nm

WDM

980nm Pump LD 980nm Pump LD

980nm Pump LD

1 km

0: 1554nm 1 km

0: 1532nm

1450 1500 1550 1600 1650 1700 1750 -70

-60 -50 -40 -30 -20 -10 0

Power (dBm/0.2nm)

Wavelength (nm) 0.42W 1.062W 2.049W

1450 1500 1550 1600 1650 1700 1750 -70

-60 -50 -40 -30 -20 -10 0

Wavelength (nm)

Power (dBm/0.2nm)

0.42W 1.062W 2.049W

1450 1500 1550 1600 1650 1700 1750 -70

-60 -50 -40 -30 -20 -10 0

Power (dBm/0.2nm)

1450 1500 1550 1600 1650 1700 1750 -70

-60 -50 -40 -30 -20 -10 0

Power (dBm/0.2nm)

c= 205 ps c= 42.1 ps

c= 18.9 ps c= 8.94 ps

Ultra broadband light source for the OCT systme

(21)

Reflection mirror(CFBGs) - high reflection grating in fiber - wideband reflection in fiber

Optical pathlength change of mm order

- amplification in optical path-length (amplification factor) - automatic dispersion cancellation (matched CFBGs)

Repeated scanning (RSOD) - small PZT stretcher of few 100 m

with high repetition rate of ~ 10 kHz

 In-fiber delay line - insertion loss-free - alignment-free

source

sample arm fiber delay line Fiber delay line-based OCT system

detector

OCT system based on tunable chirped FBGs

1530 1540 1550 1560 1570

-400 -300 -200 -100 0

Group delay [ps]

Wavelength [nm]

A : Before strain B : After tuning C : Difference

Strained CFBG

- CFBG stretching : 100 m - group delay slope unchanged

and shifted to longer  - difference(~12 ps) is nearly flat - after bending of CFBG,

dispersion also cancelled - gives an amplification factor

-1000 -500 0 500 1000

-1.0 -0.5 0.0 0.5 1.0

Interference signal [A.U]

Optical delay [m]

250 m

~100m Sample; 150 m thick cover glass

OCT system based on tunable chirped FBGs

Amplfication factor :  = 31

(22)

Optical fiber sensors

Tension Compression

Photo Detector

( Small Signal ) ( Large Signal )

Principle of optical fiber sensors

(23)

Advantages of fiber-optic sensors

Fiber Bragg grating (FBG) Technology in the field of optical sensors

 Advantages



High-sensitivity



Electro-magnetic immunity



Compactness



Ease of fabrication

 Limitations

 Multi-perturbation sensitivities

 Limitation of sensing distance about 25 km ( Rayleigh scattering, Fiber background loss )

(24)

Rebar FBG sensor

http://www.fbg.com.cn/

http://www.welltech.com/

광통신기술

나노 정보 바이오 물리

Young-Geun Han

광통신기술

Contents

 광통신 개요 및 특징

 광통신 기술

 WDM 핵심 기술

 광섬유

 광통신 핵심 소자 기술

• 1976~1977 ---최초의 현장 적용시험 및 상업화 시도

• 1977 --- 2세대 광전송 시대의 개막:

1.3µm InGaAsP 레이저

• 1980 --- 0.2dB/km 광섬유 개발

• 1981 --- 1.5µm InGaAsP 레이저 개발

• 1988 --- 최초의 대서양 횡단 광케이블 1.55µm 양자우물레이저 개발

3세대 광전송의 연구 ( 1.55µm ,~10Gb/s )

• 현재 --- 4세대: 파장분할다중화(WDM)방식, 광증폭기, Soliton 연구(5세대)

광통신의 역사

광통신의 장점

• 전송용량의 증대

• 고신뢰성

• 무중계 거리의 확대

• 보안성의 증대

• 크기 및 무게의 감소

• 무한한 성장 가능성

• 저가의 시스템

광통신 전송 기술의 발전

광통신 전송링크 구성요소

광통신 방식 I - OTDM

광통신 방식 II - WDM

WDM 핵심기술

• 1세대 WDM

– 1310 nm와 1550nm 파장대의 다중화

• 2세대 WDM

– 1550nm 파장대역에서 2~4개의 파장의 다중화 – 400 GHz 파장 간격

• 현재의 WDM - DWDM (Dense WDM)

– 16, 32, 40개의 파장의 다중화 (1550nm 파장대역) – 100 GHz 파장 간격

• 차세대 WDM

– 40~80개의 파장의 다중화 (1550nm 파장대역) – 50 또는100 GHz 파장 간격

– 1300 ~ 1600 nm 대 모두 이용

WDM 발전 동향

1Tbps급 대용량 전송 방법

광통신 핵심 소자

• 단일 모드 광섬유 (SMF: Single Mode Fiber)

• 광원 (DFB-LD)

• Photodiode (PIN, APD)

• 광 증폭기 (EDFA 등)

• 광 변조기 (LiNbO

)

• 광 스위치, OXC, Optical Router …

• 다중모드 광섬유(MMF) – 코어 직경은 50mm – 모드간 분산에 의해

전송거리 제한

• 단일모드 광섬유(SMF) – 코어 직경은 9mm – 색분산에 의해 전송

거리 제한

광섬유 종류

단일모드 광섬유 종류

Optical fiber and its parameter

Single mode (SM) and multimode (MM) fibers

Cutoff condition (SM)

Dispersion shifted fiber

Cutoff condition

Dispersion shifted fiber

Non-zero dispersion shifted fiber

Dispersion compensated fiber

Plastic optical fiber

Erbium doped fiber

Specialty optical fibers

What is a photonic crystal fiber ?

• A solid core surrounded by a cladding which is defined by a fine array of air holes

– Made of a single material, usually pure silica

– Critical design parameters: hole diameter (d) and pitch ( = hole to hol e spacing) on the scale of the wavelength of light.

Main properties of photonic crystal fibers

Fabrication of photonic crystal fibers

< Stack & Draw Procedure >

– Preform Diameter : 20mm – Preform Length : 80cm

 Optical Properties

• Transmission spectrum vs. bending radius

– Experimental set-up

Fabrication of photonic crystal fibers with

 ^{광통신 기술}

 ^광섬유