Eso 2

Introduction à la Commutation Optique II Guang-Hua DUAN

Opto+ Alcatel Research & Innovation Route de Nozay 91460 Marcoussis G-H. Duan, ESO, 2005

Sommaire • Etat de l’art de télécommunications optiques : • • • • •

Transmission Commutation Commutation de circuits Commutation de paquets Nécessité de la commutation optique

1er cours

• Commutation optique spatiale • Commutation optique temporelle • Commutation optique par routage en longueur d’onde • Répartiteurs et multiplexeurs à l'insertion-extraction • Cross-connexion optique (OXC) WDM

• Commutation optique de paquets • Traitement optique des signaux • - Conclusion G-H. Duan, ESO, 2005

2ème cours

Trend : cost reduction! • On-going convergence of metro and long haul platforms – to save development efforts – because need are also converging • more OADM and rings in long haul • longer distances required in « metro »

• Tunability – to save spares, to provide network reconfigurability

• Lower cost, small volume and low power consumption • introduction of sfp/xfp for metro DWDM

G-H. Duan, ESO, 2005

WDM XFP module • TOSA • • • • •

EML with integrated laser and driver fixed laser covering full C band 80 Kms : 1600ps/nm <2.5watts TEC + driver tunable?

• ROSA • APD and PIN • -27dBm C+ band at 2.5 Gbit/s G-H. Duan, ESO, 2005

Trend : CAPEX reduction • Metro • CWDM : 20 nm channel spacing from 1480 to 1620 • uncooled sources at 2.5 Gbit/s and 10 Gbit/s • so far cost studies show that 2.5G CWDM is still winning

• Long haul • 40 Gbit/s: design of dispersion mapping and choice of modulation format are now mature, most difficult point is now PMD mitigation, cost studies show so far interest vs 10G for some system types (vs distance, fiber type, capacity) • Raman amplification • all-optical regeneration

• OADM->wavelength transparent • OADM • tunability and reconfigurability

G-H. Duan, ESO, 2005

Trend: OPEX reduction • More flexibility and automatization – first application is to save OPEX • emergence of reconfigurable OADM, especially for US market • importance of automatic system tunings (some technologies like tunable DCM can help) • use of tunable ROADM (with tunable architectures) • sometimes contradictory or favourable to CAPEX saving

G-H. Duan, ESO, 2005

Transmission optique par WDM avec OADM

EDFA

EDFA

ADM Extra. Insertion Emetteur

Mux

OADM : Optical Add/Drop Multiplexer G-H. Duan, ESO, 2005

Demux

Récepteur

OADM dans un réseau OADM OADM

Meshed optical networks

OADM OXC

OADM

OXC

OADM OADM

Optical rings OADM

OADM OADM

G-H. Duan, ESO, 2005

Optical add-drop multiplexer: grating solutions

Demux Mux

In [1] Out [2]

Drop [4]

G-H. Duan, ESO, 2005

Add [3]

OADM par bande de λ Out [2] In [1]

Drop [4]

G-H. Duan, ESO, 2005

Add [3]

Filtre à base de réseau Bragg dans une fibre (FBG)

UV-writing technology

UV (242 nm)

 Permanent refractive index change of Ge-doped silica under UV irradiation  Grating filter written in fibre in one-step process Simplicity, low cost Low insertion loss G-H. Duan, ESO, 2005

n(z)

z

Bragg grating inscription: phase mask

- interferences between 2 diffraction orders - Bragg wavelength fixed: reproducibility -1

+1 < 5%

G-H. Duan, ESO, 2005

- possibility of synthesis - no need for coherence

Optical add-drop multiplexer: FBG solutions Circulators

Mach-Zehnder

Coupler Cost

G-H. Duan, ESO, 2005

Losses

Arrayed Waveguide Grating

Principe : interférence de différents faisceaux suivant les différents guides Fonctions : - Multiplexage en λ - Démultiplexage en λ - Routeur de λ G-H. Duan, ESO, 2005

Cyclic AWG

DMUX 1:8

standard

λ8

λ2 λ1

• each Mux/Dmux treat only 8 λs (1626LM: need of 12 ≠ Mux/Dmux ref.) Cyclic AWG (1:8 Mux/Dmux=1or 2 input, 8 outputs) – each output = a set of frequencies λ8, λ16, λ24, ….. λ2N+8 – Advantage: any band among B1,B2, …, B12 • low cost (same as standard AWG), λ2, λ10, λ18, ….. λ2N+2 single input cyclic DMUX

•

Standard AWG (1:8 Mux/Dmux=1 input, 8 outputs) – each output = a given frequency bands B1,B2, or B12 – Advantage: • low cost, mature techno, many providers – Disadvantage:

λ1, λ9, λ17, ….. λ2N+1 • 1 Mux/Dmux treat ≠ bands (1626LM: only 1 Mux/Dmux ref. for 12 bands) – Disadvantage: λ8, λ16, λ24, ….. λ2N+8 • design is more tricky (optical perf.) Even bands (B2,B4,…,B12) • Use with BOFA to be checked Odd bands (B1,B3,…,B11) 2N+2

dual input cyclic DMUX

•

G-H. Duan, ESO, 2005

λ2, λ10, λ18, ….. λ

λ1, λ9, λ17, ….. λ2N+1

Wavelength Blocker • Free space optics implementation is mostly used (Liquid Crystal, MEMS or diffractive MEMS) for both 50 and 100 GHz LC based wavelength blocker

~

V(λ) Output

Input

Loss Diffraction Grating

G-H. Duan, ESO, 2005

LC-based Attenuator Array

Diffraction Grating

Wavelength Switch • Wavelength Switch description : a 1xN WS device has : – 1 input port + N output ports – any combination/number of input λs can be sent to any output port – a given λ can be send to 1 output port at a time (no Broadcast function) – if each output port It can be seen as get rid of Drop or Add coupler – A WS is reconfigurable and tunable Mux or Dmux

WS 1 x 4 Express port Drop ports any combination of λs can be sent to any output G-H. Duan, ESO, 2005

Wavelength Switch

• Wavelength Switch description : – a WS can be used indifferently as: • a reconfigurable/tunable DMUX (all ports DROP λs) OR (exclusive OR) • a reconfigurable/tunable MUX (all ports ADD λs)

WS 1 x 4 DROP ports only

WS 1 x 4 ADD ports only

WS 1 x 4

– a WS cannot be used simultaneously w/ ADD ports and DROP ports...

G-H. Duan, ESO, 2005

DROP

ADD

Wavelength Switch • Free space optics implementation is mostly used (MEMS ) for both 50 and 100 GHz C

G-H. Duan, ESO, 2005

Tunable filters applications • Tunable receiver or tunable mux/demux for LH and metro architectures DROP

WB

1x(P+1) WS

ADD

DROP

ADD Rx

2-ports tunable filter

3-ports hitless tunable filter

WB

DROP

1x(P+1) WS

ADD 1:N

4:N

1:4

Rx

Tunable filters

DROP

ADD Rx

Tx (tunable laser)

P:N TF

1/N splitter & combiner for A/D capacity=N

G-H. Duan, ESO, 2005

Rx

…

1:

Tunable filters • Technologies available – Tunable thin film filter – Fabry-Pérot moving cavity

– Tunable pass-band bragg grating – Thermooptic ring resonators

Tunable thin film filter

Fabry Pérot moving cavity

Tunable pass-band bragg grating

Filtering functions

Gaussian and flat top. Very close to fixed TFF

Gaussian shape with wide bandwidth. CD to be checked

Tunability range

large

Airy function -> stringent tradeoff between bandwidth and isolation large

Actuation

Step motor

PZT

Wavelength control and temperature calibration Tuning speed Cost

Look-up table

Few sec. 2000 $

G-H. Duan, ESO, 2005

Thermooptic ring resonators Close to FabryPérot.

Cascade of ring resonators (tbc)

Lock-in loop

“free-space” : large VBG : 1 grating per λ VBG : step motor “free-space” : MEMS Look-up table

Few 100 ms 500 to 1000 $

50 to 300 ms 2000 $

10 to 100 ms 1000 $

Lock-in loop

Wavelength Blocker

• Functional diagram

Optical on/off switch

Variable attenuator

• Good cascadability performances even @ 50 GHz (well suited even for LH) • It can be used for per channel power balancing G-H. Duan, ESO, 2005

OADMs fixes dans le système sous-marin SEA-ME-WE-3

Goonhilly Penmarc’h

Mazara Creta Sesimbra

Tetouan

Marmaris Cyprus

Alexandria Suez

Fujairah

Karachi

Jeddah Mascat

Bombay Cochin Colombo

Djibouti

Medan

Satun

Mersing

Singapore Batam

(blue ↔ option)

G-H. Duan, ESO, 2005

Élément de base pour la commutation en longueur d ’onde - avec le WC

λ

a

λi

λ1

λj

λ2

WC

λ

b

WC Filtre fixe

- sans le WC

λi

λk

λj

λl Filtre accordable

G-H. Duan, ESO, 2005

Cross-connect avec changement de longueur d’onde

λ 1 λ2 λ 3 λ 4 B

C

M

A B C D

ul tic a

st

λ1 λ2 λ3 λ4 λ1' λ2' λ3' λ4'

λ1' λ2' λ3' λ4' A

λ1" λ2" λ3"

C

λ1" λ2" λ3" λ4" D

G-H. Duan, ESO, 2005

Architecture de WT-OXC développé par Alcatel WC

Sortie 1

λ 1 λ2 λ3 λ 4 WC

Entrée 1

Commutateur spatial

λ1 (M) λ2(M) λ3(M) λ4(M) Entrée M

G-H. Duan, ESO, 2005

Filtre accordable

Convertisseur MUX En longueur d ’onde

WC

WC

Sortie M

Résumé sur la commutation dans le domaine de λ • OADM déjà déployé dans des réseaux de télécommunications • Technologies OADM : • • • •

FBG AWG Réseau de diffraction Filtre interférentiel

• Cross-connexion optique (OXC) WDM • Architecture • Applications à venir

G-H. Duan, ESO, 2005

cellule ATM

5 octets

en-tête

routage (path) routage (path and circuit) routage (circuit) routage (circuit) erreurs en-tête

G-H. Duan, ESO, 2005

48 octets

données

Réseau à commutation optique: structure

All-optical packet switching layer Optical node

INPUTS Regeneration Packetisation Packetisation Packetisation Packetisation Packetisation Packetisation Packetisation Packetisation Packetisation Packetisation

MUX

ATM

Regeneration

ATM

Depacketisation Depacketisation Depacketisation Depacketisation Depacketisation Depacketisation Depacketisation Depacketisation Depacketisation Depacketisation Depacketisation

DEMUX

Electronic adaptation

OUTPUTS

G-H. Duan, ESO, 2005

All-optical adaptation

• Réseau optique de transport de paquets de taille fixe • Interface: – mise en paquets – synchronisation – adaptation à l’optique

structure d’un paquet optique

optical time slot : 1.6 µs fixed duration about 1 µs

payload

▼

▼ ▼ ▼

fixed duration, at predefined bit rate

header

temps de garde pour absorber les temps de commutation et d’effaçage/réinscription de l’en-tête motif de synchronisation pour la récupération de rythme motif d’identification et d’adressage (en-tête) charge utile

G-H. Duan, ESO, 2005

architecture de nœud de commutation Cell/packet Buffer 1

1

1 λN

1

K

D

I NPUT S

λ1

1 λ1

1

Wavelength Selector

N To control

1

D

Output 1 Control Logic Output NControl Logic λ1

1

OUTP UTS

Cell/packet encoder

K λN

N

N

N K

Wavelength converter MUX/DMUX D

Detector

G-H. Duan, ESO, 2005

Optical gate Fibre Delay Line coupler

λN

N

Optical Label Switching

G-H. Duan, ESO, 2005

Optical Label Switching

G-H. Duan, ESO, 2005

Optical Label Switching

G-H. Duan, ESO, 2005

Applications Tunable laser requirements for various applications Sparing tuning range (THz)

>1

Circuit switching >4

freq. accuracy (GHz)

±3

±3

output power (dBm) SMSR (dB) linewidth (MHz) tuning speed

>3 (Metro) to >13 (ULH) >30

>30

±5 >3 >30

<25 (Metro) to <5 (ULH) N.A.

Packet switching >4

<10 ms

<25 < 100 ns

ULH = ultra-long haul G-H. Duan, ESO, 2005

Cavité externe Diode laser Rmin / Rmin

Réseau de Bragg

Ibragg

Filtre du réseau de Bragg

Modes Fabry-Perot

Miroir en forme de dièdre => tolérance aux désalignements

Rotation du miroir =>

- modification de la longueur de la cavité Fabry-Perot - modification de l’angle d’incidence sur le réseau, donc de λréseau

design approprié => décalages coordonnés de λFP et λréseau => accord sans sauts de mode

+

Accord continu 40nm (ou 70nm) P forte 32mW (ou 15mW) disponible

G-H. Duan, ESO, 2005

λ

-

prix encombrement (mini-Tunics maintenant) fiabilité => applications test pour l’instant

VCSEL + MEM Cavité Fabry-Perot très courte =>1 seul mode dans la bande de gain accordabilité continue par translation du miroir supérieur gain Mode FP λ

+ Accord continu > 40nm asservissement facile émission par la surface G-H. Duan, ESO, 2005

Pfibre= 3.5 à 6mW besoin d’un pompage optique (70mW)

Laser accordable DBR Ibragg ➨ accord grossier

T° ➨ accord fin

Ibragg

Iactif ➨ puissance

Filtre du réseau de Bragg Modes Fabry-Perot

T°

+ Pfibre=20mW sur tous les canaux techno simple, caractérisations simples

G-H. Duan, ESO, 2005

λ émission

λ

-

Accord limité (~15nm) Sauts de mode =>asservissement complexe Accord lent (=> section de phase ?)

Performances en accordabilité

0

15

30

45

60

Courant dans la section Bragg

G-H. Duan, ESO, 2005

75

Laser SGDBR

Actif

Phase

RDBR

DBR-Avant

DBR-Arrière

Modes FP

Puissance

Fréquence

• Accordabilité >40nm G-H. Duan, ESO, 2005

GCSR Laser

Active

Coupler Phase

SG-DBR

• Grating assisted co-directional coupler: – Two guided modes R and S – Efficient coupling at frequency: c νc = Λ c [ n R (ν c ) − nS (ν c ) ] – Wider tuning at the cost of higher filter bandwidth G-H. Duan, ESO, 2005

GCSR Laser

Coupler Phase

Filter

Active

cavity modes

Power

Frequency

G-H. Duan, ESO, 2005

SG-DBR

Wavelength Tunable 4-ch DBR Laser Array 2000 µm

Lasing Wavelength (nm)

1540 LACT=50µm, IACT=30mA

1538 1536

600 µm

1534

∆λ(total)

1532

DBR-LDs

1530

S-Bend

DBR-LD 1 DBR-LD 2 DBR-LD 3 DBR-LD 4

12.45 nm

SOA

MMI coupler

1528 1526

0

20

40

60

80

Tuning Current (mA) IDBR

IACT

Structure of DBR Lasers Active Region : LACT=50µm Front DBR

: 200µm, k=90cm-1

Rear DBR

: 450µm, k=90cm-1

Arrayed λ Pitch: 2.5 nm(Average) G-H. Duan, ESO, 2005

Technologies Comparison of tunable laser technologies

mechanism tuning range # channels

DBR

SG-DBR

GCSR

ECL

MEMSVCSEL

DFB cascade

T+E

E

E

M

M

T

<2 THz

>4 THz

>4 THz

>4 THz

>4 THz

<2 THz

<40

>80

>80

>80

>80

<40

locked stability

depends on wavelength locker

unlocked stability

good

good

good

output power

>13 dBm >3 dBm

power uniformity

2 to 3 dB 4 to 5 dB 2 to 3 dB

SMSR linewidth

>35 dB

>35 dB

poor

poor

>3 dBm >10 dBm >6 dBm >35 dB

<25 MHz <25 MHz <25 MHz

? >3 dBm

?

2 to 3 dB

?

>40 dB

>40 dB

>40 dB

<5 MHz

<10 MHz <10 MHz >10 µs >1 s

tuning speed

>1 s

<20 ns

<20 ns

>1 ms

reliability

good

good

good

?

?

?

low

low

low

high

high

high

power consumption G-H. Duan, ESO, 2005

All-Optical Clock recovery: Where, and Why • Where ? • 3R Regeneration = Re-amplifying, Reshaping, Re-timing= Full Regeneration • Principe of operation of a regenerator

Distorted data Switching window in nonlinear gate

Regenerated data

recovered clock pulses See paper on al l-o pti cal regenerati on, B. Lav igne, et al ., thi s ses sion G-H. Duan, ESO, 2005

Clock recovery: all-optical and optoelectronic approaches

• 3 blocks structure of 3R regenerator Adaptation interface Clock recovery

B1

Opt. pulse source

Non-linear gate/ Sampling

B2

• Hybrid Optoelectronic approach Photodiode

Filter

Amplifier

Modulator Laser

• All-optical approach

Mode-locked laser, or Passive-filter, or Active-filter using stimulated Brillouin effect, or Self-pulsating laser

G-H. Duan, ESO, 2005

B3

Comparison between all-optical and optoelectronic approaches

Performances Alloptical Hybrid optoelect ronic

To be improved good

G-H. Duan, ESO, 2005

Power Consumption low high (conversion O/E/O)

Integrability reliability

Footprint

Cost

possible

good

small

Potentially low

difficult

average

average

High (high speed modulator and driver)

All-optical clock recovery • All-optical 'disruptive' solution provide advantages such as: – potentially low cost, – reduced footprint, – reduced power consumption

• Problems to be solved: – simple and robust operation conditions, – Clock quality to be comparable with the electronic approach (phase noise, maintain of clock for a larger number of consequent “0”, …)

• All-optical solution becomes competitive only at 40 Gbit/s and beyond • Potential of such a "disruptive" solution in future telecom products such as Optical Regenerators to be assessed

G-H. Duan, ESO, 2005

Integrated Actively Mode-locked lasers Rmin 0.01%

Ibragg

Q1.45 Bragg

Iphase

ISOA

H+

MQW 1.55

Phase

Active

VEAM

H+

MQW 1.50 Modulator

NTT, Lucent, ….

• High speed modulator at 40 GHz or 40/n GHz needed • External oscillator at 40 GHz or 40/n GHZ needed • Pros: – low time jitter (< 1 ps) – high extinction ratio (> 13 dB)

• Cons: – Extremely low locking range (< 100 kHz) – high cost due to high speed electronics G-H. Duan, ESO, 2005

Hybrid Actively Mode-locked lasers RF Drive

Bias Tee

Rmax

• • •

Lcavity

AR

AR

FBG

Lucent, Alcatel, ETH…. High speed modulator at 40 GHz or 40/n GHz needed External oscillator at 40 GHz or 40/n GHZ needed Pros: – low time jitter (< 1 ps) – high extinction ratio (> 13 dB)

•

Cons: – Extremely low locking range (< 100 kHz) – high cost due to high speed electronics

G-H. Duan, ESO, 2005

Passively Mode-locked lasers Rmin 0.01%

Ibragg

Q1.45 Bragg

Iphase

ISOA

MQW 1.55

H+ Phase

VSA

Active

Saturable absorber

OKI Electrical Industry Co, HHI, ....

•

Passive mode-locked lasers with saturable absorbers (one type of selfpulsating laser)

•

Observed mode-locking at 40, 80 and 500 GHz (S. Arahira, et al. OKI Electrical Industry Co., IEEE PTL, 1993)

•

Advantages: – low time jitter – high extinction ratio – low-cost without high speed electronics

G-H. Duan, ESO, 2005

Passive filtering Distorted data

High Q comb type filter

Spectrum

Egaliser

Comb-like transmission

20

Recovered Clock

10 0

P uissance ( dBm)

-10 -20 -30 -40 -50 -60 -70 -80 - 50

- 40

- 30

- 20

- 10

0

10

20

30

40

50

Fre que nce ( GHz)

•

First demonstration at 1992 (M. Jinno, et al., J. QE, vol. 28, 1992)

•

High Q filter (Q>10000) needed following the ITU-T specifications, difficult to be obtained by integrated optics

•

Combination with mode-locked lasers or SP laser to eliminate the patterning effect (T. Wang, et al., IEEE PTL, June 2002)

G-H. Duan, ESO, 2005

Stimulated Brillouin Optical Tank 20 10 0 P uissance ( dB m)

Spectrum

-1 0 -2 0 -3 0 -4 0 -5 0 -6 0 -7 0 -8 0 -50

-40

-3 0

- 20

-1 0

0

10

20

30

40

ƒclock

50

Fre que nce (GHz)

ƒ

18.4 dBm

Clock out signal in

Downshifts data by phonon frequency (ƒseed) 10.5GHz Mod

3 dBm

Polarization control

ƒ

Fiber

Pump

ƒseed

10.5 GHz

Seed

Pump

ƒdata

Seed Stokes wave provides amplification

ƒclock

ƒ

Clock=Amplified and filtered seed by stimulated Brillouin effect Pro v ided by K . R. Dem ares t, Uni v . of K ans as

G-H. Duan, ESO, 2005

Pros and Cons of Brillouin Optical Tank •Important features: •Brillouin frequency shift = 10.5 GHz •Brillouin gain bandwidth = 20 MHz •

Pros •Bit-rate insensitive, multi-λ clock recovery •Tolerance to long periods of zeros •Requires no optical filters •Rapid lock-in time

•Cons •High input power needed •Polarization dependence

G-H. Duan, ESO, 2005

DFB type Optical SP laser

intensity

DFB 1

DFB 2

∆λ

grating Λ1

beating frequency

grating Λ2

wavelength

Fro m B . S arto ri us , et al ., HHI

• Structures •Phase-comb structure (H. Sarto ri u s, H HI ) •Gain-coupled two-section DFB lasers (G. Li , et al ., Uni v . of Central Flori da )

•Characteristics •Tunable SP frequency from 10 GHz to >100 GHz •Demonstrated clock recovery at 40 Gbit/s and 80 Gbit/s

G-H. Duan, ESO, 2005

DBR lasers for all-optical clock recovery at 40GHz • •

• •

3 section devices including active, phase and Bragg sections Polarization insensitive bulk active layer, nearly square (0.6µm width x 0.4µm thickness) buried ridge waveguide Phase section for the fine tuning of the lasing wavelength Bragg section providing – a wavelength selection (central wavelength and number of modes) – TE/TM discrimination =>lasing only at TE mode

G-H. Duan, ESO, 2005

Bragg section 200µm

Phase section 130µm Active section 790µm

InP p

InP n ion implantation

Wavelength converter principle • What ? – To transfer a modulated signal from one wavelength to another

• How ? – Using non-linearity in conversion SOAs Phase modulation of CW in at least one conversion SOA

λsig

input

λCW

input

Conversion SOA output Conversion SOA input

G-H. Duan, ESO, 2005

Intensity modulation at the interferometer output filter

Convertisseur de longueur d’onde • Structure MZ à base de SOA toute active ou avec guide passif • 3 fibres d’entrée pour fonctionnement en mode différentiel • Module optimisé pour dissipation de 3 W

G-H. Duan, ESO, 2005

Conclusion générale • Démonstration convaincante de x-connect optique transparents utilisant MEMS (Lucent, Calient, Nortel) • Intégration de la fonction add-drop dans les réseaux actuels • Démonstration de x-connect optique utilisant le WDM • Commutation de paquets : démonstration convaincante utilisant convertisseur de longueur d ’onde et optical label switching • Régénération tout optique

G-H. Duan, ESO, 2005