km3netmeeting pylos, greece, 16-18 april 2007 1 of 12 mar van der hoek et al. electronic department...

KM3NeTmeeting Pylos, Greece, 16-18 April 2007

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Mar van der Hoek et al. electronic department

PROGRESS ON OPTICAL MODULATORS

FOR KM3NeT

Mar van der Hoek


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OUTLINE

P Optical modulators: a key component for KM3NeT

P The KM3NeT architecture and worldwide interest in WDM-PON

P Commercial modulators as used in telecom networks

P Impact of modulator type on KM3NeT photonic network architectureand transmission performance

P Progress on Electro Absorption Modulators (EAM)

P Progress on Thermally Poled Fibres (TPF)

P Planning for further theoretical work & experiments

P Conclusions


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THE OPTICAL MODULATOR: A KEY COMPONENT FOR KM3NeT

‘CONTINUOUS WAVE’ REGIME(OPTICAL FEED CHANNEL)

‘MODULATED WAVE’ REGIME(OPTICAL RETURN CHANNEL)

CW- MW LASER MODULATOR DETECTOR

ELECTRICAL DATA INDATA OUT

POWER

TIME

On shore Submerged On shore


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WORLD WIDE WDM-PON DEVELOPMENTS

MULTI

WAVELENGTH

SOURCE

WDM

DETECTOR

DOWNSTREAM: DATA (λ1) + CW LIGHT (λ2)

TO THE HOME

UPSTREAM: DATA-IMPRESSED MODULATED LIGHT (λ2)

TO THE HUB

OPTICAL UNIT:

DWDM FILTER + REFLECTIVE MODULATOR (+OPTIONAL AMPLIFIER)

WDM-PON:

WAVELENGHT DIVISIONAL MULTIPLEX- PASSIVE OPTICAL NETWORK

HUB

HOME


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BASELINE FOR KM3NeT: ‘LOW’ COST – PROVEN TECHNOLOGY

COMMERCIAL SEMICONDUCTOR LASER / MODULATOR MODULE

PHOTONIC INTEGRATED CIRCUIT TECHNOLOGY

ADVANCED PACKAGING TECHNOLOGY and

CUSTOM PHOTONIC INTEGRATED CIRCUITS

Discussed during a visits to CIP

(Centre for Integrated

Photonics UK) and Technical

University Eindhoven, the Netherlands


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EXAMPLE OF A COMMERCIAL LASER MODULE

LASER DIODE CHIP

OPTICAL ISOLATOR

WAVELENGTH LOCKER/ EAM MODULATOR

Millions of devices operational in telecom networks !!

MONITOR DIODE

200X400µm


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ASSUME: 1: TYPICAL LASER FWHM LINEWIDTH: 5 MHz = 0,04 nm = 40 pm2: ACHIEVABLE FBG REFLECTION PEAK SHIFT = 40 pm @ Vmod=Vmax (e.g. 10-40V)3: POCKELS COEFFICIENT FOR THERMALLY / ELECTRICAL POLED

HYDROGEN LOADED FIBRE: 0.3...10? pm/V

PMT to DIGITALOUTPUTMODULE

METALWIRES

2 SIDE HOLES IN FIBRE TO ACCOMODATE METALWIRES

FIBRE BRAGGGRATING

Electrical / Thermal Poled SINGLEMODE FIBREOD=125 m

INPUT / LASERSPECTRUM

Vmod

NOVEL TYPE OF PHOTONIC MODULATOR FOR KM3NeT

ELECTRO-OPTICAL EFFECTS IN POLED FIBRES


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POLED FIBER DEVICES AS REALIZED BY ACREO, SWEDEN

Technology

CoatingMetal: AuSn

Exposed electrode

Section free from metal

High pressure

High temperature

Metal-filled holes

Liquid metal

Splicing not possible

Contact from end (?)Side-polishing(!)

Wire bonding


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High voltage

280 oC

Using a poled fiber for electro optical switching

3 dB 3 dB

Active arm

Reference arm

Fiber Mach-Zehnder

++

--

silicasilica

280 280 ooCCR. Myers, S. Brueck et al, Opt. Lett. 16, 1732 (1991)

Poling fused silica

Integrated MZI

With holes

SECOND ORDER NON LINEARITY OF FIBERS BY POLING


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Functiongenerator

3 dB 3 dB

ns pulsegenerator

-10 -8 -6 -4 -2 0 2 4 6 8 10-40

-20

0

20

40

60

80

100

120

140

160

Time (nanoseconds)

Am

plitu

de (V

)

2,2 ns

-10 -8 -6 -4 -2 0 2 4 6 8 10-4

-3

-2

-1

0

1

2

3

4

5

6

Time(nanoseconds)

Opt

ical

pow

er o

utpu

t (m

W) 2,2 ns

Trigcw

Electrical Optical

TRAVELLING WAVE MODULATION


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Increasing sensitivity by means of spectral displacement with voltage

Principle: laser light reflects on fiber grating index change shifts reflected wavelength intensity reflected changes with applied voltage slow drifts can be compensated with voltage

λlaser

Position

Wavelength

no voltagewith voltage small index change

3 dBInterferometer

Poled fiber with chirped grating

λlaser

phase detection

Large delay with small index change

Recent (theoretical) development

CHIRPED GRATING TO REDUCE MODULATOR DRIVE VOLTAGE

Options for phase modulation!


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INPUT / LASERSPECTRUM

FBG REFLECTIONSPECTRUM SHIFT DUE TOe.g. TEMPERATURE

“PMT DATA”

REFLECTION OF CW INPUT LASERWAVELENGTH

MINIMUM OPTICALTRANSMISSION

“REGULATOR CIRCUIT”

SMALL AMOUNT OF LEAKAGE OF PEAKWAVELENGTH (e.g. -20 dB)

LOW-FREQUENCY REGULATORCIRCUIT MAINTAINS PEAK OF FBGREFLECTION CURVE COINCIDENT WITHINPUT LASER SPECTRUM

THIS COMPENSATES FOR SMALL DRIFTIN FBG REFLECTION PEAK AND/ORSHIFT OF INPUT LASER SPECTRUM

ALSO: THERMAL TUNING OF FBG PEAKAS OPTION FOR OPERATING POINTSTABILIZATION

NOT REQUIRED FOR CHIRPED

GRATING!!

UNIFORM GRATINGS FOR ALL DWDM

CHANNELS!!

CHIRPED GRATINGS:TOWARDS UNIFORM MODULATORS


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CHARACTERISTICS OF POLED FIBER MODULATORS

• All fiber construction, compatible with KM3NeT fibers• Fusion splicing to network fiber: low loss, no air gaps• Low power consumption due to capacitive switching• Low polarization dependence• Wide wavelength range for switching• Small footprint• Proven technology for grating and poling process• Potential low cost

• -/- OPTICAL GAIN not yet integrated


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CHALLENGES

FOR ELECTRO-ABSORPTION MODULATORS:• Electro-absorption modulators are already very mature• For KM3Net: optimized modulator / amplifier design• Reduction of optical loss• Integration of modulator with optical amplifier and

all-optical serialiser into a single hermetic module

FOR POLED FIBER MODULATORS• Reduce drive voltage to 2-3 V• Increase modulation speed to 10 Gb/s• Incorporation of optical gain


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RESOURCES TO REALIZE KM3NeT OPTIMIZED MODULATORS

Joint european Program on Photonic Integrated

Components and Devices

•Companies

•Technical universities

•System integrators

• Photonic device design / modeling

•Device realization

•Device packaging

•Functional testing


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SOME CONCLUSIONS

• ELECTRO ABSORPTION MODULATORS: PROVEN TECHNOLOGY• EAMs ARE USED BY HUNDERDTHOUSANDS IN TELECOM• POLED FIBER MODULATORS: STILL A STRONG CANDIDATE,

OFFERING SPECIFIC ADVANTAGES FOR KM3NeT• RECENT PROGRESS: CHIRPED GRATING, OFFERING:

– LOWER DRIVE VOLTAGE: 2-3 V

– REDUCED MODULATOR LENGHT: 100 mm

– POTENTIAL: UNIVERSAL GRATING FOR ALL DWDM CHANNELS

– EASY SPLICING OF POLED FIBER TO NETWORK FIBER

km3netmeeting pylos, greece, 16-18 april 2007 1 of 12 mar van der hoek et al. electronic department...

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