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PROGRESS ON OPTICAL MODULATORS FOR KM3NeT Mar van der Hoek. OUTLINE. THE OPTICAL MODULATOR: A KEY COMPONENT FOR KM3NeT. On shore. Submerged. On shore. ELECTRICAL DATA IN. DATA OUT. MODULATOR. CW-. MW LASER. DETECTOR. POWER. TIME. ‘MODULATED WAVE’ REGIME. ‘CONTINUOUS WAVE’ REGIME.
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PROGRESS ON OPTICAL MODULATORS FOR KM3NeT Mar van der Hoek
THE OPTICAL MODULATOR: A KEY COMPONENT FOR KM3NeT On shore Submerged On shore ELECTRICAL DATA IN DATA OUT MODULATOR CW- MW LASER DETECTOR POWER TIME ‘MODULATED WAVE’ REGIME ‘CONTINUOUS WAVE’ REGIME (OPTICAL RETURN CHANNEL) (OPTICAL FEED CHANNEL)
OPTICAL UNIT: DWDM FILTER + REFLECTIVE MODULATOR (+OPTIONAL AMPLIFIER) WORLD WIDE WDM-PON DEVELOPMENTS WDM-PON: WAVELENGHT DIVISIONAL MULTIPLEX- PASSIVE OPTICAL NETWORK DOWNSTREAM:DATA (λ1) + CW LIGHT (λ2) TO THE HOME MULTI WAVELENGTH SOURCE HOME WDM DETECTOR UPSTREAM: DATA-IMPRESSED MODULATED LIGHT (λ2) TO THE HUB HUB
BASELINE FOR KM3NeT: ‘LOW’ COST – PROVEN TECHNOLOGY COMMERCIAL SEMICONDUCTOR LASER / MODULATOR MODULE PHOTONIC INTEGRATED CIRCUIT TECHNOLOGY Discussed during a visits to CIP (Centre for Integrated Photonics UK) and Technical University Eindhoven, the Netherlands ADVANCED PACKAGING TECHNOLOGY and CUSTOM PHOTONIC INTEGRATED CIRCUITS
Millions of devices operational in telecom networks !! EXAMPLE OF A COMMERCIAL LASER MODULE MONITOR DIODE LASER DIODE CHIP WAVELENGTH LOCKER/ EAM MODULATOR OPTICAL ISOLATOR 200X400µm
NOVEL TYPE OF PHOTONIC MODULATOR FOR KM3NeT ELECTRO-OPTICAL EFFECTS IN POLED FIBRES PMT to DIGITAL OUTPUT MODULE Vmod FIBRE BRAGG GRATING Electrical / Thermal Poled SINGLEMODE FIBRE OD=125 : m METAL WIRES 2 SIDE HOLES IN FIBRE TO ACCOMODATE METAL WIRES ASSUME: 1: TYPICAL LASER FWHM LINEWIDTH: 5 MHz = 0,04 nm = 40 pm 2: ACHIEVABLE FBG REFLECTION PEAK SHIFT = 40 pm @ Vmod=Vmax (e.g. 10-40V) 3: POCKELS COEFFICIENT FOR THERMALLY / ELECTRICAL POLED INPUT / LASER HYDROGEN LOADED FIBRE: 0.3...10? pm/V SPECTRUM
Section free from metal Metal-filled holes High pressure High temperature Liquid metal Technology POLED FIBER DEVICES AS REALIZED BY ACREO, SWEDEN Side-polishing(!) Contact from end (?) Exposed electrode Wire bonding Metal: AuSn Coating Splicing not possible
SECOND ORDER NON LINEARITY OF FIBERS BY POLING High voltage 280 oC With holes Integrated MZI Active arm 3 dB 3 dB Fiber Mach-Zehnder Reference arm + Poling fused silica 280 oC R. Myers, S. Brueck et al, Opt. Lett. 16, 1732 (1991) silica - Using a poled fiber for electro optical switching
TRAVELLING WAVE MODULATION ns pulse generator Function generator Trig cw 3 dB 3 dB Electrical Optical
CHIRPED GRATING TO REDUCE MODULATOR DRIVE VOLTAGE 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 Recent (theoretical) development Wavelength with voltage small index change λlaser no voltage Position λlaser 3 dB Poled fiber with chirped grating Interferometer Large delay with small index change Options for phase modulation! phase detection
CHIRPED GRATINGS:TOWARDS UNIFORM MODULATORS NOT REQUIRED FOR CHIRPED GRATING!! UNIFORM GRATINGS FOR ALL DWDM CHANNELS!!
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 CHARACTERISTICS OF POLED FIBER MODULATORS
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 CHALLENGES
RESOURCES TO REALIZE KM3NeT OPTIMIZED MODULATORS • Photonic device design / modeling • Device realization • Device packaging • Functional testing • Joint european Program on Photonic Integrated Components and Devices • Companies • Technical universities • System integrators
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 SOME CONCLUSIONS