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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Contents
- Introduction
- Review of integrated microwave photonics
- Review: Arbitrary waveform generation
- Conclusion
Special Topics in Optical Engineering II (15/1) Soonyoung Cha - - PowerPoint PPT Presentation
Special Topics in Optical Engineering II (15/1) Soonyoung Cha - - PowerPoint PPT Presentation
Special Topics in Optical Engineering II (15/1) Soonyoung Cha Contents Introduction Review of integrated microwave photonics Review: Arbitrary waveform generation Conclusion Special Topics in Optical Engineering II (15/1)
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Introduction
- Widely used nowadays
- Speed of DSPs > several GHz
(Limit from sampling rate) Digital electronics
- Front-end analog signal process
- Microwave photonics (MWP)
:Bulky, expensive, not flexible Solution of limitation Integrated Microwave Photonics
Processing in
- ptical domain
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Category of MWP applications
High dynamic range MWP link Microwave photonic filters Optical delay line & beamforming Microwave signal generation
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Ultrabroad-bandwidth arbitrary waveform generation
Electronic arbitrary waveform generation (AWG)
- Limited in frequency and bandwidth
- Maximum bandwidth of 5.6 GHz
- Maximum frequency up to 9.6 GHz
Direct space-to-time pulse shaper Generated by spatial pattern & distance Wavelength-to-time mapping Suitable for time time-stretch operation Optic device: expensive, complicated, bulky → On-chip integrated pulse shaper Progress on MWP-based AWG techniques
- J. D. McKinney, D. E. Leaird, and A. M. Weiner, Opt. Lett. 27(15),
1345–1347 (2002).
- J. Chou, Y. Han, and B. Jalali, IEEE Photonics Technol. Lett. 15(4),
581–583 (2003).
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Ultrabroad-bandwidth arbitrary waveform generation
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Ultrabroad-bandwidth arbitrary waveform generation
Femtosecond laser pulse
- 100 fs pulse duration
- 1,525 ~ 1,610 nm band
- Coupled into Si waveguide
8 cascaded microring resonators
- Power transfer at resonant wavelength of each microring
: Creates dip in the output spectrum
- Microrings: slightly different resonance
Broadband optical source On-chip spectral shaper
Micro-heater
- Local & independent control of temperature of each rings
: Resonance λ can be tuned (thermo-optical effect of Si)
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Ultrabroad-bandwidth arbitrary waveform generation
Chromatic dispersion: propagate different speeds for λ
- Pulse envelope is broadened (wavelength-time mapping)
→ Time-domain profile follows spectral shape
5.5 km single-mode fiber
Same shape of the
- ptical spectrum(10GHz)
→ Tunable profile
RF conversion Output after resonators Controllable RF waveform generation using microring silicon photonics
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Ultrabroad-bandwidth arbitrary waveform generation
First-generation design: Heating the ring itself cannot lead wide λ control Solution: Mach-Zehnder (MZ) input coupler & heat this coupler
Problem Second-generation design
Thermally tuning the phase shift of two arms → Coupling coefficient into a ring changes → Loaded quality factor changes
Phase shift : 0 π
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Ultrabroad-bandwidth arbitrary waveform generation
Optical signals from the common port: consists of peaks (dip for output signal)
Application for apodization : control the suppression of side lobes in Fourier transform domain (Used in signal & filter design)
Tunable waveform shape Without apodization
Flat-topped envelope : Weak side-lobe suppression ~ -12 dB
With apodization
Waveform with uppressed edge : Enhanced side-lobe suppression ~ -20 dB
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Ultrabroad-bandwidth arbitrary waveform generation
4 cycle – phase shift – 4 cycle (10 GHz) : Doublet in the RF spectrum (dip @ 10 GHz) → Phase shift within the pulse burst
Phase shift inside waveform
60 GHz waveform with π-phase shift : Strong dip near 60 GHz → Beyond the edge of time-domain electronic measurement instrumentation
Could contribute to the realization of multi-GHz BW Wireless LAN, portable multimedia streaming, vehicular networks, etc.
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Ultrabroad-bandwidth arbitrary waveform generation
Frequency-modulated waveforms
Two-tone waveform
- Abrupt frequency change
: 60 GHz to 40 GHz in single waveform
- Difficult to achieve using electronic circuits
Chirped waveform
: Sweep from low to high freq. (up) : Sweep from high to low freq. (down)
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Conclusion
- Integrated microwave photonics
: to avoid bulky & expensive & complicated system
- Limitation of current DSP-based electronics
- Arbitrary waveform generation using MPF system
: High-frequency up to tens of GHz
- On-chip implementation of MPF-based AWG system
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Special Topics in Optical Engineering II (15/1) Soonyoung Cha
Reference
- D. Marpaung et al., Laser Photonics Rev. 7, 506–538 (2013)
- J. D. McKinney, D. E. Leaird, and A. M. Weiner, Opt. Lett. 27(15), 1345–1347 (2002).
- J. Chou, Y. Han, and B. Jalali, IEEE Photonics Technol. Lett. 15(4), 581–583 (2003).
- M. H. Khan et al., Nat. Photonics 4, 117-122 (2010).