| 1. |
- He, Zonglong, 1994, et al.
(author)
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Experimental Demonstration of Learned Pulse Shaping Filter for Superchannels
- 2022
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In: 2022 Optical Fiber Communications Conference and Exhibition, OFC 2022 - Proceedings.
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Conference paper (peer-reviewed)abstract
- We demonstrate a pulse shaping filter enabled by machine learning for spectral superchannels. In contrast to a 1% roll-off root-raised cosine filter, our learned filter reduces the adaptive equalizer length by 47% for the same spectral efficiency.
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| 2. |
- He, Zonglong, 1994, et al.
(author)
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Periodicity-Enabled Size Reduction of Symbol Based Predistortion for High-Order QAM
- 2022
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In: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; In press
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Journal article (peer-reviewed)abstract
- We experimentally demonstrate a novel size reduction approach for symbol-based look-up table (LUT) digital predistortion (DPD) of the transmitter impairments taking advantage of the periodicity in the pattern-dependent distortions. Compared to other reduced-size LUT schemes, the proposed method can significantly lessen the storage memory requirements with negligible performance penalty for high-order modulation formats. To further alleviate the storage memory restriction, a twice reduced-size LUT scheme is proposed to provide further size reduction. Importantly, given a targeted memory length, we verify the importance of averaging over sufficient occurrences of the patterns to obtain a well-performing LUT. Moreover, it is necessary to evaluate the performance of LUT-based DPD using random data. Finally, we demonstrate a neural network (NN) based nonlinear predistortion technique, which achieves nearly identical performance to the full-size LUT for all employed constellations and is robust against a change of modulation format. The proposed techniques are verified in a back-to-back transmission experiment of 20 Gbaud 64-QAM, 256-QAM, and 1024-QAM signals considering 3 and 5 symbol memory. The performance of the LUT-based DPD is further validated in a noise loading experiment.
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| 3. |
- He, Zonglong, 1994, et al.
(author)
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Symbol-Based Supervised Learning Predistortion for Compensating Transmitter Nonlinearity
- 2021
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In: 2021 European Conference on Optical Communication, ECOC 2021. - 9781665438681
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Conference paper (peer-reviewed)abstract
- We experimentally demonstrate a symbol-based nonlinear digital predistortion (DPD) technique utilizing supervised learning, which is robust against a change of modulation format. Back-to-back transmission of 30 Gbaud 32, 64 and 256QAM confirms that our scheme significantly outperforms the baseline of arcsine-based predistortion.
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| 4. |
- de Peppo, Giuseppe Maria, 1981, et al.
(author)
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Osteogenic response of human mesenchymal stem cells to well-defined nanoscale topography in vitro
- 2014
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In: International journal of nanomedicine. - : Informa UK Limited. - 1176-9114 .- 1178-2013. ; 9:1, s. 2499-2515
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Journal article (peer-reviewed)abstract
- Background: Patterning medical devices at the nanoscale level enables the manipulation of cell behavior and tissue regeneration, with topographic features recognized as playing a significant role in the osseointegration of implantable devices. Methods: In this study, we assessed the ability of titanium-coated hemisphere-like topographic nanostructures of different sizes (approximately 50, 100, and 200 nm) to influence the morphology, proliferation, and osteogenic differentiation of human mesenchymal stem cells (hMSCs). Results: We found that the proliferation and osteogenic differentiation of hMSCs was influenced by the size of the underlying structures, suggesting that size variations in topographic features at the nanoscale level, independently of chemistry, can be exploited to control hMSC behavior in a size-dependent fashion. Conclusion: Our studies demonstrate that colloidal lithography, in combination with coating technologies, can be exploited to investigate the cell response to well defined nanoscale topography and to develop next-generation surfaces that guide tissue regeneration and promote implant integration.
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| 5. |
- Jiang, Nan, et al.
(author)
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Stochastic Backpropagation for Coherent Optical Communications
- 2011
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In: European Conference and Exposition on Optical Communications, ECOC. - Washington, D.C. : OSA. - 2162-2701. - 9781557529312 - 9781557529312
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Conference paper (peer-reviewed)abstract
- We present stochastic backpropagation, a novel maximum a posteriori detection method for coherent optical communication. The proposed detector is shown to outperform conventional backpropagation in a scenario where nonlinear phase noise is the dominant impairment.
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| 6. |
- Johannisson, Pontus, 1976, et al.
(author)
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Convergence Comparison of CMA and ICA for Blind Polarization Demultiplexing of QPSK and 16-QAM Signals
- 2010
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In: Proceedings of European Conference on Optical Communication, ECOC 2010, Turin, Italy, September 19-23, 2010. - 9781424485352
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Conference paper (peer-reviewed)abstract
- Two algorithms for blind polarization demultiplexing, based on the constant modulus criterion and independent component analysis, are compared. It is found that the latter converges significantly faster to within a given SNR penalty tolerance.
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| 7. |
- Johannisson, Pontus, 1976, et al.
(author)
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Convergence Comparison of the CMA and ICA for Blind Polarization Demultiplexing
- 2011
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In: Journal of Optical Communications and Networking. - 1943-0620 .- 1943-0639. ; 3:6, s. 493-501
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Journal article (peer-reviewed)abstract
- An algorithm based on independent component analysis for blind polarization demultiplexing in a coherent transmission system is presented. A comparison with the constant modulus algorithm in terms of the convergence properties is performed, and it is found that the suggested algorithm has a significantly faster convergence rate and does not have any singularity problems. We also demonstrate that the algorithm convergence is strongly dependent on the choice of starting condition and show how this can be exploited to increase the convergence rate.
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| 8. |
- Johannisson, Pontus, 1976, et al.
(author)
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Modified constant modulus algorithm for polarization-switched QPSK
- 2011
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In: Optics Express. - 1094-4087 .- 1094-4087. ; 19:8, s. 7734-7741
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Journal article (peer-reviewed)abstract
- A modified constant modulus algorithm (CMA) is presentedthat allows polarization demultiplexing and equalization of polarizationswitchedQPSK. An implementation is suggested that allows easy switchingbetween the traditional and the modified CMA. Using numerical simulations,the suggested algorithm is shown to have similar performance asCMA has for polarization-multiplexed QPSK.
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| 9. |
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| 10. |
- Karout, Johnny, 1985, et al.
(author)
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CMA Misconvergence in Coherent Optical Communication for Signals Generated from a Single PRBS
- 2011
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In: Wireless & optical communications conference, New Jersey, 15-16 April 2011. - 9781457704543
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Conference paper (peer-reviewed)abstract
- In the experimental study of modulators for coherent optical communications, it is common to generate multilevel signals using a single pseudo-random binary sequence. This simple experimental realization leads to symbol correlation. When modulators are studied in combination with adaptive receiver algorithms that rely on independent data, misconvergence may result. In this contribution, we investigate the impact of such correlation on a standard blind equalization method and provide guidelines to avoid misconvergence. Our results indicate that care needs to be taken when using a single PRBS sequence and that decorrelation delays must be chosen appropriately. We present simulation and theoretical results for 16-QAM, and show how our results can be applied to other multi-level constellations.
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