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Publications (10 of 107) Show all publications
Pang, X., Hu, W., Jacobsen, G., Popov, S., Chen, J., Ozolins, O., . . . Xiao, S. (2020). 200 Gbps & x002F;Lane IM & x002F;DD Technologies for Short Reach Optical Interconnects. Paper presented at Optical Fiber Communications Conference and Exhibition (OFC), MAR 03-07, 2019, San Diego, CA, USA. Journal of Lightwave Technology, 38(2), 492-503, Article ID 8943295.
Open this publication in new window or tab >>200 Gbps & x002F;Lane IM & x002F;DD Technologies for Short Reach Optical Interconnects
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2020 (English)In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 38, no 2, p. 492-503, article id 8943295Article in journal (Refereed) Published
Abstract [en]

Client-side optics are facing an ever-increasing upgrading pace, driven by upcoming 5G related services and datacenter applications. The demand for a single lane data rate is soon approaching 200 Gbps. To meet such high-speed requirement, all segments of traditional intensity modulation direct detection (IM & x002F;DD) technologies are being challenged. The characteristics of electrical and optoelectronic components and the performance of modulation, coding, and digital signal processing (DSP) techniques are being stretched to their limits. In this context, we witnessed technological breakthroughs in several aspects, including development of broadband devices, novel modulation formats and coding, and high-performance DSP algorithms for the past few years. A great momentum has been accumulated to overcome the aforementioned challenges. In this article, we focus on IM & x002F;DD transmissions, and provide an overview of recent research and development efforts on key enabling technologies for 200 Gbps per lane and beyond. Our recent demonstrations of 200 Gbps short-reach transmissions with 4-level pulse amplitude modulation (PAM) and discrete multitone signals are also presented as examples to show the system requirements in terms of device characteristics and DSP performance. Apart from digital coherent technologies and advanced direct detection systems, such as Stokes-vector and Kramers-Kronig schemes, we expect high-speed IM & x002F;DD systems will remain advantageous in terms of system cost, power consumption, and footprint for short reach applications in the short- to mid- term perspective.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2020
Keywords
Digital signal processing, intensity modulation direct detection, optical fiber communication, optical interconnections
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-268785 (URN)10.1109/JLT.2019.2962322 (DOI)000510911600038 ()2-s2.0-85077280601 (Scopus ID)
Conference
Optical Fiber Communications Conference and Exhibition (OFC), MAR 03-07, 2019, San Diego, CA, USA
Note

QC 20200225

Available from: 2020-02-25 Created: 2020-02-25 Last updated: 2020-02-25Bibliographically approved
Estaran, J. M., Mardoyan, H., Jorge, F., Ozolins, O., Udalcovs, A., Konczykowska, A., . . . Bigo, S. (2019). 140/180/204-Gbaud OOK Transceiver for Inter- and Intra-Data Center Connectivity. Paper presented at Optical Fiber Communications Conference and Exposition (OFC), MAR 11-15, 2018, San Diego, CA. Journal of Lightwave Technology, 37(1), 178-187
Open this publication in new window or tab >>140/180/204-Gbaud OOK Transceiver for Inter- and Intra-Data Center Connectivity
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2019 (English)In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 37, no 1, p. 178-187Article in journal (Refereed) Published
Abstract [en]

We report on an ON OFF keying intensity-modulation and direct-detection C-band optical transceiver capable of addressing all datacenter interconnect environments at well beyond 100 Gbaud. For this, the transmitter makes the use of two key InP technologies: a 2:1 double heterojunction bipolar transistor selector multiplexer and a monolithically integrated distributed feedback laser traveling-wave electro-absorption modulator, both exceeding 100-GHz of 3-dB analog bandwidth. A preamplified 110-Gaz PIN photodiode prior to a 100-CHs analog-to-digital converter complete the ultrahigh bandwidth transceiver module; the device under study. In the experimental work, which discriminates between intra- and inter-data center scenarios (dispersion unmanaged 120, 560, and 960 m; and dispersion-managed 10 and 80 km of standard single-mode fiber), we evaluate the bit-error rate evolution against the received optical power at 140, 180, and 204 Gbaud ON OFF keying for different equalization configurations (adaptive linear filter with and without the help of short-memory sequence estimation) and forward error correction schemes (hard-decision codes with 7% and 20% overhead); drawing conclusions from the observed system-level limitations of the respective environments at this ultrahigh baudrate, as well as from the operation margins and sensitivity metrics. From the demonstration, we highlight three results: successful operation with >6-dB sensitivity margin below the 7% error-correction at 140 Gbaud over the entire 100 m-80 km range with only linear feed-forward equalization. Then, the transmission of a 180-Gbaud ON OFF keying carrier over 80 km considering 20% error-correction overhead. Finally, a 10-km communication at 204 (Maud ON OFF keying with up to 6 dB sensitivity margin, and regular 7% overhead error-correction.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Data center interconnects, electro-absorption modulation, InP, integrated circuits, optical fiber communication, very high-speed modulation
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-244554 (URN)10.1109/JLT.2018.2876732 (DOI)000457605700020 ()2-s2.0-85055147623 (Scopus ID)
Conference
Optical Fiber Communications Conference and Exposition (OFC), MAR 11-15, 2018, San Diego, CA
Note

QC 20190222

Available from: 2019-02-22 Created: 2019-02-22 Last updated: 2019-02-22Bibliographically approved
Pang, X., Ozolins, O., Zhang, L., Udalcovs, A., Lin, R., Schatz, R., . . . Chen, J. (2019). Beyond 200 Gbps per Lane Intensity Modulation Direct Detection (IM/DD) Transmissions for Optical Interconnects: Challenges and Recent Developments. In: 2019 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC): . Paper presented at 2019 Optical Fiber Communications Conference and Exhibition, OFC 2019; San Diego; United States; 3 March 2019 through 7 March 2019. IEEE
Open this publication in new window or tab >>Beyond 200 Gbps per Lane Intensity Modulation Direct Detection (IM/DD) Transmissions for Optical Interconnects: Challenges and Recent Developments
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2019 (English)In: 2019 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC), IEEE , 2019Conference paper, Published paper (Refereed)
Abstract [en]

All parts of an IM/DD system are being stretched to the limit as the single lane data rate approaches 200 Gbps and beyond. We report the recent developments on the key enablers conquering this target.

Place, publisher, year, edition, pages
IEEE, 2019
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-270668 (URN)000469837300155 ()2-s2.0-85065482196 (Scopus ID)9781943580538 (ISBN)
Conference
2019 Optical Fiber Communications Conference and Exhibition, OFC 2019; San Diego; United States; 3 March 2019 through 7 March 2019
Note

QC 20200313

Available from: 2020-03-13 Created: 2020-03-13 Last updated: 2020-03-13Bibliographically approved
Vasileva, E., Baitenov, A., Chen, H., Li, Y., Sychugov, I., Yan, M., . . . Popov, S. (2019). Effect of transparent wood on the polarization degree of light. Optics Letters, 44(12), 2962-2965
Open this publication in new window or tab >>Effect of transparent wood on the polarization degree of light
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2019 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 44, no 12, p. 2962-2965Article in journal (Refereed) Published
Abstract [en]

We report on the study of polarization properties of light propagating through transparent wood (TW), which is an anisotropically scattering medium, and consider two cases: completely polarized and totally unpolarized light. It was demonstrated that scattered light distribution is affected by the polarization state of incident light. Scattering is the most efficient for light polarized parallel to cellulose fibers. Furthermore, unpolarized light becomes partially polarized (with a polarization degree of 50%) after propagating through the TW. In the case of totally polarized incident light, however, the degree of polarization of transmitted light is decreased, in an extreme case to a few percent, and reveals an unusual angular dependence on the material orientation. The internal hierarchical complex structure of the material, in particular cellulose fibrils organized in lamellae, is believed to be responsible for the change of the light polarization degree. It was demonstrated that the depolarization properties are determined by the angle between the polarization of light and the wood fibers, emphasizing the impact of their internal structure, unique for different wood species.

Place, publisher, year, edition, pages
OPTICAL SOC AMER, 2019
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-255191 (URN)10.1364/OL.44.002962 (DOI)000471636700005 ()31199356 (PubMedID)2-s2.0-85067943575 (Scopus ID)
Note

QC 20190904

Available from: 2019-09-04 Created: 2019-09-04 Last updated: 2019-09-04Bibliographically approved
Van Kerrebrouck, J., Pang, X., Ozolins, O., Lin, R., Udalcovs, A., Zhang, L., . . . Yin, X. (2019). High-Speed PAM4-Based Optical SDM Interconnects With Directly Modulated Long-Wavelength VCSEL. Paper presented at Optical Fiber Communications Conference and Exposition (OFC), MAR 11-15, 2018, San Diego, CA. Journal of Lightwave Technology, 37(2), 356-362
Open this publication in new window or tab >>High-Speed PAM4-Based Optical SDM Interconnects With Directly Modulated Long-Wavelength VCSEL
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2019 (English)In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 37, no 2, p. 356-362Article in journal (Refereed) Published
Abstract [en]

This paper reports the demonstration of high-speed PAM-4 transmission using a 1.5-mu m single-mode vertical cavity surface emitting laser (SM-VCSEL) over multicore fiber with 7 cores over different distances. We have successfully generated up to 70 Gbaud 4-level pulse amplitude modulation (PAM-4) signals with a VCSEL in optical back-to-back, and transmitted 50 Gbaud PAM-4 signals over both 1-km dispersion-uncompensated and 10-km dispersion-compensated in each core, enabling a total data throughput of 700 Gbps over the 7-core fiber. Moreover, 56 Gbaud PAM-4 over 1-km have also been shown, whereby unfortunately not all cores provide the required 3.8 x 10(-3) bit error rate (BER) for the 7% overhead-hard decision forward error correction (7% OH-HDFEC). The limited bandwidth of the VCSEL and the adverse chromatic dispersion of the fiber are suppressed with preequalization based on accurate end-to-end channel characterizations. With a digital postequalization, BER performance below the 7% OH-HDFEC limit is achieved over all cores. The demonstrated results show a great potential to realize high-capacity and compact short-reach optical interconnects for data centers.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Direct detection, digital signal processing (DSP), multicore fiber (MCF), spatial division multiplexing (SDM), vertical cavity surface emitting laser (VCSEL), 4-level pulse amplitude modulation (PAM-4)
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-246287 (URN)10.1109/JLT.2018.2875538 (DOI)000459535700016 ()2-s2.0-85054661876 (Scopus ID)
Conference
Optical Fiber Communications Conference and Exposition (OFC), MAR 11-15, 2018, San Diego, CA
Note

QC 20190325

Available from: 2019-03-25 Created: 2019-03-25 Last updated: 2019-04-04Bibliographically approved
Jia, S., Lo, M.-C., Zhang, L., Ozolins, O., Udalcovs, A., Kong, D., . . . Oxenlowe, L. K. (2019). Integrated Dual-DFB Laser for 408 GHz Carrier Generation Enabling 131 Gbit/s Wireless Transmission over 10.7 Meters. In: 2019 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC): . Paper presented at 2019 Optical Fiber Communications Conference and Exhibition, OFC 2019; San Diego; United States; 3 March 2019 through 7 March 2019. IEEE
Open this publication in new window or tab >>Integrated Dual-DFB Laser for 408 GHz Carrier Generation Enabling 131 Gbit/s Wireless Transmission over 10.7 Meters
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2019 (English)In: 2019 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC), IEEE , 2019Conference paper, Published paper (Refereed)
Abstract [en]

A monolithically integrated dual-DFB laser generates a 408 GHz carrier used for demonstrating a record-high single-channel bit rate of 131 Gbit/s transmitted over 10.7 m. 16-QAM-OFDM modulation and specific nonlinear equalization techniques are employed.

Place, publisher, year, edition, pages
IEEE, 2019
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-270666 (URN)000469837300615 ()2-s2.0-85065482808 (Scopus ID)
Conference
2019 Optical Fiber Communications Conference and Exhibition, OFC 2019; San Diego; United States; 3 March 2019 through 7 March 2019
Note

QC 20200313

Available from: 2020-03-13 Created: 2020-03-13 Last updated: 2020-03-13Bibliographically approved
Pang, X., Zhang, L., Ozolins, O., Udalcovs, A., Lin, R., Schats, R., . . . Chen, J. (2019). Key technologies to enable terabit-scale digital radio-over-fiber systems. In: Broadband Access Communication Technologies XIII: . Paper presented at Broadband Access Communication Technologies XIII 2019; San Francisco; United States; 4 February 2019 through 5 February 2019. SPIE - International Society for Optical Engineering, 10945, Article ID 109450E.
Open this publication in new window or tab >>Key technologies to enable terabit-scale digital radio-over-fiber systems
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2019 (English)In: Broadband Access Communication Technologies XIII, SPIE - International Society for Optical Engineering, 2019, Vol. 10945, article id 109450EConference paper, Published paper (Refereed)
Abstract [en]

With the approach of the 5G era, stringent requirements are imposed on the data transport solutions, including both of the supported transmission reach and the capacity. Radio-over-fiber technologies are considered to be promising candidates to cope with both aspects, owing to the low-loss and broad-bandwidth nature of the optical fibers. Meanwhile with such optical transport solutions, signals can be collected from the distributed remote radio sites and processed in a centralized manner. In this report, we target on the digital radio-over-fiber systems, and discuss about several key technologies, focusing on the aspects of coding and transmission, which could potentially enable terabit-scale data transport.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2019
Series
Proceedings of SPIE - The International Society for Optical Engineering, ISSN 0277-786X ; 10945
Keywords
coding, Digital radio-over-fiber, fiber optics communications, modulation, radio frequency photonics
National Category
Communication Systems
Identifiers
urn:nbn:se:kth:diva-251913 (URN)10.1117/12.2509281 (DOI)000465823300012 ()2-s2.0-85062497561 (Scopus ID)9781510625327 (ISBN)
Conference
Broadband Access Communication Technologies XIII 2019; San Francisco; United States; 4 February 2019 through 5 February 2019
Note

QC 20190523

Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-05-23Bibliographically approved
Zhang, L., Van Kerrebrouck, J., Lin, R., Pang, X., Udalcovs, A., Ozolins, O., . . . Yin, X. (2019). Nonlinearity Tolerant High-Speed DMT Transmission With 1.5-mu m Single-Mode VCSEL and Multi-Core Fibers for Optical Interconnects. Paper presented at Optical Fiber Communications Conference and Exposition (OFC), MAR 11-15, 2018, San Diego, CA. Journal of Lightwave Technology, 37(2), 380-388
Open this publication in new window or tab >>Nonlinearity Tolerant High-Speed DMT Transmission With 1.5-mu m Single-Mode VCSEL and Multi-Core Fibers for Optical Interconnects
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2019 (English)In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 37, no 2, p. 380-388Article in journal (Refereed) Published
Abstract [en]

We experimentally demonstrate the generation of 107-Gbit/s net-rate optical discrete multitone signal using a 1.5-mu m single-mode vertical cavity surface emitting laser (VCSEL) with modulation bandwidth of 22 GHz. Utilizing a nonlinearity-tolerant channel equalization algorithm for digital signal processing, total net-rates of 726.6-Gbit/s over 2.5-km dispersion-uncompensated 7-core fiber and 533.1-Gbit/s over 10-km dispersion-compensated 7-core fiber below 7% overhead hard-decision forward error correction limit have been experimentally achieved with a 1.5-mu m VCSEL-based intensity-modulation direct-detection system. The features of the 1.5-mu m single-mode VCSEL, 2.5-km/10km multi-core fibers, and fan-in/fan-out modules are presented. Besides, the Volterra series-based nonlinearity-tolerant channel equalization algorithm, which improves the signal-to-noise ratio with more than 5 dB, is mathematically described and experimentally validated. The results have demonstrated that 1.5-mu m single-mode VCSEL and multi-core-fiber-based transmission can be a promising candidate to solve the capacity challenges in short-reach optical interconnects.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Digital signal processing (DSP), discrete multitone (DMT), multi-core fiber (MCF), nonlinearity-tolerant channel equalization, vertical cavity surface emitting laser (VCSEL), Volterra series model
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-246288 (URN)10.1109/JLT.2018.2851746 (DOI)000459535700018 ()2-s2.0-85049320190 (Scopus ID)
Conference
Optical Fiber Communications Conference and Exposition (OFC), MAR 11-15, 2018, San Diego, CA
Note

QC 20190325

Available from: 2019-03-25 Created: 2019-03-25 Last updated: 2019-03-25Bibliographically approved
Lu, X., Zhao, C., Shao, Y., Zeng, J., Konijnenberg, S., Zhu, X., . . . Cai, Y. (2019). Phase detection of coherence singularities and determination of the topological charge of a partially coherent vortex beam. Applied Physics Letters, 114(20), Article ID 201106.
Open this publication in new window or tab >>Phase detection of coherence singularities and determination of the topological charge of a partially coherent vortex beam
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2019 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 114, no 20, article id 201106Article in journal (Refereed) Published
Abstract [en]

In the theory of partial coherence, coherence singularities can occur in the spectral degree of coherence (SDOC): in case the fields at two different points are completely uncorrelated, the phase of the SDOC is undefined. For a partially coherent vortex beam, the detection of coherence singularities is linked to the measurement of topological charge, whose magnitude equals the number of ring dislocations in its far field amplitude. However, the phase distribution of coherence singularities is rarely mentioned in the literature and the amplitude distribution can hardly reflect the sign of topological charge. In this letter, we present a phase-analysis method for measuring the coherence singularities by introducing a movable perturbation at a certain point in an illumination window of a finite size. Using the proposed method, we measure experimentally the coherence singularities of a partially coherent vortex beam in the focal plane. From the results, the magnitude and sign of the topological charge can be determined simultaneously from the phase distribution of the coherence singularities. Our results can find application in information transmission.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-254102 (URN)10.1063/1.5095713 (DOI)000470153700016 ()2-s2.0-85066030494 (Scopus ID)
Note

QC 20190624

Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-06-24Bibliographically approved
Xu, T., Jin, C., Zhang, S., Jacobsen, G., Popov, S., Leeson, M. & Liu, T. (2019). Phase Noise Cancellation in Coherent Communication Systems Using a Radio Frequency Pilot Tone. Applied Sciences, 9(21), Article ID 4717.
Open this publication in new window or tab >>Phase Noise Cancellation in Coherent Communication Systems Using a Radio Frequency Pilot Tone
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2019 (English)In: Applied Sciences, E-ISSN 2076-3417, Vol. 9, no 21, article id 4717Article in journal (Refereed) Published
Abstract [en]

Long-haul optical fiber communication employing digital signal processing (DSP)-based dispersion compensation can be distorted by the phenomenon of equalization-enhanced phase noise (EEPN), due to the reciprocities between the dispersion compensation unit and the local oscillator (LO) laser phase noise (LPN). The impact of EEPN scales increases with the increase of the fiber dispersion, laser linewidths, symbol rates, signal bandwidths, and the order of modulation formats. In this work, the phase noise cancellation (PNC) employing a radio frequency (RF) pilot tone in coherent optical transmission systems has been investigated. A 28-Gsym/s QPSK optical transmission system with a significant EEPN has been implemented, where the carrier phase recovery (CPR) was realized using the one-tap normalized least-mean-square (NLMS) estimation and the differential phase detection (DPD), respectively. It is shown that the RF pilot tone can entirely eliminate the LPN and efficiently suppress the EEPN when it is applied prior to the CPR.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
coherent optical fiber communication, laser phase noise (LPN), carrier phase recovery (CPR), phase noise cancellation (PNC), equalization enhanced phase noise (EEPN), radio frequency (RF) pilot tone
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-269140 (URN)10.3390/app9214717 (DOI)000498058600242 ()2-s2.0-85075191817 (Scopus ID)
Note

Qc 20200312

Available from: 2020-03-12 Created: 2020-03-12 Last updated: 2020-04-02Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-3627-8085

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