| 1. |
-
- 2019
-
Tidskriftsartikel (refereegranskat)
|
|
| 2. |
|
|
| 3. |
- Jia, Shi, et al.
(författare)
-
Integrated dual-laser photonic chip for high-purity carrier generation enabling ultrafast terahertz wireless communications
- 2022
-
Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
-
Tidskriftsartikel (refereegranskat)abstract
- Photonic generation of Terahertz (THz) carriers displays high potential for THz communications with a large tunable range and high modulation bandwidth. While many photonics-based THz generations have recently been demonstrated with discrete bulky components, their practical applications are significantly hindered by the large footprint and high energy consumption. Herein, we present an injection-locked heterodyne source based on generic foundry-fabricated photonic integrated circuits (PIC) attached to a uni-traveling carrier photodiode generating high-purity THz carriers. The generated THz carrier is tunable within the range of 0-1.4 THz, determined by the wavelength spacing between the two monolithically integrated distributed feedback (DFB) lasers. This scheme generates and transmits a 131 Gbits(-1) net rate signal over a 10.7-m distance with -24 dBm emitted power at 0.4 THz. This monolithic dual-DFB PIC-based THz generation approach is a significant step towards fully integrated, cost-effective, and energy-efficient THz transmitters. A photonic Terahertz source based on injection-locking an integrated dual-laser chip generates and transmits a 131 Gbps THz signal over 10.7-m distance, showing great potential towards fully integrated and energy-efficient THz transmitters for 6G.
|
|
| 4. |
- Ozolins, Oskars, et al.
(författare)
-
300 Gbps Short-Reach C-Band Optical Links
- 2020
-
Ingår i: 2020 22nd international conference on transparent optical networks (ICTON 2020). - : IEEE. - 2162-7339. - 9781728184234
-
Konferensbidrag (refereegranskat)
|
|
| 5. |
- Pang, Xiaodan, Dr., et al.
(författare)
-
200 Gbps & x002F;Lane IM & x002F;DD Technologies for Short Reach Optical Interconnects
- 2020
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 38:2, s. 492-503
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 6. |
|
|
| 7. |
- Pang, Xiaodan, Dr., et al.
(författare)
-
Key technologies to enable terabit-scale digital radio-over-fiber systems
- 2019
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 9781510625327
-
Konferensbidrag (refereegranskat)abstract
- 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.
|
|
| 8. |
- Udalcovs, Aleksejs, et al.
(författare)
-
Towards 25+Gbpsλ IM-DD PON : NRZ, duobinary, PAM4, and DMT transmission and optical budget comparison
- 2019
-
Ingår i: International Conference on Transparent Optical Networks. - : IEEE Computer Society. - 9781728127798
-
Konferensbidrag (refereegranskat)abstract
- While infrastructure providers are expanding their portfolio to offer a sustainable solution for beyond 10 Gbps in optical access network segment, we compare experimentally several alternatives that may be used in future passive optical networks (PONs) to deliver 25+ Gbps net-rates. As promising candidates, we consider the intensity modulation direct detection (IM-DD) systems employing the following modulation formats: (i) duobinary, (ii) 4-level pulse amplitude modulation (PAM4), and (iii) discrete multitone (DMT), which are all more bandwidth efficient than the non-return-to-zero (NRZ) in current 10G PON solutions. In this paper, we focus on the optical budget after transmission over a 20 km single-mode fiber (SMF) link in C-band and discuss the intrinsic imperfections of optical components that may significantly reduce the received signal quality.
|
|
| 9. |
|
|
| 10. |
- Zhang, Lu, et al.
(författare)
-
Digital mobile fronthaul employing differential pulse code modulation with suppressed quantization noise
- 2017
-
Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 25:25, s. 31921-31936
-
Tidskriftsartikel (refereegranskat)abstract
- A differential pulse code modulation (DPCM) based digital mobile fronthaul architecture is proposed and experimentally demonstrated. By using a linear predictor in the DPCM encoding process, the quantization noise can be effectively suppressed and a prediction gain of 7~8 dB can be obtained. Experimental validation is carried out with a 20 km 15-Gbaud/λ 4-level pulse amplitude modulation (PAM4) intensity modulation and direct detection system. The results verify the feasibility of supporting 163, 122, 98, 81 20-MHz 4, 16, 64, 256 QAM based antenna-carrier (AxC) containers with only 3, 4, 5, 6 quantization bits at a sampling rate of 30.72MSa/s in LTE-A environment. Further increasing the number of quantization bits to 8 and 9, 1024 quadrature amplitude modulation (1024 QAM) and 4096 QAM transmission can be realized with error vector magnitude (EVM) lower than 1% and 0.5%, respectively. The supported number of AxCs in the proposed DPCM-based fronthaul is increased and the EVM is greatly reduced compared to the common public radio interface (CPRI) based fronthaul that uses pulse code modulation. Besides, the DPCM-based fronthaul is also experimentally demonstrated to support universal filtered multicarrier signal that is one candidate waveform for the 5th generation mobile systems.
|
|
| 11. |
- Zhang, Lu, et al.
(författare)
-
Digital Radio-Over-Multicore-Fiber System with Self-Homodyne Coherent Detection and Entropy Coding for Mobile Fronthaul
- 2018
-
Ingår i: European Conference on Optical Communication, ECOC. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- We experimentally demonstrate a 28-Gbaud 16-QAM self-homodyne digital radio-over-33.6km-7-core-fiber system with entropy coding for mobile fronthaul, achieving error-free carrier aggregation of 330 100-MHz 4096-QAM 5G-new-radio channels and 921 100-MHz QPSK 5G-new-radio channels with CPRI-equivalent data rate up to 3.73-Tbit/s.
|
|
| 12. |
|
|
| 13. |
- Zhang, Lu, et al.
(författare)
-
Fixed and Mobile Convergence with Stacked Modulation
- 2018
-
Ingår i: 22ND INTERNATIONAL CONFERENCE ON OPTICAL NETWORK DESIGN AND MODELING (ONDM 2018). - : IEEE. ; , s. 36-40
-
Konferensbidrag (refereegranskat)abstract
- We propose a stacked modulation mechanism to realize the transmission convergence of fixed broadband and wireless access networks. As an integrated solution, the direct current biased analog signal for wireless data is multiplied by the digital optical signal carrying fixed broadband service, where the low-speed analog signal becomes an envelope of the high-speed digital signal. At the receiver, the analog signal is firstly recovered with the image edge detection algorithm, after which the digital signal is recovered with the least-square algorithm. This scheme can realize fixed and mobile convergence with a single wavelength, which reduces the access network cost in terms of number of transceivers. Besides, the link capacity and spectrum efficiency are also improved. Moreover, this method is compatible with the existing access networks since the transceivers can be adopted to the scenario by turning off the unused modules. Simulation results show that in case of intensity modulation direct detection system sensitivity, penalty of only 1 similar to 2 dB can be obtained for the 10Gbps/lambda passive optical network when broadband access services are favored. Meanwhile, the wireless service needs more power than the broadband service to achieve the QoT requirements, and it has a higher penalty (similar to 5 dB) compared with broadband access services.
|
|
| 14. |
- Zhang, Lu, et al.
(författare)
-
K-means Clustering based Multi-Dimensional Quantization Scheme for Digital Mobile Fronthaul
- 2018
-
Ingår i: 2018 Optical Fiber Communications Conference and Exposition, OFC 2018 - Proceedings. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781943580385
-
Konferensbidrag (refereegranskat)abstract
- We propose to group highly-correlated neighboring samples into multi-dimensional vectors and adopt k-means clustering for quantization in mobile fronthaul. 30-Gbit/s transmissions have been experimentally demonstrated for up to 40 100MHz LTE channels over 20km fiber.
|
|
| 15. |
- Zhang, Lu, et al.
(författare)
-
Kernel affine projection for compensating nonlinear impairments in optical direct detection systems
- 2019
-
Ingår i: IET Conference Publications. - : Institution of Engineering and Technology. ; 2019:CP765
-
Konferensbidrag (refereegranskat)abstract
- We propose a novel kernel affine projection (KAP) algorithm, which combines kernel mapping and affine projection for channel equalization in optical direct detection systems. Experimental results show that the KAP algorithm can mitigate nonlinear impairments in short-reach communications while maintaining low computational complexity.
|
|
| 16. |
- Zhang, Lu, et al.
(författare)
-
Kernel Affine Projection for Nonlinearity Tolerant Optical Short Reach Systems
- 2020
-
Ingår i: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 68:10, s. 6403-6412
-
Tidskriftsartikel (refereegranskat)abstract
- Nonlinearity is one of the key issues that hinder the development of high-capacity optical short reach systems. This paper proposes three variants of kernel affine projection (KAP) algorithms, all of which combine kernel mapping and affine projection in a reproducing kernel Hilbert space for compensating nonlinear impairments in optical short reach systems. An intensity modulation/direct detection system with a single digital-to-analogue converter, a packaged externally modulated laser and a packaged InP photo-detector is used for experimental demonstration, achieving 238-Gbps (net rate 222-Gbps). Experimental results show that the KAP algorithms can mitigate nonlinear impairments in short-reach communications while maintaining low complexity in reproducing kernel Hilbert space.
|
|
| 17. |
- Zhang, Lu, et al.
(författare)
-
Kernel mapping for mitigating nonlinear impairments in optical short-reach communications
- 2019
-
Ingår i: Optics Express. - : OSA - The Optical Society. - 1094-4087. ; 27:21, s. 29567-29580
-
Tidskriftsartikel (refereegranskat)abstract
- Nonlinear impairments induced by the opto-electronic components are one of the fundamental performance-limiting factors in high-speed optical short-reach communications, significantly hindering capacity improvement. This paper proposes to employ a kernel mapping function to map the signals in a Hilbert space to its inner product in a reproducing kernel Hilbert space, which has been successfully demonstrated to mitigate nonlinear impairments in optical short-reach communication systems. The operation principle is derived. An intensity modulation/direct detection system with 1.5-µm vertical cavity surface emitting laser and 10-km 7-core fiber achieving 540.68-Gbps (net-rate 505.31-Gbps) has been carried out. The experimental results reveal that the kernel mapping based schemes are able to realize comparable transmission performance as the Volterra filtering scheme even with a high order.
|
|
| 18. |
|
|
| 19. |
- Zhang, Lu, et al.
(författare)
-
Nonlinearity-aware 200 Gbit/s DMT transmission for C-band short-reach optical interconnects with a single packaged electro-absorption modulated laser
- 2018
-
Ingår i: Optics Letters. - : OPTICAL SOC AMER. - 0146-9592 .- 1539-4794. ; 43:2, s. 182-185
-
Tidskriftsartikel (refereegranskat)abstract
- We experimentally demonstrate the transmission of a 200 Gbit/s discrete multitone (DMT) at the soft forward error correction limit in an intensity-modulation direct-detection system with a single C-band packaged distributed feedback laser and traveling-wave electro absorption modulator (DFB-TWEAM), digital-to-analog converter and photodiode. The bit-power loaded DMT signal is transmitted over 1.6 km standard single-mode fiber with a net rate of 166.7 Gbit/s, achieving an effective electrical spectrum efficiency of 4.93 bit/s/Hz. Meanwhile, net rates of 174.2 Gbit/s and 179.5 Gbit/s are also demonstrated over 0.8 km SSMF and in an optical back-to-back case, respectively. The feature of the packaged DFB-TWEAM is presented. The nonlinearity-aware digital signal processing algorithm for channel equalization is mathematically described, which improves the signal-to-noise ratio up to 3.5 dB.
|
|
| 20. |
- Zhang, Lu, et al.
(författare)
-
Nonlinearity Tolerant High-speed DMT Transmission with 1.5-μm Single-mode VCSEL and Multi-core Fibers for Optical Interconnects
- 2019
-
Ingår i: Journal of Lightwave Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8724 .- 1558-2213. ; 37:2, s. 380-388
-
Tidskriftsartikel (refereegranskat)abstract
- We experimentally demonstrate the generation of 107-Gbit/s net-rate optical discrete multitone (DMT) signal using a 1.5-μm 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 (DSP), 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 (HD-FEC) limit have been experimentally achieved with a 1.5-μm VCSEL based intensity-modulation direct-detection (IM/DD) system. The features of the 1.5-μm 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 (SNR) with more than 5-dB, is mathematically described and experimentally validated. The results have demonstrated that 1.5-μm single-mode VCSEL and multi-core fiber based transmission can be a promising candidate to solve the capacity challenges in short-reach optical interconnects.
|
|
| 21. |
- Zhang, Lu, et al.
(författare)
-
Spectrally efficient digitized radio-over-fiber system with k-means clustering-based multidimensional quantization
- 2018
-
Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 43:7, s. 1546-1549
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a spectrally efficient digitized radio-over-fiber (D-RoF) system by grouping highly correlated neighboring samples of the analog signals into multidimensional vectors, where the k-means clustering algorithm is adopted for adaptive quantization. A 30 Gbit/s D-RoF system is experimentally demonstrated to validate the proposed scheme, reporting a carrier aggregation of up to 40 100 MHz orthogonal frequency division multiplexing (OFDM) channels with quadrate amplitude modulation (QAM) order of 4 and an aggregation of 10 100 MHz OFDM channels with a QAM order of 16384. The equivalent common public radio interface rates from 37 to 150 Gbit/s are supported. Besides, the error vector magnitude (EVM) of 8% is achieved with the number of quantization bits of 4, and the EVM can be further reduced to 1% by increasing the number of quantization bits to 7. Compared with conventional pulse coding modulation-based D-RoF systems, the proposed D-RoF system improves the signal-to-noise-ratio up to similar to 9 dB and greatly reduces the EVM, given the same number of quantization bits. (c) 2018 Optical Society of America
|
|
| 22. |
- Zhang, Lu, et al.
(författare)
-
Toward terabit digital radio over fiber systems : Architecture and key technologies
- 2019
-
Ingår i: IEEE Communications Magazine. - : Institute of Electrical and Electronics Engineers Inc.. - 0163-6804 .- 1558-1896. ; 57:4, s. 131-137
-
Tidskriftsartikel (refereegranskat)abstract
- To support massive deployment of broadband radio applications, such as 5G and high-definition videos for terrestrial televisions, large system capacity and high spectrum efficiency are highly demanded in radio over fiber (RoF) systems. In this article, we propose a terabit digital RoF system capable of providing high-speed transmission, where multicore fiber (MCF) is introduced for the access segment between the central unit and remote unit. Two key technologies that greatly enhance system capacity and spectrum efficiency, namely MCF enabled self-homodyne detection and compressed quantization, are demonstrated.
|
|
