| 1. |
- Ozolins, Oskars, et al.
(författare)
-
100 GHz Externally Modulated Laser for Optical Interconnects
- 2017
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 35:6, s. 1174-1179
-
Tidskriftsartikel (refereegranskat)abstract
- We report on a 116 Gb/s on-off keying (OOK), four pulse amplitude modulation (PAM) and 105-Gb/s 8-PAM optical transmitter using an InP-based integrated and packaged externally modulated laser for high-speed optical interconnects with up to 30 dB static extinction ratio and over 100-GHz 3-dB bandwidth with 2 dB ripple. In addition, we study the tradeoff between power penalty and equalizer length to foresee transmission distances with standard single mode fiber.
|
|
| 2. |
|
|
| 3. |
- Hong, Xuezhi, et al.
(författare)
-
1.55-μm EML-based DMT transmission with nonlinearity- aware time domain super-nyquist image induced aliasing
- 2017
-
Ingår i: Optics InfoBase Conference Papers. - Washington, D.C. : OSA - The Optical Society. - 9781557528209
-
Konferensbidrag (refereegranskat)abstract
- We experimentally demonstrate a DMT transmission system with 1.55-μm EML using nonlinearity-aware time domain super-Nyquist image induced aliasing. Compared with linear equalization, the capacity is improved by ~16.8%(33.1%) with proposed method for 4(40) km transmission. © 2017 OSA.
|
|
| 4. |
|
|
| 5. |
- Hudson, Lawrence N, et al.
(författare)
-
The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
- 2017
-
Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 7:1, s. 145-188
-
Tidskriftsartikel (refereegranskat)abstract
- The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
|
|
| 6. |
- Kakkar, Aditya, et al.
(författare)
-
A path to use large linewidth LO in 28 Gbd 16-QAM metro links
- 2015
-
Ingår i: European Conference on Optical Communication, ECOC. - : IEEE. - 9788460817413
-
Konferensbidrag (refereegranskat)abstract
- We experimentally investigate the possibility to mitigate local oscillator induced Equalization Enhanced Phase Noise penalty. The results pave the way for the use of even 10 MHz linewidth local oscillator lasers in 28 Gbd 16-QAM metro links.
|
|
| 7. |
- Kakkar, Aditya, et al.
(författare)
-
Comprehensive study of equalization-enhanced phase noise in coherent optical systems
- 2015
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:23, s. 4834 -4841
-
Tidskriftsartikel (refereegranskat)abstract
- A thorough analysis of equalization-enhanced phase noise (EEPN) and its impact on the coherent optical system is presented. We show with a time-domain analysis that EEPN is caused due to the interference of multiple delayed versions of the dispersed signal, generated by intermixing of the received dispersed signal, and the noise side bands of the local oscillator (LO) in the photodetectors. We derive statistical properties such as the mean, variance, and error vector magnitude of the received signal influenced with EEPN. We show that in coherent optical systems utilizing electronic dispersion compensation, this noise corresponds to multipath fading in wireless communication systems. Closed-form expressions of necessary LO linewidth and/or mitigation bandwidth for a general system configuration and specified OSNR penalty are given. The expressions for system design parameters, validated with system simulations, show that higher order modulation formats, such as 16-quadrature amplitude modulation and beyond, put stringent demands on the LO linewidth unless a mitigation technique is used.
|
|
| 8. |
- Kakkar, Aditya, et al.
(författare)
-
Design of coherent optical systems impaired by EEPN
- 2016
-
Ingår i: 2016 Optical Fiber Communications Conference and Exhibition (OFC 2016). - 9781943580071
-
Konferensbidrag (refereegranskat)abstract
- We present experimental validation of novel analytical expressions essential for the design of coherent optical systems impaired by EEPN. These expressions enable a simple and accurate EEPN analysis for any system specification.
|
|
| 9. |
- Kakkar, Aditya, et al.
(författare)
-
Equalization Enhanced Phase Noise in Coherent Optical Systems with Digital Pre- and Post-Processing
- 2016
-
Ingår i: Photonics. - : MDPI AG. - 2304-6732. ; 3:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present an extensive study of equalization enhanced phase noise (EEPN) in coherent optical system for all practical electronic dispersion compensation configurations. It is shown that there are only eight practicable all-electronic impairment mitigation configurations. The non-linear and time variant analysis reveals that the existence and the cause of EEPN depend on the digital signal processing (DSP) schemes. There are three schemes that in principle do not cause EEPN. Analysis further reveals the statistical equivalence of the remaining five system configurations resulting in EEPN. In three of them, EEPN is due to phase noise of the transmitting laser, while in the remaining two, EEPN is caused by the local oscillator. We provide a simple look-up table for the system designer to make an informative decision regarding practicable configuration choice and design.
|
|
| 10. |
- Kakkar, Aditya, et al.
(författare)
-
Impact of local oscillator frequency noise on coherent optical systems with electronic dispersion compensation
- 2015
-
Ingår i: Optics Express. - 1094-4087. ; 23:9, s. 11221-11226
-
Tidskriftsartikel (refereegranskat)abstract
- A theoretical investigation of the equalization-enhanced phase noise (EEPN) and its mitigation is presented. We show with a frequency domain analysis that the EEPN results from the non-linear inter-mixing between the sidebands of the dispersed signal and the noise sidebands of the local oscillator. It is further shown and validated with system simulations that the transmission penalty is mainly due to the slow optical frequency fluctuations of the local oscillator. Hence, elimination of the frequency noise below a certain cut-off frequency significantly reduces the transmission penalty, even when frequency noise would otherwise cause an error floor. The required cut-off frequency increases linearly with the white frequency noise level and hence the linewidth of the local oscillator laser, but is virtually independent of the symbol rate and the accumulated dispersion.
|
|
| 11. |
|
|
| 12. |
- Kakkar, Aditya, et al.
(författare)
-
Laser Frequency Noise in Coherent Optical Systems : Spectral Regimes and Impairments
- 2017
-
Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Coherent communication networks are based on the ability to use multiple dimensions of the lightwave together with electrical domain compensation of transmission impairments. Electrical-domain dispersion compensation (EDC) provides many advantages such as network flexibility and enhanced fiber nonlinearity tolerance, but makes the system more susceptible to laser frequency noise (FN), e.g. to the local oscillator FN in systems with post-reception EDC. Although this problem has been extensively studied, statistically, for links assuming lasers with white-FN, many questions remain unanswered. Particularly, the influence of a realistic non-white FN-spectrum due to e.g., the presence of 1/f-flicker and carrier induced noise remains elusive and a statistical analysis becomes insufficient. Here we provide an experimentally validated theory for coherent optical links with lasers having general non-white FN-spectrum and EDC. The fundamental reason of the increased susceptibility is shown to be FN-induced symbol displacement that causes timing jitter and/or inter/intra symbol interference. We establish that different regimes of the laser FN-spectrum cause a different set of impairments. The influence of the impairments due to some regimes can be reduced by optimizing the corresponding mitigation algorithms, while other regimes cause irretrievable impairments. Theoretical boundaries of these regimes and corresponding criteria applicable to system/laser design are provided.
|
|
| 13. |
|
|
| 14. |
- Kakkar, Aditya, et al.
(författare)
-
Mitigation of EEPN in Coherent Optical Systems With Low-Speed Digital Coherence Enhancement
- 2015
-
Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 27:18, s. 1942-1945
-
Tidskriftsartikel (refereegranskat)abstract
- A method for mitigating local oscillator (LO) phase noise-induced impairment, also known as equalization-enhanced phase noise, in coherent optical systems is discussed. The method is suitable for real-time implementation and requires hardware with a bandwidth much lower than the signal baud rate, even for a system utilizing conventional semiconductor laser as LO. We evaluate the required parameters like interpolation technique, electrical signal-to-noise ratio at digital coherence enhancement (DCE) front end, for long haul transmission links having quadrature phase shift keying and 16-quadrature amplitude modulation formats. We show that the method can be implemented using a low-speed DCE front end and a simple digital linear interpolator with small (<1 dB) implementation penalty even in cases that would otherwise result in error floor.
|
|
| 15. |
- Kakkar, Aditya, et al.
(författare)
-
Overcoming EEPN in Coherent Transmission Systems
- 2016
-
Ingår i: 2016 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO). - Washington, D.C. : IEEE conference proceedings. - 9781943580118
-
Konferensbidrag (refereegranskat)abstract
- We for the first time experimentally demonstrate a simple technique to overcome EEPN. Performance recovery from above FEC to <1 dB penalty for 28 Gbd 16-QAM over 520 km with high LO linewidth is achieved.
|
|
| 16. |
- Kehoe, Laura, et al.
(författare)
-
Make EU trade with Brazil sustainable
- 2019
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 17. |
- Marinins, Aleksandrs, et al.
(författare)
-
Cylindrical polymer optical waveguides with polarization independent performance
- 2017
-
Ingår i: 2017 Conference on Lasers and Electro-Optics, CLEO 2017 - Proceedings. - : OSA Publishing. - 9781943580279 ; , s. 1-2
-
Konferensbidrag (refereegranskat)abstract
- Heating of poly(methyl methacrylate) ridge optical waveguides slightly above glass transition temperature minimizes surface roughness and provides cylindrical shape. We experimentally demonstrate propagation loss decrease and polarization insensitivity as a result of waveguide thermal treatment.
|
|
| 18. |
- Marinins, Aleksandrs, 1988-, et al.
(författare)
-
Thermal reflow engineered cylindrical polymer waveguides for optical interconnects
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Integrated polymer photonics brings low cost and high fabrication flexibility to optoelectronic industry. However, this platform needs to overcome several issues to be efficient enough for practical applications. In this work, we experimentally demonstrate a decrease of propagation losses and polarization sensitivity of polymer waveguide-based devices as a result of thermal treatment. Heating of poly(methyl methacrylate) (PMMA) strip optical waveguides above the glass transition temperature initiates a waveguide surface reflow due to a decrease of a polymer viscosity and surface tension energy. This results in a decrease of surface roughness and shape change from rectangular to cylindrical; thus, scattering losses and polarization sensitivity are minimized.
|
|
| 19. |
- Marinins, Aleksandrs, et al.
(författare)
-
Thermal Reflow Engineered Cylindrical Polymer Waveguides for Optical Interconnects
- 2018
-
Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers Inc.. - 1041-1135 .- 1941-0174. ; 30:5, s. 447-450
-
Tidskriftsartikel (refereegranskat)abstract
- Integrated polymer photonics brings low cost and high fabrication flexibility to optoelectronic industry. However, this platform needs to overcome several issues to be effective enough for practical applications. In this letter, we experimentally demonstrate a decrease of propagation losses and polarization sensitivity of polymer waveguide-based devices as a result of thermal treatment. Heating of poly(methyl methacrylate) strip optical waveguides above the glass transition temperature initiates a waveguide surface reflow due to a decrease of the polymer viscosity and surface tension energy. This results in a decrease of surface roughness and shape change from rectangular to cylindrical. Thus, scattering losses and polarization sensitivity are minimized.
|
|
| 20. |
- Navarro, Jaime Rodrigo, et al.
(författare)
-
Blind phase search with angular quantization noise mitigation for efficient carrier phase recovery
- 2017
-
Ingår i: Photonics. - : MDPI AG. - 2304-6732. ; 4:2
-
Tidskriftsartikel (refereegranskat)abstract
- The inherent discrete phase search nature of the conventional blind phase search (C-BPS) algorithm is found to introduce angular quantization noise in its phase noise estimator. The angular quantization noise found in the C-BPS is shown to limit its achievable performance and its potential low complexity implementation. A novel filtered BPS algorithm (F-BPS) is proposed and demonstrated to mitigate this quantization noise by performing a low pass filter operation on the C-BPS phase noise estimator. The improved performance of the proposed F-BPS algorithm makes it possible to significantly reduce the number of necessary test phases to achieve the C-BPS performance, thereby allowing for a drastic reduction of its practical implementation complexity. The proposed F-BPS scheme performance is evaluated on a 28-Gbaud 16QAM and 64QAM both in simulations and experimentally. Results confirm a substantial improvement of the performance along with a significant reduction of its potential implementation complexity compared to that of the C-BPS.
|
|
| 21. |
- Navarro, Jaime Rodrigo, et al.
(författare)
-
Carrier Phase Recovery Algorithms for Coherent Optical Circular mQAM Systems
- 2016
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 34:11, s. 2717-2723
-
Tidskriftsartikel (refereegranskat)abstract
- The phase noise tolerance of circular multilevel quadrature amplitude modulation (C-mQAM) constellations employing different carrier phase recovery (CPR) algorithms is studied. A differential decoding scheme and a bit mapping for this type of constellations are proposed. A novel CPR scheme for C-mQAM constellations is also presented. The particular distribution of the constellation points in a C-mQAM signal is exploited to reduce the required Nth power for the removal of the modulation component by a factor of two. Hence, the computational complexity of the proposed algorithm is drastically reduced. The combined linewidth symbol duration product (Delta nu T-s) tolerance of different CPR algorithms for C-mQAM constellations is studied and compared with the proposed CPR scheme. The results are analyzed at 3.8e-3 and 1e-2 bit error rate forward error correction limits. The proposed CPR scheme achieves similar Delta nu Ts tolerance compared to single stage BPS algorithm while its computational complexity is reduced by group factors of 27.2 vertical bar 32.3, and 30.5 vertical bar 32.6 (in the form of multipliers vertical bar adders) for C-16QAM and C-64QAM, respectively.
|
|
| 22. |
- Navarro, Jaime Rodrigo, et al.
(författare)
-
Phase noise tolerant carrier recovery scheme for 28 Gbaud circular 16QAM
- 2015
-
Ingår i: European Conference on Optical Communication, ECOC. - : Institute of Electrical and Electronics Engineers (IEEE). - 9788460817413
-
Konferensbidrag (refereegranskat)abstract
- We propose a novel carrier phase recovery scheme for circular 16QAM coherent transmission systems. Experimental results show low penalties (<1.4 dB) even for linewidths where square 16QAM exhibits irretrievable (above the FEC limit) error floor.
|
|
| 23. |
- Navarro, Jaime Rodrigo, et al.
(författare)
-
Two-Stage n-PSK Partitioning Carrier Phase Recovery Scheme for Circular mQAM Coherent Optical Systems
- 2016
-
Ingår i: Photonics. - : MDPI AG. - 2304-6732. ; 3:2
-
Tidskriftsartikel (refereegranskat)abstract
- A novel two-stage n-PSK partitioning carrier phase recovery (CPR) scheme for circular multilevel quadrature amplitude modulation (C-mQAM) constellations is presented. The first stage of the algorithm provides an initial rough estimation of the received constellation, which is utilized in the second stage for CPR. The performance of the proposed algorithm is studied through extensive simulations at the forward error correction bit error rate targets of 3.8 x 10(-3) and 1 x 10(-2) and is compared with different CPR algorithms. A significant improvement in the combined linewidth symbol duration product (Delta vT(s)) tolerance is achieved compared to the single-stage n-PSK partitioning scheme. Superior performance in the Delta vT(s) tolerance compared to the blind phase search algorithm is also reported. The relative improvements with respect to other CPR schemes are also validated experimentally for a 28-Gbaud C-16QAM back-to-back transmission system. The computational complexity of the proposed CPR scheme is studied, and reduction factors of 24.5 broken vertical bar 30.1 and 59.1 broken vertical bar 63.3 are achieved for C-16QAM and C-64QAM, respectively, compared to single-stage BPS in the form of multipliers broken vertical bar adders.
|
|
| 24. |
- Ozolins, Oskars, et al.
(författare)
-
100 Gbaud 4PAM Link for High Speed Optical Interconnects
- 2017
-
Ingår i: 43RD EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION (ECOC 2017). - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate 100 Gbaud 4PAM transmission over 400 meters SMF with monolithically integrated 1550 nm DFB-TWEAM having 100 GHz 3-dB bandwidth with 2 dB ripple. We evaluate its capabilities to enable two lanes 400 GbE client-side links for optical interconnects. © 2017 IEEE.
|
|
| 25. |
- Ozolins, Oskars, et al.
(författare)
-
High-speed optical and wireless transmission-challenges and achievements
- 2016
-
Ingår i: Advances in Wireless and Optical Communications (RTUWO), 2016. - : IEEE. - 9781509015368 - 9781509015351
-
Konferensbidrag (refereegranskat)abstract
- The cloud services together with the huge size datasets are driving demand for bandwidth in datacenters. The 400 Gbps client-side links are demanding a solution. The intensity modulation and direct-detection systems together with integrated semiconductor lasers and modulators appear as promising solution in four optical lanes at 100 Gbps net rate in order to reduce complexity, size, power consumption and cost.
|
|
| 26. |
|
|
| 27. |
- Pang, Xiaodan, et al.
(författare)
-
Experimental Study of 1.55-μ m EML-Based Optical IM/DD PAM-4/8 Short Reach Systems
- 2017
-
Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers Inc.. - 1041-1135 .- 1941-0174. ; 29:6, s. 523-526
-
Tidskriftsartikel (refereegranskat)abstract
- We experimentally evaluate high-speed intensity modulation/direct detection (IM/DD) transmissions with a 1.55-μ text broadband electro-Absorption modulated laser and pulse amplitude modulations (PAM). We demonstrate 80 Gb/s/ λ PAM-4 and 96 Gb/s/ λ PAM-8 transmissions with low-complexity digital equalizers at the receiver. Performance comparison with different types of equalizers are performed, including linear symbol-spaced feed-forward equalizer (FFE), fractional (half-symbol) spaced FFE and decision feedback equalizer (DFE), with different tap number. It is found that for both cases, a 6-Tap symbol-spaced FFE is sufficient to achieve a stable performance with bit-error-rate below the 7% overhead hard decision forward error correction (7%-OH HD-FEC) threshold over a 4 km standard single mode fiber link. Practical considerations including comparison between adaptive and static equalizer implementation and tolerable fiber chromatic dispersion are discussed.
|
|
| 28. |
- Pang, Xiaodan, Dr., et al.
(författare)
-
Gigabit free-space multi-level signal transmission with a mid-infrared quantum cascade laser operating at room temperature
- 2017
-
Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 42:18, s. 3646-3649
-
Tidskriftsartikel (refereegranskat)abstract
- Gigabit free-space transmissions are experimentally demonstrated with a quantum cascaded laser (QCL) emitting at mid-wavelength infrared of 4.65 μm, and a commercial infrared photovoltaic detector. The QCL operating at room temperature is directly modulated using on–off keying and, for the first time, to the best of our knowledge, four- and eight-level pulse amplitude modulations (PAM-4, PAM-8). By applying pre- and post-digital equalizations, we achieve up to 3 Gbit/s line data rate in all three modulation configurations with a bit error rate performance of below the 7% overhead hard decision forward error correction limit of 3.8 × 10−3. The proposed transmission link also shows a stable operational performance in the lab environment.
|
|
| 29. |
- Rodrigo Navarro, Jaime, et al.
(författare)
-
Adaptive Boundaries Scheme for Cycle-Slip Mitigation in C-mQAM Coherent Systems
- 2015
-
Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 27:20, s. 2154-2157
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a method for cycle-slip mitigation in circular multilevel quadrature amplitude modulation (C-mQAM) coherent optical systems, with constellation rotational asymmetry, based on an adaptive boundaries approach. The impact of cycle-slips in C-mQAM coming from Viterbi-Viterbi algorithm limits the phase noise tolerance. By introducing adaptive boundaries and a differential coding scheme, the ambiguity of asymmetrical rotation of constellation can be effectively removed. Performance of the proposed method is evaluated for a C-16QAM and C-64QAM for various laser linewidths. Results show a noticeable improvement in linewidth symbol duration product (Delta(upsilon) . T-S) tolerance compared with the previous studies on C-mQAM and mQAM constellations. The Delta(upsilon) . T-S tolerance reaches 4 x 10(-4) and 1.1 x 10(-4) for C-16QAM and C-64QAM, respectively, for 1 dB penalty at a symbol error rate of 10(-3).
|
|
| 30. |
|
|
| 31. |
- Rodrigo Navarro, Jaime, et al.
(författare)
-
High performance and low complexity carrier phase recovery schemes for 64-QAM coherent optical systems
- 2017
-
Ingår i: 2017 Optical Fiber Communications Conference and Exhibition, OFC 2017 - Proceedings. - : Institute of Electrical and Electronics Engineers Inc.. - 9781943580231
-
Konferensbidrag (refereegranskat)abstract
- We experimentally validate two novel CPR schemes outperforming existing CPRs in complexity and performance. A complexity reduction of at least a factor of 4 is reported compared to the BPS algorithm for a 64QAM system.
|
|
| 32. |
- Rodrigo Navarro, Jaime, 1987-
(författare)
-
Phase Noise Tolerant Modulation Formats and DSP Algorithms for Coherent Optical Systems
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Coherent detection together with multilevel modulation formats has the potential to significantly increase the capacity of existing optical communication systems at no extra cost in signal bandwidth. However, these modulation formats are more susceptible to the impact of different noise sources and distortions as the distance between its constellation points in the complex plane reduces with the modulation index. In this context, digital signal processing (DSP) plays a key role as it allows compensating for the impairments occurring during signal generation, transmission and/or detection relaxing the complexity of the overall system. The transition towards pluggable optical transceivers, offers flexibility for network design/upgrade but sets strict requirements on the power consumption of the DSP thus limiting its complexity. The DSP module complexity however, scales with the modulation order and, in this scenario, low complex yet high performance DSP algorithms are highly desired.In this thesis, we mainly focus on the impact of laser phase noise arising from the transmitter and local oscillator (LO) lasers in coherent optical communication systems employing high order modulation formats. In these systems, the phase noise of the transmitting and LO lasers translate into phase noise in the received constellation impeding the proper recovery of the transmitted data. In order to increase the system phase noise tolerance, we firstly explore the possibility of re-arranging the constellation points in a circularly shaped mQAM (C-mQAM) constellation shape to exploit its inherent phase noise tolerance. Different low-complex carrier phase recovery (CPR) schemes applicable to these constellations are proposed along with a discussion on its performance and implementation complexity. Secondly, the design guidelines of high performance and low complex CPR schemes for conventional square mQAM constellations are presented. We identify the inherent limitation of the state-of-the-art blind phase search (BPS) carrier phase recovery algorithm which hinders its achievable performance and implementation complexity and present a low complex solution to overcome it. The design guidelines of multi-stage CPR schemes for high order modulation formats, where the BPS algorithm is employed at any of the stages, are also provided and discussed. Finally, the interplay between the received dispersed signal and the LO phase noise is analytically investigated to characterize the origin of the equalization enhanced phase noise phenomena.
|
|
| 33. |
- Udalcovs, Aleksejs, et al.
(författare)
-
Towards Coherent Detection in SDM-based Optical Access Networks
- 2018
-
Konferensbidrag (refereegranskat)abstract
- To tackle the continued increase in capacity demand in optical access, self-homodyne coherent detection (SHCD) is being considered as a candidate solution, utilizing a spatial division multiplexing (SDM) in a low-crosstalk multicore fiber (MCF) [1, 2] and high-order modulation formats such as quadrature phase-shift keying (QPSK), 16-levels quadrature amplitude modulation (16-QAM) or even 64-levels QAM (64-QAM) . The latest imposes strict requirements on both the performance of digital signal processing (DSP) and the spectral purity of the free running lasers [4–6]. Although a SHCD scheme relaxes the laser linewidth requirements, eliminates the need for a carrier frequency tracking, the necessity for a carrier phase estimation remains if high-order constellations are considered. The reasons for that are (1) residual phase noise in a system and (2) a closer location of the constellation points in the complex plane, which leads to a significantly lower phase noise tolerance as compared to QPSK or even 16-QAM signals . Therefore, it is of crucial importance to propose a low-complexity (and low-latency) phase estimation algorithms for these scenarios as well, especially because traditional algorithms cannot be directly employed for 64QAM. During this presentation,first, we overview our recent activities on designing and experimental validation of a high-performance and a low-complexity DSP block, focusing on carrier phase recovery (CPR) suitable for circular and square m-QAM constellations. For more information about the efficient CPR schemes for m-QAM, we recommend theOFC2017 and ACP2017 proceedings.Second, after the efficient CPR scheme is explained, we provide an insight into a solution of SDM-based optical access network where self-homodyne coherent detection (SHCD) scheme with our novel low-complexity CPR is implemented for a 28-Gbaud 16-QAM and 64- QAM transmission in downstream links with a goal to improve their spectral efficiency and to increase a phase-noise tolerance, which paves the way towards higher cost-efficiency. The proposed architecture together with the experimental demonstration is given inCLEO2018 conference proceedings
|
|
