| 1. |
- Eriksson, Tobias, 1986-, et al.
(författare)
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625 Gbit/s Superchannel Consisting of Interleaved DP-16QAM and DP-QPSK with 4.17 bit/s/Hz Spectral Efficiency
- 2012
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Ingår i: European Conference on Optical Communications (ECOC), Amsterdam, The Netherlands, paper P4.11.
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Konferensbidrag (refereegranskat)abstract
- Abstract (40-Word Limit): We experimentally investigated a superchannel consisting of 25 GHz spaced interleaved 3x18.67 GBaud DP-QPSK and 3x18.67 GBaud DP-16QAM. We showed a 0.3 dB improvement in the Q-value averaged over the center two channels compared to an all DP-16QAM superchannel with the same SE after transmission over 480 km and 560 km of SSMF.
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| 2. |
- Li, Jianqiang, 1983-, et al.
(författare)
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Approaching Nyquist Limit in WDM Systems by Low-Complexity Receiver-Side Duobinary Shaping
- 2012
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Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 30:11, s. 1664-1676
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Tidskriftsartikel (refereegranskat)abstract
- A novel low-complexity coherent receiver solution is presented to improve spectral efficiency in wavelength-division multiplexing (WDM) systems. It is based on the receiver-side partial-response equalization and maximum-likelihood sequence detection (MLSD) in pre-filtered WDM systems. The partial- response equalization shapes the channel into an intermediate state with a known partial response which is finally recovered by MLSD without the need of channel estimation. In this scheme, the severe ISI induced by the pre-filtering can be shared between the partial-response equalization and MLSD. Therefore, a tradeoff can be made between complexity and performance. The feasibility of receiver-side partial-response shaping relaxes the efforts and requirements on the transmitter-side pre-filtering, which permits the mature WDM components to implement pre-filtering. In addition, the partial-response equalization or shaping structure is also improved based on our prior art, which further simplifies the overall scheme. For near-baudrate-spacing optically-pre-filtered WDM systems, duobinary response is experimentally proved as a good intermediate response to shape. Due to the short memory of the duobinary response, the complexity of the receiver based on duobinary shaping has been reduced to a low level. As a whole, the proposed scheme provides a good alternative to Nyquist-WDM at comparable spectral efficiencies. With the proposed receiver-side duobinary shaping technique, three sets of experiments have been carried out to verify the improved duobinary shaping scheme and meanwhile demonstrate the main features, including 5*112-Gbit/s polarization-multiplexed quadrature phase-shift keying (PM-QPSK) WDM transmission over a 25-GHz grid, single- channel 40-Gbaud PM-QPSK experiment, and 30-GHz-spaced 3*224-Gbit/s PM 16-ary quadrature amplitude modulation transmission.
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| 3. |
- Li, Jianqiang, 1983-, et al.
(författare)
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Building up low-complexity spectrally-efficient Terabit superchannels by receiver-side duobinary shaping
- 2012
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Ingår i: Optics Express. - 1094-4087. ; 20:9, s. 10271-10282
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Tidskriftsartikel (refereegranskat)abstract
- Recently, an increasing interest has been put on spectrally-efficient multi-carrier superchannels for beyond 100G. Apart from orthogonal frequency-division multiplexing (OFDM) and Nyquist wavelength-division multiplexing (WDM), another low-complexity WDM approach based on transmitter-side pre-filtering and receiver-side duobinary shaping is proposed to build up multi-carrier superchannels. This approach is referred to as receiver-side duobinary-shaped WDM (RS-DBS-WDM). Generation and transmission of a 1.232-Tbit/s 11-carrier superchannel is experimentally demonstrated. The superchannel signal can be well fit inside the passband of multiple 300-GHz reconfigurable optical add and drop multiplexers (ROADMs). In the superchannel scenario, the proposed RS-DBS-WDM is qualitatively compared with OFDM and Nyquist-WDM in terms of implementation complexity. In sum, the proposed RS-DBS-WDM approach features high transceiver analog-bandwidth efficiency, high spectral-efficiency, the absence of specific spectral manipulation, compatibility with conventional WDM technologies and coherent detection algorithms, and comparable implementation penalty.
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| 4. |
- Li, Jianqiang, 1983-, et al.
(författare)
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Exploiting the Faster-Than-Nyquist Concept in Wavelength-Division Multiplexing Systems Using Duobinary Shaping
- 2012
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Ingår i: ZTE Communications. - 1673-5188. ; 10:1, s. 23-29
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Tidskriftsartikel (refereegranskat)abstract
- This paper begins with Nyquist wavelength-division multiplexing (WDM) and then introduces faster-than-Nyquist. In faster-than-Nyquist, a certain amount of inter-symbol interference (ISI) is accepted, which violates the fundamental principle of Nyquist WDM. This results in much-relaxed transceiver bandwidth and simpler spectral design. However, in faster-than-Nyquist, implementation complexity is shifted from the transmitter side to the receiver side. Therefore, successful application of faster-than-Nyquist depends on innovation in the receiver structure. In this paper, we discuss the guidelines for implementing suboptimum, low-complexity receivers based on faster-than-Nyquist. We suggest that duobinary shaping is a good technique for trading off achievable spectral efficiency, detection performance, and implementation complexity and might be preferable to Nyquist WDM. Experiments are conducted to verify robustness of the proposed technique.
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| 5. |
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| 6. |
- Sjödin, Martin, 1983-, et al.
(författare)
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Comparison of 128-SP-QAM with PM-16-QAM
- 2012
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Ingår i: Optics Express. - 1094-4087. ; 20:8, s. 8356-8366
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we investigate an interesting modulation format for fiber optic communications, set-partitioning 128 polarization-multiplexed 16-QAM (128-SP-QAM), which consists of the symbols with even parity from the symbol alphabet of polarization-multiplexed 16-QAM (PM-16-QAM). We compare 128-SP-QAM and PM-16-QAM using numerical simulations in long-haul transmission scenarios at bit rates of 112 Gbit/s and 224 Gbit/s, and at the same symbol rates (14 and 28 Gbaud). The transmission link is made up of standard single-mode fiber with 60, 80 or 100 km amplifier spacing and both single channel and WDM transmission (25- and 50 GHz-spaced) is investigated. The results show that 128-SP-QAM achieves more than 40% increase in transmission reach compared to PM-16-QAM at the same data rate for all cases studied for a bit error rate of 10−3. In addition, we find that in single channel transmission there is, as expected, an advantage in terms of transmission distance when using a data rate of 112 Gbit/s as compared to 224 Gbit/s. However, when comparing the two different WDM systems with the same aggregate data rates, the reach is similar due to the smaller impact of nonlinear crosstalk between the WDM channels in the systems with 50 GHz spacing. We also discuss decoding and phase estimation of 128-SP-QAM and implement differential coding, which avoids error bursts due to cycle slips in the phase estimation. Simulations including laser phase noise show that the phase noise tolerance is similar for the two formats, with 0.5 dB OSNR penalty compared to the case with zero phase noise for a laser linewidth to symbol rate ratio of 10−4.
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| 7. |
- Tipsuwannakul, Ekawit, 1982-, et al.
(författare)
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Influence of Fiber-Bragg Grating-Induced Group-Delay Ripple in High-Speed Transmission Systems
- 2012
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Ingår i: Journal of Optical Communications and Networking. - 1943-0620. ; 4:6, s. 514-521
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Tidskriftsartikel (övrigt vetenskapligt)abstract
- The implementation of a chirped fiber-Bragg grating (FBG) for dispersion compensation in high-speed (up to 120 Gbit/s) transmission systems with differential and coherent detection is, for the first time, experimentally investigated. For systems with differential detection, we examine the influence of group-delay ripple (GDR) in 40 GBd 2-, 4-, and 8-ary differential phase shift keying (DPSK) systems. Furthermore, we conduct a nonlinear-tolerance comparison between the systems implementing dispersion-compensating fibers and FBG modules, using a 5 x 80 Gbit/s 100-GHz-spaced wavelength division multiplexing 4-ary DPSK signal. The results show that the FBG-based system provides a 2 dB higher optimal launch power, which leads to more than 3 dB optical signal-to-noise ratio (OSNR) improvement at the receiver. For systems with coherent detection, we evaluate the influence of GDR in a 112 Gbit/s dual-polarization quadrature phase shift keying system with respect to signal wavelength. In addition, we demonstrate that, at the optimal launch power, the 112 Gbit/s systems implementing FBG modules and that using electronic dispersion compensation provide similar performance after 840 km transmission despite the fact that the FBG-based system delivers lower OSNR at the receiver. Lastly, we quantify the GDR mitigation capability of a digital linear equalizer in the 112 Gbit/s coherent systems with respect to the equalizer tap number (N-tap). The results indicate that at least N-tap = 9 is required to confine Q-factor variation within 1 dB.
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| 8. |
- Tipsuwannakul, Ekawit, 1982-, et al.
(författare)
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Mitigation of Fiber Bragg Grating-Induced Group-Delay Ripple in 112 Gbit/s DP-QPSK Coherent Systems
- 2012
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Ingår i: 012 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference, OFC/NFOEC 2012, Los Angeles, CA, 4 March through 8 March 2012.
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Konferensbidrag (refereegranskat)abstract
- We experimentally investigate the fiber-Bragg grating (FBG)-induced group-delay ripple (GDR) mitigation capability of coherent receivers. We also show that 112-Gbit/s DP-QPSK systems with electronic-dispersion compensation (EDC) and FBG-based devices provide similar performances over 840-km transmission.
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| 9. |
- Tipsuwannakul, Ekawit, 1982-, et al.
(författare)
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Performance Comparisons of DP-16QAM and Duobinary-Shaped DP-QPSK for Optical Systems With 4.1 Bit/s/Hz Spectral Efficiency
- 2012
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Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 30:14, s. 2307-2314
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Tidskriftsartikel (refereegranskat)abstract
- This paper, for the first time, experimentally presents direct comparisons of two 25 GHz spaced wavelength division multiplexing (WDM) systems using conventional dual-polarization (DP) 16-ary quadrature amplitude modulation and duobinary-shaped DP-quadrature phase shift keying (QPSK) modulation. Both systems operate at the same bit rate per channel of 112 Gbit/s, yielding a spectral efficiency of 4.1 bit/s/Hz. The comparisons are conducted for three different cases, i.e., the back-to-back sensitivity, the nonlinear tolerance over a 640-km standard single-mode fiber link, and the phase-noise tolerance (by means of simulations). The results show that the duobinary-shaped DP-QPSK system not only provides a 3.4 dB superior back-to-back sensitivity, but also exhibits a 3 dB higher tolerance against nonlinear impairments after 640 km transmission with three WDM channels. In addition, the numerical results indicate that both investigated systems provide similar tolerances to the laser phase noise given that the block length used in the carrier phase estimation is optimized.
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| 10. |
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