| 61. |
- Drummond, Miguel V., et al.
(författare)
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Tunable Optical Dispersion Compensator Based on Power Splitting Between Two Dispersive Media
- 2010
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 28:8, s. 1164-1175
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose and experimentally demonstrate a novel tunable optical dispersion compensator (TODC). Dispersion compensation is achieved by splitting the input signal between two dispersive media and adding the resulting signals thereafter. Tunable compensation is attained by controlling the power splitting ratio of the input signal between both dispersive media. The frequency response of the TODC is theoretically assessed considering signal addition in the optical and electrical domains. The latter case is enabled by using optical single side-band (OSSB) modulation, which allows preserving the phase information of dispersive media output signals after direct detection. This is the only case experimentally tested, since it avoids stability problems related with coherent addition of optical signals. A TODC with a tuning range of -340 to 0 ps/nm was designed and experimentally assessed for a 40 Gb/s nonreturn-to-zero OSSB signal. The tunable power splitter consisted of an automatic polarization controller and a polarization beam splitter, which offered a tuning time lower than 150 mu s. A bit error rate lower than 10(-8) was measured on the entire compensation range with a maximum power penalty of 3.3 dB relatively to an SSB signal in back-to-back.
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| 62. |
- Eghbali, Amir, et al.
(författare)
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Optimal Least-Squares FIR Digital Filters for Compensation of Chromatic Dispersion in Digital Coherent Optical Receivers
- 2014
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Ingår i: Journal of Lightwave Technology. - : Optical Society of America. - 0733-8724 .- 1558-2213. ; 32:8, s. 1449-1456
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes optimal finite-length impulse response (FIR) digital filters, in the least-squares (LS) sense, for compensation of chromatic dispersion (CD) in digital coherent optical receivers. The proposed filters are based on the convex minimization of the energy of the complex error between the frequency responses of the actual CD compensation filter and the ideal CD compensation filter. The paper utilizes the fact that pulse shaping filters limit the effective bandwidth of the signal. Then, the filter design for CD compensation needs to be performed over a smaller frequency range, as compared to the whole frequency band in the existing CD compensation methods. By means of design examples, we show that our proposed optimal LS FIR CD compensation filters outperform the existing filters in terms of performance, implementation complexity, and delay.
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| 63. |
- Eriksson, Tobias A., et al.
(författare)
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Wavelength Division Multiplexing of 194 Continuous Variable Quantum Key Distribution Channels
- 2020
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 38:8, s. 2214-2218
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the first continuous variable quantum key distribution (CV-QKD) system with fully digital phase and polarization tracking, enabling the first wavelength division multiplexing experiment for CV-QKD. We transmit 194 x 0.5 GHz channels with 25 GHz channel spacing, demonstrating an aggregate estimated asymptotic secret key rate of 172.6 Mbit/s over 25 km.
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| 64. |
- Eriksson, Tobias, 1986, et al.
(författare)
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Impact of 4D Channel Distribution on the Achievable Rates in Coherent Optical Communication Experiments
- 2016
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 34:9, s. 2256-2266
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally investigate mutual information and generalized mutual information for coherent optical transmission systems. The impact of the assumed channel distribution on the achievable rate is investigated for distributions in up to four dimensions. Single channel and wavelength division multiplexing (WDM) transmission over transmission links with and without inline dispersion compensation are studied. We show that for conventional WDM systems without inline dispersion compensation, a circularly symmetric complex Gaussian distribution is a good approximation of the channel. For other channels, such as with inline dispersion compensation, this is no longer true and gains in the achievable information rate are obtained by considering more sophisticated four-dimensional (4D) distributions. We also show that for nonlinear channels, gains in the achievable information rate can also be achieved by estimating the mean values of the received constellation in four dimensions. The highest gain for such channels is seen for a 4D correlated Gaussian distribution.
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| 65. |
- Eriksson, Tobias, 1986, et al.
(författare)
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K-Over-L Multidimensional Position Modulation
- 2014
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 32:12, s. 2254-2262
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Tidskriftsartikel (refereegranskat)abstract
- We analyze a family of modulation formats based on multidimensional position modulation (MDPM) with multiple pulses per frame (K-over-L-MDPM) in combination with quadrature phase shift keying (QPSK), polarization multiplexed QPSK (PM-QPSK) and polarization-switched QPSK (PS-QPSK) for coherent communication systems. MDPM is a generalization of pulse position modulation where different pulse slots can be realized by time slots, polarization states, frequencies, modes of multimode fibers, cores in multicore fibers or a combination of these. We show that by using K-over-L-MDPM with QPSK, it is possible to simultaneously increase both the spectral efficiency and the asymptotic power efficiency over QPSK. We also identify K-ary inverse-MDPM (KiMDPM-QPSK) as the special case of K-over(K -1)-MDPM and show that 4iMDPM-QPSK has a 1.25 dB increased asymptotic power efficiency over QPSK with a maintained spectral efficiency.
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| 66. |
- Estarán, Jose, et al.
(författare)
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140/180/204-Gbaud OOK Transceiver for Inter- and Intra-Data Center Connectivity
- 2019
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Ingår i: Journal of Lightwave Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8724 .- 1558-2213. ; 37:1, s. 178-187
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Tidskriftsartikel (refereegranskat)abstract
- 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 100Gbaud. For this, the transmitter makes 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 pre-amplified 110-GHz PIN photodiode prior to a 100-GHz analog-to-digital converter complete the ultra-high bandwidth transceiver module; the device under study. In the experimental work, which discriminates between intra- and inter-data center scenarios (dispersion unmanaged 120, 560, 960m; and dispersion-managed 10, and 80km of standard singlemode fiber), we evaluate the bit-error rate evolution against the received optical power at 140, 180, and 204Gbaud 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 ultra-high 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 140Gbaud over the entire 100m-80km range with only linear feed-forward equalization. Then the transmission of a 180Gbaud on-off-keying carrier over 80km considering 20% error-correction overhead. And finally, 10-km communication at 204Gbaud on-off keying with up to 6dB sensitivity margin, and regular 7%-overhead error-correction.
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| 67. |
- Farsi, Mohammad, 1994, et al.
(författare)
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Polarization Tracking in the Presence of PDL and Fast Temporal Drift
- 2022
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 40:19, s. 6408-6416
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we analyze the effectiveness of polarization tracking algorithms in optical transmission systems suffering from fast state of polarization (SOP) rotations and polarization-dependent loss (PDL). While most of the gradient descent (GD)-based algorithms in the literature may require step size adjustment when the channel condition changes, we propose tracking algorithms that can perform similarly or better without parameter tuning. Numerical simulation results show higher robustness of the proposed algorithms to SOP and PDL drift compared to GD-based algorithms, making them promising candidates to be used in aerial fiber links where the SOP can potentially drift rapidly, and therefore becomes challenging to track.
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| 68. |
- Fei, Chao, et al.
(författare)
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Demonstration of 15-M 7.33-Gb/s 450-nm Underwater Wireless Optical Discrete Multitone Transmission Using Post Nonlinear Equalization
- 2018
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Ingår i: Journal of Lightwave Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8724 .- 1558-2213. ; 36:3, s. 728-734
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we experimentally demonstrate an underwater wireless optical communication (UWOC) system using a 450-nm gallium nitride (GaN) laser and adaptive bit-power loading discrete multitone (DMT). To enhance the system capacity, a post nonlinear equalizer based on the simplified Volterra series is employed at the receiver to mitigate the nonlinear impairments of the UWOC system. By combining the adaptive bit-power loading with nonlinear equalization, 7.33-Gb/s DMT-modulated UWOC under 15-m tap water is achieved at a bit error rate below the 7% hard-decision forward error correction (FEC) limit 3.8 x 10(-3). The electrical signal bandwidth is 1.25 GHz, which corresponds to an electrical spectrum efficiency of similar to 6 bit/s/Hz. The capacity-distance product reaches 109.95 Gb/s-m in a single channel UWOC system with tap water. Compared with the linear equalization case, the system capacity at the FEC limit for 15-m underwater transmission is improved by similar to 18% with the nonlinear equalization. Furthermore, the impact of turbidity on the performance of UWOC system is investigated by measuring the signal-to-noise ratio (SNR) under different suspension concentrations of Al(OH)(3) and Mg(OH)(2). The results show that significant SNR gains (>3 dB for transmission distance up to 11 m) can be obtained by the nonlinear equalization over a wide range of water turbidity levels representing "clear ocean," "coastal ocean," and "harbor water," which demonstrates the robustness of the proposed scheme in various ocean environments.
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| 69. |
- Foo, Benjamin, 1991, et al.
(författare)
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Distributed Nonlinear Compensation Using Optoelectronic Circuits
- 2018
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 36:6, s. 1326-1339
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the use of optoelectronic subsystems placed all the way along a fiber link to provide distributed mitigation of the distortion caused by the Kerr nonlinearity. These subsystems use power -dependent phase modulation to mitigate the low-frequency ( < 1 GHz) components of the self-phase modulation and cross-phase modulation (XPM) distortion experienced by several wavelength channels simultaneously. Furthermore, this technique compensates the nonlinear distortion on a per-span basis, and so can mitigate XPM in optically routed links, unlike transmitter- or receiver-side nonlinearity compensation techniques. We present proof-of-concept results from both experimental and numerical studies that show our optoelectronic technique can effectively mitigate the distortion caused by fiber nonlinearity. Additional simulations study the impact of various link parameters on the effectiveness of this scheme.
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| 70. |
- Fougstedt, Christoffer, 1990, et al.
(författare)
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Energy-Efficient High-Throughput VLSI Architectures for Product-Like Codes
- 2019
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 37:2, s. 477-485
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Tidskriftsartikel (refereegranskat)abstract
- Implementing forward error correction (FEC) for modern long-haul fiber-optic communication systems is a challenge, since these high-throughput systems require FEC circuits that can combine high coding gains and energy-efficient operation. We present VLSI decoder architectures for product-like codes for systems with strict throughput and power dissipation requirements. To reduce energy dissipation, our architectures are designed to minimize data transfers in and out of memory blocks, and to use parallel non-iterative component decoders. Using a mature 28-nm VLSI process technology node, we showcase different product and staircase decoder implementations that have the capacity to exceed 1-Tb/s information throughputs with energy efficiencies of around 2 pJ/bit.
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