| 101. |
- Huang, Yetian, et al.
(författare)
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Free-Space Optics Communications Employing Elliptical-Aperture Multimode Diversity Reception Under Anisotropic Turbulence
- 2022
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 40:5, s. 1502-1508
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally demonstrate an elliptical-aperture multimode diversity receiver to mitigate the impairment from anisotropic turbulence, which is emulated by employing an electrically-controlled heater. The anisotropy gradually decreases as the flow-level of the introduced airflow from fans increases. In contrast to circular-aperture reception, the elliptical-aperture multimode diversity receiver can effectively resist beam wander under anisotropic turbulence, reducing outage probability from 14.63% to 0.38% for detecting a dual-polarization 30-Gbaud QPSK signal. Without the aid of an adaptive optics system, this work demonstrates the feasibility of realizing an anisotropic-turbulence-resistant FSO link using multimode and multi-aperture diversity reception employing digital coherent combining techniques.
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| 102. |
- Huang, Yetian, et al.
(författare)
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Optical Broadcasting Employing Incoherent And Low-Coherence Spatial Modes for Bi-Directional Optical Wireless Communications
- 2021
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 39:3, s. 833-838
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Tidskriftsartikel (refereegranskat)abstract
- We introduce recently developed space division multiplexing (SDM)-associated technologies into optical wireless communications (OWC) and propose to use incoherent and low-coherence spatial modes to realize optical broadcasting with reliable performance by mitigating coherent interference. We experimentally demonstrate reconfigurable optical beam steering using a programmable multi-plane light conversion (MPLC)-based mode multiplexer (MMUX) and realize point-to-multi-point optical wireless communications with low-loss up-link optical beam combining and reach extension using multimode fiber (MMF). Both incoherent and low-coherence spatial modes can be generated employing the cost-efficient components such as multimode vertical cavity surface emitting laser (MM-VCSEL) and broadband amplified spontaneous emission (ASE) noise source.
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| 103. |
- Häger, Christian, 1986, et al.
(författare)
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Terminated and Tailbiting Spatially-Coupled Codes with Optimized Bit Mappings for Spectrally Efficient Fiber-Optical Systems
- 2015
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:7, s. 1275-1285
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Tidskriftsartikel (refereegranskat)abstract
- We study the design of spectrally efficient fiber- optical communication systems based on different spatially cou- pled (SC) forward error correction (FEC) schemes. In particular, we optimize the allocation of the coded bits from the FEC encoder to the modulation bits of the signal constellation. Two SC code classes are considered. The codes in the first class are protograph-based low-density parity-check (LDPC) codes which are decoded using iterative soft-decision decoding. The codes in the second class are generalized LDPC codes which are decoded using iterative hard-decision decoding. For both code classes, the bit allocation is optimized for the terminated and tailbiting SC cases based on a density evolution analysis. An optimized bit allocation can significantly improve the performance of tailbiting SC codes codes over the baseline sequential allocation, up to the point where they have a comparable gap to capacity as their terminated counterparts, at a lower FEC overhead. For the considered terminated SC codes, the optimization only results in marginal performance improvements, suggesting that in this case a sequential allocation is close to optimal.
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| 104. |
- Iglesias Olmedo, Miguel, et al.
(författare)
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Gigabit Access Passive Optical Network Using Wavelength Division Multiplexing-GigaWaM
- 2014
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 32:22
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes the research and technical achievements done under the EU project GigaWaM. The goal of this project was to develop a cost-effective solution that can meet the increasing bandwidth demands in access networks. The approach was to use a novel wavelength division multiplexing passive optical network (WDM-PON) architecture that can deliver symmetric 1 Gb/s to 64 users over 20 km standard single mode fiber using the L and C bands for down and upstream, respectively. During the course of the project, a number of key enabling technologies were developed including tunable transceivers, athermal 50 GHz spaced arrayed waveguide grating multiplexer devices, novel hybridization technologies for integration of passive and active electro-optic devices, and system-level algorithms that ensure the quality of service. The outcome of the project proved a reliable, cost-effective, flexible, and upgradable WDM-PON solution, achieving per-user datarates of 2.5 and 10 Gb/s for up and downstream, respectively. The proposed solution is not only suitable for access networks, but also for metro aggregation and mobile backhaul.
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| 105. |
- Iglesias Olmedo, Miguel, et al.
(författare)
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Multiband Carrierless Amplitude Phase Modulation for High Capacity Optical Data Links
- 2014
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 32:4, s. 798-804
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Tidskriftsartikel (refereegranskat)abstract
- Short range optical data links are experiencing bandwidth limitations making it very challenging to cope with the growing data transmission capacity demands. Parallel optics appears as a valid short-term solution. It is, however, not a viable solution in the long-term because of its complex optical packaging. Therefore, increasing effort is now put into the possibility of exploiting higher order modulation formats with increased spectral efficiency and reduced optical transceiver complexity. As these type of links are based on intensity modulation and direct detection, modulation formats relying on optical coherent detection can not be straight forwardly employed. As an alternative and more viable solution, this paper proposes the use of carrierless amplitude phase (CAP) in a novel multiband approach (MultiCAP) that achieves record spectral efficiency, increases tolerance towards dispersion and bandwidth limitations, and reduces the complexity of the transceiver. We report on numerical simulations and experimental demonstrations with capacity beyond 100 Gb/s transmission using a single externally modulated laser. In addition, an extensive comparison with conventional CAP is also provided. The reported experiment uses MultiCAP to achieve 102.4 Gb/s transmission, corresponding to a data payload of 95.2 Gb/s error free transmission by using a 7% forward error correction code. The signal is successfully recovered after 15 km of standard single mode fiber in a system limited by a 3 dB bandwidth of 14GHz.
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| 106. |
- Irukulapati, Naga Vishnukanth, 1987, et al.
(författare)
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Improved Lower Bounds on Mutual Information Accounting for Nonlinear Signal--Noise Interaction
- 2018
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 36:22, s. 5152-5159
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Tidskriftsartikel (refereegranskat)abstract
- In fiber-optic communications, evaluation of mutual information (MI) is still an open issue due to the unavailability of an exact and mathematically tractable channel model. Traditionally, lower bounds on MI are computed by approximating the (original) channel with an auxiliary forward channel. In this paper, lower bounds are computed using an auxiliary backward channel, which has not been previously considered in the context of fiber-optic communications. Distributions obtained through two variations of the stochastic digital backpropagation (SDBP) algorithm are used as auxiliary backward channels and these bounds are compared with bounds obtained through the conventional digital backpropagation (DBP). Through simulations, higher information rates were achieved with SDBP, which can be explained by the ability of SDBP to account for nonlinear signal--noise interactions
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| 107. |
- Irukulapati, Naga Vishnukanth, 1987, et al.
(författare)
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Stochastic Digital Backpropagation with Residual Memory Compensation
- 2016
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 34:2, s. 566-572
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Tidskriftsartikel (refereegranskat)abstract
- Stochastic digital backpropagation (SDBP) is an extension of digital backpropagation (DBP) and is based on the maximum a posteriori principle. SDBP takes into account noise from the optical amplifiers in addition to handling deterministic linear and nonlinear impairments. The decisions in SDBP are taken on a symbol-by-symbol (SBS) basis, ignoring any residual memory, which may be present due to non-optimal processing in SDBP. In this paper, we extend SDBP to account for memory between symbols. In particular, two different methods are proposed: a Viterbi algorithm (VA) and a decision directed approach. Symbol error rate (SER) for memory-based SDBP is significantly lower than the previously proposed SBS-SDBP. For inline dispersion-managed links, the VA-SDBP has up to 10 and 14 times lower SER than DBP for QPSK and 16-QAM, respectively.
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| 108. |
- Jamid, H. A., et al.
(författare)
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A new higher order finite-difference approximation scheme for the method of lines
- 2001
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Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 19:3, s. 398-404
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Tidskriftsartikel (refereegranskat)abstract
- A new 5-point and a 7-point nonuniform mesh finite-difference scheme is introduced to approximate the second-derivative operator. The scheme is applied using the method of lines. The necessary interface conditions for the TE and TM fields at an index discontinuity are appropriately included in the derivation. This scheme can model lossy dielectrics as well as metallic layers in a unified way. Numerical results are given for the fundamental TE and TM modes of a high-contrast waveguide and for a metal/dielectric single interface TM surface-plasmon mode showing excellent convergence behavior to the analytical results.
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| 109. |
- Jamid, H. A., et al.
(författare)
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Analysis of deep waveguide gratings : an efficient cascading and doubling algorithm in the method of lines framework
- 2002
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 20:7, s. 1204-1209
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a computationally fast, numerically stable, and memory-efficient cascading and doubling algorithm is proposed within the method of lines framework to model long planar waveguide gratings having thousands of periods in the propagation direction. This algorithm can model 2(n) grating periods in n calculational steps and needs N-2 matrices for N sample points in the problem space. It can model periodic, quasi-periodic, symmetric, and asymmetric, gratings efficiently. Different deep waveguide gratings are modeled using this scheme and results for the fundamental TE mode spectral reflectivity are compared with published results showing excellent agreement.
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| 110. |
- Jia, Shi, et al.
(författare)
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0.4 THz Photonic-Wireless Link with 106 Gbit/s Single Channel Bitrate
- 2018
-
Ingår i: Journal of Lightwave Technology. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8724 .- 1558-2213. ; 36:2, s. 610-616
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Tidskriftsartikel (refereegranskat)abstract
- To accommodate the demand of exponentially increased global wireless data traffic, the prospective data rates for wireless communication in the market place will soon reach 100 Gbit/s and beyond. In the lab environment, wireless transmission throughput has been elevated to the level of over 100 Gbit/s attributed to the development of photonic-assisted millimeter wave (MMW) and THz technologies. However, most of recent demonstrations with over 100 Gbit/s data rates are based on spatial or frequency division multiplexing techniques, resulting in increased system's complexity and energy consumption. Here, we experimentally demonstrate a single channel 0.4 THz photonic-wireless link achieving a net data rate of beyond 100 Gbit/s by using a single pair of THz emitter and receiver, without employing any spatial/frequency division multiplexing techniques. The high throughput up to 106 Gbit/s within a single THz channel is enabled by combining spectrally efficient modulation format, ultra-broadband THz transceiver and advanced digital signal processing (DSP) routine. Besides that, our demonstration from system-wide implementation viewpoint also features high transmission stability, and hence shows its great potential to not only decrease the system's complexity, but also meet the requirements of prospective data rates for bandwidth-hungry short-range wireless applications.
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