Analysis of laser and detector placement in MIMO multimode optical fiber systems

Appaiah, Kumar; Zisman, Sagi; Vishwanath, Sriram; Bank, Seth R.

doi:10.1109/icc.2012.6363770

Cited by 3 publications

(4 citation statements)

References 15 publications

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“…where H is the 2N R ×2N T channel matrix (the factor of two arising from polarization multiplexing), and C X is the optimizing input covariance matrix for each H. The H matrix is obtained for each U total by performing an overlap of the electric field that each laser and detector couples to with the fiber modes, and is described in detail in [42], although the analysis therein concerns incoherent detection. For the case of coherent MMF links, the evaluation of the capacity differs from the wireless MIMO communications scenario in two ways, as described below.…”

Section: Metrics For Evaluating Performancementioning

confidence: 99%

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Impact of fiber core diameter on dispersion and multiplexing in multimode-fiber links

2014

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Large-core silica multimode fibers, whose core diameters are generally 50 μm or 62.5 μm, form the bulk of short and medium haul optical fiber links in existence today, owing to their low cost and ease of deployment. However, modal dispersion significantly limits the maximum data rates that they support. Recently, the ability to multiplex several streams of data through optical fibers has spawned the development of few-mode multimode fibers. These fibers possess the low-dispersion characteristics of single-mode fibers and the ability to multiplex several data streams using multiple-input multiple-output (MIMO) techniques and mode-specific filtering to increase data rates. While fibers with larger core diameters possess a larger number of spatial modes, they do not support data rates as high as few-mode fibers. In this paper, we describe a simulation based approach to characterize the tradeoffs between fiber diameter, achievable data rates and alignment tolerances of coherent links that employ graded-index multimode fibers (MMFs) of various dimensions, using the information theoretic outage capacity as the metric. The simulations used fibers' intermodal coupling characteristics to measure its multiplexing abilities and dispersion limitations with mode-specific filters and launch and detection spatial filter arrays. The simulations indicate that the bandwidth-length product achievable over few-mode fibers with MIMO techniques can exceed 250 Gb/s-km, while heavy mode spreading and limited mode selectivity limits the bandwidth-length product to under 25 Gb/s-km in fibers core diameters larger than 50 μm.

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Section: Metrics For Evaluating Performancementioning

confidence: 99%

“…7. This is because launch/detection spatial arrays achieve data rates comparable to mode-specific filters for fibers that have a larger core diameter [42], while being easier to realize than mode-specific filters for large core MMFs. The achievable data rates through fibers of various diameters are shown in Fig.…”

Section: Outage Capacity µmentioning

confidence: 99%

Impact of fiber core diameter on dispersion and multiplexing in multimode-fiber links

2014

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“…The restriction of structure imposed due to submodularity did not allow laser positions to be optimized using this technique. Although this appears to be a limitation, significant performance benefits can be obtained even with regular geometries for laser arrays [45]. For finer grids, an exhaustive search was prohibitive, and submodularity provided an alternate and more viable solution.…”

Section: B Submodular Searchmentioning

confidence: 99%

Analysis of Laser and Detector Placement in Incoherent MIMO Multimode Fiber Systems

Appaiah¹,

Zisman²,

Das³

et al. 2014

J. Opt. Commun. Netw.

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Abstract-Conventional large-core multimode fibers (MMFs) are preferred for use in short to medium haul optical fiber links, owing to their tolerance to misalignment and low deployment costs; however, data rates through MMFs are limited by modal dispersion. Digital signal processing with multiple-input multiple-output (MIMO) techniques has offered promising solutions to overcome the dispersion limitations of MMFs, but the impact of the geometry of laser and detector arrays on the achievable data rate is not established. To this end, we use a field-propagation-based model to gauge the impact the geometry of lasers and detectors can have on the achievable ergodic and outage rates of incoherent MIMO-MMF links. Laser and detector array geometries were investigated using a grid-based method to optimize the positions of lasers and detectors for a 1 km MIMO-MMF link. Simulations reveal that systems with appropriately designed laser/detector geometries could improve the achievable rate over the fiber by more than 200% over random laser/detector arrays. The grid-based search technique, however, is limited due to high computational requirements for fine grids. As an alternative, we developed a suboptimal "greedy" selection approach to design detector geometries, which produces detector geometries that attain more than 90% of the rate obtained with an exhaustive search, while requiring less than 0.2% of the computation. The low computation requirements and high performance of the greedy selection approach also motivate the use of dynamically reconfigurable detector arrays to achieve high data rates with reduced signal processing complexity. Methods are also presented for clustering detector elements to obtain more consolidated segmented detectors with better fill factors, while still offering significant data rate benefits. The achievable ergodic rate using these systems is verified to be close to the link's ergodic capacity.

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“…The details of the model can be found in in another paper 16 . Combining the above, we obtain a linear inputoutput relation describing the transformation from the transmit-end to the receive-end.…”

Section: Mmf Propagation Modelmentioning

confidence: 99%

Device design and signal processing for multiple-input multiple-output multimode fiber links

2012

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Multimode fibers (MMFs) are limited in data rate capabilities owing to modal dispersion. However, their large core diameter simplifies alignment and packaging, and makes them attractive for short and medium length links. Recent research has shown that the use of signal processing and techniques such as multiple-input multipleoutput (MIMO) can greatly improve the data rate capabilities of multimode fibers. In this paper, we review recent experimental work using MIMO and signal processing for multimode fibers, and the improvements in data rates achievable with these techniques. We then present models to design as well as simulate the performance benefits obtainable with arrays of lasers and detectors in conjunction with MIMO, using channel capacity as the metric to optimize. We also discuss some aspects related to complexity of the algorithms needed for signal processing and discuss techniques for low complexity implementation.

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Analysis of laser and detector placement in MIMO multimode optical fiber systems

Cited by 3 publications

References 15 publications

Impact of fiber core diameter on dispersion and multiplexing in multimode-fiber links

Impact of fiber core diameter on dispersion and multiplexing in multimode-fiber links

Analysis of Laser and Detector Placement in Incoherent MIMO Multimode Fiber Systems

Device design and signal processing for multiple-input multiple-output multimode fiber links

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