Capacity limits of spatially multiplexed free-space communication

Zhao, Ningbo; Li, Xiaoying; Li, Guifang; Kahn, Joseph M.

doi:10.1038/nphoton.2015.214

Cited by 241 publications

(151 citation statements)

References 30 publications

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“…The TE 5 mode is the highest-order TE mode while the TM 3 mode is the highest-order TM mode. According to the design rules given above, the widths w ia2 and w ia3 are chosen as w ia2 = w ia3 = 1.8 μm, so that the TE 5 and TM 3 modes are cut-off at the narrow end of the wide-core waveguide (see Figure 2(b)). Meanwhile, the width w ib2 should be large enough to support the TE 0 and TM 0 modes at the wide end of the narrow-core waveguide, and also satisfy the following two conditions: n eff TE (w ia2 , 5) < n eff TE (w ib2 , 0) < n eff TE (w ia2 , 4), and n eff TM (w ia2 , 4) < n eff TM (w ib2 , 0) < n eff TM (w ia2 , 3), as discussed in the design rule.…”

Section: Structure Fabrication and Characterizationmentioning

confidence: 99%

“…. , 10) to excite the TE 0 , TE 1 , TE 2 , TE 3 , TE 4 , TE 5 , TM 0 , TM 1 , TM 2 , and TM 3 , modes, respectively. The measured transmissions at output ports O 1 ßO 10 are shown in Figure 7(a)-(j), respectively.…”

Section: Structure Fabrication and Characterizationmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8] Wavelength-division-multiplexing (WDM) is one of the most successful technologies, and uses different wavelength-channels to carry different signals in a single optical fiber/waveguide simultaneously. [1] In order to…”

Section: Introductionmentioning

confidence: 99%

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10‐Channel Mode (de)multiplexer with Dual Polarizations

Dai

Wang

et al. 2017

Laser & Photonics Reviews

233

107

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A dual-polarization 10-channel mode (de)multiplexer is proposed and realized with cascaded dual-core adiabatic tapers on a silicon-on-insulator (SOI) platform. The mode demultiplexer has a 2.3 μm-wide multimode bus waveguide, which supports six mode-channels of TE polarization and four mode-channels of TM polarization. These ten mode-channels are (de)multiplexed with five cascaded dual-core adiabatic tapers based on SOI nanowires. The widths for these dual-cores are chosen optimally according to the dispersion curves of the dual-core SOI nanowire, so that the desired highest-order modes of TE-and TM-polarizations are extracted simultaneously. These two extracted mode-channels are coupled very efficiently to the fundamental modes of TE-and TM-polarizations (TE 0 and TM 0 ) in the narrow waveguide, respectively, which are then separated by using a polarization beam splitter based on bent directional couplers. A chip consisting of a pair of 10-channel mode (de)multiplexers is fabricated and then tested with data transmission of 30Gbps/channel. The measurement results show that all TM-and TE mode-channels have low crosstalks (-15ß-25 dB) and low excess losses (0.2ß1.8 dB) over a broad wavelength band of ß90 nm, which makes it WDM (wavelength-division-multiplexing)-compatible and thus suitable for high capacity on-chip optical interconnects.

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Section: Structure Fabrication and Characterizationmentioning

confidence: 99%

Section: Structure Fabrication and Characterizationmentioning

confidence: 99%

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10‐Channel Mode (de)multiplexer with Dual Polarizations

Dai

Wang

et al. 2017

Laser & Photonics Reviews

233

107

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“…When applied to the encoding of information, it might be expected that all modal sets offer the same information capacity, where the number of modes that can be transmitted with low loss is comparable to the Fresnel number of the optical system [11]. Put simply, for beams of a given radius, modes of higher order diverge more quickly [12], requiring a collection telescope of larger aperture.…”

Section: Modementioning

confidence: 99%

Comparing the information capacity of Laguerre–Gaussian and Hermite–Gaussian modal sets in a finite-aperture system

et al. 2016

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Using a spontaneous parametric down-conversion process to create entangled spatial states, we compare the information capacity associated with measurements in the HermiteGaussian and Laguerre-Gaussian modal basis in an optical system of finite aperture. We show that the cross-talk imposed by the aperture restriction degrades the information capacity. However, the Laguerre-Gaussian mode measurements show greater resilience to cross talk than the HermiteGaussian, suggesting that the Laguerre-Gaussian modal set may still offer real-world advantages over other modal sets.

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“…10,11 Orthogonal modal bases along with multimode and multicore fibers are employed for spatial multiplexing in optical systems. [11][12][13] Because the waves are physically separated and/or spatially orthogonal, each stream can be exploited as an independent channel for communication. The following article has been submitted to Applied Physics Letters.…”

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confidence: 99%

Exploiting spatial degrees of freedom for high data rate ultrasound communication with implantable devices

Wang

Arbabian

2017

Applied Physics Letters

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We propose and demonstrate an ultrasonic communication link using spatial degrees of freedom to increase data rates for deeply implantable medical devices. Low attenuation and millimeter wavelengths make ultrasound an ideal communication medium for miniaturized low-power implants. While small spectral bandwidth has drastically limited achievable data rates in conventional ultrasonic implants, large spatial bandwidth can be exploited by using multiple transducers in a multiple-input/multiple-output system to provide spatial multiplexing gain without additional power, larger bandwidth, or complicated packaging. We experimentally verify the communication link in mineral oil with a transmitter and receiver 5 cm apart, each housing two custom-designed mm-sized piezoelectric transducers operating at the same frequency. Two streams of data modulated with quadrature phase-shift keying at 125 kbps are simultaneously transmitted and received on both channels, effectively doubling the data rate to 250 kbps with a measured bit error rate below 10 -4 . We also evaluate the performance and robustness of the channel separation network by testing the communication link after introducing position offsets. These results demonstrate the potential of spatial multiplexing to enable more complex implant applications requiring higher data rates.Advances in miniaturized, wireless, and deeply implantable medical devices (IMDs) can enable coordinated closed-loop diagnostics and treatments for applications like neuromodulation and drug delivery. 1 As their capabilities become more complex and numerous, robust and low-power communication becomes increasingly important. Research into wireless networks in the body have largely focused on radio frequency (RF) communications. 2 However, a major challenge for the propagation of electromagnetic (EM) waves in the body is power absorption in tissue. The absorbed power is dissipated as heat leading to both health concerns and significant path loss. 3 More recently, there has been increased interest in using ultrasonic waves for intra-body communication and power transfer. 2,4 At low MHz frequencies, reduced scattering due to relative homogeneity in tissue density and compressibility as well as low attenuation of about 1 dB·cm -1 ·MHz -1 in soft tissue allow ultrasonic waves to safely propagate much farther in tissue than EM waves. 1 The orders of magnitude slower propagation velocity of acoustic waves in the body (~1500 m/s) also results in millimeter wavelengths around a MHz, allowing for simpler circuits, beamforming capabilities, and smaller transducers. 1 On the other hand, the lower operating frequency and fundamentally smaller bandwidth drastically limit the achievable data rate and available modulation schemes. Required data rates can vary considerably depending on the application. For example, glucose monitoring may need kbps speeds while imaging/video may require Mbps speeds. 2 Recent studies have proposed and demonstrated different protocols with varying data rates for intra-body ultrasou...

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Capacity limits of spatially multiplexed free-space communication

Cited by 241 publications

References 30 publications

10‐Channel Mode (de)multiplexer with Dual Polarizations

10‐Channel Mode (de)multiplexer with Dual Polarizations

Comparing the information capacity of Laguerre–Gaussian and Hermite–Gaussian modal sets in a finite-aperture system

Exploiting spatial degrees of freedom for high data rate ultrasound communication with implantable devices

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