The free-space narrow infrared beams can offer unprecedented data capacity to devices individually, as they can provide non-shared connections that have a large link power budget. By means of a fully ...passive module based on a high port count arrayed waveguide grating router (AWGR), many infrared beams can be 2D steered individually using wavelength tuning. By applying the defocusing techniques, a compact beam steering module has been realized. A simultaneous communication at up to 112 Gbit/s PAM-4 per beam has been shown with an 80-ports AWGR, thus offering a total wireless throughput beyond 8.9 Tbit/s. The wireless provisioning of multiple ultrahigh-definition video streams has been demonstrated in a proof-of-concept laboratory setup.
Free-space indoor optical communication deploying pencil beams can offer ultra-high wireless capacity individually per user device. By means of two-dimensional (2D) diffractive modules, such as a ...pair of crossed gratings, 2D steering of multiple beams by just tuning the wavelength of each beam can be achieved. The design aspects of an indoor system fed via an intelligent optical fiber backbone network are discussed. 2D angular beam steering over a 6° × 12° area was achieved by wavelength tuning from 1505 to 1630 nm. System experiments using PAM-4 modulation have shown a capacity of 32 Gbit/s per infrared beam. With radio-overfiber techniques and optical carrier recovery from the downstream signal, 10 Gbit/s upstream transmission of a 60 GHz radio signal has been shown using adaptive DMT modulation.
In this paper, we experimentally demonstrated a four-channel wavelength-division-multiplex (WDM) 560 Gbit/s 128 quadrature amplitude modulation (128QAM)-Discrete MultiTone (DMT) signal transmission ...in a short reach interconnect. Coordinated discrete Fourier transform-spread and preequalization are jointly used to simultaneously overcome serious frequency domain power attenuation and reduce the peak-to-average power ratio of the DMT signal. An additional postdecision-directed least mean square equalizer is used afterward to further compensate the channel response and mitigate the devices' implementation penalty. These proposed algorithms and equalizer are validated through experiment in this paper, we achieved the highest capacity signal transmission in the four-channel WDM transmission system using intensitymodulation and directdetection over a 2.4-km single mode fiber with a bit-error-ratio under the hard-decision forward error correction limit of 3.8 × 10 -3 .
Abstract
In this paper, we propose a reconfigurable beam-shaping system to permit energy-efficient non-line-of-sight (NLOS) free-space optical communication. Light is steered around obstacles ...blocking the direct communication pathway and reaches a receiver after reflecting off of a diffuse surface. A coherent array optical transmitter (CAO-Tx) is used to spatially shape the wavefront of the light incident on a diffuse surface. Wavefront shaping is used to enhance the amount of diffusely reflected light reaching the optical receiver. Synthetic NLOS experiments for a signal reflected over an angular range of 20° are presented. A record-breaking 30-Gbit/s orthogonal frequency-division multiplexing signal is transmitted over a diffused optical wireless link with a >17-dB gain.
We experimentally demonstrated a seamlessly integrated fiber-wireless system that delivers 30.67-Gb/s polarization division multiplexing-multiple input multiple output-orthogonal frequency division ...multiplexing (PDM-MIMO-OFDM) signal through 40-km fiber and 5-m wireless transmission over free-space at 100 GHz adopting heterodyne coherent detection. De-multiplexing is realized by channel estimation based on a pair of time-interleaved training sequences (TSs). The bit-error ratio (BER) for the 30.67-Gb/s PDM-MIMO-OFDM signal is less than the pre-forward-error-correction (pre-FEC) threshold of 3.8 × 10 -3 when the optical signal-to-noise ratio (OSNR) is larger than 19.3 dB after both 40-km single-mode fiber-28 (SMF-28) transmission and 5-m wireless delivery at 100 GHz. We also find that the BER performance is sensitive to the multipath effects induced by the transmission distance difference in the wireless link.
Recently, the desired very high throughput of 5G wireless networks drives millimeter-wave (mm-wave) communication into practical applications. A phased array technique is required to increase the ...effective antenna aperture at mm-wave frequency. Integrated solutions of beamforming/beam steering are extremely attractive for practical implementations. After a discussion on the basic principles of radio beam steering, we review and explore the recent advanced integration techniques of silicon-based electronic integrated circuits (EICs), photonic integrated circuits (PICs), and antenna-on-chip (AoC). For EIC, the latest advanced designs of on-chip true time delay (TTD) are explored. Even with such advances, the fundamental loss of a silicon-based EIC still exists, which can be solved by advanced PIC solutions with ultra-broad bandwidth and low loss. Advanced PIC designs for mm-wave beam steering are then reviewed with emphasis on an optical TTD. Different from the mature silicon-based EIC, the photonic integration technology for PIC is still under development. In this paper, we review and explore the potential photonic integration platforms and discuss how a monolithic integration based on photonic membranes fits the photonic mm-wave beam steering application, especially for the ease of EIC and PIC integration on a single chip. To combine EIC, for its accurate and mature fabrication techniques, with PIC, for its ultra-broad bandwidth and low loss, a hierarchical mm-wave beam steering chip with large-array delays realized in PIC and sub-array delays realized in EIC can be a future-proof solution. Moreover, the antenna units can be further integrated on such a chip using AoC techniques. Among the mentioned techniques, the integration trends on device and system levels are discussed extensively.
Indoor optical wireless communication (OWC) using steerable infrared beams is regarded as an important component in future 5G network. Photonic integration technologies can meet the criteria of such ...application, and provide low-cost, high-performance and very compact chips. In this paper, we review the recent development of photonic integration technologies suitable for indoor OWC application, and discuss in detail the current status and future opportunities of several key devices, such as the chip to free space couplers, integrated receivers and transmitters.
Cladding layers of waveguides prevent interchannel interference yet are unfavorable for the integration of photonic circuits. Here, we report the realization of ultracompact waveguide arrays, bends, ...and circuits with essentially zero interchannel separation. This supercompactness is achieved via arrays of waveguides with shifted spatial dispersions, where each waveguide functions as both the transmission channel and an effective “cladding layer” of its neighboring waveguides, and has been experimentally realized in low-loss all-dielectric photonic crystals. We show that the zero-spacing transmission array possesses the remarkable features of negligible crosstalk, high-efficiency sharp bending, and ultracompact photonic routing where the light can traverse the entire physical space. This finding opens a new avenue for extreme space utilization efficiency in waveguide physics and integrated photonics.
The reversely modulated optical single sideband scheme (IM-OSSB) based on a parallel Mach-Zehnder modulator (P-MZM) is proposed. In this P-MZM, one sub-MZM is employed for data modulation and the ...other is used for optical millimeter wave (mm-wave) generation. Due to the individual modulation, this scheme is data-format-transparent and can be used to generate a high performance optical mm-wave signal at the optimized direct current (dc) bias. There is electrical mixer free at the transmitter and thus the bandwidth limitation, nonlinearity and conversion loss from the electrical mixer are released in this scheme. Moreover, the modulation power efficiency of IM-OSSB can be improved by adjusting the dc bias in the modulator. Based on IM-OSSB, we demonstrate a 60-GHz full duplex radio-over-fiber system. The experimental results show that the power penalty of 2.9-Gb/s on-off keying data carried by 58-GHz mm-wave after transmission over 50-km SMF-28 is negligible.
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