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.
Non-uniform pulse amplitude modulation (PAM) utilizes unequal distances between its modulation levels. In a multilevel PAM symbol, multiple bits are encoded. Due to the unequal level spacing, some ...bits can be decoded successfully at a lower received optical power than others. This is well suited for practical passive optical network (PON) deployments wherein the optical powers received by the different optical network units (ONUs) typically vary over a broad range. Thus, more ONUs in the PON can successfully decode non-uniform PAM-4 and PAM-8 than standard PAM-4/8, thereby increasing the aggregated capacity of the network. In systems where signal-dependent noise makes up a significant part of the total received noise level, the non-uniform PAM constellation can be adapted to take this signal-dependent variance into account. In doing so, a lower unequal level spacing can be used, decreasing the received optical power required to successfully decode all the bits in the PAM symbol. The impact of non-uniform PAM on the network throughput is presented by comparison of the experimental results with the actual loss distribution of a commercially deployed PON.
In order to meet the massively increasing requirements of big-data applications, data centers (DCs) are key infrastructures to cope with the associated demands, such as high performance, easy ...scalability, low cabling complexity and low power consumption. Many research efforts have been dedicated to traditional wired data center networks (DCNs). However, DCNs’ static and rigid topology based on optical cables significantly limits their flexibility, scalability, and even reconfigurability. The limitations of this wired connection can be addressed with optical wireless technology, which avoids cable complexity problems while allowing dynamic adaption and fast reconfiguration. Here, we propose and investigate a novel optical wireless data-center network (OW-DCN) architecture based on nanoseconds semiconductor optical amplifier (SOA)-based wavelength selectors and arrayed waveguide grating router (AWGR) controlled by fast field-programmable gate array (FPGA)-based switch schedulers. The full architecture, including the design, packet-switching strategy, contention solving methodology, and reconfiguration capability, is presented and demonstrated. Dynamic switch scheduling with a FPGA-based switch scheduler processing optical label and software-defined network (SDN)-based reconfiguration were experimentally confirmed. The proposed OW-DCN was also achieved with a power penalty of less than 2 dB power penalty at BER < 1 × 10−9 for a 50 Gb/s OOK transmission and packet-switching transmission.
Scalability of packet switched cross-connects that utilize all-optical signal processing is a crucial issue that eventually determines the future role of photonic signal processing in optical ...networks. After reviewing several labeling techniques, we discuss label stacking and label swapping techniques and their benefits for scalable optical packet switched nodes. All-optical devices for implementing the packet switch based on the labeling techniques will be described. Finally, we present a 1×4 all-optical packet switch based on label swapping technique that utilizes a scalable and asynchronous label processor and label rewriter. Error-free operation indicates a potential utilization of the swapping technique in a multihop packet-switched network.
The predominant focus of research in high-speed optical wireless communication (OWC) lies in line-of-sight (LOS) links with narrow infrared beams. However, the implementation of precise tracking and ...steering necessitates delicate active devices, thereby presenting a formidable challenge in establishing a cost-effective wireless transmission. Other than using none-line-of-sight (NLOS) links with excessive link losses and multi-path distortions, the simplification of the tracking and steering process can be alternatively achieved through the utilization of divergent optical beams in LOS. This paper addresses the issue by relaxing the stringent link budget associated with divergent Gaussian-shaped optical beams and narrow field-of-view (FOV) receivers in LOS OWC through the independent optimization of geometrical path loss and fiber coupling loss. More importantly, the geometrical path loss is effectively mitigated by modifying the transverse intensity distribution of the optical beam using manipulations of multi-mode fibers (MMFs) in an all-fiber configuration. In addition, the sufficiently excited higher order modes (HOMs) of MMFs enable a homogenized distribution of received optical powers (ROPs) within the coverage area, which facilitates the mobility of end-users. Comparative analysis against back-to-back links without free-space transmission demonstrates the proposed scheme’s ability to achieve low power penalties. With the minimized link losses, experimental results demonstrate a 10 Gbps error-free (BER < 10−13) LOS OWC downlink transmission at 2.5 m over an angular range of 10° × 10° without using any optical pre-amplifications at a typical PIN receiver. The proposed scheme provides a simple and low-cost solution for high-speed and short-range indoor wireless applications.
In order to circumvent radio spectrum congestion, we propose an innovative system which can provide multiple infrared optical wireless beams simultaneously where each beam supports ...multi-gigabit-per-second communication. Scalable two-dimensional beam steering by means of wavelength tuning is proposed. A passive beam-steering module constructed with cascaded reflection gratings is designed for simultaneous multi-user coverage. We experimentally characterized the beam-steered system and thoroughly evaluated the performance of steered channels using the spectrally efficient and robust discrete multitone modulation in a bandwidth-limited system deploying 10 GHz telecom transceivers. This study reports the achievement of at least 37 Gbps free-space transmission per beam over a distance of up to 2 m over 5.61° × 12.66° scanning angles.
A beam-steered Gigabit Ethernet (GbE) bidirectional OWC system with user-hosted automatic self-calibrated alignment of the upstream beams has been designed and realized, using stepper motor ...translators, miniature retro-reflectors and a novel self-alignment center-of-gravity (CoG) algorithm. Broadband receivers with a Field-of View (FoV) >10 degree are used, which relaxes beam alignment. The accuracy of the CoG algorithm and the impact of lens aberrations in the upstream beam launching is analyzed. A good accuracy of the automated upstream beam steering within 200 μm relative to the center of the upstream receiver's aperture has been found up to a beam incident angle of 10 degree; this is well within the 25 mm aperture and the FoV of the upstream receiver. Hereto a relatively simple low-aberration triplet lens is used at the user site. The upstream beam alignment takes less than 10 seconds. The full system laboratory setup provides individual narrow beams for high user densities. It also includes automatic self-calibrated alignment of the downstream beams using similar retroreflector technology and a wavelength-tuned beam steering. TCP measurements show transfer speeds of 940 Mbit/s per user within 10 degree FoV. Real-time high-definition GbE video streaming to laptop computers via individual bidirectional OWC links has been demonstrated.
Ultra-high-capacity wireless communication by means of steered narrow optical beams Koonen, Ton; Mekonnen, Ketemaw; Cao, Zizheng ...
Philosophical transactions - Royal Society. Mathematical, Physical and engineering sciences/Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences,
04/2020, Letnik:
378, Številka:
2169
Journal Article
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The optical spectrum offers great opportunities to resolve the congestion in radio-based communication, aggravated by the booming demand for wireless connectivity. High-speed infrared optical ...components in the 1500 nm window have reached high levels of sophistication and are extensively used already in fibre-optic networks. Moreover, infrared light beyond 1400 nm is eye-safe and is not noticeable by the users. Deploying steerable narrow infrared beams, wireless links with huge capacity can be established to users individually, at minimum power consumption levels and at very high levels of privacy. Fully passive diffractive optical modules can handle many beams individually and accurately steer narrow beams two-dimensionally by just remotely tuning the wavelength of each beam. The system design aspects are discussed, encompassing the beam-steering transmitter, wide field-of-view optical receiver and the localization of the user's wireless devices. Prototype system demonstrators are reported, capable of supporting up to 128 beams carrying up to 112 Gbit s
per beam. Hybrid bidirectional systems which use a high-speed downstream optical link and an upstream radio link at a lower speed can provide powerful asymmetric wireless connections. All-optical bidirectional beam-steered wireless communication will be able to offer the ultimate in wireless capacity to the user while minimizing power consumption. This article is part of the theme issue 'Optical wireless communication'.
In this paper, two different paradigms to realize a scalable all-optical packet switch with label swapping will be reviewed. The two paradigms are based on wavelength routing switch and space routing ...switch. All the functions required for switching the packets, namely, the label processor, the label rewriter, and the optical switch, are based on all-optical signal processing with no electronic control. This allows for very fast processing time and potential photonic integration of the systems. We report, for both techniques, experimental results showing the routing operation of the 160-Gb/s packets and beyond. We will discuss and compare both techniques in terms of devices and bit-rate scalability, power consumption, power penalty performance, and cascadability as key parameters for the realization of an all-optical packet switch.
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