Multispectral imaging involves capturing the same scene at different wavelengths using various narrowband filters stacked or integrated into digital camera sensors. This technology makes it possible to extract the additional information that a human eye or conventional camera fails to capture and thus has important applications in object identification, precision agriculture, and medicine. Multispectral imaging in visible wavelengths is readily possible due to the availability of digital imaging sensors and existing narrowband filter designs like metal-dielectric-metal films, dielectric films, or Fabry-Perot cavities [1-2]. Multispectral imaging in thermal longwave infrared (LWIR) wavelengths of 8-14 μm range has more advanced applications as they can see through fire, detect various gases, and investigate materials non-destructively through thermal signatures. However, conventional thermal image sensors can image in a single spectral band only. Thermal multispectral imaging is hindered by traditional filter technology where many layers of different materials are required for obtaining various spectral bands and limited wavelength tunability. On-chip integration of the infrared filters on the thermal image sensors to build a compact multispectral thermal camera is still an emerging area [3-5]. In the current work, we design and demonstrate a low-cost single sensor-based multispectral thermal sensor system composed of copper-based plasmonic imaging filter mosaic (multiple spectral filters are fabricated on a single substrate using only one lithography step and two deposition steps) integrated into an uncooled monochrome thermal sensor. The proposed work is mass-fabricable, scalable, and integrable, thereby leveraging next-generation LWIR thermal snapshot multi- and hyperspectral imaging.
Plasmonic colour filters are promising candidate for making colour filters in image sensors. Hexagonally arranged hole array based plasmonic colour filters in aluminium has several advantages for image sensor applications such as polarization insensitivity, CMOS compatibility and fine tuning of colours using a nanometer thick film. However, the hole array based filters are limited by their transmission efficiency (transmittance). This paper presents a new filling scheme of adding optimized extra coaxial holes in hole array to increase the transmittance. The results will have potential applications in CMOS and CCD image sensors, filter wheels, and submicron pixels development.
In this paper, we investigate the indoor near-infrared optical wireless communication (OWC) systems with spatial diversity. Both repetition-coding (RC) and Alamouti-type space-time-block-coding (STBC) schemes are studied to reduce the impact of optical beam blockage in OWC links. Delay-tolerant RC technologies are also discussed to relax the synchronization requirement of transmitters, using the orthogonal filters based scheme or the recurrent neural network (RNN)-based decision scheme.
KEYWORDS: Integrated optics, Interfaces, Optical networks, Radon, Modulation, Network architectures, Signal detection, Antennas, Radio over Fiber, Signal processing
We present a review of physical networking options and enabling system technologies for efficient unification of optical and wireless access backhaul infrastructure. Different physical layer integration architectures are reviewed in conjunction with the possible wireless signal transport schemes. We also review some of our research work as one possible physical layer integration technique using RF-overlay passive optical network incorporating an optical tandem single sideband (OTSSB) modulation scheme for simultaneous transport of wired and wireless signals.
High-speed card-to-card optical interconnects are highly demanded in high-performance computing and data centers. Compared with other solutions, free-space optical interconnects have the capability of providing both reconfigurability and flexibility. In this paper we propose and experimentally demonstrate a free-space based reconfigurable optical interconnect architecture and it is capable of connecting cards located both inside the same rack as well as in different racks. Results show that 3×10 Gb/s data transmission is achieved with a worst-case receiver sensitivity better than -9.38 dBm.
We present an analysis of polarization sensitive electro-optic measurement using Jones matrix formulation. Based on our
formulation, we present an optimisation of the angle of incidence within the electro-optic probe and its ability to measure
electric-fields in a three dimensional Cartesian coordinate system.
In this paper a novel high bandwidth optical wireless communication system for indoor personal area networking
applications with both ubiquitous coverage and mobility feature is proposed and tradeoffs are studied. Gigabit-per-second
optical wireless communication system with limited mobility provided to users has been demonstrated by proof-of-
concept experiments for the first time. It has also been shown that when incorporating with the WiFi-based
localization system, our proposed system can provide high-speed error-free operation with mobility over the entire room.
Hybrid fiber-wireless networks for fixed wireless access operating in the millimeter-wave wave (mm-wave) frequency
region have been actively pursued to provide untethered connectivity to ultra-high bandwidth communications. The
architecture of such radio networks requires a large number of antenna base stations with high throughput to be deployed
to maximize the geographical coverage with main switching and routing functionalities located in a centralized location.
The transportation of mm-wave wireless signals within the hybrid network is subject to low opto-electronic conversion
efficiency, fiber chromatic dispersion and also signal degradation due to nonlinearity along the link. One of the major
technical challenges in implementing such networks lies in the mitigation of the various optical impairments that the
wireless signals experience within the hybrid network. In this paper, we present an overview of the different techniques
and schemes to overcome some of the signal impairments in transporting mm-wave radio signals over optical networks.
Broadband sources (BBSs) are commonly used in a wide range of applications in optical communication systems and biophotonics. They are particularly useful tools for Optical Coherence Tomography (OCT), which is a biomedical imaging technique that uses low-coherence light sources. In order to obtain high image quality, we have developed a novel, spectrally-flat S+C+L band source with > 120 nm bandwidth and more than 4 mW output power based on two cascaded semiconductor optical amplifiers (SOA) mixed with an Erbium-doped fiber (EDF) amplifier.
Bandwidth and output power improvements are achieved by modifying the former configuration and mixing the EDF with the first SOA before amplification in the second SOA. This configuration results in bandwidth and output power enhancements of up to 146 nm and 8 mW, respectively.
The source was then tested in an OCT system. It gives a 10 &mgr;m FWHM, low sidelobe OCT autocorrelation trace. Images and OCT autocorrelation traces were compared for the two aforementioned (which two; you mentioned one?) configurations. Images of miscellaneous samples made with the BBS show an image aspect and sharpness that is comparable with more expensive sources such as Ti:Sapphire lasers.
We study the impact of Amplified Spontaneous Emission (ASE) noise on a Semiconductor Optical Amplifier (SOA)-based optical pulse delay discriminator and SOA-based distance ranger. Our experiments show that ASE reduces the sensitivity of these SOA-based devices and we confirm this finding by carrying out extensive simulations by modeling the ASE response of SOAs. The simulation results, obtained by numerical integration of these equations in MATLABTM using the NIMRODTM portal, are in qualitative agreement with experimental results.
Broadband wireless access operating in the microwave and millimeter-wave frequency windows has been actively investigated for future ultra broadband communications. The drastic increase in the throughout of each base station in these systems necessitates the use of an optical fiber backbone to provide broadband interconnections between the central office and all the antenna base stations. With such a network layout, significant reduction of the antenna base station complexity can be achieved by moving the routing, switching and processing functionalities to the central office. By taking advantage of optical networking techniques such as wavelength division multiplexing (WDM), the total capacity of the hybrid fiber-wireless network can be greatly enhanced and efficient optical fiber architectures can be realized. In this paper we present an overview of the research that has been carried out in fiber-wireless networks incorporating WDM, with a particular focus on the optical interfaces in such networks.
We describe two optical layer schemes which simultaneously facilitate local area network emulation and automatic protection switching against distribution fiber breaks in passive optical networks. One scheme employs a narrowband fiber Bragg grating placed close to the star coupler in the feeder fiber of the passive optical network, while the other uses an additional short length distribution fiber from the star coupler to each customer for the redirection of the customer traffic. Both schemes use RF subcarrier multiplexed transmission for intercommunication between customers in conjunction with upstream access to the central office at baseband. Failure detection and automatic protection switching are performed independently by each optical network unit that is located at the customer premises in a distributed manner. The restoration of traffic transported between the central office and an optical network unit in the event of the distribution fiber break is performed by interconnecting adjacent optical network units and carrying out signal transmissions via an independent but interconnected optical network unit. Such a protection mechanism enables multiple adjacent optical network units to be simultaneously protected by a single optical network unit utilizing its maximum available bandwidth. We experimentally verify the feasibility of both schemes with 1.25 Gb/s upstream baseband transmission to the central office and 155 Mb/s local area network data transmission on a RF subcarrier frequency. The experimental results obtained from both schemes are compared, and the power budgets are calculated to analyze the scalability of each scheme.
Broadband wireless networks based on a number of new frequency windows at higher microwave and millimeter-wave frequencies have been actively pursued to provide ultra-high bandwidth services over a wireless networks. These networks will have a large number of antenna base-stations with high throughput. Significant reductions in antenna base-station complexity can be achieved if most of the signal routing and switching functions centralized at a central office in the network. In such a network, fiber feed networks can be effectively deployed to provide high bandwidth interconnections between multiple antenna base-stations and the central office. With wavelength division multiplexing, efficient optical fiber feed network architectures could be realised to provide interconnection to a large number of antenna base-stations. In this paper, we present an over view of our recent research into system technologies for fiber wireless networks.
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