Proc. SPIE. 8713, Airborne Intelligence, Surveillance, Reconnaissance (ISR) Systems and Applications X
KEYWORDS: Signal to noise ratio, Optical transfer functions, Point spread functions, Imaging systems, Spatial frequencies, Image processing, Image filtering, Deconvolution, Modulation transfer functions, Image deconvolution
This paper presents experimental results obtained with Ziva Corp.’s image processing approach called Computational Imaging for Aberrated Optics (CIAO), which is a multi-image deconvolution algorithm. CIAO enhances the performance of imaging systems by accommodating wavefront error. This accommodation allows the designer to improve system performance or reduce system cost. CIAO has been successfully tested in a wide field of view imaging system, which has significant aberrations. These experimental results show CIAO restoration of high quality images from highly blurred images. Specifically, CIAO allows the pupil to open <50% beyond the diffraction limited aperture, which allows more light capture and higher cut-off resolution.
A Ziva team has recently demonstrated a novel technique called Collaborative Beamfocusing Radios (COBRA) which
enables an ad-hoc collection of distributed commercial off-the-shelf software defined radios to coherently align and
beamform to a remote radio. COBRA promises to operate even in high multipath and non-line-of-sight environments as
well as mobile applications without resorting to computationally expensive closed loop techniques that are currently
unable to operate with significant movement.
COBRA exploits two key technologies to achieve coherent beamforming. The first is Time Reversal (TR) which
compensates for multipath and automatically discovers the optimal spatio-temporal matched filter to enable peak signal
gains (up to 20 dB) and diffraction-limited focusing at the intended receiver in NLOS and severe multipath
environments. The second is time-aligned buffering which enables TR to synchronize distributed transmitters into a
collaborative array. This time alignment algorithm avoids causality violations through the use of reciprocal buffering.
Preserving spatio-temporal reciprocity through the TR capture and retransmission process achieves coherent alignment
across multiple radios at ~GHz carriers using only standard quartz-oscillators.
COBRA has been demonstrated in the lab, aligning two off-the-shelf software defined radios over-the-air to an accuracy
of better than 2 degrees of carrier alignment at 450 MHz. The COBRA algorithms are lightweight, with computation in
5 ms on a smartphone class microprocessor. COBRA also has low start-up latency, achieving high accuracy from a
cold-start in 30 ms.
The COBRA technique opens up a large number of new capabilities in communications, and electronic warfare
including selective spatial jamming, geolocation and anti-geolocation.
We report the demonstration of the uplink of a low-cost passive optical network (PON), utilizing a superluminescent light emitting diode (SLED) as a broadband light source, a coarse wavelength division multiplexer (CWDM) to slice the spectrum into standard CWDM channels, and a reflective semiconductor optical amplifier (RSOA) as modulator and amplifier at the remote site. We demonstrate 2.5-Gbps transmission over 1 km of single-mode fiber for all four channels of the CWDM link (1511, 1531, 1551, and 1571 nm), with the bit rate error (BER) of the system measured to be below 10−12. The main applications for this communication system are remote monitoring systems.
As carriers and service providers continue their quest for profitable network solutions, they have shifted their focus from raw bandwidth to rapid provisioning, delivery and management of revenue generating services. Inherently transparent to data rate the transmission wavelength and data format, MEMS add scalability, reliability, low power and compact size providing flexible solutions to the management and/or fiber channels in long haul, metro, and access networks. MEMS based photonic switches have gone from the lab to commercial availability and are now currently in carrier trials and volume production. 2D MEMS switches offer low up-front deployment costs while remaining scalable to large arrays. They allow for transparent, native protocol transmission. 2D switches enable rapid service turn-up and management for many existing and emerging revenue rich services such as storage connectivity, optical Ethernet, wavelength leasing and optical VPN. As the network services evolve, the larger 3D MEMS switches, which provide greater scalability and flexibility, will become economically viable to serve the ever-increasing needs.
A multidisciplinary team of end users and suppliers has collaborated to develop a novel yet broadly enabling process for the design, fabrication and assembly of Micro-Opto- Electro-Mechanical Systems (MOEMS). A key goal is to overcome the shortcomings of the polysilicon layer used for fabricating optical components in a conventional surface micromachining process. These shortcomings include the controllability and uniformity of material stress that is a major cause of curvature and deformation in released microstructures. The approach taken by the consortium to overcome this issue is to use the single-crystal-silicon (SCS) device layer of a silicon-on-insulator (SOI) wafer for the primary structural layer. Since optical flatness and mechanical reliability are of utmost importance in the realization of such devices, the use of the silicon device layer is seen as an excellent choice for devices which rely on the optical integrity of the materials used in their construction. A three-layer polysilicon process consisting of two structural layers is integrated on top of the silicon device layer. This add-on process allows for the formation of sliders, hinges, torsional springs, comb drives and other actuating mechanisms for positioning and movement of the optical components. Flip-chip bonding techniques are also being developed for the hybrid integration of edge and surface emitting lasers on the front and back surfaces of the silicon wafer, adding to the functionality and broadly enabling nature of this process. In addition to process development, the MOEMS manufacturing Consortium is extending Micro-Electro-Mechanical Systems (MEMS) modeling and simulation design tools into the optical domain, and using the newly developed infrastructure for fabrication of prototype micro-optical systems in the areas of industrial automation, optical switching for telecommunications and laser printing.
Optical interconnects at the cabinet-to-cabinet, board-to-board, and multichip module-to- multichip module levels will enable future avionics systems requirements to be met by eliminating undesirable compromises associated with electrical interconnects. Fiber optics is the well established medium of choice for cabinet-to-cabinet applications, while planar polymeric interconnects are required at the backplane level. Significant advances have been made in demonstrating practical polymer interconnects compatible with existing board fabrication principles, however both waveguide loss and interfaces to optoelectronic components require further improvement before the technology is broadly applicable.
Analytical modeling and practical experience reveal that interconnection networks for large-scale parallel architectures are severely limited by the I/O bandwidth of electrical interconnects. Optical interconnects offer far greater potential in meeting these bandwidth demands. The development of an operational 1024x1024 polyimide waveguide perfect shuffle network and high-density modulator arrays demonstrate how optics can meet this challenge. Further optical switching networks would be possible with the development of single-mode 2x2 waveguide switches. We envisage as feasible the insertion of active optical interconnection networks in future large-scale parallel architectures using integrated arrays of waveguide modulators photodetectors switches and interconnects.