KEYWORDS: Fluid dynamics, Near infrared, Calibration, Water, Pulsed laser operation, Prototyping, Sensors, Temperature metrology, Data modeling, Refractive index
Fluidic measurement is a critical part of clinical care and homeostasis maintenance. This paper reports feasibility study
of measuring flow velocities over a wide dynamic range using a non-contact measurement technique, optical time-of-flight
(OTOF), with the objective of developing a compact instrument that can be used to measure fluid flow for IV
medication delivery. In this study, a 1480nm laser diode focused to a 20μm spot introduces a heat bolus into the fluid.
This localized temperature increase results in a correlated change in refractive index, detected downstream by observing
defocusing of the visible beam, focused to a 10μm spot in the center of the fluid path. The OTOF measurement provides
the centerline velocity of the fluid flow. CFD modeling ensured that laminar flow was fully developed; prior to the
OTOF measurement point, thus providing a simple, empirical relationship between OTOF and fluid velocity, and hence
volumetric flow rate. Measurements have been performed over a wide range of flow velocity from 1 mm/s to 1 m/s with
approximately ±5% measurement error for broad ranges of fluid properties such as viscosity (0.77-13.88 cp), density
(0.98-1.17 g/cm3) and temperature (5-35 °C). The dynamic range of measured velocity/flow rates is a function of the
distance between the heating and the detection laser beams.
Two optical beam forming network (BFN) architectures that are deemed viable for on-board satellite phased-array antenna applications are assessed for functional capacity and technology feasibility: specifically, the implementation issues, reliability, and long-term performance are discussed for an M-beam, N-element phased-array antenna operating at Ka-band. Also included are the results of recently demonstrated proof-of-concept BFNs employing fiber optic true-time delay elements and coherent optical processor (COP) based approaches. The details of the trade-off study results and relevant POC hardware developed will be presented in the conference to demonstrate the advantage of light weight and large bandwidth capability of photonic beamforming which are at premium in large antenna arrays. Coherent optical processor using Fourier transform has many advantages.
Application of photonics in beam forming and steering for phased-array antennas is addressed in this paper. Several photonic beam forming and steering network (BFN) architectures are assessed for their capability and technology feasibility, including the mass, prime power, and volume of the payload feeding a multibeam multi-element phased-array antenna. Trade-off issues in BFN architecture and technology selection processes and critical long lead time technical areas that must be developed before its successful deployment on-board communications satellite have been identified. Results of already demonstrated proof-of-concept schemes are also presented.
Characterizing propagation losses in integrated optical structures is quite cumbersome and time consuming. Particularly for single-mode optical polymer channel waveguide devices that are butt-coupled, uncertainty of end facet preparation can add considerable error in estimated propagation losses. At COMSAT Laboratories, we have produced NLO polymer channel waveguides of buried and stripe designs by reactive ion etching and evaluated their loss performance by cutback and retro-reflection techniques. The first method, which is based on optical transmission in polished butt-coupled devices, is commonly used. The second method requires retro-reflection of the transmitted beam so that the input light beam (retro-reflected) is matched to the optical waveguide beam profile. This method has a higher accuracy because there is no need to correct for the mode-mismatch loss typical of the first method. Also, loss measured at different wavelengths can be used to distinguish true propagation and scattering losses contributed by structural imperfections in the channel waveguide sidewalls.
Results of e-beam-written electro-optic (EO) organic polymeric integrated optical (IO) channel waveguide devices developed for onboard satellite applications are reported. Processing for both strip-loaded and ridge guide structures was developed to fabricate several types of devices, such as linear and curved waveguides, optical power splitters, combiners, and phase modulators, on a 3-in.-diameter silicon wafer. A large number of polished, butt-coupled devices were tested for optical loss and EO modulation at 830- and 1,310-nm wavelengths. These devices are highly reproducible, capable of very high frequency modulation (currently at 18 GHz) with a small rf drive (0 dBm), and can be made reasonably long if required. For the optical phase modulation measurements, both subcarrier modulation with phase-sensitive detection by a lock-in amplifier, and direct detection of the rf-modulated optical carrier in a lightwave analyzer, were used. The short- and long-term stability of the corona-poled EO polymer films investigated by second harmonic generation were found to be good. IO channel waveguide development considerations leading to above performance characteristics also are presented.
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