Bipolar Optical Code Division Multiple Access Techniques Using a Dual Electro-Optical Modulator Implemented in Free-Space Optics Communications.

This study developed a bipolar optical code division multiple access (Bi-OCDMA) technique based on spectral amplitude coding for the formation and transmission of optical-polarized and coded signals over wireless optical channels. Compared with conventional Bi-OCDMA schemes, the proposed free-space optics communication system that uses a dual electro-optical modulator design improves the transmission rate. In theory, multiple access interference can be removed by using correlation subtraction schemes. The experiment results revealed that the proposed system can be employed to accurately extract codewords from an M-sequence and subsequently reconstruct the desired original data. Moreover, the proposed architecture can be implemented easily in simple and cost-effective designs and may be beneficial for broadening the use of Bi-OCDMA schemes in wireless optical communications.

Optical Design with Narrow-Band Imaging for a Capsule Endoscope.

The study proposes narrow-band imaging (NBI) lens design of 415 nm and 540 nm of a capsule endoscope (CE). The researches show that in terms of the rate of accuracy in detecting and screening neoplastic and nonneoplastic intestinal lesions, the NBI system outperformed that of traditional endoscopes and rivaled that of chromoendoscopes. In the proposed NBI CE optical system, the simulation result shows the field of view (FOV) was 109.8°; the modulation transfer function (MTF) could achieve 12.5% at 285 lp/mm and 34.1% at 144 lp/mm. The relative illumination reaches more than 60%, and the system total length was less than 4 mm. Finally, this design provides high-quality images for a 300-megapixel 1/4″ CMOS image sensor with a pixel size of 1.75 µm.

The enhanced locating performance of an integrated cross-correlation and genetic algorithm for radio monitoring systems.

The rapid development of wireless broadband communication technology has affected the location accuracy of worldwide radio monitoring stations that employ time-difference-of-arrival (TDOA) location technology. In this study, TDOA-based location technology was implemented in Taiwan for the first time according to International Telecommunications Union Radiocommunication (ITU-R) recommendations regarding monitoring and location applications. To improve location accuracy, various scenarios, such as a three-dimensional environment (considering an unequal locating antenna configuration), were investigated. Subsequently, the proposed integrated cross-correlation and genetic algorithm was evaluated in the metropolitan area of Tainan. The results indicated that the location accuracy at a circular error probability of 50% was less than 60 m when a multipath effect was present in the area. Moreover, compared with hyperbolic algorithms that have been applied in conventional TDOA-based location systems, the proposed algorithm yielded 17-fold and 19-fold improvements in the mean difference when the location position of the interference station was favorable and unfavorable, respectively. Hence, the various forms of radio interference, such as low transmission power, burst and weak signals, and metropolitan interference, was proved to be easily identified, located, and removed.

Using a fiber loop and fiber bragg grating as a fiber optic sensor to simultaneously measure temperature and displacement.

This study integrated a fiber loop manufactured by using commercial fiber (SMF-28, Corning) and a fiber Bragg grating (FBG) to form a fiber optic sensor that could simultaneously measure displacement and temperature. The fiber loop was placed in a thermoelectric cooling module with FBG affixed to the module, and, consequently, the center wavelength displacement of FBG was limited by only the effects of temperature change. Displacement and temperature were determined by measuring changes in the transmission of optical power and shifts in Bragg wavelength. This study provides a simple and economical method to measure displacement and temperature simultaneously.

Experimental demonstration of high-speed full-range Fourier domain optical coherence tomography imaging using orthogonally polarized light and a phase-shifting algorithm.

This study describes a phase-shifting method based on orthogonal polarized light by using complex Fourier domain optical coherence tomography (FD-OCT) to increase the speed of image scanning and to resist vibration and other environmental disturbances. Two FD-OCT interferograms corresponding to orthogonal polarization components can be obtained simultaneously. After using a π/2 phase-shifting algorithm, removing unwanted components becomes possible, including dc and autocorrelation terms, from the interferogram. This method doubles the measurement range. In other words, this approach enables one-shot and full-range FD-OCT. Experimental results show that the reconstruction parameters of the sample are close to the conventional time-domain optical coherence tomography.

Simultaneous measurement of group refractive index and thickness of optical samples using optical coherence tomography.

Optical coherence tomography (OCT), based on a Michelson interferometer and utilizing low coherence light as the optical source, is a novel technique for the noninvasive imaging of optical scattering media. A simple OCT scheme based on a 3 x 3 fiber coupler is presented for the simultaneous measurement of the refractive index and thickness of optical samples. The proposed system enables the refractive index and thickness to be determined without any prior knowledge of the sample parameters and is characterized by a simple and compact configuration, a straightforward measurement procedure, and a low cost. The feasibility of the proposed approach is demonstrated experimentally using BK7 and B270 optical glass samples.

Development of dimethyl sulfoxide biosensor using a mediator immobilized enzyme electrode.

A mediator immobilized dimethyl sulfoxide (DMSO) sensor using DMSO reductase (DMSO-R) was constructed. Methyl viologen (MV) was used as a mediator and immobilized on a glassy carbon (GC) electrode with Nafion polymer. DMSO-R from Rhodobacter sphaeroides f. sp. denitrificans was retained by a dialysis film on the modified GC electrode. The amperometric signal in response to DMSO was observed. The linear range of the calibration curve for DMSO was between 0 and 600 microM. The response time was within 100 s and the relative standard deviation was 4% at 200 microM DMSO (n = 4). To eliminate the background noise derived from oxygen in samples, the glucose oxidase-catalase retained DMSO sensor was also examined.