So far, the study of the optical clearing is almost always about healthy tissue. However, the ultimate goal is to detect diseases for clinical application. Optical clearing on diseased skins is explored. The effect is evaluated by applying a combined liquid paraffin and glycerol mixed solution on several kinds of diseased skins in vitro. Scanning experiments from optical coherence tomography show that it has different effects among fibroma, pigmented nevus, and seborrheic keratosis. Based on the results, we conclude that different skin diseases have different compositions and structures, and their optical parameters and biological characteristics should be different, which implies that the optical clearing technique may have selectivity and may not be suitable for all kinds of skin diseases.
KEYWORDS: Dispersion, Microwave radiation, Telecommunications, Signal processing, Digital signal processing, Signal detection, Sensors, Transmitters, Fiber optic communications, Optical amplifiers
A feasible and cost-effective online chromatic dispersion (CD) monitoring scheme for high speed optical communication system is demonstrated in this paper. Based on the formerly verified theoretical model, the output electrical power of a specific frequency band is tested to reflect the residual chromatic dispersion online. Thus the microwave devices are selected to form the electrical power detecting circuit, which consists of a PIN photodiode, a microwave power filter and a power detector in tandem. In the experiments, frequency band center were chosen at 5 GHz for the 10 Gbit/s system and 12 GHz for the 40 Gbit/s system. Then the output voltage of the detector was processed and converted to digital signal and the signal was processed to obtain the amount of the chromatic dispersion of the tested systems. For the 40 Gbit/s system, the maximum detectable chromatic dispersion was around 130-ps/nm and a resolution of 5-ps/nm/db was achieved at the chosen frequency band centered at 12 GHz. Performance of the microwave devices and comparison of the experimental results at different frequency bands are also discussed, which verified that the chosen center frequency was suitable for detection of CD in optical communication system beyong 10 Gbit/s speed.
A vertical-shaft-type Mirau white-light phase-shifting interferometer is designed based on white-light phase-shifting interference microscopy in this paper. The interferometer is composed of an illumination and interference imaging part, a piezoelectric transducer in the vertical direction, a two-dimensional scanning part in the test surface, image collection and interferograms analysis part. The light illuminates the sample and the test surface uniformly, and the interferogram is formed. In order to get phase-shifting, the move of the objective is driven by PZT. The three-dimensional scanning system consists of a two-dimensional horizontal motorized stage and a vertical piezoelectric transducer. Multi-aperture stitching extends the measurement range in the test surface. A new pixel divided phase-extracting algorithm was put forward in combination with a residues-pretreatment phase-unwrapping algorithm based on image segmentation. The algorithm is used to minimize the phase-shifting error and nonlinearity error of the detector. The surface profile of a fiber connector with fiber inserted was measured. Mean value of the protrusion between fiber and fiber connector was measured to be 45.7nm, with 0.9 nm error. The mean height of a spot on the end surface of fiber connector was measured to be 23.6nm, with 0.7nm error.
A high-performance switched optical interconnection network is designed. The top layer of optical fiber ring network builds upon wavelength division multiplexing and hardware routing technologies. The bottom layer of star network has a throughput of 10 Gbit/s based on an 8-channel digital cross-point switch. Two types of optical network interface cards are developed to meet the requirements of interconnection bandwidth and support PCI bus full bandwidth of 1.056 Gbit/s and 4.224 Gbit/s, respectively. Field programmable gate array (FPGA) is adopted for frame head analysis, hardware routing and dynamic switch configuration. By adding a subnet to enlarge the network, the maximal delay increment is only 1.5 μs.
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