We report a novel design of photonic crystal fiber (PCF) with a rectangular array of four closely-spaced, highly elliptical
air holes in the core region and a circular-air-hole cladding. The proposed PCF is able to support ultra-wideband singlepolarization
single-mode (SPSM) transmission from the visible band to the near infrared band. With the aid of the inner
cladding formed by the central air holes, one polarization of the fundamental mode can be cut off at very short
wavelengths and ultra-wideband SPSM propagation can be achieved. The inner cladding also suppresses the higher order
modes and allows large air filling fraction in the outer cladding while the proposed fiber remains SPSM, which
significantly reduces the mode effective area and the confinement loss. Our simulation results indicate that the proposed
PCF has a 1540 nm SMSP range with < 0.25 dB/km confinement loss and an effective area of 2.2 m2. Moreover, the
group velocity dispersion (GVD) of the proposed PCF can also be tuned to be flat and near zero at the near infrared band
(~800 nm) by optimizing the outer cladding structure, potentially enabling many nonlinear applications.
Different-source image matching is still a difficult problem in computer vision. In this paper, we propose a novel
algorithm based on edge information, shape context descriptor and graph matching to make a good performance in the
different-source image matching field, especially optical and infrared image. First, as the edge information is a relatively
stable in these two kinds of images, we detect the feature point based on the edge information which can reflect the
construction information. Then shape context descriptor, which is rotation invariant, scale invariant and translation
invariant, is adapted to describe the feature point. Finally, the graph matching algorithm is used for the image matching
to eliminate the false matching point. From experimental results, our algorithm is efficient in different-source image
Multisensor images registration is the necessary premise for multisensor image fusion in military field. The
goal of image registration is to establish the geometrical correspondence among images which are acquired by
different sensors or by the same sensor but in different modalities. In this paper, a research on multisensor image
registration is done and two methods are presented. One method is based on edge matching, the other is based on
point matching. Experimental results with various kinds of image have verified the robustness of the two methods. It
is showed that point-based method works well for image pairs with large scale and rotation transformation while the
gray level characteristics is well preserved, such as same sensor images but different times. Edge-based method
works well for image pairs with small scale and rotation transformation while edge characteristics can be well
preserved, such as multisensor or multispectral images. Both methods are automatic and computationally quite
efficient. Root mean square error at the control points are given and outperformed by manual registration.
Building recognition is an important field in computer vision. Building target line features which represent the
target geometry information are stable features in infrared images. In this paper, the stable building line features are
acquired by morphology filter algorithm and the number of the correctly obtained line features and the distance
similarities of these features are used to measure the probability of the target emerge in the infrared image. From the
recognition results, we can see that our algorithm can efficiently recognize this kind of targets.
In this paper, combined with Canny's criteria, we proposed an improved Rothwell edge detection method which
aims to recover more reliable topological relations from the extracted edges. Distance transform is used to optimize
location of the edge and B-Spline interpolation is applied for the detection of zero-crossing in the sub-pixel interpolation
step, and edge refinement is used to adjust topology. Experiments results show our improved Rothwell edge detection
algorithm  could retain more accurate geometry features while generate more stable topology than the original one.
The all optical window equivalent-time sampling method using SMIOS and a numerical algorithm used for waveform
recovery are present. A system model based on SOA dynamic model was founded to analyze sampling process. The pulse
broadening in low bandwidth PIN and its response are discussed too. The relationships between sampling windows and
sensitivity due to SOA bias current, aptitude of control pulse and input measured signal wavelength are analyzed
theoretically. The results have shown that the SMIOS sampler system combined with numerical algorithm can measure
short pulses with low error.
The transmission performance of SCI avionic fiber-optic data bus is analyzed in this paper. An analysis on the
relationship between the transmission range and the data rate under certain attenuation and dispersion is presented. A
simulation of the receiver with the M-sequence data and trapezoid pulses as input data stream is discussed in detail, the
relationship between the sensitivity of the receiver and its bandwidth is simulated. The transmission delay due to the
bandwidth of receiver is calculated too. Some operational suggestions on how to apply SCI fiber-optic data bus to the
avionic field are given.
The all optical pulses replicating technique to measure single-shot or low repetition optical pulses and pulses with poor stability based on optical pulse active replicator (OPAR) is present. The OPAR can provide an identical pulse sequence for equivalent-time sampling method. The analysis show replication error of OPAR caused by nonlinear gain and amplified spontaneous emission (ASE) of semiconductor optical amplifier (SOA) could be reduced by pumping light injecting. Bias current of SOA should choose an intermediate value to confine nonlinear gain and ASE simultaneously. This result is validated by experiment. The stability of OPAR and baseline shift in output pulses sequence are discussed too. The results show that OPAR is suitable to generate low-distortion pulses sequence for equivalent-time sampling with high replicating stability.
Many vision tasks can be posed as Bayesian inference, and the entropy of the posterior probability is a measure for
uncertainty of perception, imperceptibility. In this paper, we studied the imperceptibility of multiple object tracking,
intrackability. Entropy theory and Bayesian framework are used to represent multiple objects intrackability.
Intrackability is computed by different kinds of tracking features. Feature selection is crucial for intrackability
computation. An example of umbrellas tracking is shown in this paper. The intrackability which is computed by
appearance and shape feature is compared. At last, we use intrackability to guide one application--Automatic grouping.
Objects are dynamically merged and tracked as a group when they come close to each other. Automatic grouping
reduces the representation when some details can't be perceived. After the intrackable part of the representation is
discarded, the computation is reduced.
We propose a novel method to compensate the nonlinear distortion from an optical pulse replicator based on an active optical fiber loop. It could be used to faithfully recover the input optical pulse shape from the sampled results of the replicated pulse train, despite of the distortion in the loop. Thus, the replicator could be applied to the measurement of optical pulses for optical fiber communication applications. Our proposed post-processing technique is based on modelling the nonlinear amplification behaviour of the optical amplifier in the loop. The methodology of our technique is described in detail, as well as the simulated recovered results using the proposed algorithm.
Based on the analyses of the key limiting factors for duobinary signals in dispersion limited fiber systems, we propose a novel optical receiver design that can further overcome the deterministic timing 'jitter' resulted from the dispersion-induced inter-symbol interference. Our idea is based on over-sampling of the received waveform and a novel decoding scheme. Our technique would provide better estimations of the received bits based on a decision feedback and feedforward scheme that takes advantage of the knowledge of adjacent bits. We study, through extensive simulations, the effectiveness of our novel receiver design in increasing the dispersion tolerance, and our promising results show that our innovative solution can provide significantly improvement over even the best reported schemes thus far.
Proc. SPIE. 5628, Semiconductor Lasers and Applications II
KEYWORDS: Signal to noise ratio, Optical fibers, Optical amplifiers, Semiconductor optical amplifiers, Signal attenuation, Interference (communication), Receivers, Distortion, Analog electronics, Active optics
We have proposed a simple and convenient gain control scheme of the semiconductor optical amplifier (SOA) utilizing the amplified spontaneous emission (ASE) from the SOA itself. Based upon this scheme, an optical pulse active replicator using a SOA could be used for high-fidelity replication of short analog optical pulses. Taking into account the ASE noise, a numerical model of the SOA is developed to investigate the optical pulse recirculating propagation in the active replicator. Results indicate that the replicator is feasible and effective. Selecting appropriately operating parameters, such as the loss within the loop, the power of signal pulse and the front-end receiver electrical bandwidth, the replicator can generate a sequence of precise periodic optical pulse trains with low distortion and good SNR.