In recent years,tunable optical delay line has attracted much research interest for its applications in optical
communications,optical signal processing and optical control of phased array antennas in microwave communications.
Compared with optical delay line based on slow light techniques, all-optical wavelength conversion followed by signal
propagation in a dispersive medium presents an alternative approach to control the delay time because it is simpler and
more controllable. In this paper, a tunable optical delay line with a large time delay up to 650ps based on four-wave
mixing (FWM) wavelength conversion in 420m high nonlinearity fiber (HNLF) and dispersion in 8km standard single
mode fiber (SMF) is experimentally demonstrated.Our experimental results are in good agreements with the principle.
Passively mode-locked fiber laser (MLFL) has been widely used in many applications, such as optical communication system, industrial production, information processing, laser weapons and medical equipment. And many efforts have been done for obtaining lasers with small size, simple structure and shorter pulses. In recent years, nonlinear polarization rotation (NPR) in semiconductor optical amplifier (SOA) has been studied and applied as a mode-locking mechanism. This kind of passively MLFL has faster operating speed and makes it easier to realize all-optical integration. In this paper, we had a thorough analysis of NPR effect in SOA. And we explained the principle of mode-locking by SOA and set up a numerical model for this mode-locking process. Besides we conducted a Matlab simulation of the mode-locking mechanism. We also analyzed results under different working conditions and several features of this mode-locking process are presented. Our simulation shows that: Firstly, initial pulse with the peak power exceeding certain threshold may be amplified and compressed, and stable mode-locking may be established. After about 25 round-trips, stable mode-locked pulse can be obtained which has peak power of 850mW and pulse-width of 780fs.Secondly, when the initial pulse-width is greater, narrowing process of pulse is sharper and it needs more round-trips to be stable. Lastly, the bias currents of SOA affect obviously the shape of mode-locked pulse and the mode-locked pulse with high peak power and narrow width can be obtained through adjusting reasonably the bias currents of SOA.
We propose a novel image-fusion framework for compressive imaging (CI), which is a new technology for simultaneous sampling and compressing of images based on the principle of compressive sensing (CS). Unlike previous fusion work operated on conventional images, we directly perform fusion on the measurement vectors from multiple CI sensors according to the similarity classification. First, we define a metric to evaluate the data similarity of two given CI measurement vectors and present its potential advantage for classification. Second, the fusion rules for CI measurement vectors in different similarity types are investigated to generate a comprehensive measurement vector. Finally, the fused image is reconstructed from the combined measurements via an optimization algorithm. Simulation results demonstrate that the reconstructed images in our fusion framework are visually more appealing than the fused images using other fusion rules, and our fusion method for CI significantly saves computational complexity against the fusion-after-reconstruction scheme.