An optimized 1.66μm Q-switched fiber laser is demonstrated for Raman-based distributed temperature sensor. In a ring
type Q-switched erbium-doped fiber laser, 850m TrueWave fiber is introduced to serve as both delay line fiber and
Raman gain medium so that in addition to the wavelength shifted to 1.6μm, the pulse duration and the buildup time can
be relatively extended. By properly controlling the fall edge of the acousto-optic switch, the pulse duration of 30-74ns
with peak power of 1.3-3.3W is achieved. Based on this light source, a 2.4km Raman-based distributed temperature
sensor is obtained with temperature resolution of 1°C and spatial resolution of 8m.
The influences of the Ge doped core to the properties of holey fibers are investigated in this paper. Numerical simulation shows that for holy fibers with conventional triangular transverse structure, proper-doped core can enhance the nonlinear coefficient and shift the near zero flattened dispersion region to long wavelength. By introducing a Ge doped core, a high nonlinearity holey fiber design for 1.55μm is proposed, with a nonlinear coefficient of 22 W-1km -1 and a wavelength region of 165nm in which the dispersion value is within ±1 ps/km/nm.
In this paper we introduce steganalysis and present three detection types. By the comparison of several watermark benchmark tools, which are Stirmark, Checkmark and Optimark, we discuss the validity of watermarking system, and propose a basic condition and outline to evaluate the validity of image watermarking system.
A novel storage system is introduced which bases on the "multilayer multilevel storage model." Three kinds of lasers that are different in wavelength are used to record data or test some storage material in this system. An example that is testing the photochromic material is also introduced to explain the usage of the system in testing storage material.
An experiment for focusing in chromatic multilayer optical storage system is presented in this paper. There laser diodes with different wavelength as respectively light sources are used in this experiment system so that focusing and servo approach are different from that in traditional optical system. Astigmatic approach is applied for defocusing detection while servo controlling and signal processing circuits are redesigned. The model of the actuator suited this chromatic multilayer optical system is established and analyzed. The static and dynamic parameters of actuator are measured. This paper specifies the design and implementation technologies of focusing and servo controlling in the chromatic multilayer experiment optical system. The preliminary result gotten from this experiment system is also given in the paper.
In this paper, a new kind of automatic method to test the Parameters of CD/DVD Optical Discs is introduced and named near-line inspector. Being connected to product lines, sampling and testing the discs automatically in batches, our inspector can provide a brief yet revealing profile of optical disc parameters such as electrical variables (HF, Jitter, etc.), physical variables and digital error variables in an acceptable short time so as to reflect the up-to-date condition of the product lines. As a real-time and relatively high-efficiency measurement method, it will be integrated into a perfect test system together with on-line and off-line inspectors. Such a system would be especially suitable for the replication of high-quality optical discs in large volume. The layout of the whole set of test system is described. The feasibility and reliability of near-line method are analyzed based on study by means of a high-precision DVD off-line test system developed by us.