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A simulation of the properties of the shifting scintillator neutron detector using 6LiF/ZnS(Ag) scintillation screens is performed.The simulation results show that the light attenuation length of standard BC704 scintillator is about 0.65 mm.Its thermal neutron detection efficiency,gamma sensitivity ...

A cascaded buffer based on nonlinear polarization rotation in semiconductor optical amplifiers is proposed, which is suitable for fast reconfiguration of buffering time at picoseconds. With the proposed buffer, sixty different buffer times are demonstrated at 2.5 Gb/s.

A new charge measurement method, time over threshold (TOT), has been used in some gas detectors lately. Here TOT is studied for TOF system, made of plastic scintillator counter, which can simplify the electronics of the system. The signal characteristics are measured and analyzed with a high quality oscilloscope, including noise, pedestal, signal amplitude, total charge, rise time and the correlation between them. The TOT and charge are related and can be fitted by some empirical formula. The charge measurement resolution by TOT is given and this will help the design of TOF electronics.

In this paper, we investigate the dual-wavelength packet signal storage in the semiconductor optical amplifier (SOA)-based dual-loop optical buffer (DLOB). The loadable and unloadable function of the DLOB is implemented by the cross phase modulation induced by the SOA. After a temporal model is proposed for the dual-wavelength packet signal interaction, the influence of nonlinear phase shift on the chirp and distortion of the stored packet pulse is examined for the case of the dual wavelength loadable operation. It is found that, when the overlapping area of the stored dual-wavelength pulse is less than half of the pulsewidth, the distortion of output pulses after storage is negligibly small. However the most severe distortion appears when the dual-wavelength pulses overlap completely. The peak power of output packet pulse is approximately reduced by 30%. The observed experimental results agree well with the theoretical calculation. In a conclusion, these works confirm the validity of the proposed model t...

The radiation damage characteristics of three types of plastic scintillators, BC-408, EJ-200 and BC-404, are experimentally studied. The results show that after irradiation, the light yield and light transmission of these scintillators decrease and the shapes of the excitation and emission spectra remain unchanged. Recovery of light yield is not observed after weak irradiation.

We present two numerical approaches to calculate the geometrical birefringence from two-dimensional refractive-index profile in single-mode fibres. One is the improved perturbation model theory, the other is based on the general solution of noncircular uniform optical waveguide in an arbitrary coordinate system. Using these methods, we can obtain not only the magnitude of geometrical birefringence, but also the orientation of birefringent axes. We report the calculation results of geometrical birefringence in a real single-mode fibre.

We propose a new polarization sensitive optical time domain reflectometry (P-OTDR) setup assisted with a piezoelectric polarization controller (PPC). The input state of polarization can be changed by varying the voltage of PPC without any rotatable instrument, and only one optical receiver is used to detect the backward beam. We measure a single mode fibre and get the distribution of birefringence along the SMF.

It is essential to extend the optical buffer depth to meet the burst-mode packet requirement. In this paper, we propose to incorporate the Mach-Zehnder interferometer (MZI) into our successful SOA-based dual loop optical buffer (DLOB) configuration. The maximum packet length for the DLOB storage is evaluated theoretically, and the fiber loop utilization can be greatly enhanced with our modified configuration. Then we have successfully demonstrated the 2.5 Gbps variable-length packet loadable function with the MZI-DLOB configuration. The waveform of variable-length packet is little degraded after optical storage. Meanwhile an effective polarization stable method is also experimentally implemented to reduce the instability of MZI-DLOB. All the obtained results confirm the feasibility of our configuration to apply in variable-length optical packet switching.

A laser ultrasound stably detecting has been demonstrated by a new type fiber optic Michelson interferometer with 3times3 direction coupler. The experimental result suggests that it's able to sense an ultrasound vibration frequency from 10 KHz to 1.5 MHz.

The slow light technology of the rectangle signal propagating in erbium-doped fiber (EDF) has potential applications in the fields of all optical communication and optical fiber sensing. The method of using harmonics fractional delay to evaluate the slow/fast light of rectangle signal propagating in the EDF is proposed, and the characteristics of phase delay for fundamental and high order harmonics components are analyzed for the first time based on the rate equations and the theory of the coherent population oscillations (CPO). We experimentally demonstrate the dependences of fundamental fractional delay on input power and optical gain. The maximum fractional delay 20% is obtained when the input power is about 8 mW without pump. The negative fractional delay-20% is also achieved and it will increase with the rising of the optical gain. The Nth-order fractional delays (N=1, 3, 5, 7) of rectangle signal propagating in EDF without pump are investigated. Their maximum fractional delays are all about 0.07 and the corresponding fundamental modulation frequencies are 22, 7, 5 and 3 Hz, respectively. What is more, the Nth-order fractional delays (N=1, 3, 5, 7) with pump are also investigated. Their maximum fractional delays are all about-0.135 and the corresponding fundamental modulation frequencies are 175, 58, 35 and 25 Hz, respectively. The experiments indicate that the maximum Nth-order fractional delays are equal and they will be achieved at the frequency f/N (the fundamental harmonic fractional delay is maximum at the modulation frequency f). The results show good agreement with CPO and the frequency is also located in the spectral burning hole.

Analyzes the switching characteristics of a single mode optical fiber. In the dispersion fiber not only is the switching signal delayed, but also the switching speed is limited. The formula for calculating the switching time (rise time or fall time) is given. The results show that the switching time is proportional to the square root of the absolute value of the fiber dispersion, and is proportional to the square root of the fiber length, too. In a 1 km G.652 optical fiber operating at 1.55 /spl mu/m, the switching time is about 7 ps. This time is the final limit for the switching speed of a switching element with two optical levers constructed by this kind of fiber.

The method of complete polar decomposition for arbitrary Mueller matrixes is introduced to analyze the birefringence vector induced in a fiber, and then based on the Mueller matrix (MM) method, three kinds of computation methods including the absolute, the relative, and the differential rotation methods are proposed and investigated in detail. A computer-controlled measure system is employed to measure the Mueller matrix and birefringence vector for a 2.5-km fiber system with length 5 mm under lateral press in complicated environment with much perturbation. Experimental results show that the differential rotation (DR) method is the optimal approach to achieve fiber birefringence vectors in a large dynamic range of lateral press on fibers in perturbed situations, which reaches the highest linearity of 0.9998 and average deviation below 2.5%. Further analyses demonstrate that the DR method is also available for accurate orientation of lateral press direction and the average deviation is about 1.1°.

This paper analyzes the signals impairment in the semiconductor optical amplifier (SOA) based optical buffer for optical packets switching networks, including the shape distortion of single pulse and the pattern dependent distortion of the continuous bit stream due to the SOAs nonlinearity and the limitation of its carrier lifetime, the deterioration of signal-to-noise ratio caused by the accumulation of amplified spontaneous emmision noise of the SOA, and the power leakage. The theoretical analysis and experimental results indicate that the buffered circle is restricted to 20—30, as determined by the signals impairment when a negative control optical pulse with high power is injected into SOA.

Linewidth enhancement factors (LEFs) of the transverse electric mode and the transverse magnetic mode in bulk semiconductor optical amplifiers are measured using the nonlinear optical loop mirror method and the principal state of polarization vector method. The polarization dependence of LEFs plays an important role in the nonlinear polarization rotation. The relationship between the polarization-dependence of LEFs and nonlinear polarization rotation in the Stokes space is demonstrated.

An all-optical encryption-decryption method using an exclusive-or gate based on the cross-phase modulation between O-band and C-band light waves is proposed. The feasibility of the encryption-decryption technique is verified by handling binary signals at 2.5 Gbps, with less than 3 dB penalty of extinction ratio and 1 dB polarization dependent loss.

This paper describes the effect of spinning single-mode fibres on the second-order polarization mode dispersion(PMD). We find theoretically that spinning fibr es can reduce the first-order PMD, but it may be harmful to the second-order PMD , which is an important problem to the fibre communication system over 10 Gb/s.

This paper presents the general solution of noncircular uniform waveguides in an arbitrary coordinate system. It can be expressed as exp{i(+ΔβV)z}E0(x,y),where V is a matrix depending uniquely on the angle θ between polarization principal axis (PPA) and coordinate axis. As a kind of application, we give the method to find , Δβ and V(θ) in the weak-guided fiber, whose distortion is smaller.It is easier to use it for analyzing the effect of birefringence decreasing due to the lognitudinal asymmetry in a fiber, compared with Jones matrix.

Polarization mode dispersion (PMD) is the ultimate limitation to high bit-rate fibre communication system. The stability of PMD is very important to its measurement and compensation. This paper puts forward a method to measure the stability of PMD by measuring the stability of the state of polarization (SOP) and introduces the conception of time evolution vector (TEV) of SOP. We observe the fact that the regularity of the principal state of polarization changing with time is the same as other SOPs', if we neglect the dependence of TEV on wavelength. We also measure the SOP's stability of some fibres with different lengths and obtain results of PMD changing with time.