Experimental verifications of the feasibility of using chirped fiber grating (CFG) as the dispersion compensation device in a bi-directional hybrid dense-wavelength-division-multiplexing (DWDM) system to reduce the dispersion and cross-phase modulation (XPM) induced crosstalk were proposed and demonstrated. Not only channel capacity was increased, but also good performances of carrier-to-noise ratio (CNR) ≥ 50 dB, composite second order (CSO) ≥ 72 dB, composite triple beat (CTB) ≥ 69 dB and low bit error rate (BER) < 10^(-9) were achieved in our proposed system over a 50-km single-mode fiber (SMF) transport.

The dimensions of input waveguide and output waveguide of arrayed waveguide gratings (AWGs) determine the crosstalk, insertion loss and 1-dB bandwidth. In cascaded optical add/drop multiplexers (OADMs), the value of these parameters will largely affect the power penalty of system. The power penalty of cascaded OADMs is calculated with different waveguide dimensions of AWGs in this paper. Considering of wavelength misalignment, an optimization design of AWGs is obtained.

A novel method for writing long fiber Bragg grating (FBG) with arbitrary multi-wavelength and chirp at the same place of a fiber by using a phase mask is presented. An experimental equation is derived for Bragg wavelength, and the Bragg wavelength is found to be a function of the distance between the fiber and the phase mask. The chirp of the overlapped FBG is decided by the angle between phase mask and fiber. A multi-wavelength FBG with 4, 8, 16 channels has been written by using a unique phase mask.

The effect of distributed Raman amplification (DRA) on the optical signal to noise ratio (OSNR) of an all optical network (AON) is examined by analyzing two types of node isolated principal (NIP). Based on the parameters used in calculation, it is found that in the first case of NIP, the OSNR of a signal passing through such AON can be improved by about 8 dB compared with no DRA. Whereas in the second case of NIP, the OSNR of the signal can be reduced by 11 dB. This kind of phenomena is analyzed and attributed to the dependence of noise figure of amplification system on the way of the active amplification utilization.

The short Hermite-Gaussian optical pulse transmission over 1440 km in a dense dispersion compensated system is investigated based on numerical simulation. In the simulation, compensation is made not only for the group-velocity dispersion but also for the third order dispersion. It is demonstrated that the pulse with reasonably lower power can propagate steadily in net zero, positive and negative dispersion system.

Three group velocity dispersion (GVD) compensation schemes, i.e., the post-compensation, precompensation and hybrid-compensation schemes, are discussed with considering polarization mode dispersion (PMD). In the 10- and 40-Gbit/s non-return-zero (NRZ) on-off-key (OOK) systems, three physical factors, Kerr effect, GVD and PMD are considered. The numerical results show that, when the impact of PMD is taken into account, the GVD pre-compensation scheme performs best with more than 1 dB better of average eye-opening penalty (EOP) when input power is up to 10 dBm in the 10-Gbit/s system. However the GVD post-compensation scheme performs best for the case of 40 Gbit/s with input power less than 13 dBm, and GVD pre-compensation will be better if the input power increased beyond this range. The results are different from those already reported under the assumption that the impact of PMD is neglected. Therefore, the research in this paper provide a different insight into the system optimization when PMD, Kerr effect and GVD are considered.

In this paper, we present simulation results of an electrooptical variable optical attenuator (VOA) integrated in silicon-on-insulator waveguide. The device is functionally based on free carriers absorption to achieve attenuation. Beam propagation method (BPM) and two-dimensional semiconductor device simulation tool PISCES-II were used to analyze the dc and transient characteristics of the device. The device has a response time (including rise time and fall time) less than 200 ns, much faster than the thermooptic and micro-electromechanical systems (MEMSs) based VOAs.

In this paper, the GaN based epitaxial wafer is fabricated on big 1 mm ×1 mm chips, and packaged with a special technology. At working current 350 mA and working voltage 3.74 V, the full viewing angle, the axial brightness and the output integral power of the 465 nm LED can reach 125°, 210, 000 cd/m2 and 1.5 lm, respectively. The LED with such good performances has promising application potential in the fields of display, traffic and the development of solid-state white light source.

An all-fiber Yb^(3+)-doped double-clad fiber laser using FBGs as cavity mirrors is investigated in this paper. Continuous-wave (CW) output power of 1.18 W with defined wavelength at 1.06 μm and narrow line-width of less than 0.1 nm is obtained. The slope efficiency and the maximum optical-to-optical efficiency of laser output are 68% and 51%, respectively, with respect to absorbed pump power.

We report a simple approach to amplify Ti:sapphire femtosecond pulses to moderate energy levels by a chirped regenerative amplifier. The seed pulses are broaden naturally because of the material dispersion of system components in regenerative cavity. The off-focusing Ti:sapphire crystal avoids effectively the optical damage. It sustains amplification over a wavelength range from 775 nm to more than 810 nm with a birefringent filter and an oscillation bandwidth of 7.7 nm, and produces 2.1 ps chirped output pulse energy of 100 μJ at 1.1-mJ pumping energy. This system shows good performances in stability and efficiency with the benefits of two thin-film polarizers and TEM00 mode pumping laser.

A new set of nonlinear rate equations that can describe the external cavity semiconductor laser with two optical feedbacks is proposed. The dynamics of the semiconductor laser with two optical feedbacks are studied. It is found that when lasers are biased above the threshold and operate in regime V, another feedback can induce low frequency fluctuations.

The Richardson plots method is employed to measure the fractal dimensions D of the surface of magnetic dielectric film fractured by excimer laser irradiation near the ablation threshold. It is shown that the fractured surfaces are fractal character. The value of D decreases while the laser pulse number increases. This relation may reflect how the fractured surface changes from irregular structure to regular structure with laser pulse number.

Digital image difference method monitorring coating status of microsphere targets automatically is suggested. A CCD micro-imaging system is developed for monitoring the status of bouncing and adherence between microspheres and the bouncing pan. A new bouncing pan with multiple holes is adopted for microsphere coating to enhance the microsphere coating efficiency.

Investigation results on linear and non-linear optical properties, damage threshold and potential efficiencies of biaxial negative LiInS_(2) crystal are represented. It shows that the crystal has phase-matching and groupvelocity matching in wide spectral range for second harmonic, sum- and difference-frequency generation of visible, near and middle IR lasers. The possibilities of designing middle IR optical parametric oscillator (OPO) pumped by Nd:YAG and dye lasers and specially possibility of frequency conversion with 3 μm range femtosecond erbium lasers are given.

A simple all-optical switch based on photoinduced birefringence effect is demonstrated in azo dye (DR1) doped polymer (PMMA) thin films. The all-optical switching effect has been studied at different control beam power and different temperatures of the sample. With a control power of 30.7 mW and at 56 ℃, the response time of the switching is less than 5 ms, and the depth of the modulation reaches 80%.

Most alternating current (ac) polymer EL (electroluminescent) devices to date are based on symmetrical structure. Here novel alternating current EL devices with asymmetric structure are successfully fabricated by using a hole type polymer PDDOPV [poly (2,5-bis (dodecyloxy)-phenylenevinylene)] and an electron type polymer PPQ [poly (phenyl quinoxaline)]. We report that performance of polymer devices with heterojunction in ac operation is not so sensitive to thickness of the two polymer layers as in direct current (dc) operation. This new advantage of ac operation mode over dc means easy production and cheap facilities in large-scale production in the near future. Different emission spectra are obtained when our ac devices operate in ac mode, forward and reverse bias. Emission spectrum at reverse bias includes two parts: one is from PDDOPV, the other is from PPQ.

Penning type discharge was adopted to excite helium atoms. It is suitable for generating high density of metastables at a range from 0.1 mTorr to 0.5 Torr. The highest metastable density of 3.5 * 10^(10) cm^(-3) was observed at a static gas pressure of 0.5 Torr. The highest fraction of metastables (N_(2^(1)S) = N_(He)) of 10^(-3) in a low gas pressure was obtained. The variation of the magnetic field strength on the discharge does not result in a significant density change of the metastable helium atoms. When no magnetic field was applied, no discharge took place.

The resonance-enhanced multiphoton ionization (REMPI) spectrum of NO has been obtained in the range of 420 - 480 nm with a Nd:YAG pumped optical parametric generator and amplifier. The spectral lines can be attributed to NO X^(2)(v" = 0; 1) → A^(2)Σ(v' = 0; 1) transitions. In this wavelength range, NO molecules are ionized via the resonant intermediate state A^(2)Σ^(+) and by a (2 + 2) REMPI process. The dependence of ion signals on laser intensity and gas pressure is discussed. The variation of the ionization signal versus laser intensity is near quartic. This is in good agreement with theory.

In this paper, the structure of a top-face-sway electromagnetic micromotor and its principle, fabrication and performance are introduced. A combination of the electromagnetic actuating and the planetary reducing provides this micromotor an advantage of low rotational speed and high torque. In addition, since a flexible coupling absorbs the sway and only outputs rotation, it gives this micromotor a balanced output. The dimension of the micromotor is 5 mm. Its rotation speed has a range of 20 - 860 rpm, and its driving current is 300 mA. The output torque of the micromotor is measured to be 13.0 μNm.

A novel no-guide light pen type 3D-coordinate measurement system with three sets of position sensitive devices (PSDs) to realize intersection converge imaging is introduced. It is called as the light pen type measurement system, because the measuring head is shaped as a pen with several light sources on it. The structure design, measurement principle and experimental results are presented. The theoretical analysis and experimental results prove that this system has advanced features of simple structure, high automation, and high accuracy, and can be used in the measurement fields of mechanical manufacture, robot, auto, aviation and medicine effectively.

The limitations in electronics in arithmetic, algebraic & logic processing are well known. Very high speed performance (above GHz) are not expected at all in conventional electronic mechanism. To achieve high speed performance we may think on the introduction of optics instead of electronics for information processing and computing. Non-linear optical material is a successful candidate in this regard to play a major role in the optically controlled switching systems and therefore in all-optical parallel computation these materials can show a very good potential aspect. In this paper, we have proposed a new method of an optical half adder as well as full adder circuit for binary addition using non-linear and linear optical materials.