Multiwavelength fiber laser in four mode fiber

Multiwavelength fiber laser is a nonlinear phenomenon that has a great potential for optical communication system. A stable triple-wavelength fiber laser in four mode fiber had been demonstrated experimentally by employing Sagnac filter in a simple close loop laser cavity. The Sagnac loop filter configuration was constructed using a 2 m of polarization maintaining fiber (PMF), a 3 dB coupler and a polarization controller. The laser is able to sustain triple-wavelength laser generation at 13.1 dBm output power of Erbium-Doped Fiber Amplifier (EDFA) as all laser wavelengths produced less than 0.25 nm fluctuation for over 20 min of unstoppable lasing operation. This laser configuration also has flexibility to perform single, dual and triple wavelength laser by controlling the EDFA output power

Effects of tides on the hydrology and geometry of a freshwater channel

The situation of Sungai Sengkuang becomes worse because it is under tidal influence. Flood was reduced after removing the temporary culvert. Analysis is carried out for the existing system to investigate whether it is still able to accommodate the volume of water comprises the discharge from upstream and high tide from downstream. The computer program such as HEC-HMS 2.2.2 will be used to carry out the Hydrologic Model Calibration. By using HEC-RAS, Hydraulic Model Calibration will be carried out for the channel. The discharge with different ARI will be used as the upstream boundary condition during the flow analysis. Frequency analysis for the tide level which is collected from JUPEM. The tide level with different ARI is used as the downstream boundary condition. From the Energy Grade Line of the channel, which energy is dominant, the energy from downstream or the energy from upstream.Keywords: tidal influence; dominant energy; flow analysis; hydraulic and hydrology model analysi

The comparison of dual wavelength fiber laser spectrum in SMF and HNLF by utilizing laser diode

A dual-wavelength erbium-doped fiber (EDF) fiber ring laser in single mode fiber and highly nonlinear fiber is demonstrated and both optical spectrums are compared at 400 mA of Laser Diode (LD) output. The fiber ring laser cavity incorporated sagnac loop had been applied for the laser to lase two wavelengths simultaneously due to high birefringent in polarizaton-maintaining fiber (PMF). Experimental results show that, owing to the contributions of two degenerate fourwave mixings (FWM) in the HNLF and the dual-wavelength proposed fiber laser is quite stable with small fluctuation power in 1.93 dB within 24 minutes in HNLF

The Influence of Nonlinearity Properties in Generating Octave-spanning Light

An efficient system for nonlinear parameter characterization in Highly Nonlinear Fiber (HNLF) is described using four wave mixing (FWM) technique, the FWM plays an important role in enhancing the spectrum development in most cases. The Nonlinear parameters like zero-dispersion wavelength (ZDW), chromatic dispersion (CD) and the non-linear coefficient of HNLF were successfully investigated using this technique. The results of this technique have been almost identical to factory specifications. By FWM technique, a CD at 1550 nm slope is obtained from 0.007 ps.nm-2km-1, ZDW of 1531 nm and nonlinear parameters of 10.7 W-1km-1

Short term durability of steel-strap confined concrete

Steel strapping tensioning technique (SSTT) confinement has been proven as a type of external confinement to retrofit and upgrade concrete structures. Their remarkable enhancement to concrete mechanical properties, practicing active lateral confinement, low cost, easy to operate, time saving and no structure interruption during application have brought this technique as of the most affordable technique for column confinement, especially for high strength concrete (HSC) which naturally behaves insufficient in ductility. Although a great number of previous studies have demonstrated the performance of SSTT confinement, there are several anxieties related to the long term behaviour of SSTT confined columns which have yet been implemented especially in real hostile condition. Environmental effects, such as ultraviolet radiation exposure and saline solution (sea water) may affect the confining material properties, and therefore decrease the performance of the confined columns. In this study a total of twenty HSC specimens with dimension of 100 mm and 200 mm in diameter and height respectively were prepared, volumetric-identically pre-tensioned with steel strap and exposed to three conditions: indoor, outdoor and saline water for three months. The exposed specimens were monotonically tested and their performance was studied through the stress-strain relationship, mode of failure and degree of corrosion. The results show that none of the forenamed environmental conditions have exaggerating influence on the performance of the SSTT confined concrete specimens even some material has been severely corroded. It is then parallel compared with existing FRP confinement studies and the result proves that SSTT confinement able to possess the highest strength performance under similar environmental exposure

Characterization of a-CNx Thin Films prepared by RF-PECVD Technique for humidity sensor

In this work, amorphous carbon nitride (a-CNx) thin films were deposited by radio frequency (RF) plasma enhanced chemical vapor deposition (RF-PECVD) technique. The RF power and gas mixture of methane (CH4) and nitrogen (N2) flow was kept constant, while the electrode distance was varied from 1 to 6 cm. The effect of electrode distance on the chemical bonding, morphology and humidity sensing responses of the films were investigated. Fourier transform infra-red spectroscopy (FTIR) studies showed a systematic change in the spectra and showed three main peaks namely the G and D-peak, C≡N triple bonds and C-H/O-H groups. Uniform and porous morphology was observed for films deposited at smallest distance followed by non-porous cubicle-like grain as electrode distance increased. Subsequently formation of vertically aligned nanostructures apparent both from its surface and cross section images by increasing of electrode distance to the fullest. The humidity sensing property has been studied by recording their resistance response to relative humidity (RH) at room temperature. It was found that the resistance value decreases from 15.4 to 3.6 kΩ with the increase in RH from 9 to 85%, with the highest sensitivity of 77% for film deposited at smallest distance of 1 cm

Passively mode-locked laser using an entirely centred erbium-doped fiber

This paper describes the setup and experimental results for an entirely centred erbium-doped fiber laser with passively mode-locked output. The gain medium of the ring laser cavity configuration comprises a 3 m length of two-core optical fiber, wherein an undoped outer core region of 9.38 μm diameter surrounds a 4.00 μm diameter central core region doped with erbium ions at 400 ppm concentration. The generated stable soliton mode-locking output has a central wavelength of 1533 nm and pulses that yield an average output power of 0.33 mW with a pulse energy of 31.8 pJ. The pulse duration is 0.7 ps and the measured output repetition rate of 10.37 MHz corresponds to a 96.4 ns pulse spacing in the pulse train

Influence of crystal structural orientation on impedance and piezoelectric properties of KNN ceramic prepared using sol-gel method

The aim of this study was to investigate the effect of structural orientation on the impedance and piezoelectric properties of Ka0.5Na0.5NbO3 (KNN) ceramic synthesized using modified sol-gel method. Dried xerogel was heated at 800oC for 90 min and the aggregates were grinded to powder form. SEM micrographs confirmed that the powder consist of bimodal particles in nm and μm size regimes. The powder was compacted into 13 mm diameter pellet and sintered at 1000oC for 6 h. Then the pellets were poled at 4.0kV/mm at 100oC for 30 min. The as-sintered pellets displayed different sizes of cuboidal granules forming a relatively dense sample. The XRD and Raman spectroscopy results confirmed the formation of perovskite KNN with monoclinic crystal structure. The compositional analysis using Vegard’s law showed that the K:Na ratio was 0.5:0.5. Dramatic intensity enhancement in (110) reflection and subsequent reduction in (100) reflection as observed in X-ray diffractograms for the poled pellet suggest permanent shift in crystal orientation. Consequently, the Nyquist impedance plot of a Debye type semicircular arc was altered to a combination of a depressed semicircular arc. Unlike the initial plot, the real impedance, Z′ exhibited frequency dependence at low frequency regime. In addition, the relaxation time, τ of KNN sample shifted to lower frequency after the structural re-orientation while piezoelectric constant, d33 along (110) direction significantly improved from 5 to 35 pC/N

Degeneration of four wave mixing in 500 m step index two mode fiber

Four wave mixing (FWM) in two-mode fiber was experimentally demonstrated at 24.7 dBm of output Erbium doped fiber amplifier (EDFA). The 0.5 km two mode fiber in laser cavity enhances the performance of four wave mixing by suppressing the homogenous broadening effect in erbium-doped fiber and perform a stable oscillation. At output EDFA approaches to 24.7 dBm, FWM is generated and the increasing of output EDFA induced the optical signal to noise ratio (OSNR) of all laser peaks