Localization Techniques for Water Pipeline Leakages: A Review

Pipeline leakages in water distribution network (WDN) is one of the prominent issues that has gain an interest among researchers in the past few years. Time and accuracy play an important role in leak localization as it has huge impact to the human population and economic point of view. The complexity of WDN has prompt numerous techniques and methods been introduced focusing on the accuracy and efficacy. In general, localization techniques can be divided into two broad categories; external and internal systems. This paper reviews some of the techniques that has been explored and proposed including the limitations of each techniques. Â

Investigation of Multiwavelength Performance Based on Different SOAs

We investigated multiwavelength fiber laser (MWFL) performance using different types of semiconductor optical amplifiers (SOAs) utilizing Lyot filter as comb filter. The lasing performances of linear SOA (LSOA), nonlinear SOA (NLSOA) and booster optical amplifier (BOA) at different current settings were observed. Among the three SOAs, LSOA has the best lasing performance due to the lowest peak power difference with the highest number of lasing lines, a high ER value of 42 dB and considerable high peak power of -14.1 dBm at 550 mA. The multiwavelength laser is stable within 60 minutes at power fluctuation of less than 0.2 dB. The output spectra at 550 mA for all the SOAs are 70 nm to 80 nm wavelength difference from the ASE spectra

Multiwavelength Random Fiber Laser based on Bidirectional SOA and Lyot filter

We investigated the performance of multiwavelength random fiber laser (MWRFL) using a bidirectional semiconductor optical amplifier (SOA) and Lyot filter inside a ring cavity. The bidirectional nature of linear SOA acts as the gain medium while the Lyot filter functions as the wavelength-selective device. The input SOA current, half-wave plate (HWP) angles of polarization controllers (PCs), and the stability of the laser were measured to determine the best optimized lasing line. The best MWRFL performance of 57 lasing lines within the 5 dB spectral range, 27.5 dB extinction ratio (ER), and 11.4 nm multiwavelength bandwidth are achieved through 550 mA of SOA current. The HWP angles of 90° and 120° for PC1 and PC2 respectively aid in the best polarization state of the output spectrum compared to other HWP angles measured at every interval of 30°. The laser had good stability with a maximum peak value deviation of 0.35 dBm at a wavelength range from 1541.0 nm to 1549.0 nm

Stable Triple-Wavelength Random Fiber Laser Based on Fiber Bragg Gratings

We demonstrate a generation of three lasing wavelengths with the assistance of Rayleigh backscattering as the stabilizer of peak power variations. The proposed laser consists of a combination of the semiconductor optical amplifier (SOA) and erbium-doped fiber amplifier (EDFA) as the amplifying media. Three fiber Bragg gratings are employed as the selective wavelength selectors at 1544, 1547 and 1550 nm. At 110 mA SOA current and 18 dBm EDFA output power, a flattened output spectrum with 0.9 dB peak power variation is attained. In terms of stability, the maximum peak power fluctuation for the individual laser is 0.24 dB within 120 minutes observation period. Without the Rayleigh backscattering effect, the peak power flatness is severely degraded. This shows that the weakly distributed photons can be utilized as peak power stabilizers in fiber laser systems

Stable Triple-Wavelength Random Fiber Laser Based on Fiber Bragg Gratings

Peer reviewed: TrueWe demonstrate a generation of three lasing wavelengths with the assistance of Rayleigh backscattering as the stabilizer of peak power variations. The proposed laser consists of a combination of the semiconductor optical amplifier (SOA) and erbium-doped fiber amplifier (EDFA) as the amplifying media. Three fiber Bragg gratings are employed as the selective wavelength selectors at 1544, 1547 and 1550 nm. At 110 mA SOA current and 18 dBm EDFA output power, a flattened output spectrum with 0.9 dB peak power variation is attained. In terms of stability, the maximum peak power fluctuation for the individual laser is 0.24 dB within 120 minutes observation period. Without the Rayleigh backscattering effect, the peak power flatness is severely degraded. This shows that the weakly distributed photons can be utilized as peak power stabilizers in fiber laser systems