Performance of Gallium-Erbium Fiber Amplifier in a Double-Pass Configuration

In a previous amplifier setup, a Gallium co-doped Erbium fiber (Ga-EDF) with a length of 2 m has been used as a gain medium. The amplifier which was designed as a single-pass configuration, achieving a highest gain of 22.45 dB. In this paper, the Ga-EDF amplifier is designed as a double-pass setup. The gain and noise figure at the input signal’s wavelength of 1520 nm - 1580 nm is investigated at various input powers, which are from -30 dBm to 0 dBm. This study compares the performance of the amplifiers as it is pumped by a laser signal at the wavelength of 980 nm and 1480 nm, with a power of 140 mW. The amplifier obtained the highest gain of 36.62 dB and 35.77 dB for the pump wavelength of 980 nm and 1480 nm, respectively. The corresponding noise figures are 3.48 dB and 5.01 dB, which occurs at the input signal’s wavelength of 1555 nm. The results indicate that the double-pass Ga-EDF amplifier pumped at 1480 nm outperforms the single pass Ga-EDF amplifier by 15.08 dB, with a comparable noise figure. The results also show that the double-pass Ga-EDF’s performance are comparable at both pump wavelengths

Review on Digital Signal Processing (DSP) Algorithm for Distributed Acoustic Sensing (DAS) for Ground Disturbance Detection

Fiber break because of third-party intrusion has become one of the challenges in maintaining the fiber-based communication link, especially those buried underground. Hence, we investigate the feasibility of using Distributed Acoustic Sensing (DAS) system to sense possible surrounding activities that might cause fiber break. This paper reviews the current digital signal processing (DSP) algorithm used in the DAS system designed to detect ground disturbance, highlighting the specific design parameters for each technique. These parameters include identification rate, classification accuracy, detection accuracy, training time, and signal-to-noise ratio (SNR). The algorithms used are near-field beamforming, phased-array beamforming, image edge detection, gaussian mixture model (GMM), gaussian mixture model - hidden Markov model (GMM-HMM), faster region-based convolutional neural networks (R-CNN), transfer learning, dual-stage recognition network, group convolutional neural network (100G-CNN), and support vector machine (SVM). By reviewing the existing techniques used in the DAS system for ground disturbance detection, we can determine the best DSP algorithm that should be implemented for fiber break prevention, enabling us to design a DAS system specifically for it in the near future

Development of fibre interferometer sensors based on double cladding fibre for multi-parameter sensing

The role of sensors in the future industrial environment is becoming more crucial and complex. One of the important sensor characteristics is the multi-parameter sensing capability. Fibre interferometer is a type of optical sensor that has been proven for its excellent sensing performance, high design flexibility and high capability for multi-parameter sensing. This research work assesses the potential use of double cladding fibre (DCF) as an interferometric multi-parameter sensor. In light of the importance of multi-parameter sensing capability required in future industry environment, three novel sensor designs were proposed and experimentally demonstrated. These proposed designs incorporated DCF as the main sensor structure to maintain high commonality, as well as to fully utilize the unique sensing properties of DCF. The first design proposed in this study is the fibre Michelson interferometer based on DCF, which is used for refractive index (RI) and temperature sensing. This sensor operates based on two sensing mechanisms to detect RI and temperature. RI sensing relies on Fresnel reflection at the tip of DCF, whereby RI change is quantified from power change in the sensor spectrum. Meanwhile, temperature sensing depends on the interference between the core mode and the first cladding modes of DCF. Thermo-optic effect causes a change of wavelength in the sensor spectrum. The experimental results retrieved from the proposed sensor revealed that temperature and RI spectra responses were indeed distinguishable. The second design proposed in this study is the Mach-Zehnder interferometer with dual sensing points used for RI and discrete liquid level sensing. These two sections are separated by an RI insensitive region formed by the DCF section. The sensor can be utilised to measure RI in single- or dual-point configuration. The third design proposed in this study is the DCF-based Mach-Zehnder used for small curvature (or displacement) and large curvature (or circumference) sensing. In this proposed design, two optical paths are paved in the core and in the inner cladding of the DCF. The outer cladding of DCF provides confinement of light in the inner cladding, hence enabling higher curvature to be imposed without any significant optical loss. This research work covers conceptual sensor designs, sensor fabrication and experimentation work. At conceptual level, mathematical models of particular sensor structures were studied and further developed in order to understand the sensor behaviour. The particular sensor structures were analysed numerically using BeamProp software to understand its function from the field distribution. Systematic fabrication procedures were developed for the sensor to ensure high process efficiency and repeatability. Additionally, this thesis contributes to the development of experimentation setup and data acquisition process. The proposed multi-parameter sensors have great potential to be deployed in various industrial applications

Development of fiber bragg grating (FBG) as temperature sensor inside packed-bed non-thermal plasma reactor

This paper presents early work on Fiber Bragg grating (FBG) as temperature sensor to monitor temperature variation inside a packed-bed non-thermal plasma reactor. FBG made from germania-doped fiber with center Bragg wavelength of 1552.5 nm was embedded inside non-thermal plasma reactor with sphere shape dielectric bead (barium titanate) and used to probe the temperature variation inside the reactor. The experimental works have proven that FBG is a suitable sensor to monitor temperature variation inside of reactor via LabVIEW program. Besides that, Optical Spectrum Analyzer (OSA) recorded Bragg wavelength shift as voltage of power supply increases, which indicate the non-uniform temperature variation occurring inside the reactor. However, it does not affect the chemical reaction inside the reactor because the temperature condition is in steady stat

Surface plasmon resonance in gold-silver bilayer coated D-shaped multimode optical fiber: An approach to refractive index sensing

This paper presents the surface plasmon resonance (SPR) characteristics of D-shaped silica multimode optical fiber coated with bilayer silver-gold film. The effect of various coating thicknesses on the SPR characteristics was investigated through simulation using COMSOL Multiphysics. The inner layer Ag thickness varied from 20 nm to 60 nm, and the outer layer Au thickness ranged from 5 nm to 25 nm. Prior simulation results indicated that a single-layer silver (Ag) coating produces a narrower plasmonic curve than a single-layer gold (Au) coating. The confinement loss and the resonance wavelengths were simulated for the sensing medium with a refractive index (RI) range of 1.40–1.45. The simulation results show that the Ag/Au bilayers coated sensors have better full-width-half-maximum (FWHM) and figure-of-merit (FOM) than the single-layer coated sensors. The Ag/Au with a 40 nm/5 nm thickness exhibits the highest confinement loss, with a wavelength sensitivity of 10 000 nm/RIU and a figure-of-merit (FOM) of 500 RIU−1. The proposed sensor using a D-shaped optical fiber coated with Ag/Au layers has a high potential for remote sensing applications involving chemical liquids, offering robust and accurate measurements within the tested refractive index range

Non-Uniformity of Non-Thermal Plasma Formation: Using FBG as Temperature Sensors

This research investigates fiber Bragg grating (FBG) temperature sensing performance in monitoring non—uniformity of non-thermal plasma (NTP) formation in a packed-bed reactor using FBG operating at atmospheric pressure. Two FBGs made from germanium doped fiber were embedded inside and outside the PBNTP reactor to allow for comparison between the temperatures inside and outside of the reactor to be made. Each FBG comes with three grating series, which allow the reactor temperatures at three different locations inside or outside the reactor to be measured and compared. Two types of plasma, namely nitrogen (N2) and argon (Ar) were generated in the reactor at a gas flow rate in the range of 2 - 7 L/min and applied voltage in the range of l - 20 kV. It was found that the PBNTP reactor temperature varies up to 20 oC at different positions inside and up to 40 oC outside of the reactor. This finding shows the non-uniformity of plasma formation and the nature of the plasma's localized thermodynamic equilibrium (LTE). The sensitivity of the FBG temperature sensor used in this study is estimated at 10.36 - 10.50 pm/oC

Application of packaging technique in fiber bragg grating temperature sensor for measuring localized and nonuniform temperature distribution

The development of Fiber Bragg Grating (FBG) sensing technique has improved significantly especially in the sensor head design and real-time data acquisition technique. This paper presents the development of a simple and cost effective packaging technique that further enhances the performances of the FBG sensor. The packaged FBG sensor overcomes the nonuniform heat distribution of a bare FBG that causes eccentric response of FBG spectrum. Therefore, the packaged FBG sensor could be operated for a localized area with high temperature differential. The packaging also compensates the unwanted strain effect from the surrounding which makes temperature measurement become more accurate. The experimental works have been successfully carried out to demonstrate the system operation and the packaging functionalities. The temperature sensitivity coefficient of the bare FBG sensor measured in experiment is 10.05 pm/°C, while the packaged fiber sensor is 10.09 pm/°C, which are expected from the desig

Dual sensing points Mach–Zehnder interferometer for refractive index and discrete liquid level sensing

An in-line all-fiber Mach–Zehnder interferometer (MZI) based on the combination of etched single mode fiber (ESMF) and double cladding fiber (DCF) is proposed for refractive index and discrete liquid level sensing. In the proposed structure, two sensing points are devised using two ESMF section of length. The two sections are separated by a refractive index insensitive region formed by DCF section. The sensor may be deployed to measure refractive index in single- or dual-point configuration. The experimental work revealed maximum refractive index (RI) sensitivity at - 37.2 nm/RIU for 1.305–1.335 RI range, with 1 mm compact sensor size. Additionally, the sensor performed as a two-point liquid level sensor with wavelength shift ranging between 0.84 nm and 1.44 nm. The proposed sensor displayed great potential to be deployed in liquid chemical storage to monitor liquid quality and level