Faidz Abd Rahman

Gain and noise figure improvements in a shorter wavelength region of EDFA using a macrobending approach

Gain and noise figure improvements are demonstrated in a shorter wavelength region of a double-pass EDFA using a macrobending approach. The EDF is wound in a small radius to suppress the amplified spontaneous emission at the longer wavelength in order to achieve a high amplification in the shorter wavelength. Gain enhancements of about 12–14 dB are obtained with macrobending at the wavelength region between 1480 and 1530 nm. The macrobending also reduces the noise figure of the EDFA at wavelengths shorter than 1525 nm with a maximum improvement of 25 dB.

Towards the Characteristic Dispersion Relation for Step-Index Hyperbolic Waveguide with Conducting Helical Winding

Astudy is presented of the light wave propagation in a new type of dielectric optical waveguide with hyperbolic kind of cross- section. Further, the waveguide is assumed to have a conducting helical winding. The analysis essentially requires the use of elliptical coordinate system, which finally results into Mathieu and modified Mathieu functions as the representatives of the electromagnetic fields within the lightguide. Field components in the different sections of the guide are deduced, and the characteristic dispersion equation for the system is derived. The preliminary investigation on such type of waveguide throws the idea that the presence of helix pitch angle (which serves the purpose of additional controlling parameter for the guide) in the dispersion relation would greatly affect the propagation characteristics of the guide, and this can be of great practical importance.

A scheme to improve the coupling efficiency and working distance between laser diode and single mode fiber

A new scheme is proposed for a hemispherical lensed fiber having a high coupling efficiency and a long working distance between the laser diode (LD) and the single mode fiber (SMF). An analytical approach based on the theory of Gaussian beam propagation is used to predict the coupling efficiency. The measured coupling efficiency for a LD operating at a wavelength of 1.31 mum is as high as 55%, with a working distance of 65 mum and these values are close to the predicted one

Arc-induced long period fiber gratings (LPFG) characterization: Comparison between cladding etched and non-etched LPFG

We investigated the effect of cladding etching on an arc induced long period fiber grating (LPFG). We compared the characteristics of the arc induced LPFG for changes in temperature, ambient refractive index and stress, i.e. between the etched and non-etched LPFG. The LPFG was etched using HF solution for 30 minutes and a red shift in wavelength was observed. We also found that the sensitivity of the LPFG increases after etching.

Review on an arc-induced long-period fiber grating and its sensor applications

This paper presents a systematic review on the long-period fiber grating (LPFG) formed by the electric arcing method. The basic concept of LPFG and the background of the electric arcing method are thoroughly discussed. The paper also discussed on the methods to improve the sensitivity of LPFG towards external perturbations. The LPFG has been reported to have potential usage as sensor, thus a section of the paper has focused on some application of arc-induced LPFG as sensors.

Theoretical analysis of coupling between laser diodes and conically lensed single-mode fibres utilising ABCD matrix method

In this paper, we present a simple technique to determine the coupling efficiency between a laser diode and a conically lensed fibre, based on the ABCD transformation matrix method. In the analysis we have also taken into account the effect of multiple reflection between the laser facet and lens surface. The calculated results were compared for conical microlens etched at different times to see the power variation difference. We have also compared our analysis technique to that of previous work and we have found that the present method is reliable in predicting the coupling efficiency of conical microlens.

Simultaneous Sensing System for Identical Long-Period Gratings Sensors Using Subcarrier Multiplexing

A novel system based on subcarrier multiplexing is presented for simultaneous sensing of identical long-period grating sensor array. The experimental results show that the system facilitates excellent discrimination of two sensors at identical resonance wavelength.

Shorter Wavelength Gain Shift In EDFA Using A Macro-Bending Approach

Gain and noise figure improvements are demonstrated in a shorter wavelength region of double-pass EDFA using a macro-bending approach. The EDF is wound in a small radius to suppress the amplified spontaneous emission at the longer wavelength in order to achieve a high amplification in the shorter wavelength. Gain enhancements of about 12 ~ 14 dB are obtained with macro-bending at wavelength region between 1480 nm and 1530 nm. The micro-bending also reduces the noise figure of the EDFA at wavelengths shorter than 1525 nm with maximum improvement of 25 dB.

Fundamental Study on the Development of Fiber Optic Sensor for Real-time Sensing of CaCO3 Scale Formation in Geothermal Water

This study proposes an optical fiber sensor for calcium carbonate (CaCO3) scale formation in water. The sensor is easily fabricated by removing the cladding of a multimode fiber to expose the core towards the surrounding medium in order to detect refractive index change. A variation of the transmittance response from the high refractive index of CaCO3 which precipitated on the fiber core surface was observed. The proposed setup can be used to analyze the transmittance response over wide range of wavelength using white light as a source and also a spectroscopy detector. The curve of the transmittance percentage over time showed that a fiber core with 200 μm has higher sensitivity as compared to a fiber core with 400 μm. The findings from this study showed that the sensor detection region at near infrared (NIR) wavelengths showed better sensitivity than visible light (VIS) wavelengths. Field tests were conducted using natural geothermal water at Matsushiro, Japan in order to verify the performance of the proposed sensor. The optical response was successfully evaluated and the analytical results confirmed the capability of monitoring scale formation in a geothermal water environment.

An Experimental Study on S-band Depressed Cladding EDFA

This paper presents an experimental study of the performance characteristics of an S-band single pass and double pass erbium-doped fiber amplifier (EDFA), using depressed cladding erbium-doped fiber (EDF). The depressed cladding EDF is essentially used to suppress the amplified spontaneous emission (ASE) at the longer wavelength to achieve high amplification in the S-band region. Both single pass and double pass 980 nm pumping are considered. Gain and noise figure of the EDFA are measured. Double pass EDFA shows a significant gain increase of 14 dB in comparison to single pass configuration.