M. I. Zulkifli

New Design of a Thulium–Aluminum-Doped Fiber Amplifier Based on Macro-Bending Approach

A new method for gain enhancement in a S-band thulium-doped fiber amplifier (TDFA) co-doped with aluminum is demonstrated using a macro-bending approach. The macrobending of the doped fiber in a small radius suppresses both amplified spontaneous emissions (ASEs) at 800 and 1800 nm band and thus increases the population inversion in the S-band region. The numerical aperture and core radius of the doped fiber are optimized so that 800 nm ASE propagates with higher order modes to achieve a significant suppression while the loss is minimum in the S-band region. Meanwhile, the 1050 nm pump wavelength should propagate in the fundamental mode to maximize the overlap factor and thulium ion absorption so that the ASE loss is maximum at the 1800 nm region. Gain enhancements of about 5-8 dB are obtained with macrobending at the wavelength region between 1420 and 1470 nm.

Photosensitivity of gallium-doped silica core fiber to 193 nm ArF excimer laser.

Grating inscription in a Ga-doped silica core fiber (~5 wt. % Ga) has been demonstrated using ArF (193 nm) and KrF (248 nm) excimer lasers. In a comparative study with germanosilicate fiber with similar Ge concentration, a Ga-doped silica core fiber shows greater photosensitivity to an ArF excimer laser due to the higher absorbance in the region of 190-195 nm. In addition, the photosensitivity of a Ga-doped silica core fiber has been greatly enhanced with hydrogenation. Ga-doped fibers are potential photosensitive fibers for fiber Bragg grating production with an ArF excimer laser.

Design and performance of an S-band Thulium doped modified silica fiber amplifier

A new design of an S-band Thulium-doped modified Silica fiber co-doped with aluminum is presented. The design goal is high gain and low noise figure in the wavelength range of 1450 - 1520 nm. The optimization considers design parameters such as the cut-off wavelength, dopant concentration, waveguide structure, index profile and numerical aperture. These design parameters are optimized to achieve long fluorescence lifetime, high overlap factor and selected mode excitation. The amplifier performance is theoretically modelled and simulated considering the proposed design optimization. We show that the amplifier can achieve a gain of 16 dB and 3dB noise figure.

Thermal Activation of Regenerated Grating in Hydrogenated Gallosilicate Fiber

The thermal regeneration of fiber Bragg gratings inscribed on hydrogenated gallosilicate optical fiber, fabricated using a modified chemical vapor deposition (MCVD) technique followed by a solution doping process, is demonstrated for the first time. A type-I seed grating is thermally regenerated and the evolution of the grating reflectivity in a temperature range between 25 °C and 720 °C is investigated. Temperature responses of 15.2 pm/°C and 15.0 pm/°C are obtained during heating and cooling processes of the regenerated grating (RG), respectively, when performing thermal calibration over a temperature range of 25 °C-750 °C and vice versa. Gallosilicate-based RGs are potential candidates as high-temperature resistant gratings in rare-earth-doped fiber, since they provide high photosensitivity and thermal sustainability with the involvement of a single dopant with a concentration as low as 5 wt%.

S-Band Gain Improvement Using a Thulium–Aluminum Co-Doped Photonic Crystal Fiber Amplifier

An extended method for gain and noise figure enhancement in the S-band using a thulium-doped photonic crystal fiber amplifier (TD-PCFA) is proposed and shown by numerical simulation. The principle behind the enhancement is the suppression of unwanted amplified spontaneous emission (ASE) using the PCF structure. This proposed PCF achieves the intended band-pass by doping the cladding with high index material and realizes appropriate short and long cut-off wavelengths by enlarging the air-holes surrounding the doped core region. The PCF geometrical structure is optimized so that high losses occur below the short cut-off wavelength (800 nm) and beyond the long cut-off wavelength (1750 nm). Furthermore, the PCF geometrical structure design allows for high ASE suppression at 800- and 1800-nm band, thus increasing the population inversion needed for amplification in S-band region as the 1050-nm pump propagates light in the band-pass. The proposed TD-PCFA demonstrates gain enhancements of 3-6 dB between 1420 and 1470 nm.

Fabrication of Tm 2 O 3 /Al 2 O 3 -silica preform by improved MCVD-chelate delivery system

The fabrication of Tm/Al-doped silica preforms by an improved MCVD method with metal chelate precursors is discussed. Two fabrication techniques are employed, namely; simultaneous soot-dopant deposition (or standard MCVD) and stepwise soot-dopant deposition. The preforms are characterized by refractive index profiler and EPMA. The results show that the stepwise soot-dopant technique has a higher incorporation of Al2O3 and Tm2O3 as compared to the simultaneous soot-dopant method. This is due to the drawbacks of our chelate delivery system such as the temperature gradient and flow design. For the stepwise technique, the measured index difference of the preform is 0.006 with 0.8 wt% (maximum) Tm incorporated in the core.

Multiple soaking with different solution concentration in doped silica preform fabrication using modified chemical vapor deposition and solution doping

Abstract Incorporation of alumina (Al2O3) into a silica matrix by modified chemical vapor deposition and a solution doping technique is investigated in this study. Multiple soaking cycles were used to increase the aluminum content in the core layer. The effect of alumina retention in silica matrix soot is focused by multiple cycles of soaking with different solution concentrations, while the effect of the adsorption mechanism is fixed by maintaining the soot deposition process (such as temperature [1,800°C], precursor, total gas flow, and soaking time). The deposited soot is examined for porosity characteristics and effective surface area by a gas adsorption technique with Brunauer–Emett–Teller surface area analysis and the surface and cross-section morphology using scanning electron microscopy. Three different concentrations are used in this work (0.3, 0.7, and 1.2 M) with multiple cycles of soaking. Sintering and the collapsing process is controlled for each preform. The result shows that the alumina content is increased substantially as the number of soaking processes is increased, which may be due to the retention effect as only a small amount of adsorption process takes place as indicated by the slight decrease in the surface area of soot. The collapsed preforms are analyzed using a preform analyzer. Energy dispersive x-ray spectrometry is used to check aluminum content and distribution into the core layer.

Aluminum doped silica preform fabrication using MCVD and solution doping technique: Effects of various aluminum solution concentrations

This work is described for solution doping in Modified Chemical Vapor Deposition (MCVD) used for silica optical fiber fabrication. This paper will concentrate on aluminum solution doping and the effect of different solution concentrations. The effect of three different concentrations of aluminum (0.3M,0.7M and 1.2M) with the soot undergo heat treatment are studied while the other parameters of MCVD and solution doping are fixed such as deposition temperature, SiCl4 flow, and soaking time. The refractive index profile(RIP) of each doped preform is measured using preform analyzer to investigate aluminum distribution in the core region. Further investigation about Al distribution across the core sintered layer is also examined by EDX techniques.

Net deposition efficiency of step-index GeO 2 doped silica glass fabricated by MCVD

The net deposition efficiency which describes the successful incorporation of germania in silica was studied by varying the GeCl4 flow rate while maintaining that of SiCl4 constant. Both theoretical and experimentally-derived net deposition efficiencies were determined. The radial and longitudinal homogeneities of the fabricated preform were also determined. EDX analysis was also carried out to confirm the germanium presence in the fabricated preform.

Fabrication and characterization of a Gallium co-doped Erbium optical fiber

In this paper, fabrication and characterization of a Gallium co-doped Erbium fiber is presented, highlighting Gallium as a new potential co-dopant to be used in rare-earth doped fibers. This fiber was fabricated using standard MCVD and solution doping method. Fiber characterization setups for fluorescence lifetime, absorption and ASE spectrum are discussed in detail. We go on to show that fluorescence lifetime of 6.02 ms, NA of 0.12, cutoff wavelength of 1.4 μm and a peak absorption of 45 dB/m at 1550 nm is achievable using Gallium as the co-dopant for an Erbium doped fiber.