Suhairi Saharudin

Implementation of two-way free space quantum key distribution

We report an implementation of a two-way, four-state quantum key distribution (QKD) protocol (namely, the LM05 protocol) over a free space medium. A stable quantum bit error rate of 3.34% and maximum tolerable channel loss for secure key generation of 5.68 dB in the absence of a photon number splitting attack were recorded. The result strongly indicates the feasibility of a two-way QKD protocol implementation over a free space medium.

Fluorescence characteristic of ruthenium nanoparticles as a dissolved oxygen sensing material in gas and aqueos phase

The fabrication and characterization of a fiber optic dissolved oxygen sensor based on the dynamic quenching of fluorescence from a ruthenium complex in gas and aqueous phase is presented. The unclad portion of the multimode optical fiber is coated with an oxygen sensitive ruthenium complex, which is immobilized by the sol-gel route. The intensity of the fluorescence emission has been found to decrease as the oxygen content increases. The dynamic range and the temporal response of the sensor are investigated for three different environment, gas, deionized water and sea water. The performance of the device is evaluated in terms of the results obtained during actual measurements.

Performance evaluation of optical fiber sensor using different oxygen sensitive nano-materials

Three different oxygen sensitive nano-materials namely Pt (II) meso-tetra(pentafluorophenyl) porphine (PtTFPP), Tris (4,7-diphenyl-1,10-phenanthroline) ruthenium (II) and Pd (II) meso-tetra (pentafluorophenyl) porphine (PdTFPP) has been coated on one end tip of an optical fiber to form optical fiber dissolved oxygen sensor. The performance in terms of fluorescence intensity when exposed to oxygen at various (gaseous) concentrations between the three optical fiber sensors has been performed. Optical fiber sensor probe coated with PdTFPP exhibits the highest sensitivity while Ru (II) complex coated optical fiber sensor demonstrates the highest linearity of all three nano-materials.

An efficient modeling and simulation of quantum key distribution protocols using OptiSystem

In this paper, we propose a modeling and simulation framework for quantum key distribution protocols using commercial photonic simulator OptiSystem™. This simulation framework emphasize on experimental components of quantum key distribution. We simulate BB84 operation with several security attacks scenario and noise immune key distribution in this work. We also investigate the efficiency of simulators inbuilt photonic components in terms of experimental configuration. This simulation provides a study to analyze the impact of experimental photonic components in quantum key distribution process.

Characterization of four states polarization flipper for single photon application

We report characterization result using weak coherent pulses on four states polarization flipper utilizing two Pockels cells. Visibility of nearly 90% and above was achieved for each four linear polarization input states. A good polarization contrast between not flipped and flipped states shows that this configuration can be applied for single photon applications.

Performance improvement of optical fibre oxygen sensor detection scheme incorporating narrow bandpass emission optical filter

We report performance improvement of an optical fibre oxygen sensor based on direct measurement fluorescence quenching of oxygen sensitive ruthenium complex and indirect measurement of lifetime through phase fluorometry. Comparison between detection scheme with and without emission filters using various bandpass ranges are being investigated. A 1.7 fold increase in fluorescence intensity is observed with a detection scheme employing broad (195 nm) bandpass emission filter compared to a system without emission filter. Six fold increase in fluorescence emission is detected when a narrow (25 nm) emission filter is adopted in the system. Similarly, six fold increase in phase angle value φω is demonstrated in an in-direct O2 sensor measurement when 25 nm bandpass emission filter is employed in such system. Improvement in O2 sensor sensitivity and linearity are also reported with the inclusion of narrow bandpass emission filter.

Effect of catalyst on the fluorescence quenching of [Tris (4, 7-diphenyl-1, 10-phenanthroline) ruthenium (II) dichloride] for dissolved oxygen detection

We present the effect of the catalyst for sol-solution preparation of tris (4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride on the fluorescence quenching behavior. Two types of [Ru(dpp)3]2+ sol-solution were prepared with two types of catalyst namely acid hydrochloric (HCl) and ammonium hydroxide (NH4OH) and each of them was mixed with the dye-solution to form [Ru(dpp)3]2+ sol-gel solution. A polymer optical fiber tip was then coated by each of the solutions respectively by immersion method. A LED source at 460 nm was used as the excitation source and fluorescence emissions intensity was measured using a UV/VIS spectrometer. The results showed that the fiber optic coated with the solution using NH4OH gave higher fluorescence intensity.

Analysis of passive compensation for linear and non linear SOP on standard single mode optical fiber

We report experimental result on passive compensation on standard single mode optical fiber. The states of polarization (SOP) were analysed and the six main states normally used for QKD system are investigated. Passive control of SOP approach seems very unpractical, but through simple setup, compensation at each communicating arm seems to be a potential method. The results show that the SOP state remains similar to the source after compensation and the passive compensation setup compensate all 6 SOPs source value over time. We achieved to maintain the related stoke value (S1, S2, S3) at each SOP state above 93%.

Bromophenol blue thin film coated fiber optic response towards pH sensing

The fabrication and characterization of a fiber optic pH sensor based on the evanescent wave absorption is presented in this paper. The sensor is prepared by coating the immobilized indicator in a sol-gel thin film onto the uncladded middle portion of a multimode plastic clad silica (PCS) fiber. The evanescent wave is used to selectively excite the indicator molecules within the fiber cladding for sampling the aqueous media surrounding the fiber. Changes in the pH of the analyte are detected by measuring the absorption spectrum of the sol-gel cladding in the sensing region of the optical fiber. pH buffer 1-14 were used to examine the response of the sensor. The sensor response and its dynamic range are reported for bromophenol blue (BPB) dye. The intensity of the absorption measured in the 470-850 nm spectral range has been found to increase as the pH value increases. The performance of the device is evaluated in terms of the results obtained during actual measurements.

Emission performance of optical fibre dissolved oxygen sensor using various optical fibre materials and parameters

We demonstrate the performance of optical fibre dissolved oxygen (DO) sensor when subject to different core material and sizes. It was found that fluorescence emission from oxygen sensitive material coated at the end-face of an optical fibre DO sensor varies with core material and sizes. Glass core optical fibre provides higher emission when compared to plastic core optical fibre. Using glass core optical fibre, up to 20 meter of optical fibre length can be achieved compared to other reported work.