Development And Implementation of a Novel Code Family for Optical Code Division Multiple Access Systems

Future telecommunication systems and networks are expected to provide a variety of integrated broadband services to the customers. There has been a tremendous interest in applying Code Division Multiple Access (CDMA) techniques to fiber optic communication systems. This technique is one of the multiple access schemes that is becoming popular because of the flexibility in the allocation of channels, ability to operate asynchronously, enhanced privacy and increased capacity in bursty networks. The performance of any Optical CDMA (OCDMA) system strongly depends on the codes properties. In this study we introduce a new code for Optical CDMA namely Double Weight Code family (DW). Double Weight Code (DW) has a basic fixed weight of 2 and exists for every natural number. The DW codes possess ideal cross correlation properties, which have important characteristics in OCDMA systems since these can eliminate multiple access interference (MAI) and reduce noise. Also proposed in this study, a Modified Double-Weight (MDW) code, which is a variation of DW code family that can have a variable weight greater than two. The MDW code possesses ideal crosscorrelation properties and exists for every natural number too. It is shown through simulations, theoretical analysis and partially by the experiments that the transmission performance of DW code family is significantly better than that of existing codes such as Modified Frequency Hopping code (MFH) and Hadarnard code. The performance of DW code family, MFH and Hadamard codes were simulated using commercial simulation software, OptiSystem Version 3.0. The performance of the systems was characterized by referring to the bit error rate (BER) and the eye patterns. DW code family has shown superior performance compared to other OCDMA codes. The simulated eye pattern of one of the four MDW coded carriers running at lOGbps over a cornrnunication-standard fiber shows a good quality transmission at the BER of 10 -12 as opposed to only 1o ' ~an d 1o 4 for Hadamard and MFH codes. In optical CDMA systems, the detection process affects the design of transmitters and receivers. Cross-correlation functions are generated which creates Multiple Access Interference (MAI) and this will degrade the system performance. MA1 can be reduced by using subtraction techniques. The most common subtraction technique is the complementary subtraction technique and also known as balanced detection technique. In this thesis, we also introduce a new approach called AND subtraction technique. This method rejects unwanted signals that interfere with the original signals. Furthermore, the purpose of this new subtraction technique is to reduce the receiver complexity and increase system performance. It has been shown through theoretical analysis, simulation and experimental work, the performance of the system with AND subtraction technique can be improved significantly. Based on the theoretical analysis, BER as good as 10-l2is achieved at the bit rate of 622 Mbps over 70 km distance

Preparation of an Exponentially Rising Optical Pulse for Efficient Excitation of Single Atoms in Free Space

We report on a simple method to prepare optical pulses with exponentially rising envelope on the time scale of a few ns. The scheme is based on the exponential transfer function of a fast transistor, which generates an exponentially rising envelope that is transferred first on a radio frequency carrier, and then on a coherent cw laser beam with an electro-optical phase modulator (EOM). The temporally shaped sideband is then extracted with an optical resonator and can be used to efficiently excite a single Rb-87 atom.Comment: 3 pages, 4 figures, small technical not

Capacity of public health laws enforcement by health inspectors in state of Selangor, Malaysia

A cross sectional study initiated among the Public Health Enforcement Inspectors in state of Selangor, Malaysia in July 2003 using a self administered questionnaire and universal sampling with the purpose to determine the capacity of public health laws enforcement and factors influencing it. A total of 99 respondents from the Health Districts Ofices and I00 respondents from the Local Municipal Health Departments participated in this study. It was found that the level of enforcement is generally low in all the units except for two units; the Food Unit and Sanitary and Hygiene Units. Factors found to influence enforcement capacity are the units' the enforcers work in and the length of service being in the same unit. Further analysis using multiple logistic regression, showed that respondents from the Food Unit (adjusted odds ratio 22; CI 95% : 7.851, 58.896), enforcers from the middle level category (adjusted odds ratio 5; CI 95%: 1.397, 17.630), duration of service of 4 years and above in the same unit (adjusted odds ratio 6; CI 95%: 2.174, 13.747), past acceptance of formal service rewards from their departments (adjusted odds ratio 3; CI 95% : 1.150, 6.917); low exposure to bribery (adjusted odds ratio 46; CI 95% : 2.336, 1000) and have in the past being oflered bribes while on the field (adjusted odds ratio 3; CI 95% : 1.018, 4.772) are associated with higher enforcement capacity. In conclusion; die attention must be looked into the enforcement organization with respect to the duration of service, acknowledgement via service rewards and monitoring of bribes exposure will help shape a better public health laws' enforcement capacity

Parents‘ and healthcare professionals’ perception toward the introduction of a new fully liquid hexavalent vaccine in the Malaysian national immunization program: a cross-sectional study instrument development and its application

A newly developed fully liquid hexavalent vaccine that comprises six antigens for Diphtheria, Tetanus, acellular Pertussis, Inactivated Poliomyelitis, Haemophilus Influenza type b., and Hepatitis B, is proposed to be introduced in the Malaysian national immunization program, instead of the non-fully liquid pentavalent vaccine and monovalent Hepatitis B vaccine that is currently employed in the immunization schedule. Although the introduction of new vaccines is a necessary intervention, it still needs to be accepted by parents and healthcare professionals. Hence, this study aimed to develop three structured questionnaires and to investigate the participants’ perception and acceptability toward the incorporation of the new fully liquid hexavalent vaccine. A cross-sectional study was conducted among a sample of 346 parents, 100 nurses, and 50 physicians attending twenty-two primary health care centers in the states of Selangor and the Federal Territory of Kuala Lumpur and Putrajaya during 2019-2020. The study found that Cronbach’s alpha coefficients for the study instruments ranged from 0.825 to 0.918. Principal components analysis produced a good fit with KMO>0.6. For the parents’ perception questionnaire, the only extracted factor explained 73.9 % of the total variance; for the nurses’ perception toward a non-fully and fully liquid combined vaccine, there was a sole extracted factor that explained 65.2 % and 79.2% of the total variance, respectively. Whereas for the physicians’ perception, there was one factor extracted that explains 71.8 % of the total variance. The median score for all the questionnaire items ranged from 4 to 5 (Q1 and Q3 vary between 3-5). Parents' ethnicity was significantly associated (P-value ≤ 0.05) with the perception that the new hexavalent vaccine would reduce their transportation expenses. Moreover, a significant association (P-value ≤ 0.05) was found between physicians' age and the perception of the hexavalent vaccine's ability to decrease patient overcrowding in primary healthcare centers. The instruments used in this study were valid and reliable. Parents of Malay ethnicity were the most concerned about transportation expenses since they have the lowest income and are more concentrated in rural areas compared to other races. Younger physicians were concerned about reducing patient crowding and hence reducing their workload and burnout

Doppler-free approach to optical pumping dynamics in the 6S1/2−5D5/26S_{1/2}- 5D_{5/2} electric quadrupole transition of Cesium vapor

The $6S_{1/2}-5D_{5/2}$ electric quadrupole transition is investigated in Cesium vapor at room temperature via nonlinear Doppler-free 6P-6S-5D three-level spectroscopy. Frequency-resolved studies of individual E2 hyperfine lines allow one to analyze optical pumping dynamics, polarization selection rules and line intensities. It opens the way to studies of transfer of light orbital angular momentum to atoms, and the influence of metamaterials on E2 line spectra.Comment: 4 pages, 5 figures, minor updates from previous versio

Incidence of moral hazards among health care providers in the implementation of social health insurance toward universal health coverage: evidence from rural province hospitals in Indonesia

ObjectiveTo identify the incidence of moral hazards among health care providers and its determinant factors in the implementation of national health insurance in Indonesia.MethodsData were derived from 360 inpatient medical records from six types C public and private hospitals in an Indonesian rural province. These data were accumulated from inpatient medical records from four major disciplines: medicine, surgery, obstetrics and gynecology, and pediatrics. The dependent variable was provider moral hazards, which included indicators of up-coding, readmission, and unnecessary admission. The independent variables are Physicians' characteristics (age, gender, and specialization), coders' characteristics (age, gender, education level, number of training, and length of service), and patients' characteristics (age, birth weight, length of stay, the discharge status, and the severity of patient's illness). We use logistic regression to investigate the determinants of moral hazard.ResultsWe found that the incidences of possible unnecessary admissions, up-coding, and readmissions were 17.8%, 11.9%, and 2.8%, respectively. Senior physicians, medical specialists, coders with shorter lengths of service, and patients with longer lengths of stay had a significant relationship with the incidence of moral hazard.ConclusionUnnecessary admission is the most common form of a provider's moral hazard. The characteristics of physicians and coders significantly contribute to the incidence of moral hazard. Hospitals should implement reward and punishment systems for doctors and coders in order to control moral hazards among the providers

Excitation of a single atom with exponentially rising light pulses

We investigate the interaction between a single atom and optical pulses in a coherent state with a controlled temporal envelope. In a comparison between a rising exponential and a square envelope, we show that the rising exponential envelope leads to a higher excitation probability for fixed low average photon numbers, in accordance to a time-reversed Weisskopf-Wigner model. We characterize the atomic transition dynamics for a wide range of the average photon numbers, and are able to saturate the optical transition of a single atom with ~50 photons in a pulse by a strong focusing technique. For photon numbers of ~1000 in a 15ns long pulse, we clearly observe Rabi oscillations.Comment: 5 pages, 6 figure

Tailoring optical metamaterials to tune the atom-surface Casimir-Polder interaction

Metamaterials are fascinating tools that can structure not only surface plasmons and electromagnetic waves but also electromagnetic vacuum fluctuations. The possibility of shaping the quantum vacuum is a powerful concept that ultimately allows engineering the interaction between macroscopic surfaces and quantum emitters such as atoms, molecules or quantum dots. The long-range atom-surface interaction, known as Casimir-Polder interaction, is of fundamental importance in quantum electrodynamics but also attracts a significant interest for platforms that interface atoms with nanophotonic devices. Here we perform a spectroscopic selective reflection measurement of the Casimir-Polder interaction between a Cs(6P_{3/2}) atom and a nanostructured metallic planar metamaterial. We show that by engineering the near-field plasmonic resonances of the metamaterial, we can successfully tune the Casimir-Polder interaction, demonstrating both a strong enhancement and reduction with respect to its non-resonant value. We also show an enhancement of the atomic spontaneous emission rate due to its coupling with the evanescent modes of the nanostructure. Probing excited state atoms next to nontrivial tailored surfaces is a rigorous test of quantum electrodynamics. Engineering Casimir-Polder interactions represents a significant step towards atom trapping in the extreme near field, possibly without the use of external fields.Comment: 21 pages, 9 figure