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Free-space optical links use modulated beam of light to transmit high amount of data from transmitter to receiver to get line-of-sight communication link. Free-space optical is cost effective solution to provide higher data rate to end-users. Free-space optical links are also considered as a better alternative to RF links due to their advantages of low power consumption and higher data rate of the range Gbps, and are highly secure to electromagnetic interference. Despite of having all these advantages free-space optical links are highly affected by the severe weather conditions like fog, rain, snow, smoke and dust or aerosol particles suspended in air. Fog is one of a major challenge for free-space optical to achieve carrier class availability and causes high amount of attenuation. In this paper we presented the performance analysis of free-space optical links by estimating signal-to-noise ratio, bit error rate, under fog conditions during winter season in Lahore, Pakistan. [ABSTRACT FROM AUTHOR]

Video on demand technology is a modern wireless communication application which requires a large bandwidth. Optical wireless networks, as a potential alternative to radio frequency, is an emerging technology that is easier to set up and provides a cost effective solution, where a physical network is difficult to deploy. Optical wireless networks can be used as a backbone to provide the much needed bandwidth for video on demand application. In this paper, Wavelength Division Multiplexing modulation scheme is proposed for the optical wireless networks due to its significance of transmitting distinct data channels at different wavelengths. Wavelength Division Multiplexing can be easily integrated with optical wireless networks, consequently resulting in an increased data rate. This paper presents a novel approach of integrating video on demand with the state of art Wavelength Division Multiplexing based optical wireless networks. Furthermore, the paper discusses the challenges and advantages over the convention modulation schemes. [ABSTRACT FROM AUTHOR]

For the last three decades, the phenomenon of four-wave mixing is a significant technique for generation of light at new distinct wavelength. When two distinct laser beams (pump and probe) beat together in a non-linear medium, few modes are increased in the power at same distance from the probe and pump, as a result of four-wave mixing. In this paper, cascading structure of two semiconductor optical amplifiers produces very strong four-wave mixing. This technique is exploited to devise a tunable radio frequency signal generator. The wavelength distance between pump and probe laser beams determines the radio frequency of the generated signal. Using this scheme, it can be observed from the experimental results, that there is an increase of more than 3 dB in signal to noise ratio at 7 Gbits/sec data rate of the 60 GHz generated mm-wave signal. Moreover, the radio frequency can be tuned to hundreds of GHz by varying the distance between the pump and probe signals. This scheme will readily serve as future all optical radars. It is also a key technique for short-range communication systems for military applications. The above scheme can also be monolithically integrated. [ABSTRACT FROM AUTHOR]

It has been successfully investigated for the first time that strength of optical injection locking also depends on the size of semiconductor ring laser. Theoretical study for frequency response of optical injection locking semiconductor ring laser in the master slave configuration using direct, amplitude and phase modulation of master laser is discussed. In the unidirectional regime the locking range of semiconductor ring laser becomes wider when semiconductor ring laser with smaller size is used. Simulation results predict an incredible enhancement in the modulation bandwidth (> 500 GHz) of the slave semiconductor ring laser when used with smaller laser cavity length (50 μm) in the stable unidirectional regime. [ABSTRACT FROM AUTHOR]

Theoretical study for frequency response and modulation bandwidth of slave semiconductor ring laser in the master-slave configuration using optical injection locking has been investigated. Equations for frequency response of optical injection locking–semiconductor ring laser to the direct modulation, amplitude modulation of master laser, respectively, are derived and simulated. Enhancement in the modulation bandwidth of > 100 GHz is reported between negative to positive detuning frequency and increasing injection power ratio. [ABSTRACT FROM AUTHOR]

Novel all-optical implementations for logic AND and XOR gates are experimentally demonstrated at 2.5 Gbit/s based on cavity-enhanced four-wave-mixing (CE-FWM) combined with optical injection locking phenomena in monolithically integrated semiconductor ring lasers (SRLs). An all-optical AND gate with simultaneous wavelength conversion has been achieved using CE-FWM. An XOR function is demonstrated using two parallel SRLs, each performing one part of the XOR Boolean equation A + B=AB+AB. Error-free operation with extinction ratio higher than 10 dB confirms the suitability of SRLs for all-optical logic applications. [ABSTRACT FROM AUTHOR]

A novel all-optical multicast scheme based on cavity-enhanced four wave mixing in a monolithically integrated semiconductor ring laser (SRL) is proposed. By employing an injecting optical signal resonant with a cavity mode of the SRL, one-to-seven all-optical multicast by means of highly efficient simultaneous multi-wavelength conversion has been experimentally demonstrated up to multi-gigabit data rates. The scheme offers several advantages including low power penalty, reconfigurability, monolithic integration and low cost. [ABSTRACT FROM AUTHOR]

The aim of study was to determine the relationship between widespread presence of clinical/sub-clinical mastitis and different conditions of farm management for Friesian x Sahiwal (FxS) crossbred cows in Lahore district of Punjab, Pakistan. A total of 107 FxS crossbred cows were selected from three dairy farms having different management conditions (A: Very good, B: Good and C: Poor). The data of clinical and sub-clinical mastitis was collected using the cardinal sign (inflammation of udder) and white side test. Overall incidence of mastitis was recorded 26.2% including 12.72, 13.63 and 16.66% at farms with very good, good and poor management conditions, respectively. However, sub-clinical mastitis was recorded 9.09, 13.63 and 16.66% at farms with very good, good and poor management conditions. Prevalence of mastitis was 7.71% Sub-clinical and 7% clinical in udder quarters. It was concluded that mastitis level has linear relation with management conditions of farms. [ABSTRACT FROM AUTHOR]

Stability and effects of optical injection locking in semiconductor ring laser is modeled in detail. It is verified that the injection locking in slave semiconductor ring laser depends on detuning frequency and external optical injection ratio between the master laser and the slave semiconductor ring laser. The stability of injection was locked using the resonance frequency and damping factor. The parasitic phase modulation response due to amplitude modulation (chirp response) is derived and simulated. Similarly parasitic amplitude modulation due to phase modulation response is also investigated. [ABSTRACT FROM AUTHOR]

Hepatobiliary manifestations occur quite frequently in patients suffering from chronic ulcerative colitis and Crohn's disease and carry with them considerable morbidity and mortality. Although the true incidence is difficult to determine, clinically significant hepatobiliary disease occurs in 5%-10% of patients. At the present moment, the aetiology and pathogenesis of inflammatory bowel disease and its systemic manifestations remains speculative. For those hepatobiliary manifestations that respond to therapy of the underlying bowel disease, medical and/or surgical therapy must be aggressively pursued. More urgent research is required towards understanding the underlying cause(s) of the primary bowel disease and its systemic manifestations in order to improve the overall management of this condition.