Maninder Lal Singh

Design of 3-D Wavelength/Time/Space Codes for Asynchronous Fiber-Optic CDMA Systems

A new family of three-dimensional (3-D) wavelength/time/space codes for asynchronous optical code-division multiple access (OCDMA) systems with off-peak auto-correlation, ¿a = 0, and peak cross-correlation, ¿c = 1, is reported. With W wavelengths and T time-slots, (W 2 T + W) codes are generated. Antipodal signaling/differential detection is employed in the system. The performance is compared to the recently reported two-dimensional (2-D)/3-D codes. Arrayed waveguide grating-based reconfigurable 2-D implementation for encoder/decoder is presented. Suitability of our 3-D codes for secure OCDMA networks is discussed.

Simultaneous all-optical half-adder, half-subtracter, comparator, and decoder based on nonlinear effects harnessing in highly nonlinear fibers

Abstract. A multifunctional combinational logic module capable of performing several signal manipulation tasks all-optically, such as half-addition/subtraction, single-bit comparison, and 2-to-4 decoding simultaneously is proposed. Several logic functions (A+B¯, A.B, A¯.B, A.B¯, A⊕B, and A⊙B) between two input signals A and B are implemented by harnessing a number of nonlinear effects, such as cross-phase modulation (XPM), cross-gain modulation (XGM), and four-wave mixing (FWM) inside only two highly nonlinear fibers (HNLF) arranged in a parallel structure. The NOR gate (A+B¯) is realized by the means of XPM effect in the first HNLF, whereas, A‾.B, A.B¯, and A.B logics have relied on utilization of XGM and FWM processes, respectively, in parametric medium made up of the second HNLF of parallel arrangement. The remaining A⊕B and A⊙B logics required for successful implementation of the proposed simultaneous scheme are attained by temporally combining previously achieved (A‾.B and A.B‾) and (A.B and A+B‾) logics. Quality-factor ≥7.4 and extinction ratio ≥12.30  dB have been achieved at repetition rates of 100 Gbps for all logic functions (A+B‾, A.B, A¯.B, A.B¯, A⊕B, and A⊙B), suggesting successful simultaneous implementation.

Optimization of Interchannel Separation in WDM Transmission Systems in the presence of Fibre Nonlinearities

Wavelength division multiplexing (WDM) can give two benefits at the same time: enhancement of transmission capacity and increase in flexibility in optical network design. It is possible to build long distance transparent optical transmission links without electrical regenerators with the help of erbium-doped fiber amplifiers (EDFAs). In such systems, fibre nonlinearities are likely to impose a transmission limit due to increased total interaction length. Most of the work so far has been concentrated on the study of the limitation of input power per channel imposed by fibre nonlinearities. There are a number of optical nonlinear effects in optical fibers, such as stimulated Raman scattering (SRS), stimulated brillouin scattering (SBS), carrier induced phase modulation and four wave mixing (FWM). Out of these SRS and FWM are the dominant effects. The maximum possible transmission distance has been reported to be dependent on various system parameters like number of channels, channel spacing, the allowable power per channel, the amplifier spacing etc. In this paper an algorithm has been suggested for the optimization of interchannel separation considering the combined effect of SRS and FWM in the presence of amplifier spontaneous noise (ASE).

Estimation of Effective Rain Height at 29 GHz at Amritsar (Tropical Region)

The effect of precipitation present in the path of Earth-space communication links, in terms of fading of the signal, is well known. The calculation of fade margin required for 99.99% of the time availability of such links requires the knowledge of various location-specific meteorological parameters, amongst which rain height is prominent. This paper presents results from measurements conducted at Amritsar during a single rain event that took place on September 19, 2005, using a zenith-pointing Dicke-type radiometer at 29 GHz in the form of sky noise temperature. The output of the radiometer along with rain rate, derived from colocated tipping-bucket rain gauge, has been used to obtain a formula relating zenith path attenuation and rain rate. Further, the values of zenith path attenuation and rain rate along with specific attenuation coefficients a and b to obtain effective rain height. It was found that rain height cannot be taken as constant as it is dependent on rain rate. The average rain height during the event was estimated to be 3.54 km with root mean square error of 3.0 km

Enhanced performance of all-optical half-subtracter based on cross-gain modulation (XGM) in semiconductor optical amplifier (SOA) by accelerating its gain recovery dynamics

In this article, the acceleration attained in gain recovery dynamics of travelling-wave-type semiconductor optical amplifier (SOA) at the expense of structural optimization is illustrated via numerical simulations. A pump–probe scheme has been utilized in order to study the outcomes of optimization of SOA operational and structural parameters on its effective gain recovery time (

Automated color prediction of paddy crop leaf using image processing

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Performance evaluation of various classifiers for color prediction of rice paddy plant leaf

τe). A set of optimized SOA parameters are formulated from gain recovery dynamics studies after keeping practical implementation considerations in vision. Further, the impacts of altering SOA structural and operational parameters such as injection current (I), amplifier length (L), active region width (w), active region thickness (t) and optical confinement factor (