Nor ida Mohd Shah

2R Regeneration of Time-Interleaved Multiwavelength Signals Based on Higher Order Four-Wave Mixing in a Fiber

All-optical 2R regeneration of two-wavelength time-interleaved signals is demonstrated using higher order four-wave mixing in a fiber. In this regeneration scheme, a single fiber and a pump are shared by the two channels. The results show that interchannel crosstalk can be avoided when pulses in the two channels are time separated by more than ~3 times their pulsewidth. A possible power monitoring to determine suitable time-interleaving condition is also discussed.

Analysis of the effect of haze on free space optical communication in the Malaysian environment

This paper presents the effect of atmospheric attenuation during hazy days for free space optical (FSO) communication in point-to-point connection. The analysis focuses on scattering coefficient and atmospheric attenuation effects on low visibility, which falls in the range of 1.8 km to 4.5 km. The performance comparison is also done for the wavelength of 850 nm and 1550 nm. The result shows that the performance of 1550 nm is better than 850 nm in both performance parameters. As the link range between transmitter and receiver increases, the atmospheric attenuation increases too. Deployment distance of less than 1km can reduce the effect of atmospheric attenuation. These challenges limit FSO to the short distance application.

Indoor channel prediction and measurement for wireless local area network (WLAN) system

There are two basic way to deploy wireless local area network (WLAN) access point in an indoor scenario. Manual deployment of a system using site measurement based on empirical measurement and prediction using software tool that have signal propagation models. The measurement campaign was based on 2.4 GHz ISM band and conducted within campus KUiTTHO building. A measurement of signal level within indoor environment is done without presence of people movement. The measurement aims was to find empirical parameters for one slope models. Statistical analysis for site measurement in this paper follows the analysis that had been done in [3]. Results from both prediction and measurement campaign were compared and conclusions are drawn for the need of practical planning of indoor WLAN system coverage.

Comparison between regenerative-feedback and cofeedback gain-clamped EDFA

The erbium-doped fiber amplifier (EDFA) with regenerative feedback is compared with the cofeedback scheme. Without the bandpass filter, the injected signal experiences regenerative amplification and results in a higher signal gain. Such an above-threshold regenerative amplifier also exhibits a lower noise figure due to a higher inversion for the transition corresponding to the signal wavelength of 1550 nm. A near quantum-limited noise figure of 3.1 dB is achieved at the maximum pump power of 134.5 mW, showing nearly complete inversion at the EDF input end in the regenerative-feedback scheme. A low (<10/sup -10/) bit-error rate has been achieved with saturation input signal power above -12 dBm.

Spectral amplitude coding OCDMA using AND subtraction technique

A new detection scheme, namely AND subtraction technique is proposed and presented in this paper. The theory is being elaborated and the calculated and simulation results have been done by comparing AND subtraction technique against complementary subtraction technique by using DW code. In this paper we have proved that AND subtraction technique gives better bit error rate (BER) performance than complementary subtraction technique.

All Optical Signal Restoration for 10G DPSK System

Ultrafast Kerr nonlinearity, offers various signal processing functions to be used. Several nonlinear transmission impairment such as phase noise, amplitude noise and power spectral efficiency loss become proficient to degrade the performance of optical systems, when intense power is launched in optical fiber. In modern communication system, all optical regeneration is one of the solution to mitigate transmission impairments instead of O-E-O conversion. In this paper, all optical regeneration is demonstrated for 10G DPSK system using 3R regeneration and phase sensitive amplification to mitigate amplitude and nonlinear phase noise form 10G noisy DPSK transmission system. Bit error rate of 10−12 is achieved at power penalty of 5 dBm. In developed system the novelty exist in compensating two noise simultaneously; ASE noise and phase noise using integrated algorithm developed using 3R and PSA. The system is developed and tested using commercial software package optisystem to check the feasibility of the system design in real time implementation. The developed all optical regeneration system is very demanding for long distance high-speed communication systems. The result conclude the positive feasibility for real time implementation of designed system.

Energy-efficient Pseudo Noise generator based optical transmitter for Ethernet(IEEE 802.3az)

In this paper Pseudo Noise generator based optical transmitter is designed to increase the range of Ethernet based networks. Structural changes are proposed in PN generator based optical transmitter for energy efficient Ethernet (IEEE802.3az) to be integrate with different IEEE802.3 protocols (IEEE fiber optic standard). Energy efficient Ethernet design is realized by choosing the most energy efficient IO standards between LVCMOS12 and HSTL_II. Compatibility of this PN generator based optical transmitter is tested for different IEEE802.3 fiber optic standards. The PN generator has operating frequency for 1000BASE-T i.e. IEEE802.3ab, 10GBASE-CX4 i.e. IEEE 802.3ak, 100BASE-T1 i.e. IEEE 802.3bw, 1GBASE-PR i.e. IEEE802.3av is 1000GHz, 10GHz, 100GHz and 1GHz respectively. The LVCMOS12 IO standard will be use in final design to make PN generator more energy efficient, because the power saving for LVCMOS12 is 77.1% more than HSTL_II. There is 96.7% reduction in clock power and 99% reduction in signal power is observed for LVCMOS12 design when using 1GBASE-PR Ethernet configuration for Energy efficient PN generator based optical transmitter. Finally this system will be integrated with other optical components to make optical communication system green. Xilinx ISE14.7 design tool is used to perform the experiment.

DSP techniques for reducing chromatic dispersion in optical communication systems

In this paper the chromatic dispersion is reduced for enhancement in the performance of optical communication system. For this an analog test signal is generated and converted into digital domain and modulated with 16 QAM by gray code mapping. Through Split Step Fourier technique the signal is propagated in the optical fiber link for 15 km of simulated distance. At the end of this distance the chromatic dispersion is observed and to reduce Chromatic Dispersion (CD) signal is converted in electrical form at end of optical fiber link. Digital Signal Processing techniques are applied on dispersed signal to reduce the CD. Analysis is based on Bit Error Rate that are compared before and after the induction of chromatic dispersion. In this research CD is reduced electronically so it will save the requirement of optical amplifiers.

Adaptive delay control for time-interleaved multi-channel amplitude limiter based on saturation of four-wave mixing in a fiber

An adaptive delay control to maintain time-interleaving condition of multi-channel input signals of all-optical amplitude limiter based on saturation of four-wave mixing (FWM) in a nonlinear fiber is demonstrated. The delay control utilizes as a monitor signal the optical power after the nonlinear fiber at a wavelength that is affected by interchannel FWM in the fiber. When the scheme is applied to 2 x 10 Gbit/s return-to-zero differential phase-shift keying signals where the time separation between the input channels is intentionally changed randomly, the delay control works well and error free detection after transmission is obtained.

Unidirectional and bidirectional feedback regenerative erbium-doped fiber amplifier

In this letter, the performance of a unidirectional feedback regenerative erbium-doped fiber amplifier (EDFA) is compared with that of a bidirectional feedback one. The systems operate above the laser oscillation threshold, and exhibit the gain-clamping effect. The experimental results show that the unidirectional system has a higher gain and a lower noise figure than the bidirectional system. At high input signals, an injection-locking phenomenon is observed and the resonant-amplification characteristic of regenerative amplifier vanishes.