Khazani Syed Research Articles

Optical fiber sensor network integrating SAC-OCDMA and cladding modified optical fiber sensors coated with nanomaterial

Three modified single mode optical fiber ammonia sensors coated with nanocomposite of polyaniline/graphite nanofiber (PANI/GNF) are integrated with optical code division multiple access utilizing spectral amplitude coding (SAC-OCDMA) optical fiber sensors network. The sensors are modified using both etching and tapering processes. A thin layer of PANI/GNF is spared on the etched–tapered SMF sensors. The sensors based on the evanescent wave absorption are investigated by measuring the output optical power in the C-band wavelength range (1535–1560 nm) at room temperature. SAC-OCDMA using Khazani Syed (KS) code is deployed as it has the capability to remove multiple access interference (MAI) and it is cost effective. The performance of the developed optical fiber sensor network based on star topology is investigated remotely over 3 km using Erbium doped fiber amplifier for NH3 sensing in terms of received optical power, crosstalk, and optical signal-to-noise ratio (OSNR). OSNR is observed to vary with fiber diameter and NH3 concentration level. The smaller tapering diameter and higher NH3 concentrations generate lower OSNR at the output of the related decoder. The measured OSNR for the developed optical fiber sensor network was 22 and 18.45 dB when sensors implied in the network exposed to 0.125% and 1% NH3 concentrations, respectively.

Design of Variable Weight code for multimedia service in SAC–OCDMA systems

Variable weight (VW) codes for spectral amplitude coding–optical code division multiple access system are useful in multimedia applications. VW code algorithm is proposed which is based on enhanced and modified double weight codes. The proposed algorithm can be used for any combination of weights >2. The cross-correlation among all users is at most 1. This code construction algorithm ensures higher power at receiver for higher-weight users. Lower-weight users receive less power compared with higher-weight users. The difference in received power translates as varying performance, and are useful for multimedia applications. The performance of VW code is analysed using balanced detection (BD) exclusive-OR operation and direct detection with exclusive-OR operation. VW code gives comparable or better performance than previously reported code. It is observed that supportable number of users for higher weight, at bit error rate (BER) of 10−9 (data) are 28, 33 and 35 for random diagonal (RD) code, Khazani-Syed (KS) code and VW code, respectively, using BD. Supportable number of users for lower weight, at BER of 10−4 (voice) are 23, 31 and 37 for RD code, KS code and VW code, respectively, using BD.

SAC-OCDMA over Hybrid FTTx Free Space Optical Communication Networks

This paper presents an investigation of Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) over hybrid Fiber-to-the-x (FTTx) Free Space Optical (FSO) link under different weather conditions. FTTx and FSO are the last mile technologies that complement each other in delivering secure and high speed communication to customers’ residence or office. SAC-OCDMA is one of the potential multiplexing techniques that has become a research area of interest in optical communications and considered a promising technique for FTTx access networks. It is based on Khazani-Syed (KS) code with Spectral Direct Decoding (SDD) technique. All the components involved in the network were specified according to the available market product in order to simulate the actual environment as close as possible. The result shows that for bit error rate (BER) of 10−9, the network is able to perform with 20 km Single Mode Fiber ( SMF ) spanning from the central office (CO) and 1.48 km FSO range with transmission rate of 1.25 Gb/s during heavy rain.

Performance and comparison of fiber vibration sensing using SAC-OCDMA with direct decoding techniques

Intensity modulated fiber vibrations sensing using Khazani Syed (KS) and Modified Quadratic Congruence Code (MQC) code for quasi distributed vibration measurement have been evaluated. The systems employed Spectral Direct (SD) Decoding for Spectral Amplitude Coding-Optical Code Division Multiple Access (SAC-OCDMA). SAC-OCDMA is adopted because of its enormous impact in dealing with Multiple Access Interference (MAI). The setup was carried out for three sensor points in three consecutive measurements. The performance of the sensing system with the KS and MQC codes were compared at the same weight and number of code sequence. It was observed that the applied vibration frequencies were obtained at the receivers and the signal employing MQC are received at slightly better power than KS code. However, KS code setup employed less number of components and therefore, reduce the cost and complexity of achieving quasi-distributed vibration sensing.

Fiber vibration sensor multiplexing techniques for quasi-distributed sensing

A multiplexing technique for fiber vibration sensors is experimentally investigated using Khazani Syed (KS) code in SAC/OCDMA with direct decoding. The system is proposed to implement vibration sensor multiplexing which can eliminate the Multiple Access Interference (MAI) at low cost and complexity. The results show the proposed system having better SNR, less complex, and low cost when compared with complementary decoding, and higher power level when compared with simplified WDM. A frequency range of 0 to 400 Hz measured shows its suitability for quasi-distributed sensing in bridges, pipelines, transformers, and industrial machine that exhibit low vibrations within this range.

Performance of SAC OCDMA-FSO communication systems

In this paper, the performance of free space optical (FSO) communication system employing the spectral amplitude coding optical code division multiple access (SAC OCDMA) technique is presented. SAC OCDMA is one of the multiplexing schemes that have become a research area of interest in optical communication because of its flexibility in allocating channels, ability to operate asynchronously, enhanced privacy and increased network capacity. It utilizes Khazani–Syed (KS) code with spectral direct decoding (SDD) technique. The SAC OCDMA-FSO communication system was compared with the FSO system employing intensity modulation/direct detection (IM/DD) technique. The results of this study show that the performance of the proposed system is better than the system employing the IM/DD technique.

Performance improvement of hybrid subcarrier multiplexing optical spectrum code division multiplexing system using spectral direct decoding detection technique

This paper proposes a hybrid subcarrier multiplexing/optical spectrum code division multiplexing (SCM/OSCDM) system for the purpose of combining the advantages of both techniques. Optical spectrum code division multiple-access (OSCDMA) is one of the multiplexing techniques that is becoming popular because of the flexibility in the allocation of channels, ability to operate asynchronously, enhanced privacy and increased capacity in bursty nature networks. On the other hand, subcarrier multiplexing (SCM) technique is able to enhance the channel data rate of OSCDMA systems. In this paper, a newly developed detection technique for the OSCDM called spectral direct decoding (SDD) detection technique is compared mathematically with the AND subtraction detection technique. The system utilizes a new unified code construction named KS (Khazani–Syed) code. The results characterizing the bit-error-rate (BER) show that SDD offers a significant improved performance at BER of 10 −9.

Optical domain service differentiation using spectral-amplitude-coding

We have implemented a new service differentiation technique in the optical domain using a spectral-amplitude-coding (SAC) variant of optical code division multiple access (OCDMA). The newly developed code, named KS (Khazani–Syed) is compared mathematically with other codes which use similar techniques. In our proposal, multiple weights are used to support ‘triple-play’ services (audio, video and data) with different quality-of-service (QoS) requirements. The results characterizing the bit-error-rate (BER) with respect to the total number of active users show that KS offers a significantly improved performance over the previous reported techniques by accommodating additional 30 users with shorter code length and smaller code weight at BER of 10 −9. In variable weight system, we have shown that KS codes with larger weight always have the best performance when other users of different weights are present in the system.