Mohammad M. N. Hamarsheh

Design and analysis of a dynamic code division multiple access communication system based on tunable optical filter

A dynamic optical code division multiple access (DOCDMA) communication system is proposed for high-bandwidth communication systems. An implementation of the system is proposed based on a fast tunable optical filter (TOF) in each encoder and decoder. This technique actively modulates the central wavelength of a TOF according to a functional code at the transmitter during the bit period before the transmission of the data. The system is modeled and analyzed taking into account multiple access interference (MAI), thermal noise, and phase-induced intensity noise (PIIN). The performance of this system is compared to that of a spectral amplitude coding system that uses either a Hadamard code or a modified quadratic congruence (MQC) code. The results show that the proposed DOCDMA system reduces the PIIN effect on the performance of the system and improves the bit error rate (BER) performance at a large number of users. Furthermore, it is found that when the effective power is large enough, the MAI becomes the main factor that limits system performance, whereas when the effective power is relatively low, both thermal noise and PIIN become the main limiting factors with thermal noise having the main influence.

Analytical comparison of optical code-division multiple-access systems with and without a successive interference cancellation scheme using modified prime-sequence codes

We analyzed direct-sequence code-division multiple-access system using a successive interference cancellation (SIC) scheme. Modified prime-sequence codes are utilized as signature sequences, and the performance measure studied in this paper takes into account the the effect of imperfect interference cancellation. The basic principle of the SIC scheme is to subtract the strongest received signals from the original signal one by one till all users have been detected and demodulated. In this analysis we have compared optical code-division multiple-access systems with and without the cancellation scheme, and it is shown that the SIC scheme with −20-dBm effective power can suppress multiple-access interference better than the system without cancellation.

Tunable fiber Bragg grating phase shift by simple pressure packaging

Abstract. An accurate fiber Bragg grating (FBG) phase-shift tuning system is proposed and demonstrated. It depends on a localized pressure applied to a specially packaged FBG filter using an accurate micrometer single-axis stage. Continuous range of phase shift from 0 to π is achieved with linear relation to the stage position. An acceptable degree of repeatability of the process is noticed in the experiment.

Proposal of successive interference cancellation scheme in optical code-division multiple access systems

Proposes one of the multiuser detection schemes, a new technique that has the potential to reduce interference or suppress multiple-access interference and, therefore, increase the capacity of optical code-division multiple access (CDMA) systems. It is a successive interference cancellation (SIC) scheme known as a low-complexity multiuser detection method for direct sequence CDMA systems. A SIC scheme is analyzed using an optical orthogonal code, with a different power for each user, that takes into account the impact of imperfect interference cancellation.

Performance enhancement of successive interference cancellation scheme based on spectral amplitude coding for optical code-division multiple-access systems using Hadamard codes

A successive interference cancellation scheme is applied to optical code-division multiple-access OCDMA systems with spectral amplitude coding SAC. A detailed analysis of this system, with Had- amard codes used as signature sequences, is presented. The system can easily remove the effect of the strongest signal at each stage of the cancellation process. In addition, simulation of the prose system is per- formed in order to validate the theoretical results. The system shows a small bit error rate at a large number of active users compared to the SAC OCDMA system. Our results reveal that the proposed system is efficient in eliminating the effect of the multiple-user interference and in the enhancement of the overall performance.

Design and analysis of a dynamic spectral encoding code-division multiple-access communication system

An optical dynamic spectral encoding code division multiple access (CDMA) communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. Two-dimensional code, named functional code, is also proposed based on a shifted sine function. The function defines the dynamic coding pattern of the central wavelength of the transmitted narrowband optical signal. Thus, the system will allow for an easy reconfiguration of the transmitter without the need for a sophisticated encoder. At the receiver, a synchronized TOF with the same function is used as a decoder. The system is modeled and analyzed taking into account the multiple access interference, phase-induced intensity noise (PIIN), and thermal noise. The performance of this system is shown to be better compared with a fast frequency hopping (FFH) system and a spectral amplitude coding (SAC) system that uses either a Hadamard code, a modified quadratic congruence (MQC) code, or a modified frequency hopping (MFH) code.