Enhanced structure of a double-pass erbium-doped fiber amplifier for multiple wavelength amplifications.

We demonstrate an enhanced double-pass erbium-doped fiber amplifier for multichannel amplification. The multichannel selection is formed by combining a demultiplexer and a multiplexer together in the fiber-loop mirror. The structure is able to filter out the amplified spontaneous emission that saturates the amplifier gain in the small signal regime. The maximum average gain of 47.2 dB is obtained with a gain enhancement of 12.8 dB at a -50-dBm signal power per channel. The noise figure penalty is almost negligible for a signal power per channel of less than -15 dBm

High-gain erbium-doped fiber amplifier incorporating a double-pass amplification technique as a preamplifier

We present a high-gain erbium-doped fiber amplifier to be utilized as a preamplifier. A double-pass amplification technique is used in the first-stage amplifier together with a tunable bandpass filter. The secondstage amplifier is a counter-pumped configuration and another tunable bandpass filter is utilized to filter out amplified spontaneous emission from the first-stage amplifier. This design is able to produce a high gain of 55.6 dB and a noise figure of 6.02 dB at 1530 nm with a signal power of −45 dBm. The receiver sensitivity measurement shows that the proposed amplifier improves the minimum detectable power from −33.7 to −40.8 dBm for a bit-error rate of 10−11 at 155 Mbps

Performance of ultra-wideband systems in the presence of WiFi and 3G signals

An analysis of the power spectral density of ultra-wideband (UWB) signals is presented in order to evaluate the effects of cumulative interference from multiple UWB devices on victim narrowband systems in their overlay bands like WiFi (i.e. IEEE802.11a) and 3rdG systems (Universal mobile telecommunications system/wideband code division multiple access). In this paper, the performances are studied through the bit-error-rate as a function of signal-to-noise ratio as well as signal-to-interference power ratio using computer simulation and exploiting the realistic channel model (i.e. modified Saleh-Valenzuela model). Several modifications of a generic Gaussian pulse waveform with lengths in the order of nanoseconds were used to generate UWB spectra. Different kinds of pulse modulation (i.e. antipodal and orthogonal) schemes were also taken into account

Performance and cost comparisons for A-PON and S-PON FTTH systems

The high cost of fibers has always been a main concern as to why they have not been deployed in access networks. As the fiber technology is maturing, the costs fibers are slowly decreasing, and hence the above issue is no longer an issue. This paper discusses the performance comparison of A-PON and S-PON FTTH architecture as well as its cost. It is established that the relationship between the fiber span and distributed area offered by S-PON is due to the power enhancement boosted by an amplifier. Meanwhile the cost of S-PON will be reasonable if there are enough users sharing the same feeder line or transmission path

Performance analysis of ultra-wideband system in presence of IEEE802.11a and UMTS/WCDMA frequency bands

In order to evaluate the effects of cumulative interference from multiple UWB devices to victim narrowband systems (i.e. IEEE802.11a and UMTS/WCDMA) in its overlay band, an analysis on the power spectral density (PSD) of UWB signal is presented. In this paper, the performances are studied through the bit-error-rate as a function of signal-to-noise ratio as well as signal-to-interference power ratio using computer simulation exploiting realistic channel model (i.e. modified Saleh-Valenzuela (S-V) model). Several modifications of a generic Gaussian pulse waveform with a length in the order of nanoseconds were used to generate UWB spectra. Different kinds of pulse modulation (i.e. antipodal and orthogonal) schemes have been also taken in account

Double-pass chirped Bragg grating erbium-doped fiber amplifier: improved transmission distance

The paper discussed on experimental result that improve the transmission distance by use of an integrated dispersion compensated double-pass erbium-doped fiber amplifier (DPC-EDFA). The chromatic dispersion compensation is achieved using chirped fiber Bragg grating as part of the EDFA design. The eye-pattern, eye-opening and timing jitter obtained using this technique shows an improvement equivalent to the distance of about 50km compared with the conventional double-pass EDFA (DP-EDFA)

Integrating RLP and Fast Zero algorithm to improve routing performance in optical multistage interconnection networks

In this paper, we explore the idea of integrating the Remove Last Pass (RLP) algorithm to the Fast Zero (FastZ) algorithm as the prior initial solution to improve routing performance in optical multistage interconnection networks (OMINs). OMINs are popular for its cost-effectiveness and self-routable characteristics to meet the demand for high speed switching capability. A great challenge in dealing with OMINs is the optical crosstalk caused by optical signal coupling when propagating through the switching elements comprising the architecture. Many algorithms have been developed to solve optical crosstalk using different approaches. The new Fast Zero with RLP (FastRLP) algorithm is developed based on the time domain approach for solving optical crosstalk in the optical Omega network. Simulation results have shown that integrating RLP to FastZ algorithm successfully improved routing performance

Fast ZeroY algorithm for efficient message routing in optical multistage interconnection networks

Limited by the properties of optical signals, it is not possible to route more than one message simultaneously, without optical crosstalk, over a switching element in an Optical Multistage Interconnection Networks (OMINs). One solution, called the time domain approach, avoids optical crosstalk by arranging the permutation in such a way that a set of crosstalk-free connections can be established and each connection set be made active in different time slots. Based on the Zero algorithms, we proposed a fast and efficient crosstalk-free algorithm for message routing in optical Omega multistage networks. The Bitwise Window Method (BWM) is used to identify potential message conflicts that may further lead to optical crosstalk. In addition, the inverse Conflict Matrix (iCM) is used to map identified conflicts between messages in the network. It is shown that the new algorithm successfully improved the execution time in comparison to the original Zero algorithm

A fast and efficient crosstalk-free algorithm for routing in optical multistage interconnection networks

In this paper, a fast and efficient crosstalk-free routing algorithm is proposed to enhance message routing in optical multistage interconnection networks (OMINs). The new Fast ZeroXY algorithm is designed based on the Zero algorithms, which uses the time dilation approach to eliminate the negative effect of crosstalk associated with optical switching in the optical Omega network. To evaluate the performance of the new algorithm, a crosstalk-free version of the original ZeroXY algorithm is developed extended from the Improved ZeroXY algorithm, called the Modified ZeroXY algorithm. The Fast ZeroXY algorithm is shown to efficiently route permutations without crosstalk with improved routing time compared to the original crosstalk- free ZeroXY algorithm

Public facilities and human wellbeing in the context of Maqasid al-Shari’ah

Public facilities are one of the most important land use categories in town planning. It transcends basic human needs that contribute to the overall liveability and wellbeing in its human welfare sense. The provision of public facilities somehow realizes the Maqasid al-Shariah (the objectives of Islamic law) that is to preserve the maslahah (benefits) for humankind. This study examines seven types of public facilities in Malaysia against the five essentials of Maqasid al-Shari’ah namely faith, self, intellect, posterity, and wealth. Hence it is exploratory in nature adopting the content analysis and interview with several experts from planning and Islamic background to match the public facilities provided in the plans with the Maqasid al-Shari’ah principles. The conclusive findings are that the provision of public facilities is very much conceptually related to the Maqasid al-Shari’ah. This approaches simultaneously provides an insight to the policy makers on the level of importance of the five essentials and the need to fulfill each one of them to ensure balanced provision and enjoyment of the public facilities. This also shows all those objectives of Islamic Law that should take into considerations in planning and this have been highlighted by Malaysian Government through their effort to develop the Maqasid al-Shari’ah Index to measure the “Islamicity” of the country