The Half-t adaptive error correction algorithm for SDH-based WDM optical networks

This paper proposes an adaptive forward error correction (FEC) algorithm, referred to as the Half-t algorithm for synchronous digital hierarchy (SDH) based wavelength division multiplexing (WDM) optical networks. Unlike most previous adaptive FEC algorithms which change to a stronger code for error correction based on either packet losses or erroneous condition, the Half-t algorithm is able to do so before an error occurs. Simulation results show that the Half-t algorithm can maintain the output bit error rate (BER) below a target BER by assigning an appropriate value of waiting delay before changing to a weaker code

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

Towards ternary optical communication by soft decoding

Unlike the conventional 2M level soft decision, a new soft decoding technique is proposed on optical ternary system. It is shown that (852,742,6) code improves at 10 dB coding gain whilst increasing the code efficiency

Web-based network device management using SNMP servlet

As the complexity and size of data networks increases, network management faces a great challenge. Fortunately, the emergence of the SNMP (simple network management protocol) management framework and Web technology release network managers from the difficult circumstance. The paper explains the function and design of a prototype network device management station based on leading-edge Java servlet technologies and the World Wide Web. Web technologies bring valuable cost improvements, flexibility, and security enhancement to configuration management and performance management. The paper also discusses the functional requirements of Web-based network management and proposes the architecture for Web-based network configuration management, which is capable of controlling and monitoring remotely the configuration information of enterprise networks

Optical power limitations in spectral-amplitude- coding optical code-division multiple-access systems due to stimulated Raman scattering

In is paper, the maximum power per chip to keep the Stimulated Raman Scattering (SRS)- induced tilt below a specific level in Spectral-Amplitude-Coding Optical Code-Division Multiple-Access (SAC-OCDMA) is evaluated for different number of users. A number of computer simulations have been conducted for this purpose. It is shown that as number of users grows, the power per chip must be decreased to control the SRS-induced tilt and to keep it below acceptable levels. It is also shown that SRS-induced tilt can significantly limit the power per chip levels when the number of users is large. This is the first time such a study is reported for OCDMA systems

Signal distortion due to stimulated Raman scattering in optical CDMA transmission systems

In this paper, the signal distortion due to stimulated Raman scattering (SRS) in incoherent optical code-division multiple-access (OCDMA) transmission systems is evaluated at different transmission distances. A number of computer simulations have been conducted for this purpose. It is shown that as the total transmit power exceeds Raman threshold level, the SRS will cause severe signal deterioration over long distances even in the absence of the other signal impairment factors

Protection mechanism and deployment cost analysis for Ethernet PON FTTH access network

In this paper, a new protection method for access network is proposed where redundant equipments are not required and protection is provided to end user through sharing of available timeslots during the failure time

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