Wavelength Division Multiplexing/optical Code Division Multiplexing Research Articles

Particle swarm optimization in WDM/OCDM networks with physical impairments

In this paper, optimization procedures based on particle swarm optimization (PSO) are investigated, aiming to efficiently solve the optimal resource allocation for signal-to-noise plus interference ratio (SNIR) optimization of optical code paths (OCPs) from wavelength division multiplexing/optical code division multiplexing (WDM/OCDM) considering imperfections on physical layer. The characteristic of the PSO is attractive due their performance-complexity tradeoff and fairness regarding the optimization methods that use numerical methods, matrix inversion and other heuristics. The SNIR model considers multiple access interference (MAI) between the OCP based on 2-D codes (time/wavelength), amplifier spontaneous emission (ASE) at cascaded amplified spans, and group velocity dispersion (GVD) and polarization mode dispersion (PMD) dispersion effects. The numerical results have revealed the viability of the PSO algorithm considering solution quality and convergence. Besides, the numerical results have shown a penalty when the ASE, GVD and PMD effects are considered.

Uplink transmission of a 60-km-reach WDM/OCDM-PON using a spectrum-sliced pulse source

We propose and experimentally demonstrate the uplink transmission of a 60-km-reach wavelength division multiplexing/optical code division multiplexing (WDM/OCDM) passive optical network (PON) using a spectrum-sliced pulse source. As a single light source, a broadband pulse source with a bandwidth of 6.5nm and a repetition rate of 1.25GHz is generated at a central office and supplied to a remote node (RN) through a 50-km fiber link. At the RN, narrow-band pulses (as a source for uplink transmission) are obtained by spectrum slicing the broadband pulse source with a cyclic arrayed waveguide grating and are then supplied to all optical network units (ONUs) via 1×4 power splitters and 10-km drop fibers. Eight wavelengths are obtained with a 6.5-nm bandwidth of the broadband pulse source, and the qualities of the pulses with a repetition rate of 1.25GHz and a pulse width of 45ps for the eight wavelengths are sufficient for four-chip OCDM encoding at the ONUs. In our experiments, four signals are multiplexed by OCDM at one wavelength, and another encoded signal is also multiplexed by WDM. The bit error rates (BERs) of the signals exhibit error-free transmission (BER<10−9) over a 60-km single-mode fiber at 1.25Gb/s.

Upstream Transmission of WDM/OCDM-PON in a Loop-Back Configuration With Remotely Supplied Short Optical Pulses

We propose and experimentally demonstrate upstream transmission in a wavelength division multiplexing/optical code division multiplexing (WDM/OCDM) passive optical network (PON) without using any high-cost devices such as mode-locked lasers or LiNbO3 external modulators. To make optical network units (ONUs) simple, a loop-back transmission of short optical pulses for OCDM in upstream transmission was investigated. The quality of the short optical pulses, remotely supplied via 23 km of single-mode fiber (SMF), was sufficient for 4-chip OCDM encoding at the ONUs.2WDM/4OCDM signals, generated by multiplexing four OCDM signals using the same wavelength as well as another signal with a different wavelength, showed error-free transmission (bit error rate BER <; 10-9) over a 23 km SMF at 1.25 Gb/s.

Impact of the MAI and beat noise on the performance of OCDM/WDM Optical Packet Switches using Gold codes

Recent advances in optical devices greatly enhance the feasibility of Optical Code Division Multiplexing/Wavelength Division Multiplexing (OCDM/WDM) Optical Packet Switch. In this paper, the performance of an OCDM/WDM switch is investigated when impairment due to both Multiple Access Interference and Beat noise are taken into account. Analytical models are proposed to dimension the switch resources as the number of optical codes carried on each wavelength and the number of needed optical converters. The Packet Loss Probability due to output packet contentions is evaluated as a function of the main switch and traffic parameters when Gold coherent optical codes are adopted. When the available bandwidth is fixed for the WDM/OCDM signal, due to a statistical multiplexing effect, we show that the use of more length codes and fewer wavelengths lead to lower packet loss probability, especially for low offered traffic.

Design of multi-rate optical code paths considering polarisation mode dispersion limitations

The authors propose an original design based on multi-rate optical code paths (OCPs) for transport in advanced wavelength-division multiplexing/optical code division multiplexing (WDM/OCDM) networks. The authors utilise multi-length optical orthogonal codes (OOC) to obtain multi-rate OCPs. The performance of the proposed scheme is analysed and the impact of multiple access interference (MAI) and polarisation mode dispersion (PMD) over these OCPs is evaluated. Results show that not only multi-rate operation can be achieved but also MAI effects can be reduced, while mitigating PMD effects.

Performance analysis of optical code switching router

AbstractIn this work we study and evaluate the performance of an optical code switching router (OCSR), intended to be utilised in hybrid wavelength‐division multiplexing/optical code‐division multiplexing (WDM/OCDM) networks. This OCSR can transport and route efficiently user data over optical code paths without departing from the optical domain. Limitations of the proposed OCSR are investigated and its superior performance demonstrated based on non‐coherent prime codes. Our results indicate that our solution is useful in showing the effects of the optimum threshold level on the OCSR performance. We propose a continuous adjustment of the optimum threshold level based on the measurement of the mean optical power before the decoder. The influence of various parameters of the optical codes on the OCSR performance are also considered and evaluated. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Analysis of the blocking performance of hybrid OCDM‐WDM transport networks

AbstractThis study focuses on the blocking performance of hybrid optical code‐division multiplexing wavelength‐division multiplexing (OCDM‐WDM) networks under dynamic traffic conditions. Novel lightpath concepts for those hybrid networks are introduced. Simulation of the blocking performance for different lightpath concepts indicate that networks upgraded with wavelength converters offer the best performance. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 61–68, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10374