Optical Communication : Optimising negative chirp of an electroabsorption modulator for use in high-speed optical networks

The original article can be found at: http://www3.interscience.wiley.com Copyright John Wiley & Sons, Ltd. [Full text of this article is not available in the UHRA]Optical networks using singlemode fiber rely on negative chirp to improve the transmission performance. In particular for an electroabsorption modulator (EAM) optimal chirp control is required when it is used to achieve various network functions in high-speed optical networks. An approach to modelling the negative chirp for the EAM is presented that is suitable to apply to a cross-absorption modulation scheme. A novel feature of this modelling process is that it allows cubic polynomials to incorporate the nonlinear coefficients of chirp describing the α-parameter related to the nonlinear transmission coefficients. In addition to the two-tone signal parameters (i.e. bias and modulating signal voltages), the model also includes wavelength-temperature-dependent absorption variation and the effects associated with the length of the device. It therefore enables accurate determination for the values of the nonlinear coefficients of the chirp responsible for the negative chirp of an EAM. Using this model an optimised range of ± 0.5 is obtained for the nonlinear coefficients of the chirp to exhibit negative chirp for specific values of nonlinear transmission coefficients (within a range of −10 and 2) at a reverse bias voltage of less than 2 V. Since negative chirp optimisation of an EAM can minimise the unwanted effects of dispersion on a singlemode fiber in high-speed optical networks an improvement of performance without employing expensive dispersion compensation management techniques can be achieved. Copyright © 2006 AEITPeer reviewe

Optical Fiber Communications : Principles and Practice

Full text of this book is not available in the UHRA

Chirp control of an electroabsorption modulator to be used for regeneration and wavelength conversion at 40 gbit/s in all-optical networking

Copyright 2008 Elsevier B.V., All rights reserved.Chirp control to produce low or negative values of chirp at the output of an electroabsorption modulator ( EAM) is an important mechanism for reducing the signal degradation due to chromatic dispersion in high- speed transmission over standard single- mode fibre. An analytical model for the chirp performance of an EAM capable of optical regeneration and simultaneous wavelength conversion operating at 40 Gbit/ s is derived. A chirp control approach is identified using this model by exploring the tradeoff between the alpha- parameter describing the chirp factor ( based on the nonlinear absorption coefficients) and bias voltage requirements of an EAM. In particular, an optimum range of bias voltage is determined to ensure reduced chirp operation when a two- tone signal ( i. e., comprised of bias and modulating voltages) is applied to the EAM. It is also demonstrated for large signal operation at 40 Gbit/ s that the optimum range of reverse bias voltage is between 0 and 2V to obtain low values for the chirp factor ( between + 1 and - 2) in order to facilitate the necessary chirp control in all- optical networking. In addition, it is identified that at 40 Gbit/ s higher positive values of the second- and third- order nonlinear coefficients of chirp must be avoided when operating at reverse bias voltages less than 1V.Peer reviewe

Minimization of amplified spontaneous emission noise in upstream SuperPON 512 ONU, 10 Gbit/s

We demonstrated the effect of presenting optical band pass filter for point to multipoint architecture such SuperPON. The position of optical filter and the range of optical filter bandwidth to minimise amplified spontaneous emission noise for upstream SuperPON with 512 ONU at transmission speed of 10 Gbit/s will also be explore

Optical amplifier number and placement in the SuperPON architecture

Three alternative optically amplified long reach, wide splitting ratio PON (SuperPON) amplifier placement strategies (i.e architectural configurations) are modelled using the Virtual Photonic Integration (VPI) simulation package. In particular optical power budgetary analysis is carried out on three SuperPON dimensions of 100 km, 110 km and 130 km for the three configurations with the range of splitting ratios from 256 to 131,072 optical network units (ONUs). From the simulations the optimum placement and the minimum number of optical amplifiers required for SuperPON architecture is determined and graphical data is discussed in relation to the different network sizes and dimensions. Using this approach it is demonstrated that a single amplifier is sufficient to provide for up to 1,024 ONUs and that this number increases to six amplifiers with three in cascade to service 131,072 ONUs

Modified ShuffleNet for Multihop All-Optical WDM Networks Employing Wavelength Reuse

Copyright 2004 Elsevier Science B.V., Amsterdam. All rights reserved.A modified multihop ShuffleNet configuration for WDM all-optical networks is described which is rearrangeable and allows wavelength reuse at each node as it expands. This configuration does not require any rearrangement of preceding node and wavelength assignments when new nodes and wavelengths are added and it can function with fewer overall number of nodes. By comparison, the traditional Perfect ShuffleNet requires a large number of nodes to be available for any updating of the configuration. Most of these nodes remain idle during the normal signal routing process leading to reduced network link capacity. Furthermore, to facilitate wavelength reuse when updating, the Perfect ShuffleNet necessitates the rearrangement of preceding node and wavelength assignments. This leads to generalized forms of ShuffleNet where wavelength reuse forces network architecture into irregular topologies. The modified ShuffleNet proposed here is capable of facilitating wavelength reuse without the modification of initial node and wavelength assignments and could be realised by using a star topology.Peer reviewe

Modeling Chirp and Phase Inversion in Wavelength Converters based on Symmetrical MZI-SOAs for use in All-Optical Networks

Copyright 2008 Elsevier B.V., All rights reserved.All-optical wavelength conversion based on multi-section semiconductor optical amplifiers (SOAs) in a symmetrical Mach-Zehnder interferometer (SMZI) is modeled for use in optical networks. It incorporates an enhanced SOA model that is implemented using the time domain transfer matrix approach and hence the overall numerical model determines simultaneously the wavelength and gain parameters for the wavelength converter. The overall model accurately predicts the optimal conditions for the SMZI arrangement in order to achieve the best results for the chirp, the phase inversion and the converted probe signal power. It is also demonstrated that large chirp and mismatch of the phase inversion reduces the eye opening ratio (EOR) which can seriously affect the performance of the wavelength converter to be used as a subsystem component in all-optical networks.Peer reviewe

Chirp in a wavelength converter based on a symmetrical-MZI employing SOAs

Copyright 2008 Elsevier B.V., All rights reserved.A wavelength converter based on cross-phase modulation using semiconductor optical amplifiers (SOAs) in a symmetrical MZI is modelled. Since the model of the SOAs considers both amplitude and wavelength-dependent parameters simultaneously it provides an accurate prediction of the peak chirp variation for both inverting and non-inverting converted probe signals. The peak chirp variation and the eye-opening ratio are determined for ITU-T grid wavelength up- and down-conversion and they show a sharp dependence on the injection current of the SOAs. Optimal operating conditions for the wavelength converter are demonstrated in order to achieve nominal chirp on the output signal for either an inverting or non-inverting converted probe signal.Peer reviewe