Elsevier

Optik

Volume 146, October 2017, Pages 1-7
Optik

Original research article
An approach for realistic estimation of BER due to signal-component crosstalk in a WDM receiver

https://doi.org/10.1016/j.ijleo.2017.07.066Get rights and content

Abstract

In this paper, an approach is proposed to estimate the Bit Error Rate (BER) in a Wavelength Division Multiplexing (WDM) receiver with component crosstalk considering all possible bit combinations in the interfering channels instead of the usual worst-case approach. In addition, probability density function (pdf) and bit error rate (BER) with finite interferers are studied using a new mathematical formulation based on Maclaurin series expansion of the N-th power of zero order Bessel Function. This analysis results in more realistic estimation of BER and optimum detection threshold for minimum BER than that obtained using worst-case study. The improvement in accuracy of estimation of BER with the present approach over the worst-case approximation approach is more for higher crosstalk level and large number of interfering channels.

Introduction

Wavelength Division Multiplexing (WDM) which increases spectral efficiency of the fiber-optic transport system, has major impact on the evolution of high transmission network [1], [2]. To ensure this high efficiency, transparency and isolation to different bit rates and data formats are necessary through all optical components in a WDM link. In practice, due to non-ideal performance of optical nodes, such as wavelength selection and switching devices, the complete isolation between the wavelength channels are not achieved and this leads to crosstalk. Thus, the quality of the obtainable optical signal at the receiving end is degraded and, hence, the bit error rate (BER) is increased [3], [4], [5]. In case of linear crosstalk, depending on the optical filters two types of crosstalk are possible: ‘in-band’ and ‘out-band’ according to the spectral location of crosstalk signal inside or outside the optical pass band. The limitation in system performance is mainly delivered by in-band crosstalk which is also known as component crosstalk. A schematic diagram of an optical network configuration with possible origins of component crosstalk is shown in Fig. 1(a). In case of a WDM system, Component crosstalk is considered as one of the most severe physical impairments because this phenomenon consists multiple interfering signals which have the same nominal wavelength as the desired signal and cannot be eliminated through filtering [5], [6]. Several literatures [5], [6], [7], [8], [9], [10], [11], [12], [13] report the instance of this crosstalk, where the estimation of BER is done by usual worst-case approximation considering all the interfering channels to be effective (i.e. at ‘1′ state) simultaneously. In few approaches [7], [8], [11] the calculation of BER is based on some mathematical approximations also, which lead to unrealistic estimation of BER.

In this paper, a study on the effect of component crosstalk on the performance of a WDM receiver is carried out following a new approach to estimate the BER where all possible bit combinations in the interfering channels are considered and this leads to a more realistic estimation of BER. Furthermore in presences of multiple interfering channels, exact mathematical expression of probability distribution function (pdf) and BER is presented, which is examined and analyzed as a function of detection threshold assuming both small and large number of interfering channels. The remaining sections of this paper are organized as follows. In section II, the mathematical formulation of BER is discussed. In section III, the results of the analysis are given and finally, conclusion is given in section IV.

Section snippets

Mathematical formulation of BER

In the present analysis the realistic estimation of BER is shown considering a direct detection On-Off Keying (OOK) receiver as an example. The schematic of receiver configuration, as shown in Fig. 1(b), comprises of optical amplifier, optical filter, photodiode, receiver filter, sample & hold and comparator. The output of the receiver filter triggers the sample & hold device and comparing the successive values from sample & hold with a fixed threshold (d) completes the detection process.

Results and discussions

Using the expressions presented in the previous section, the bit error rate is calculated as a function of different parameters. In Fig. 3, BER is plotted as a function of input power to compare the data of present model with the experimental data taken from literature [5] and a very good agreement is found. The study also shows a better match with this realistic approach using (14) than with the worst-case approach for analysis given by (17). In Fig. 4, BER is plotted as a function of

Conclusion

A new approach is presented for the first time for realistic estimation of bit error rate in a WDM receiver in presence of component crosstalk, considering all possible combinations of bits in interfering channels. The approach results in a new formula to estimate realistic BER which does not incorporate any approximation within calculation. The estimated BER using present model shows better agreement with the experimental data than that using worst-case analysis. Overestimation of BER using

Pinakpani Mukherjee is presently an Assistant Professor in the Academy of Technology, MAKAUT, West Bengal. He is currently pursuing his Ph.D. work in Institute of Radio Physics and Electronics, University of Calcutta, and his field of research is on the performance studies of WDM receiver systems in presence of crosstalk and receiver noise.

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Pinakpani Mukherjee is presently an Assistant Professor in the Academy of Technology, MAKAUT, West Bengal. He is currently pursuing his Ph.D. work in Institute of Radio Physics and Electronics, University of Calcutta, and his field of research is on the performance studies of WDM receiver systems in presence of crosstalk and receiver noise.

Santu Sarkar (M05, SM10-) was born in Bally, West Bengal, India, on January 4, 1975. He received his B.Sc. (Hons) degree in physics from Calcutta University, Kolkata in 1995 and B.Tech, M.Tech and Ph.D. degrees in Radio Physics and Electronics, University of Calcutta, Kolkata, India, in 1998 and 2000, respectively. From 2000–2004, he was working as a Lecturer in Asansol Enginering College, University of Technology, West Bengal. In August 2004, he joined in the Academy of Technology, University of Technology, West Bengal, as a Lecturer, where he is currently an Assistant Professor and Head of the Department of Electronics and Communication Engineering. His field of research is on the performance studies of WDM receiver systems in presence of crosstalks and receiver noise. He published some of his work in international journals and conferences. He has served actively on holding National and International Conferences in various capacities. Mr. Sarkar is a recipient of the National Scholarship based on his academic performance in the undergraduate course (Physics Hons.). He is a Senior member of the IEEE Photonics Society.

Nikhil Ranjan Das received his B.Sc. (Hons.) degree in physics from Krishnath College, University of Calcutta, India, in 1982, B.Tech. and M.Tech. degrees in radio physics and electronics in 1985 and 1987, respectively, and the Ph.D. degree in 1993, respectively, all from the University of Calcutta. During 1993–1994, he was a Senior Project scholar in a project sponsored by the Ministry of Human Resources and Development of India. He then joined the Department of Radio Physics and Electronics, University of Calcutta, as a full-time Lecturer in 1994, as a Senior Lecturer since 1998, where he is currently a Professor. He served as the Dean, Faculty for Post Graduate Studies in Engineering & Technology, and also the Head of the Department of Radio Physics & Electronics, University of Calcutta. He is presently the Director, Centre for Research in Nanoscience and Nanotechnology (CRNN) of the University of Calcutta. His research interests include semiconductor nanostructures and optoelectronic/photonic devices towards their design, simulation and optimization studies. He spent nearly 3 years (1999–2002) in the Department of Electrical and Computer Engineering, McMaster University, Hamilton, Ontario, Canada as a Post-Doctoral Fellow and later as a Post-Doctoral Research Associate. He visited Trieste, Italy as a Senior Guest Scientist in Nov. 2004, the McMaster University, Canada in May-July 2005, the University of Sheffield, UK in August/Sep. 2008, and Pohang University of Science & Technology (POSTECH), Korea during Aug.-Nov., 2010, etc. as Visiting Professor. Dr. Das was a recipient of National Scholarship. He is a Fellow of the IE(I), Fellow of the IETE, a Senior Member of IEEE, and Life Member of the Indian Physical Society and the Indian Association for the Cultivation of Science. He has been the reviewer of several IEEE, IET and other journals. Dr. Das has been the founder Chair of LEOS (presently, PHOTONICS Society) Calcutta Chapter, and also presently the Chapter Chair. He is also the Student Branch Counselor of the IEEE Calcutta University Student Branch.

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