Limitation Imposed by Polarization-Dependent Loss on a Fiber Optic Communication System Farhan Hussain and M.S.Islam Abstract Analytically the effect of polarization dependent loss on a high speed fiber optic communication link has been investigated. significant co-relation between them and their various combinations produces different effects on the system behavior which has been together to observe the attenuation effect induced by PDL in a link containing multiple PDL elements. It is found that in the presence of PDL the Q-factor and BER at the receiver undergoes fluctuation causing the system to be unstable and results show that it is mainly due to optical signal-to-parallel-noise ratio (OSNR par ) that these parameters fluctuate. Generally the Q-factor, BER deteriorates as the value of average PDL in the link increases except for depolarized light for which the system parameters improves when PDL increases. Keywords Bit Error Rate (BER), Optical-signal-to-noise ratio (OSNR), Polarization-dependent loss (PDL), State of polarization (SOP). I. INTRODUCTION S the network bandwidth is increased, either by increasing modulation rates or by multiplexing channels in wavelength or time domain, performance begins to suffer as a result of the detrimental effects produced by polarization- dependent loss. So PDL has become an important parameter in -haul fiber-optic communication systems. PDL mainly occurs in optical components, such as isolators and couplers, whose insertion loss is dependent on the polarization states of input signals. When many PDL elements are linked together by optical fibers, the end-to-end transmission properties in terms of total PDL and insertion loss become statistical quantities [1]. In practice, spontaneous emission noise is generated by optical amplifiers along the link which then becomes partially polarized and fluctuates due to PDL concatenation. The fluctuation of noise, signal power and the global attenuation due to global PDL [2] all affect the quality of the transmitted signal. In previous papers the effect on signal concerned with attenuation due to PDL were analyzed by using simulations. Here the same attenuation pattern in a link containing multiple PDL elements is obtained erators and PDL parameters. Similarly many facts were drawn from the behavior of the system parameters of an optical communication link with PDL in the Farhan Hussain is an M.Sc Engg student in the Institute of Information and Communication Technology, Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh (email:farhusengg@gmail.com). M.S.Islam is an Associate Professor in the Institute of Information and Communication Technology, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh ( email: mdsaifulislam@iict.buet.ac.bd) previous papers [3],[4]. Here some new findings regarding OSNR, Q-factor, BER and their relation with average PDL of the link has been acquired. II. THEORETICAL ANALYSIS A. Derivation of Attenuation Equations In the process of relating the Pauli spin operators to PDL parameters [5] a relationship has been derived describing the transmission co-efficient which is given below, (1) is the loss co-efficient, is an unit vector in Stokes space and points in the direction of maximum transmission.The transmission depends not only on the loss co-efficient of PDL to the incoming state of polarization . From (1) it is found that for a particular value of T p is maximum when ) is maximum i.e. )=1 and T p is minimum when ) is minimum i.e. )=-1.So the following is acquired, So by simplifying the above equations the following is obtained, =T max =1 (2) =T min = (3) When the input is completely depolarized, the transmission is averaged over all polarization states. In case of completely depolarized situation, ) =0 i.e. orientation of the PDL is perpendicular to the incoming state of polarization . (4) The global PDL or the cumulative PDL over a concatenation is also known as normalized loss co-efficient. The relation between normalized co-efficient and the transmission extrema is, = (5) In Fig.1 a signal is transmitted through an optical fiber having n PDL elements including the optical fiber. The PDL A World Academy of Science, Engineering and Technology International Journal of Electronics and Communication Engineering Vol:4, No:8, 2010 1244 International Scholarly and Scientific Research & Innovation 4(8) 2010 scholar.waset.org/1307-6892/1698 International Science Index, Electronics and Communication Engineering Vol:4, No:8, 2010 waset.org/Publication/1698