Influence of if narrow‐band filtering on bit error rates in coherent optical heterodyne CPFSK receiver using variable delay demodulation

Abstract

I n thi.s arricle we discuss a coherenr opiical heierodyne CPFSK recen'er itsing optinium i7ariable delay denloriularion considering ihe effecr of 17arroiv-band IF filtering or inrerrynlhol inrerference (ISI) caused hy it. Firsr n e ini*estigaie ihe error probabiliry af rhe normali:ed handwidrh of IF filter BT = 1 for a Gaussian 1F filler. Numerical resirlts show ihar rhe impact of narrow,-band IFfiliering increases with an increase it1 normalized I F speciral linewidth 1 vT arid a decrease in nioditlaiion index h. Second. in order to decrease ihe impact of ISI. the optitnum BT values are determined. which can minimize the error probabiliiv for given SNR. If a Gaussian IF .filter is used, the optimal BT values are 1.3 for 9vT = 0.254. 1.4 for 1 v T = 0.5% ai h = 0.5, 1.2 for J U T = 0.255. 1.4 for AvT = 0 . 5 9 at h = 0.7, and l..?for all AvT I 0.5% at h = I .Finally, rhe performance of an oprimal receiver emploving optimum Gaussian IF filler is studied. W e knoM. that h = I is optimum and AvT 5 0.5% IS necessary for 1-dB EBIN" penally per bii at BER of lo-'. ' C 1992 John Wilev & Sons. Inc. INTRODUCTON Received 10-25-91; revised 3-25-92Microwave and Optical Technology Letters, 5/9, 442-447 -layer dielectrics with a microstrip feed line in between. The input impedance of the antenna is studied as a function of the patch width, the patch-feed overlap, and the dielectric constants of two layers. 0 1992 John Wiley & Sons, Inc. ABSTRACT An experimental investigalion is carried out into the operation of an electromagnetically coupled (EMC) microstrip patch antenna consisting of double