Effects of Ellipticity Angle on Modulation Instabilities in Birefringent Optical Fibers**Supported by the National Natural Science Foundation of China under Grant Nos. 11447113 and 11305031, Natural Science Foundation of Jiangsu Provincial Universities under Grant No. 14KJB140009, and the Startup Foundation for Introducing Talent of Nanjing University of Information Science and Technology under Grant No. 2241131301064

Abstract

Previous studies on modulation instabilities (MIs) in birefringent optical fibers focus on the ordinary linearly and circularly ones. This paper reports an analysis of MIs in the general elliptically birefringent fibers with the emphasis on investigating the effects of ellipticity angle (0° ≤ θ ≤ 90°). Both symmetric and antisymmetric CW states are considered. In the anomalous dispersion regime, for the symmetric (antisymmetric) CW states, we show that MI gain increases dramatically (reduces first and then enhances greatly) as the increment of θ. In the normal dispersion regime, for the both CW states, the distinctive feature is that the gain of the MI bands reduces first, vanishes at θ = 45°, reappears across this ellipticity angle, and quickly increases after then.