Abstract

Polarization-independent modulators may happen to be key devices for a practical implementation of soliton systems. For instance, the use of an in-line electroabsorption modulator in a 20-Gbit/s soliton system allowed to increase the amplifier spacing to 140 km.¹ However pigtailing these modulators still pertains to the laboratory because of small spot-size. Increasing spot-size would decrease the optical confinement and thus the electroabsorption efficiency. Integrating spot-size converters should maintain efficiency, ease pigtailing, and bring more stability in a repeater environment. Up to now, very few attempts of converter-electroabsorption modulator integration have been reported. Integration of beam expanders on a switch ineluding electro-refractive couplers has been previously demonstrated with a 2-GHz bandwidth.² Koren et al., described an electroabsorption modulator integrated with spot-size converters.³ It however suffered from optical leakage degrading the extinction ratio.³ No bandwidth was given. Speed is yet an important parameter because the frequency response is very sensitive to the parasitic capacitance of the taper region and to the waveguide modulator structure. We report here on an electroabsorption modulator integrated with simple spot-size converters, preserving polarization independence and without speed degradation.

© 1996 Optical Society of America