Reflective Electroabsorption Modulators for Beyond 25 Gb/s Colorless Transmissions

Abstract

We present a complete characterization of reflective electroabsorption modulators (EAMs) monolithically integrated with semiconductor optical amplifiers (SOAs), components that are capable of operating beyond 50 Gb/s in the C-band. The devices are based on GaInAsP multiple quantum wells on InP substrate, leveraging semi-insulating buried heterostructure waveguide definition and butt-joint integration technologies. Different device configurations, based on 80-m and 150-m long EAMs, are fabricated and characterized in both static and dynamic modes. The frequency response of the 80-m long EAM is still flat at 26.5 GHz (setup upper limit) whereas the 150-m long EAM exhibits a 3-dB cutoff bandwidth of 23 GHz. A zero-chirp is achieved for EAM reverse bias voltages between 1.2 V and 1.5 V depending on the wavelength. Under large-signal modulation, the frequency chirp induced by the shorter EAM is almost half that of the longer EAM, with their respective peak values being +1.5/2 GHz and +3.2/3.7 GHz (rising/falling edges) at 1545 nm (1.3 V bias, 2.6 V voltage swing). We obtained high dynamic extinction ratios of ~14.5 dB and ~8 dB from the longer and the shorter EAMs, respectively, when they are operated at 25 Gb/s using non-return-to-zero coding. Finally, we achieved 12 km and 16 km colorless transmissions in the C-band (between 1530 nm and 1545 nm) over a standard single-mode fiber without equalization using the 150-m and the 80-m EAMs, respectively, with 4.5 dB and 2.5 dB dispersion penalties at a bit error rate of 10³.