Reflective Electroabsorption Modulators for beyond 25 Gb/s Colorless Transmissions

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- and 150-μm long EAMs, are fabricated and characterized in both static and dynamic modes. The frequency response of the 80 μm long EAM is still flat at 26.5 GHz (setup upper limit) whereas the 150 μm long EAM exhibits a 3-dB cutoff bandwidth of 23 GHz. A zero-chirp is achieved for EAM reverse bias voltages between -1.2 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 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 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 and 16 km colorless transmissions in the C-band (between 1530 and 1545 nm) over a standard single-mode fiber without equalization using the 150- and the 80 μm EAMs, respectively, with 4.5 and 2.5 dB dispersion penalties at a bit error rate of 10-3.