A 4 GB S 2-LEVEL TO 2 GSYMBOL/S 4-LEVEL CONVERTER GAAS IC FOR SEMICONDUCTOR OPTICAL AMPLIFIER QPSK MODULATORS/

The design of a 50 Omega impedance matched two-to-four level converter GaAs IC for two-electrode semiconductor optical amplifier (SOA) modul ators is presented. The designed IC exhibits eye diagrams with eye ope nings of better than 0.30 V and a spacing between adjacent output sign al levels of 0.33 V for output symbol rates of up to 2 Gsymbol/s corre sponding to input bit rates of up to 4 Gb/s. A novel differential supe r buffer output driver is applied, for which output reflection coeffic ients \S-22\ Of less than -12 dB for frequencies up to 10 GHz are obta ined. A 1 Gb/s optical QPSK microwave link transmission experiment usi ng a packaged sample of the designed IC and a two-electrode semiconduc tor optical amplifier phase modulator has been conducted.