For 40 Gb/s, make mine a double [double-stage tapered photodiodes]

After describing the design of double-stage tapered photodiodes (DSTPs), the optical simulation method was explained in detail. The calculated responsivity takes into account losses linked to materials and technology, and it is obtained by 2-D modal and 3-D-BPM computations. The modeling was validated by measurements, showing a responsivity as high as 0.6 A/W and low polarization dependence, below 0.2 dB. Exhibiting high-frequency characteristics (>40 GHz) and high-power handling capabilities (> +14 dBm), this component can be used with lensed fiber as well as cleaved fiber without significant penalty. The consequence is that the DSTP is suitable for 40 Gb/s optical transmission requiring performance and radio-over-fiber applications demanding low-cost packaging.