Wavelength division multiplexing (WDM) optical modules

A method comprising:

• establishing a (M/2)×N array of photodetectors on a front side of an active silicon interposer;
• building N chips for N Wavelength Division Multiplexing wavelengths by, for each chip:
• establishing M lenses for the M optical signals on a back side of a GaAs substrate, and
• establishing M/2 Vertical Cavity Surface Emitting Lasers (VCSELs) on a front side of the GaAs substrate.

A method comprising:

• receiving at the WDM optical module M×N optical signals via M optical fibers, the WDM optical module comprising:
• an active silicon interposer comprising a (M/2)×N array of photodetectors established on a front side of the interposer, and
• a chip for each WDM wavelength, each chip comprising:
• M lenses for M optical signals, the M lenses established on a back side of a GaAs substrate, the M lenses comprising a first group of M/2 lenses to focus M/2 optical input signals and a second group of M/2 lenses to collimate M/2 optical output signals;
• converting the M/2 optical input signals entering each chip into electrical output signals by means of M/2 photodetectors of the (M/2)×N array;
• and
• converting electrical input signals into the M/2 optical output signals exiting each chip by means of M/2 Vertical Cavity Surface Emitting Lasers (VCSELs) established on a front side of the GaAs substrate.