In this study, a low-cost (with bare chips) and high (optical, electrical, and thermal) performance optoelectronic system with
a data rate of 10Gbps is designed and analyzed. This system consists of a rigid printed circuit board (PCB) made of FR4
material with an optical polymer waveguide, a vertical cavity surface emitted laser (VCSEL), a driver chip, a 16:1 serializer,
a photo-diode detector, a Trans-Impedance Amplifier (TIA), a 1:16 deserializer, and heat spreaders. The bare VCSEL, driver
chip, and serializer chip are stacked with wire bonds and then solder jointed on one end of the optical polymer waveguide on
the PCB via Cu posts. Similarly, the bare photo-diode detector, TIA chip, and deserializer chip are stacked with wire bonds
and then solder jointed on the other end of the waveguide on the PCB via Cu posts. Because the devices in the 3D stacking
system are made with different materials, the stresses due to the thermal expansion mismatch among various parts of the
system are determined.
In this paper, the optical design of 4-channel WDM Transmission Optical Subassemblies (TOSA)/Receiver Optical
Subassemblies (ROSA) is reported. The TOSA and ROSA are being developed for uncooled modules for CWDM
applications and are compatible with the SFP/SFF form factor TOSA and ROSA. The physical dimension of OSA
together with the electronic circuitries is limited to 10×6×5 mm3. The designs of TOSA and ROSA are employed using
four thin film filters (TFFs) to select the specific channel wavelength, four 500 μm ball lenses, one 2.5 mm ball lens and
a high reflection mirror using folded optical configuration. The optical elements are to be assembled on a SiOB, except
the 2.5 mm ball lens. The simulation results are used to estimate the required optical components assembly accuracy.
Based on the simulation results, the tolerance requirement for tilting the mirror and first thin film filter is approximately
± 0.2° for the longest optical path namely Channel 4.
An optical sub-assembly of MUX/DEMUX where optical devices are hybrid-integrated on a silicon optical bench (SiOB)
using a low cost passive alignment method was reported. A tight tolerance of positional and tilting angular accuracy is
required for optical devices attachment in order to maximize the coupling efficiency. The critical positioning transverse
to the optical axis merely depends on the symmetry, and accuracy of the position and shape of trenches. Any inaccuracy
primarily affects the non-critical positioning, i.e., z-axis & θz, in the direction along the optical axis; misalignment
accumulated and causes undesired insertion loss. All the piece parts, i.e., mirror, thin-film filters (TFFs), ball lens, SiOB
etc., have a defined tolerance in their dimensions and surfaces which increases the challenge in achieving high placement
accuracy along the optical axis. The effects from these inherent inaccuracies of the position and shape of trenches and
piece parts could be minimized by improve the bottom flatness, and proper procedure selection. Misalignment at each
axis, e.g. x-, y-, z-, θx, θy & θz was characterized and its effect to the coupling efficiency was discussed.