Fig. 1. Proposed TOSA configuration. (a) Cross-sectional view of the TOSA. (b) Side view of the butt-coupling region. (c) Top view of the coupling region with the DFB-LDs connected with an FPC. (d) Top and side views of silicon sub-mount.

Fig. 2. Coupling efficiency as a function of d for the proposed butt-coupling configuration.

Fig. 3. (a) Schematic of the silica-PLC AWG. (b) Scanning electron microscope image of the PLC waveguide before the depositing of cladding. (c) Transmission spectra of the silica-PLC AWG.

Fig. 4. Measurement setups for (a) the proposed scheme and (b) the lens-based solution. (c) Relative CE as a function of position variation. (d) Output power degradation after UV adhesive curing.

Fig. 5. (a) Photograph of the fabricated silica-PLC sub-block. (b) External dimension of the developed TOSA. (c) Top and side views of the butt-coupling region.

Fig. 6. (a) Output power of the packaged TOSA as a function of injection current for the four lanes. (b) Lasing spectra of the TOSA at an injection current of 40 mA.

Fig. 7. Small-signal frequency response of S21 when each DFB-LD was discretely driven.

Fig. 8. Eye diagrams for the BtoB transmission of the TOSA.

Fig. 9. Bit error ratio characteristics for BtoB and after a 10 km transmission, when all four lanes were driven using the eye diagram condition shown in Fig. 8.