Monolithically lens-integrated surface-emitting distributed-feedback (DFB) laser arrays and p–i–n photodiode arrays were developed. A combination of dry etching and wet chemical etching was used to fabricate a monolithic InP lens. The lens profile within ±10 µm from the lens center was estimated to be parabolic shape, which is ideal for the collimation of a Gaussian beam. A fabricated lens-integrated surface-emitting DFB laser exhibited a circular, narrow far-field pattern with full-width at half maximums of 3.9×3.5°. An efficient direct coupling of the lens-integrated DFB laser to a single-mode fiber with a coupling efficiency of -3 dB was confirmed. A four-channel lens-integrated surface-emitting laser array and a lens-integrated p–i–n photodiode array were used to fabricate a very compact 100 Gbps (25 Gbps × 4 channel) optical transceiver with 14×9 mm2 footprint.