Integrated Spatial Optical System for Compact 28-Gb/s \(\times \) 4-lane Transmitter Optical Subassemblies

A compact 28 Gb/s \(\times 4\) -lane transmitter optical subassembly is developed for 100Gb/s Ethernet (100 GbE)/OTU4 applications with a hybrid integrated spatial multiplexer optical system. The system simply comprises three bandpass filters and a mirror, despite the narrow guardband specification. Moreover, by an intensively improved precise lens manipulation technique acting in an upward direction in addition to horizontally and downward, high-coupled power into the single-mode output fiber can be achieved, with resolving the previously reported issue that the controllable direction was limited. Finally, we show that eye diagrams with adequate mask margins (≥15%) and high extinction ratio (≥8 dB) are obtained at 28 Gb/s with a low modulating voltage (≤1.6 V \(_{\mathrm {\mathbf {pp}}}\) ).