Low-Loss Passive Si$_{3}$N $_{4}$ Serial-to-WDM Interface for Energy-Efficient Optical Interconnects

The increasing number of computational servers in data centers is imposing tighter constraints on the networking infrastructure. Scalable power efficient optical interconnect network becomes necessary to leverage the bandwidth capacity of current electronic switches or opto-electronic components. Hence, novel optical interconnect technology can enhance the network capacity by harnessing the feasibility of simultaneous processing of optical signal in the wavelength and time domains. In this paper, we present a four channel optical passive wavelength-striped mapping (PWSM) device, which passively time compresses/expands serial packets through optical wavelength multiplexing/demultiplexing. The PWSM device, which has a 1 × 4 channel optical wavelength demultiplexer with integrated optical delay lines, is designed in a low-loss Si₃N₄ (propagation loss ~3.1 dB/m) waveguide platform. The PWSM device multiplexes/demultiplexes four WDM channels and offsets in time the adjacent channels to optically serialize/deserialize data packets. In this demonstration, a 64 ns long data packet is formed at the output of the device by combining four 16 ns data segments of the packet in time domain. Incremental optical insertion loss between adjacent channels is ~9.7 dB due to the integrated passive optical delay waveguides. The data rate of the four segmented packets and the combined packet is 25 Gb/sec. We have measured a bit error rate performance below 1 ×10^-9 for the 64 ns serial data packet regenerated by the PWSM device for a received optical power of -6.7 dBm.