Compact multi/demultiplexer system consist of stacked dielectric interference filters and aspheric lenses

We report both system design and experimental evaluation of SMOP (Simple and small Multi/demultiplexer consisting of OPtical elements) system used for intra-cabinet-level optical interconnections. To increase the interconnection bandwidth, wavelength division multiplexing (WDM) is an important technology. However, dense WDM is not suitable for the intra-cabinet-level interconnections due to its system complexity and expensive production cost. Instead, we chose wide-channel-spacing wavelength division multiplexing (WWDM) since it is expected to reduce fabrication cost by using uncooled lasers. The SMOP consists of three dielectric interference filters and a reflecting mirror, and aspheric lenses. The lens array pitch is set to be 0.25 mm to fit the optical fiber pitch at the end facet of MT connectors. Three dielectric interference filters are stacked to perform wavelength multiplexing and demultiplexing functionalities. An incident signal light from an MT connector with four different wavelengths (1280 nm, 1300 nm, 1320 nm, 1340 nm) is first collimated and deflected by an off-axis collimator lens. Three layers of dielectric filters differentiate different wavelengths by reflecting the incident beam at different locations. The SMOP is packaged as small as 6.4 mm by 2.5 mm with 8.1 mm thickness small enough for the intra- cabinet-level interconnections. The proto-type experiments confirmed low insertion loss of below 5 dB. The proposed wafer-level fabrication of SMOP may be effective in packaging such applications.