We propose and demonstrate wavelength-selectable filters available for 32 WDM channels using a micro-mechanically movable mechanism with miniaturized voice-coil motors (VCMs). A simple straight geometry with a staggered configuration is used to densely pack 32 in/out moving elements into a small space of 452411 mm. The elements are precisely arranged along a collimated beam between fiber facets to provide flat-top passbands centered at ITU-T grids while maintaining small total insertion losses of less than 2.5 dB for all elements. The driving condition of the VCMs is also optimized for quick dynamic response with typical settling time of less than 10 ms. A repetition test 106 repetitions per element showed good wavelength reproducibility to an accuracy of below 0.1 nm, indicating the switches are feasible for practical system equipped with reconfigurable functionality for the next generation of optical networks.

This study investigates the improvement of the channel capacity of 5-GHz-band multiple-input multiple-output (MIMO) communication using microwave-guided modes propagating along a polyvinyl chloride (PVC) pipe wall for a buried pipe inspection robot. We design a planar Yagi-Uda antenna to reduce transmission losses in communication with PVC pipe walls as propagation paths. Coupling efficiency between the antenna and a PVC pipe is improved by attaching a PVC adapter with the same curvature as the PVC pipe's inner wall to the Yagi-Uda antenna to eliminate any gap between the antenna and the inner wall of the PVC pipe. The use of a planar Yagi-Uda antenna with a PVC adaptor decreases the transmission loss of a 5-GHz-band microwave signal propagating along a 1-m-lomg straight PVC pipe wall by 7dB compared to a dipole antenna. The channel capacity of a 2×2 MIMO system using planar Yagi-Uda antennas is more than twice that of the system using dipole antennas.