In this paper, a polymer/silica hybrid waveguide thermo-optic variable optical attenuator (VOA), covering the O-band, is demonstrated. The switch is fabricated by simple and low-cost direct ultraviolet (UV) lithography. The multimode interferences (MMIs) used in the Mach–Zehnder interferometer (MZI)-VOA are well optimized to realize low loss and large bandwidth. The VOA shows an extinction ratio (ER) of 18.64 dB at 1310 nm, with a power consumption of 8.72 mW. The attenuation is larger than 6.99 dB over the O-band. The rise and fall time of the VOA are 184 μs and 180 μs, respectively.

Mode converters is a key component in mode-division multiplexing (MDM) systems, which plays a key role in signal processing and multi-mode conversion. In this paper, we propose an MMI-based mode converter on 2%-Δ silica PLC platform. The converter transfers E00 mode to E20 mode with high fabrication tolerance and large bandwidth. The experimental results show that the conversion efficiency can exceed −1.741 dB with the wavelength range of 1500 nm to 1600 nm. The measured conversion efficiency of the mode converter can reach −0.614 dB at 1550 nm. Moreover, the degradation of conversion efficiency is less than 0.713 dB under the deviation of multimode waveguide length and phase shifter width at 1550 nm. The proposed broadband mode converter with high fabrication tolerance is promising for on-chip optical network and commercial applications.

Wavelength division (de)multiplexing (WDM) device is a crucial component for optical transmission networks. In this paper, we demonstrate a 4 channel WDM device with a 20 nm wavelength spacing on silica based planar lightwave circuits (PLC) platform. The device is designed using an angled multimode interferometer (AMMI) structure. Since there are fewer bending waveguides than other WDMs, the device footprint is smaller, at 21 mm × 0.4 mm. Owing to the low thermo-optic coefficient (TOC) of silica, a low temperature sensitivity of 10 pm/°C is achieved. The fabricated device exhibits high performance of an insertion loss (IL) lower than 1.6 dB, a polarization dependent loss (PDL) lower than 0.34 dB, and the crosstalk between adjacent channels lower than −19 dB. The 3 dB bandwidth is 12.3∼13.5 nm. Moreover, the device shows a high tolerance with a sensitivity of central wavelength to the width of multimode interferometer < 43.75 pm/nm.