Two types of silicon-on-insulator thermo-optic variable optical attenuators (VOAs) based on a Mach-Zehnder interferometer and a multimode-interference coupler are fabricated, one with thermal isolating grooves to improve heating efficiency and the other without. Comparison of optical and electrical properties, such as insertion losses, the maximum attenuation levels and the corresponding power consumptions, and the response times, is carried out between the two types of VOAs. The comparison results indicate that use of thermal isolating grooves leads to better values for most characteristics and is an effective way to improve the performance of Mach-Zehnder interferometer-type thermo-optic devices.
OADM is a key component in DWDM due to many merits such as good performance in low loss, low price, simple and flexible integration structure. One of the critical issues focused on the research of OADM is to design multiplexer/demultiplexer hoping to reduce the insertion loss and improve the propagation efficiency of the total device. In this paper, we present the design of 4×1 and 8×1 multiplexers based on SOI materials. The devices show several advantages including low insertion loss, phase-insensitiveness, polarization independence and compact size. The devices' performances are simulated under different conditions and all exhibit satisfying results. It's ideal to equip them in compact optical system.
A thermo-optic variable optical attenuator (VOA) based on a Mach-Zehnder interferometer and multimode-interference coupler is fabricated. Not a single-mode but a multimode waveguide is used as the input and output structures of the optical field, which greatly reduces the coupling loss of the VOA with a normal single-mode fiber. The insertion loss of the fabricated VOA is 2.52 to 2.82 dB at the wavelength of 1520 to 1570 nm. The polarization dependent loss is 0.28 to 0.45 dB at the same wavelength range. Its maximum attenuation range is up to 26.3 dB when its power consumption is 369 mW. The response frequency of the fabricated VOA is about 10 kHz.