Low power consumption 4-channel variable optical attenuator array based on planar lightwave circuit technique

The power consumption of a variable optical attenuator（VOA） array based on a silica planar lightwave circuit was investigated. The thermal field profile of the device was optimized using the finite-element analysis. The simulation results showed that the power consumption reduces as the depth of the heat-insulating grooves is deeper, the up-cladding is thinner,the down-cladding is thicker, and the width of the cladding ridge is narrower. The materials component and thickness of the electrodes were also optimized to guarantee the driving voltage under 5 V. The power consumption was successfully reduced to as low as 155 mW at an attenuation of 30 dB in the experiment.

Realization of simultaneous balanced multi-outputs for multi-protocols QKD decoding based onsilica-based planar lightwave circuit

Silica-based planar lightwave circuit(PLC)devices can reduce transmission loss and cost in a quantum key distribution(QKD)system,and have potential applications in integration and production.A PLC-based quantum decoding integrated chip for multi-protocols is designed and fabricated,which is composed of variable optical splitters(VOSs),asymmetric Mach-Zehnder interferometers(AMZIs),and variable directional couplers(VDCs).Balanced pulse-pairs of four outputs are obtained simultaneously with measured delay times of 405 ps and 402 ps,respectively.The chip has advantages in achieving high interference visibility and low quantum bit error rate(QBER).

Temperature characterizations of silica asymmetric Mach–Zehnder interferometer chip for quantum key distribution

Quantum key distribution(QKD)system based on passive silica planar lightwave circuit(PLC)asymmetric Mach–Zehnder interferometers(AMZI)is characterized with thermal stability,low loss and sufficient integration scalability.However,waveguide stresses,both intrinsic and temperature-induced stresses,have significant impacts on the stable operation of the system.We have designed silica AMZI chips of 400 ps delay,with bend waveguides length equalized for both long and short arms to balance the stresses thereof.The temperature characteristics of the silica PLC AMZI chip are studied.The interference visibility at the single photon level is kept higher than 95%over a wide temperature range of 12℃.The delay time change is 0.321 ps within a temperature change of 40℃.The spectral shift is 0.0011 nm/0.1℃.Temperature-induced delay time and peak wavelength variations do not affect the interference visibility.The experiment results demonstrate the advantage of being tolerant to chip temperature fluctuations.

Monolithic integration of a 16-channel VMUX on SOI platform

A 16-channel variable attenuator multiplexer/demultiplexer （VMUX） device is demonstrated. The VM UX is based on a rib-type structure on a silicon-on-insulator （SOI） platform. It consists of a 100-GHz arrayed waveguide grating （AWG） and an electro-optic variable optical attenuator （VOA） array with a p-i-n lateral diode structure. The insertion loss of the demonstrated device is about 9.1 dB and the corresponding crosstalk is about 10 dB. The injected current of the VOA is 60.74 mA at 20 dB attenuation and the whole area of the device is 2.9 × 1 mm2. The VMUX performs an excellent function of wavelength demultiplexing and optical power balancing in 16 channels.

Performance Study of Silica-on-Silicon Based Multimode Interference （MMI） Optical Coupler

In recent years, the silica-on-silicon based multimode interference （MMI） optical waveguide is an interesting research topic. It is being advanced various researches on the silica based MMI coupler. This paper represents the considerations of the optimal design of the silica-on-silicon based MMI optical coupler for better performance. For that, we have illustrated the simulation results on a particular case of the 4x4 silica-on-silicon based MMI coupler. From the simulation results, it is seen that the performance of the MMI coupler depends on multiple width and length combinations of the MMI waveguide. The results also show that the width of the multimode waveguide could not be too small or too large for optimal performance, and at the widths, 100~tm, 120~tm and 130~tm, the performance could be optimized and be almost 0.62 - 0.64 in a given length range. Finally, the results have been compared with the optical coupler presently available in the market and show that the silica-on-silicon based MMI coupler is much more efficient in terms of losses and the performance associated with it and the size of the coupler.

A novel fabrication approach for an athermal arrayed-waveguide grating

A novel method for fabricating an athermal AWG is proposed, using a unique apparatus for ITU-T center wavelength adjustment and optical coupling of two cut-parts. UV adhesive or sticky gel is applied into the gap between the cut-elements and the alignment base substrate by capillary infiltration. The spectrum profiles are almost the same as those of the original chip state, and no deterioration is observed resulting from athermalization. Flat-top athermal AWG modules of 100 GHz × 40 ch are fabricated. Over a temperature range of-40 to 85 ℃, the center wavelength shift is ±22 pm, and the insertion loss change is less than ±0.11 dB.