Reconfigurable WDM add/drop multiplexer based on optical switches and fibre Bragg gratings

A reconfigurable wavelength-division-multiplexing (WDM) add/drop multiplexer (WADM) is constructed using optical switches (OSWS) and fibre Bragg gratings (FBGs). Selected one or two channel(s) can be added/dropped at the same multiplexer by properly controlling the optical switch pair and fibre Bragg grating arrangement. Afour-channel system is experimentally demonstrated for a data rate of 2.5 Gb s–1 and a single-mode fibre (SMF) distance of 100km. A negligible maximum power penalty of only 0.3dB is observed when compared with back-to-back transmission.     

Novel 0.98/1.55 μm dichroic coupler based on lithium niobate

A novel 0.98/1.55 μm dichroic coupler with high-extinction ratio and low insertion loss has been designed and implemented on LiNbO₃ for Erbium-doped fiber amplifier applications. The design of dichroic coupler is based on a modified directional coupler structure with a single bend in each channel. Beam propagation method is used to analyze the coupler performance to get the optimal parameters for device design, such as channel width, titanium thickness, channel gap, and interaction length. Samples with the signal coupling ratio as high as 100% and pumping power ratio as high as 95% have been obtained.     

Recent developments in photonic devices for telecommunication applications in Taiwan

We report recent activities and achievements on the development of photonic devices for telecommunication applications. Opto-electronic devices such as high performance 1.55 m complex-coupled InGaAsP-InP distributed feedback (DFB) and 1.3 m uncooled AllnGaAs-InP lasers, the InGaAs-InP p-i-n photodetector on semi-insulating substrate, the 0.98 m InGaAs-GaAs-InGaP pumping laser, and 12-channel laser and detector arrays, are presented. Work on the development of in-house vertical integration for the fabrication of a 1.55 m single frequency transmitter, a 1.3 m multimode transmitter and receiver, and an Er-doped fibre amplifier, and their applications in system trials in the Taiwan National Information Infrastructure network, is described.     

Single-mode SiON/SiO2/Si optical waveguides prepared by plasma-enhanced chemical vapor deposition

We present the characteristics of low-propagation-loss single-mode SiON / SiO₂ / Si planar optical waveguides using plasma-enhanced chemical vapor deposition (PECVD). Using a thermal annealing process and a thick silicon dioxide buffer layer, we get an improvement on the propagation loss by the amounts of 1.24 dB /cm and 1.1 dB /cm, respectively. Optical waveguides with propagation loss lower than 0.3 dB /cm can be achieved.     

High-speed InGaAs metal-semiconductor-metal photodetectors with improved responsivity and process yield

High-performance In_0.9Ga_0.1P-InP-InGaAs metal-semiconductor-metal photodectors with semi-transparent Au Schottky contacts are fabricated and studied. The devices, with an active area of 50×50 m² and different finger spacings of 2, 3 and 4 m, all exhibit high responsivities over 0.7 AW^-1 and low dark currents below 10 nA. Extremely linear photoresponse without low frequency internal gain is also observed in these devices. The novel fabrication process used in this work is simple and has nearly 100% high yield. A device with a small finger spacing has also been demonstrated to have improved speed performance without sacrificing its responsivity.