Improving high-speed optical telecommunications: faster photodiodes and wavelength division multiplexing

Recent developments and enhanced gain-bandwidth products have led to a resurgence in the use of avalanche photodiodes (APDs) in optical telecommunications. High-speed APDs operating at 1.55 µm wavelengths are of great interest in current research due to rapidly growing internet traffic and potential growth opportunities for developed and developing economies.
An InGaAs PIN diode and an AlGaAsSb APD are characterised. Results from the InGaAs PIN diode suggest that the contacts and bond pads may have a negative impact on the bandwidth. The AlGaAsSb APD is found to have a gain-bandwidth product of 224 GHz, which is high relative to current APDs.
Wavelength division multiplexing is a potential way of increasing the data transmission rates in optical telecommunication systems. A photonic crystal demultiplexer was designed with 5-11 channels, 30-40% transmission efficiency but a relatively small footprint