Masahito Morimoto, Koji Morimoto, Kouki Sato and Shin'ichiro Iizuka
With the rapid increases in traffic on optical telecommunications systems, there is an active program for developing transmission devices for use in wavelength division multiplexing (WDM), which is becoming the mainstream technology for providing higher transmission speeds and a larger number of signal channels. It has been proposed that in the WDM systems of the future, variations in power due to wavelength could be reduced and the quality of transmission improved by adjusting the power after demultiplexing into individual signal wavelengths. It is envisaged that the current method, in which the power of all the multiplexed optical signals is adjusted by a single variable optical attenuator (VOA) would give way to a method in which one VOA is used for each wavelength. Given the number of multiplexed wavelengths, this change will require VOAs that are considerably more compact. This paper reports on the development of a VOA that has loss characteristics of low wavelength dependence and can also be used with multiplexed signals, and employs micro-electromechanical system (MEMS) technology, occupying only 1/25th the space of conventional devices.