Tunable filters with an ultrawide tuning range

By allocating channels in the wavelength domain, wavelength division multiplexing (WDM) has demonstrated the most efficient use of the signal bandwidth offered by silica fiber. A key component for the WDM system is a wavelength tunable filter, which is used at the receiver front-end and at the transmitter site for wavelength monitoring. In this paper, we present results of tunable filters designed for wavelength monitoring. The device has demonstrated a record wide tuning range (341 nm) covering both 1.3 /spl mu/m and 1.55 /spl mu/m wavelength regimes. In combination with a custom designed electronic waveform generator and a photoreceiver, this device has also demonstrated its function as a wavelength meter with an accuracy of 0.7 nm. The surface micromachined tunable Fabry-Perot filter was fabricated on a double polished silicon substrate.