a fiber - optic tunable filter and an intensity modulator respectively includes : a fiber having a polished surface and an evanescent - field ; and a photonic crystal having plural cavities and a filler filled therein and attached to the polished surface , wherein the plural cavities and the filler decide a photonic band - gap of the photonic crystal and the photonic band - gap is adjusted to reflect a light with a specific wavelength through the evanescent interaction with the photonic crystal material . based on the fiber side - polishing technique , all kinds of fiber active and passive devices are able to be manufactured easily , especially for a high speed intensity modulator using an eo polymer as the filler .