The manually adjustable variable bandwidth tunable filter is a pigtailed component with adjustment knobs that allow both the wavelength and bandwidth of the filter to be controlled. The device contains two independently variable tunable bandpass filters in series. With the two filters tuned to cover slightly different wavelength ranges, the overall passband becomes the region where the two individual passbands overlap. The amount of overlap determines the width of the filter.

Each individual filter consists of a multi-layer thin film bandpass filter, designed to give a flat-top passband, with steep roll-off shapes. The center wavelength of the filters is adjusted by changing the angle of incidence of the light as it impinges upon the filter. In the Variable Bandwidth Tunable Filter, each filter is independently rotated relative to the incoming light to change the passband. The product is available in single-mode, polarization maintaining, and multimode fiber versions.