Manually Adjustable Polarization Insensitive Variable Bandwidth Tunable Filters

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. Since each filter can be tuned over a range of wavelengths, both the center frequency and width of the passband can be controlled.Each individual filter consists of a multi-layer thin film band pass filter,designed to give a flat top pass band, 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, in order to change the passband. OZ Optics uses a special technique to minimize polarization dependencies, allowing PDL effects to be kept below 0.3 dB, and making the spectral response virtually polarization independent. This feature makes it ideal for today’s DWDM system applications.