The realization of all-pass filters for third-order dispersion compensation in ultrafast optical fiber transmission systems

Thin film (TF)-based coupled cavity all-pass filters (CCAP) have the potent ial for providing compact, low-loss, and highly stable third-order dispersi on (TOD) compensation in ultrafast optical fiber transmission systems emplo ying optical time-division multiplexing (OTDM). In this paper, a methodolog y for designing CCAP filters for TOD compensation is presented. First, we d evelop a theory necessary for designing the cavity structure, that is, mirr or reflectivity and cavity spacing, of CCAP filters. As a next step, we dis cuss how we can represent such filters as TF devices and demonstrate severa l TF-layer design examples. Finally, a coupled two-cavity filter is constru cted and tested. The filter has a center wavelength that can be varied over a range of 8 nm and can compensate for fiber TOD between 2.0 and 15.5 ps(3 ) over a bandwidth between 3.6 and 1.2 nm, respectively. The peak spectral ripple of the filter is 1.0 dB. The experimentally measured dispersion curv es of the filter agree well with the theory.