Periodic Optical Filter

A periodic optical filter comprising:

• an infinite-impulse response filter having a first end and a second end,
• wherein the first end is an input port receiving an optical signal and the second end is a multiplexing branch to provide a filtered optical signal;
• and,
• a finite-impulse response filter having a first end and a second end,
• wherein the first end of the finite-impulse response filter is an intermediate port that receives the filtered optical signal from the infinite impulse response filter, and the second end is an output port that provides a multiplexed signal, the infinite-impulse response filter having an associated first dispersion slope, the first dispersion slope having a sign and a magnitude, the finite-impulse response filter having an associated second dispersion slope having a sign opposite the sign of the first dispersion slope, and a magnitude of the second dispersion slope is substantially equal to the magnitude of the first dispersion slope.

An optical comprising:

• a finite-impulse response filter having a first end and a second end, wherein the first end of the finite-impulse response filter is an input port for receiving a multiplexed signal and the second end is an intermediate port for providing filtered optical signals;
• and,
• an infinite-impulse response filter having a first end and a second end,
• wherein the first end of the infinite-impulse response filter receives the filtered optical signals and the second end of the infinite-impulse response filter is an output port.