12.5-GHz spacing compact and low-loss interleave filter using 1.5% Δ silica-based waveguide

We describe the fabrication of a compact lattice-form waveguide interleave filter with a narrow channel spacing of 12.5 GHz. The circuit size was reduced to 1/4 the size of the original circuit by employing a novel folding layout and a waveguide with a high refractive index difference (Δ) of 1.5% that can reduce the minimum bending radius to 2 mm. The 12.5-GHz spacing interleave filter was fabricated on a single chip by using silica-based planar lightwave circuit technology. We achieved a low insertion loss of <2.3 dB, a wide 1-dB passband width of >8.1 GHz, a 20-dB stopband width of >7.3 GHz, a low crosstalk of <-25 dB, and a low chromatic dispersion of within ±300 ps/nm.