Figure 5: Multi-wavelengh-based four-tap MWP filter.
From: Integrable microwave filter based on a photonic crystal delay line
(a) The delay profiles, based on the experimental results obtained for the TE mode, for the TE and TM modes as a function of the wavelength for illustrative purposes of the filter operation. The green arrows show the spectral placement of the carriers and modulation sidebands (at 50 GHz) for all the four taps within the TE delay profile. This wavelength set is related to the green markers in figure (c), and corresponds to a constant group delay of 20 ps from tap to tap, which means a free spectral range of 50 GHz in the green filter transfer function in (c). (b) Experimental setup of the multi-wavelength filter. Four TLS (λ0 to λ3) are combined and intensity modulated to carry the input electrical signal si(t). The four wavelengths are then coupled into the photonic crystal delay line, along the TE mode, the RF delay for each tap being therefore a function of the tap wavelength. The polarization controllers perform the same functions as in the case of a single optical source. A photodetector provides the output filtered electrical signal so(t). (c) Calculated (dashed lines) and measured (colored squares) results for the filter response with different spectral scenarios of the emission wavelengths. The experimental wavelengths sets are 1,530, 1,546.4, 1,550.4, 1,552.6 nm (blue), 1,541.5, 1,548.9, 1,551, 1,552.7 nm (green), 1,545.2, 1,549.9, 1,551.2, 1,552.6 nm (red) and 1,546.8, 1,550.4, 1,551.5, 1,552.6 nm (cyan).
