An integrated reconfigurable four-channel wavelength-division-multiplexed drop module for use in the long-wavelength was demonstrated using a tunable wavelength-selective photodetector array. The array consists of an InP-based p-i-n absorption structure and a GaAs-based multistep Fabry-Pérot filtering cavity. The high quality GaAs/InP heteroepitaxy was realized by employing a thin low temperature buffer layer. The GaAs-based multistep cavity was fabricated by wet etching and regrowth. The dropped central wavelengths were 1538, 1550, 1559, and 1570nm. The tunable range reached 10nm with a tuning power efficiency of 14.2nm/W. A spectral linewidth less than 0.5nm (FWHM), a 3dB bandwidth of 9.2GHz, and the peak quantum efficiencies from 13% to 20% were simultaneously obtained, in agreement with the theoretical simulation.