Peripheral coupled waveguide (PCW) design has been deployed in InGaAsP multiple quantum-well (MQW) electroabsorption modulator (EAM) at 1.55-mum wavelength. PCW enhances the optical saturation power and reduces the optical insertion loss and the equivalent V-pi simultaneously. A radio-frequency link using a 1.3-mm-long lumped-element PCW EAM has achieved experimentally a link gain of -3 dB, at 500 MHz and at input optical power of 80 mW. The corresponding two-tone multioctave spurious-free dynamic range (SFDR) at the same bias is measured at 118 dB (.) Hz(2/3). The single-octave SFDR at the third-order null bias is 132 dB (.) Hz(4/5).