• This work appraises a facile method for detecting lead ions. • A d -shaped optical fiber is functionalized with gold nanoparticles. • The throughput in terms of intensity via the functionalized fiber varies. • The modulated intensity is then assessed through an optical detector. • The reported scheme overall renders a cost-effective compact scheme. This work appraises a facile method for detecting lead ions in an aqueous medium. For this purpose, a d -shaped optical fiber is functionalized with gold nanoparticles with further accompaniment of aspartic acid. Subject to aggregation of gold nanoparticles as induced by Pb 2+ ions, the throughput in terms of intensity via the functionalized fiber varies. Consequently, the modulated intensity is then assessed through optical detector. The attained findings show a remarkable response down to ppb scale especially for lead ion with least selectivity to other ions. Overall, the reported scheme renders a cost-effective compact scheme for sensing heavy metal ion contaminant in aqueous solution.