Two chromophores C1 and C2 based on a fluorene electron donor with different π-electron bridges and the same electron acceptor have been synthesized and systematically characterized using NMR, MS and UV-vis absorption spectra. The energy gap between the ground state and the excited state and molecular nonlinearity were studied using UV-vis absorption spectroscopy, Density Functional Theory calculations and cyclic voltammetry measurements. The different properties between C1 and C2 were systematically compared. The results showed that C2 had a better performance than C1. The electrooptic coefficient of a poled film containing 25 wt% of C2 doped in amorphous polycarbonate afforded a value of 40 pm V⁻¹ at 1310 nm. In addition, the excellent thermostability of C2 made itself a favourable candidate for practical application.