The fabrication tolerance of the designed polarization splitter is considered, the structural parameters fluctuate up and down two percent. d₁ is changed to d₁ × 0.98 and d₁ × 1.02, the bandwidth in which the extinction ratio is lower than −13 dB is 210 nm, 330 nm respectively in panel (a), d₂ is changed to d₂ × 0.98 and d₂ × 1.02, the bandwidth in which the extinction ratio is lower than −13 dB is 310 nm, 240 nm in panel (b), d₁, d₂ are changed to d₁ × 0.98 and d₁ × 1.02, the bandwidth in which the extinction ratio is lower than −13 dB is 250 nm, 310 nm in panel (c).