We design and demonstrate a cost-effective 2times2 ultrafast multicast-capable optical switch (MCOS) based on a Sagnac interferometer. The Sagnac interferometer is composed of a LiNbO3 phase modulator (PM) with two polarization-maintaining pigtail fibers and a 3-dB polarization-maintaining coupler. The MCOS works at three states: cross, bar, and multicast, in the entire C-band (1525-1565 nm) by controlling the driven voltage of the PM. Polarization- dependence is eliminated by splicing the pigtail fibers of the PM and the 3-dB coupler with 0degand 90deg angles, respectively. The measured switching time is ~0.6 ns. Multiple 2times2 MCOS elements can be constructed into a large nonblocking N x N MCOS matrix.