We experimentally demonstrate a linearly polarized, passively Q-switched, erbium (Er)-doped fiber laser using a saturable absorber (SA) based on a composite consisting of a bulk-structured bismuth telluride (Bi2Te3) topological insulator (TI) and polyvinyl alcohol (PVA). The SA was constructed on a polarization maintaining (PM) fiber ferrule platform, which had a sandwich structure. Its saturation intensity and modulation depth were measured to be ∼47.56 MW/cm2 and ∼4.1%, respectively. Using the prepared Bi2Te3/PVA SA in a PM Er-doped fiber ring laser, stable Q-switched pulses with a degree of polarization of ∼98.6% and an azimuth angle of ∼−0.34 deg were demonstrated. The minimum pulse width was measured to be ∼1.58 μs at a repetition rate of 47.1 kHz. This experimental demonstration verifies that a thin film based on a bulk-structured Bi2Te3 TI can fit into a sandwich-structured SA based on PM fiber ferrules.