Oxy-halide glasses in systems of –– ( = F, Cl, and Br) doped with were prepared by a melt quenching method and their optical properties were characterized by measurements of UV-visible luminescence, hole burning, and electron spin resonance (ESR) spectra. For the - and -based samples, ions were partially reduced during the heating process in ambient atmosphere, so that room temperature persistent spectral hole burning was observed on them. Meanwhile, no obvious band emission or characteristic ESR signal of ion was recorded on the -based samples also prepared in ambient atmosphere, and consequently any hole peak was hardly detected even at . However, hole peaks were produced and persisted at room temperature on the -based samples remelted in a reducing atmosphere. The self-reduction mechanism for ion in the - and -based samples is discussed as well as the hole formation in all samples.