The objective of the thesis is to fabrication an optical demultiplexer using Thin-film filter(TFF) based on Si-bench technology. The advantage over conventional bulk-optics technology in fact that the active alignment is performed in only 1-dimension. There fore the cost of package of the demultiplexer can be reduced significantly. Lights at multiple wavelengths were launched into the demultiplexer through a Dual-core single mode fiber(SMF). Due to the wavelength selection of the TFF, only the designate wavelength can pass through the filter and is refocused by the C-lens to the output Single-core single mode fiber(SMF). The other wavelengths will be reflected by the TFF, pass through the Grin-lens again and return to the Dual-core single mode fiber(SMF). The measured reflection(1470nm¡B1490nm¡B1510nm¡B1530nm¡B1550nm) and transmission (1470nm¡B1490nm¡B1510nm¡B1530nm)lasers of the lights are around 0.5dB.