A Y-junction optical planar lightwave circuit (PLC) interleaver is analyzed and a polymeric interleaver is fabricated. This interleaver is composed of two identical but reversed Y-junction components. The formula for channel spacing of this device is generated and influence factor of channel spacing is analyzed. The fabrication tolerance of this device is provided. Our analysis shows that there is a less than 2% deviation from the design value of 1.6 nm when the core width varies by 10%.