The present invention is a lens system used to relay the light from one region to another and increase the workable optical path length to make Wavelength Division Multiplexing (WDM) devices with a high port count. Inside the WDM device based on thin filters, collimators produce parallel light beams, and when the light path is over the collimator working distance, there can be substantial coupling loss. However, within the working distance, light can pass through the filters and collimators to follow the zig-zag pattern and eventually couple into a desired fiber without substantial insertion loss. A lens relay system can increase the optical path length to achieve high port count DWDM without fiber routing that takes more space and without a high coupling loss that is caused by multiple coupling between free space and fibers.