This 12-Channel DWDM Optical Passive Mux/Demux is engineered to maximize the capacity of existing fiber optic networks while minimizing the need for new fiber deployment. Operating with 100GHz channel spacing and supporting ITU channels C16-C27 (1625-1670nm range), this module enables the multiplexing or demultiplexing of four discrete wavelengths over a single-mode fiber. The unit includes OTDR(1625nm-1670nm ),Test TX/RX, Upgrade Port (UPG) and an Express Port (EXP) to ensure seamless scalability and future expansion. The UPG supports additional wavelengths within the 1525-1570nm range (excluding active channels), while the EXP accommodates O-band and L-band wavelengths (1260-1520nm and 1580-1620nm), providing a cost-effective path for network growth. Equipped with LC/APC connectors and built in an industry-standard LGX form factor, this DWDM Mux/Demux delivers reliable performance and easy integration into existing fiber management systems. Optimized for low signal attenuation, the DWDM channels deliver a maximum insertion loss of 3.4 dB, while the Upgrade and Express ports support up to 5 dB maximum insertion loss, ensuring efficient signal performance across both active and expansion paths. Equipped with LC/APC connectors and built in an industry-standard LGX form factor, this DWDM Mux/Demux delivers reliable performance and straightforward integration into existing fiber management systems.