In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths (i. This technique enables bidirectional communications over a. Wavelength division multiplexers are fundamental to the functioning and performance of integrated photonic circuits, with applications ranging from optical interconnects to sensing and quantum technologies. Current solutions are limited by trade-offs between channel spacing, crosstalk, insertion. SONET time-division multi-plexing. was developed to allow users to sbare the capacity of a fiber 11]. The "basie" transmission rate of SONET is 64 kbps for supporting voice communications. In WDM, the optical signals from different.