The WDM system supports signle transmission in two modes: Single-Fiber Unidirectional and Single-Fiber Bidirectional.
In Single-Fiber Unidirectional mode, the WDM system transmits multi-wavelength optical signals in receive and transmit directions through separate fibers.
This mode is characterized by its simple design and low requirements, easy fault isolation and performance monitoring, convenient O&M, and flexible networking that facilitating upgrading and capacity expansion.
In Single-Fiber bidirectional mode, multi-wavelength otpical signals are transmitted through only one fiber is both receive and transmit directions.
This mode is mainly used on the client side, implemented through the filtering function of a signle-fiber bidirectional optical module. Different center wavelengths are used for the two directions.
This mode is characterized by a 50% saving in fiber resources compared with the single-fiber unidirectional mode. However, its design and O&M of the WDM system are more complicated. Protection ranges must be configured for separating wavelengths to prevent signal interference in two directions, which wastes spectrums.