optical transport hierarchy (optical network) (OTH)
The optical transport hierarchy ( OTH) defines uniform signal structures, monitoring and alarm functions in optical networks at the transmission level.
The optical transport hierarchy is the transport technology for the optical transport network( OTN). It consolidated proven techniques from synchronous digitalhierarchy( SDH) and dense wavelength division multiplexing( DWDM), eliminating elaborate multiplex structures and instead imposing moderate clocking requirements. OTH technology provides a converged electrical and optical transmission technique optimized for broadband data streams and can switch these data streams between the electrical and optical planes.
Data streams are transported via containers known as optical channels( OCh) in OTH technology. These high-bit-rate data streams can originate from Gigabit Ethernet, Fibre Channel, from the SDH network or from the ATM network. Framing is used to generate data packets from these packet-switched signals, which are converted into optical signals via E/O converters and modulated onto a wavelength. The individual wavelengths are multiplexed in the downstream optical multiplexer( OMUX) to form an optical group signal and fed to the optical fiber via an optical amplifier. The signal for monitoring and management, the Optical Supervisory Channel( OSC) is fed with its own wavelength to the optical output amplifier.
OTH is standardized by the International Telecommunication Union( ITU) in Recommendation G.709 and provides an optical transport unit( OTU) to the various client signals.