In ultra-long haul transmission, the light signals are transmitted via single mode fibers and processed with 3R regeneration. In addition, these transmission techniques operate with forward error correction and with dispersion compensation. Another aspect in terms of transmission reliability is provided by the significantly improved link control compared to the shorter transmission technologies Long Haul and Very Long Haul.
The International Telecommunication Union( ITU) specifies the ultra-long haul range as 160 km at wavelengths of 1,550 nm. This distance range can be bridged without intermediate amplification. In addition to this optical SDH interface, the International Telecommunication Union has defined further SDH interfaces for Short Haul, Long Haul and Very Long Haul ( VLH).