China Telecom, Huawei and Corning have announced the completion of China’s first 100G wavelength division multiplexing (WDM) ultra long haul transmission test. The trial also set a new record of 100G WDM transmission distance of over 3,000km in a terrestrial fibre system. Along with the steady development of FTTx broadband infrastructure, China Telecom is looking for state-of-the-art 100G WDM ultra-high-speed transmission technology as a possible successor to its backbone network based on 40G WDM transmission technology. In the test, the 100G WDM transmission equipment was based on coherent polarisation multiplexed quadrature phase-shift keying (PM-QPSK) technology, which is recognised as the optimal technology for 100G WDM long-haul transmission. Moreover, C-band 50GHz-spacing and hybrid transmission of 100G/40G were also adopted in the test.