ITU-T Introduces Multi-Vendor Interoperable Standard for 100G Coherent Transmission


ITU today announced that its standardization experts have accomplished a major feat of engineering in the delivery of multi-vendor interoperable 100G DWDM coherent line interfaces. The achievement of ITU experts to create a standard for multi-vendor interoperability is an industry first.

The standard interfaces will accelerate industry innovation to achieve greater capacity in metro networks. This is the first 100G coherent multi-vendor interoperable optical specification.’s standardization work on ‘characteristics of optical systems for terrestrial transport networks’ (Q6/15).

Multivendor Interoperability is necessary to ensure faster, cost-effective optical networks. As an international organization, initiating and managing the specifications for network and its components, ITU plays a major role to help network owners across the world to deploy networks that are compatible with each other. The ability for interoperation is the key to ensure global connectivity.

a picture of earth illuminated with the light coming out of optical fibers and fiber optic cable The revised ITU standard, ITU G.698.2 “Amplified multichannel DWDM applications with single channel optical interfaces”, supports a phase-modulated signal using DP-DQPSK (Dual Polarization – Differential Quadrature Phase Shift Keying). DP-DQPSK is a “complex modulation format according to the ITU committee member, Anslow.

The Committee expert further added that DP DQPSK is a major reset on the modulation format. DP DQPSK raises questions on how should we define the quality of an optical signal with the data encoded in the phase. ITU-T Study Group 15 has been first to answer this question with a metric called ‘error vector magnitude’. The metric defines the quality of a transmitter, a consideration fundamental to multi-vendor interoperability.

The term ‘error vector magnitude’ comes from the wireless world, which is repurposed for optics and ITU committee did a considerable amount of work to show that the metric correlates properly with actual link performance. The committee’s success in adapting this metric to optics is an industry first, which will also be an industry-leading innovation in applying this specification methodology to optical communication. Other standards bodies are beginning to consider the inclusion of the metric in their specifications for coherent line interfaces.

ITU-T Study Group 15 has started validating the ‘error vector magnitude’ metric for 16QAM modulation with a view to standardizing 400G line interfaces. Interoperability for 400G transmission is the next step.


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