NEC performs world’s first successful trial of real-time 1Tb/s superchannel transmission over a trans-oceanic distance

NEC performs world’s first successful trial of real-time 1Tb/s superchannel transmission over a trans-oceanic distance

In recent years, the international demand for bandwidth is growing at a remarkable pace, thanks in part to the globalisation of resource-hungry applications such as VoD, High Definition videoconferencing and cloud computing. As a result, efforts are continuously being made to increase the bit-rate capacity and transmission reach of submarine cable systems, which support more than 99% of trans-oceanic data traffic.

With 100Gb/s technologies now commercially deployed, the focus of recent development is turning to high capacity channels, beyond 100Gb/s, with more efficient bandwidth utilisation. As part of this movement, NEC has proposed optical superchannels to increase fiber capacity in both terrestrial and submarine networks. Optical superchannels are based on advanced technologies such as parallel high-speed transceivers, advanced modulation formats and advanced pulse shaping. Superchannels constitute a practical platform for next-generation submarine systems specifically designed to help carriers to significantly increase transmission capacity in a cost efficient, scalable and flexible manner.

As a result of these proposals, NEC successfully tested a 1Tb/s superchannel for submarine ultra-long haul systems that uses the latest optical and digital technologies to provide traffic management flexibility and improve transmission performance over ultra-long haul transmission distances. Results from this real-time operation with error-free performance were presented at the Asia Communications and Photonics Conference in Shanghai in November 2012.

Key technologies of the 1Tb/s superchannel are as follows:

a) NEC combined a software-defined pulse shaper (*2) together with flexible-grid (*3) real-time 100Gb/s subcarriers (*4) to create a 1Tb/s superchannel. The pulse-shaper is designed to mitigate transmission impairments and to offer flexible bandwidth allocation capabilities. NEC achieved error-free transmission over a 5,400km link consisting of commercially available optical fiber and cost-effective repeater spacing. This technology provides a 43% improvement over the bandwidth utilisation of current commercial systems.

b) NEC also implemented a 1Tb/s superchannel composed of full-digital (*5) 100Gb/s subcarriers. Each subcarrier is equipped with a digital signal processor at the transmitter, which can potentially extend the re-configurability to a variable modulation format and/or for variable error-correction capabilities. This cutting-edge digital-transmitter technology enables the 1Tb/s superchannel to successfully transmit beyond 7,200-km.

NEC’s strength in ultra-long-haul transmission technologies is supported by its achievements providing the world’s first transmission of Optical-OFDM over 10,000km and the world’s first trans-pacific transmission of 16QAM signals. Now, NEC has reinforced its position by demonstrating the first real-time 1Tb/s superchannel transmission designed for ultra-long haul communications.

Notes:

*1: As of January 17, 2013. Source: NEC

*2: Software-defined pulse shaper
An optoelectronic device that changes the shape of an optical pulse according to values predefined by the user.

*3: Flexible-grid transponder:
A transponder capable of modifying the wavelength of the optical subcarrier.

*4: Real-time 100 Gb/s subcarrier
Based on an in-house commercial transceiver module incorporating results from “R&D on High Speed Optical Transport System Technologies (2009)” and “R&D on Ultra-high Speed Optical Edge Node Technologies (2010-2011),” which are supported by the Ministry of Internal Affairs and Communications of Japan.

*5: Full-digital subcarrier
An optical carrier that is generated with a digital transmitter and it is detected with a digital-coherent receiver.

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