What happens after 100G?

A recurrent theme throughout many of the technical presentations at ECOC was “what happens after 100G”. Different aspects of this theme were addressed in a variety of symposia, workshops and technical sessions. It certainly seems that there will be some really interesting technology being deployed as we head towards Terabit data rates. An interesting summary was that we will be dependent upon 3 ‘M’ technologies, not 3M Technologies www.mmm.com but

Multi-level
Multi-core and
Multi-mode.

Multi-level refers to multi-level coding schemes such as QAM and/or OFDM that may be used to improve the spectral efficiency and therefore the capacity of conventional singlemode fibres.

Multi-core means that we can expect to fibres being constructed with many cores, each of which may be used for transmission. Results were presented on successful manufacturing and even splicing of such fibres. Investigations into cross talk between the cores were also presented.

Multi-mode refers not just to conventional multimode fibre, but the techniques that may be used to implement Mode Division Multiplexing in multimode fibre. This is the process of launching different channels into multimode fibre at different radial positions to increase the total capacity. An array of detectors is used to select different mode groups at the receiver and digital signal processing used to separate the channels and cancel out crosstalk between them. Successful transmission of 8Gb/s over 5km of multimode fibre was demonstrated.