/Updates To Transmission Technology
Updates To Transmission Technology2018-03-15T12:46:35+00:00


The presentations will address the following topic areas and will bring the attendee up to speed on the latest trends and debates in this sector.

Overview and constraints

Submarine systems differ from terrestrial ones in addressing very long spans and requiring very high reliability elements because repairs are time-consuming and expensive. Power for amplifiers and active elements (e.g. ROADM Branching Units) is limited by the resistance and voltage capacity of cables. The overview will examine the boundaries that exist and consider how these may evolve in the future.


Coherent transmission and DSP have allowed systems to evolve from complex dispersion-managed maps to using just a single type of fiber throughout a system. Reducing non-linear effects, however, has pushed fiber manufacturers to larger core sizes and there is now demand for increased bandwidth for C+L band systems – possibly even broader bandwidth using the S-band. How do these factors affecting fiber design?


Simple Erbium-Doped Fiber Amplifiers (EDFAs) have so far been used, but greater bandwidth can be offered by C+L and Hybrid Raman amplifiers. Semiconductor amplifiers are very compact, but have yet to be exploited in subsea systems; could recent developments change this? While extra bandwidth is the best route to greater capacity, it comes with greater complexity, cost and power consumption. This section will review what is possible, practical and cost-effective.

Modulation formats

The shift from binary to higher order modulation (e.g. QPSK, 8QAM, 16QAM) has been a significant factor in system capacity and we are now seeing constellation shaping to further enhance performance.  This section will describe useful types of shaping and what they can add in terms of performance.

Non-linear mitigation, FEC etc.

Using complex signal processing to mitigate the effects of non-linear optical propagation has been studied for a long time without yet yielding industrial solutions. The ever-increasing power of DSP chips, however, has always suggested that at some point there will be a useful solution. The most recent progress will be reviewed and assessed to determine whether this is now an applicable technology.

FEC has been a significant factor in the past, but has the move to soft-decision codes with overheads in the region of 25% reached the point where further useful improvements are no longer possible? Are there other forms of processing which can improve overall performance?

Principal Instructor, Updates To Transmission Technology
Tony Frisch, Chief Technical Officer

Tony joined Xtera in 2004 initially managing Marketing and Proposals for terminal equipment and upgrades and then responsible for products such as Repeaters and Branching Units, and now serves as CTO. Tony started work at BT’s Research labs investigating cable problems and then moved to Alcatel Australia, becoming involved in testing and commissioning submarine systems.  A move to Bell Labs gave him experience in terminal design and troubleshooting, after which he went back to Alcatel France, where he worked in Alcatel Submarine Networks’ Technical Sales before moving to head Product Marketing.