Alien Wavelengths
Alien wavelengths are WDM wavelengths which are driven by equipment other than the JANET optical transmission equipment.
If the JANET transmission infrastructure was able to accomodate alien wavelengths, then there would be the potential to use the JANET fibre footprint to support some projects which might otherwise need dedicated fibre. There would clearly be important constraints on any such use to avoid disruption of exsiting services being carried on other wavelengths within the fibres, and the notes below summarise some of the issues which were highlighted at a meeting with Verizon and Ciena (18th April 2007) where this topic was discussed.
Notes
1) To some extent alien wavelengths are already in use in the sense that at particular locations on JANET the 4200 systems are sourcing wavelengths which are then delivered to the optical multiplexers on the Corestream systems for transmission on the fibres.
2) The 4200 systems have optics which conform to the 100GHz ITU grid, the Corestream systems conform to the 50GHz grid. This would need to be taken into account when looking for available channels for potential cross-JANET wavelengths (Regional-arc, Core, Regional-arc)
3) Some mechanism might be needed to ensure that the optical power accepted from third party equipment sourcing alien wavelengths is restricted to normal operating levels. The current JANET equipment has no such mechanism, though Ciena reported that Variable Optical Attenuators (VOAs) would be available on future versions of some interfaces for the systems of interest.
4) Alien wavelengths could in principle use aribitrary/experimental (non-standard) modulation and framing schemes (this would be the major reason for wanting to use such a wavelength to support a research project), however the operational constraint is that these wavelengths must not disrupt service operation on adjacent channels, and so they must restrict their power spectra to be contained within normal levels appropriate for the grid they are operating within.
5) It may be possible to support non-standard alien waves without amplification, compensation, or regeneration on shorter spans across the network (such as a regional collector-arc), but longer distances would imply the location of additonal equipment to perform these tasks within the network. This may be possible, but would need more detailed study of a particular proposal to asess feasibility and costs.
6) Although not discussed specifically at the meeting, some interest had been expressed in the use of JANET core routers as sources of alien waves. If suitable optics were to be available then none of the points noted above would exclude this use, but broader operational considerations such as maintenance and spares holdings would need to be examined more closely before pursuing this further.
Summary
Sufficient understanding of the issues related to support of alien wavelengths on JANET has now been obtained and for the time being no further work is proposed in this area.
Although it would not be impossible to support such wavelengths, there is no general solution and if there is interest from the JANET community in pursuing this concept then further discussions would be needed to understand the specific details of any project being proposed.
The community which would benefit from arbitrarily structured alien wavelengths is quite small (probably restricted to photonics or network research and specialised Radio Astronomy use at present). Other projects are generally only interested in high-capacity point-to-point links and they are well catered for by the JANET Lightpath service using standard transmission mechanisms.
It may still be feasible to permit some projects to proceed within the environment provided by a single collector arc, but the additional constraints and complexities associated with broader cross-JANET transmission may make such use infeasible (technically, operationally, economically.)