ATDnet Quick Report

Overview:

An OC-48 SONET ring segment was provisioned over a prototype WDM transmission system. Regenerative ADMs were replaced with optical amplifiers and dispersion compensating fiber to allow 10 Gbps/per wavelength capability. More detail can be found at http://www.bell-atl.atd.net/s-wpaper/s-w.html

Purpose:

To gain experience in the use of WDM to increase capacity of embedded fiber plant. This includes conditioning of facilities originally optimized for 1310 nm optical transmission for better performance in the 1550 nm window.

Description of Experiment:

An AON (All-Optical Network, see http://www.ll.mit.edu/aon) was established involving NRL, NSA, and DISA. The ATDNet OC-48 ring segment between NRL and NSA was provisioned over dedicated wavelengths on the AON system. The SONET performance was monitored as it coexisted with other applications that were added or removed from the AON. These other applications included videoconferencing, cryptography and distributed computing.

Results of Experiment:

The AON and SONET performed well for several weeks. After this period, several SONET ADMs required circuit pack replacement due to failures that could not be directly explained. It is hypothersized that the improper removal of a regenerative ADM placed the ring soft/firmware in an unstable mode which led to these circuit pack failures. Several tunable AON lasers also apparently failed due to building AC power instability.

Conclusions:

Standard fiber (i.e. 1310 nm chromatic dispersion optimized Corning SMF-28) is very susceptible to microbend attenuation. Many connectors, including some FC/PC, exhibit poor return loss and needed to be replaced for 10 Gbps application. As WDM is introduced, careful planning is needed to properly remove (from software) any SONET elements that will be bypassed. Integration of WDM and SONET element mangement systems is needed to better equip those who will maintain large networks comprised of this technology.