Advanced fibre Bragg gratings for high performance dispersion compensation in DWDM systems

Abstract

The increasing application of DWDM transmission schemes with bit rates of 10 Gb/s and 50 GHz channel spacing places a strict requirement on dispersion management. The use of chirped fibre Bragg gratings to compensate the dispersion of fibre links is a well-known approach that has become increasingly prevalent over recent years. An ideal dispersion compensator should either provide continuous operation over the full bandwidth of a transmission system, or be capable of being closely packed with other such devices in order that every available DWDM channel can be transmitted. These criteria have, to date, been difficult to fulfill with grating technology: a single dispersion compensating grating with a bandwidth of >30nm needs to be several metres in length raising questions of fabrication practicality and packaging concerns; traditional short (<10cm) chirped gratings, which may be packaged athermally and are more straightforward to fabricate, have a low bandwidth filling-factor, and a non-linear group delay response. In this paper, we present, for the first time, experimental results of gratings designed by a newly-developed layer-peeling inverse-scattering algorithm for single-channel dispersion compensation compatible with 50 GHz DWDM channel spacing. Gratings made by this design procedure have a very high bandwidth utilisation factor, both in terms of reflectivity and linear group delay. They are designed to accommodate RZ signals on a 50 GHz grid, but alternatively will provide high ASE rejection on a 100 GHz grid whilst maintaining a broad useable bandwidth. We believe that this approach overcomes the limitations normally associated with short chirped gratings, whilst retaining their desirable fabrication and packaging characteristics.

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ORCID for M.N. Zervas: orcid.org/0000-0002-0651-4059

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