Optical communications

Details Optical communications Optical communications

2000-08-31

2003-11-18

Negash, Kinfe-Michael (Department: 2633)

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

C359S199200

Reexamination Certificate

active

06650452

ABSTRACT:

This invention relates to optical communications and, in particular, to optical communications systems in which information is transmitted by soliton or soliton-like pulses.
BACKGROUND OF THE INVENTION
Laboratory demonstrations have recently been reported of soliton transmission in systems where the dispersion was not uniformly anomalous along the fibre, instead being periodically compensated by fibre of opposite (normal) sign dispersion. In this manner transmission was achieved at 20 Gb/s over 9000 km in a recirculating loop, and 8100 km in a straight line experiment. These figures are substantially in excess of what has previously been achieved without the use of soliton control techniques such as sliding filters and synchronous modulators. While it is thus clear that there are significant benefits to be gained from adopting dispersion management in soliton systems, to date there has been little conceptual explanation of the mechanisms behind this improvement.
The correct selection of dispersion is a critical issue in the design of amplified long haul optical communication systems. In the case of soliton formatted data, it is dictated by compromise between the desire to minimise timing jitter problems (implying low dispersion), and the need to maintain adequate energy per bit for successful detection. As the energy needed to form a soliton in a uniform fibre is proportional to the dispersion, the latter constraint places a lower limit on the permitted dispersion. Dispersion management is a technique in the context of non-return-to-zero (NRZ) formatted data in which fibres of opposite sign dispersions are concatenated together. This produces a high local dispersion at any given point, and yet a low path-average dispersion. We have found that, by adopting a suitable dispersion management scheme for soliton or soliton-like transmission, it is possible to increase the soliton energy substantially compared with the equivalent uniform fibre with equal path-average dispersion.
DESCRIPTION OF THE INVENTION
According to the present invention there is provided a dispersion management system for soliton or soliton-like transmission in which the duration of a dispersion compensation phase is short in comparison with the propagation interval in the remainder of the system.
Preferably the system excludes arrangements in which the dispersion map of one fibre is substantially closer to zero than that of its complementary fibre.


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