The present disclosure relates to an arrangement for compensating a scattering of wavelength division multiplex signals induced by “stimulated Raman scattering”.
Stimulated Raman scattering leads to a power transfer from optical data signals with high frequencies to data signals with low frequencies which are transmitted via an optical fiber. Typically the contribution of the stimulated Raman scattering to the transmission function of a fiber, represented logarithmically, can be described as a straight line, the gradient of which is proportional to the power of the Raman source. The Raman scattering causes the individual data signals of a wavelength division multiplex signal to be amplified or attenuated to different degrees in the transmission fiber, as a result of which different signal levels and consequently different signal-to-noise ratios are produced at the receiver.
Different methods are known for compensating the undesirable scattering or, as the case may be, for setting the desired scattering. Thus, for instance, the scattering can be controlled by means of additional Raman sources, whereby the additional Raman sources also output and/or absorb additional power. The scattering can also be compensated by means of controllable filters.
It becomes problematic when channels or entire channel groups are added or disconnected. The same problems arise with planned transmission networks in which optical channels are switched (routed) dynamically via different transmission fibers. If a transmission fiber breaks, it is even possible for an entire transmission band to fail.
An electro-optical component consisting of ferroelectric material is known from the patent U.S. Pat. No. 6,584,260, which is incorporated by reference herein in its entirety. It is possible to achieve a wavelength-dependent transmission by means of different control voltages. However, a disadvantage of the double-refracting structures is the heavy dependence on the polarization of the impinging light.
Under exemplary embodiments, an arrangement is disclosed for compensating/adjusting the scattering of wavelength division multiplex signals.
On advantage of said the disclosed arrangement is the ease with which it can be implemented and the short reaction time for compensating the scattering. This is dependent on the microelectromechanical systems and can reach the range of 1 μs-10 μs. A linear damping can be set with the aid of a second microelectromechanical system. A control or regulation means is designed such that the system can react very quickly to changes in the scattering. In order to determine the scattering it is usually sufficient to ascertain the total power of all the signals. The scattering can also be determined by a measurement of the power of a small number of characteristic data signals or control signals. The gradient is calculated on the basis of the known mathematical principles and then the necessary control signals are issued to the microelectromechanical systems in accordance with a required transmission characteristic curve.
The various objects, advantages and novel features of the present disclosure will be more readily apprehended from the following Detailed Description when read in conjunction with the enclosed drawings, in which:
An adjustable linear damping element can also be used instead of the second microelectromechanical system MES2 and in principle the position of the Bragg filters can be changed instead of a swiveling of the mirrors being performed.
With reference to
The damping is preferably generated by swiveling of the second mirror MR2 which operates as a linear damping element in that only a part of the light beam is coupled into the fiber F via the collecting lens OS. Other linear damping elements can be used instead of the second mirror or the compensated WDM signal can be amplified accordingly.
Cascading a plurality of mirror-filter combinations SBG1, SBG2, each of which includes a mirror and a Bragg filter, increases the range of adjustment of scattering and damping. An arrangement of this kind is shown in
While the invention has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
Number | Date | Country | Kind |
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10358011.5 | Dec 2003 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP04/52957 | 11/15/2004 | WO | 00 | 6/12/2006 |