Coded data generation or conversion – Digital code to digital code converters – Serial to parallel
Reexamination Certificate
2002-03-04
2003-06-24
JeanPierre, Peguy (Department: 2819)
Coded data generation or conversion
Digital code to digital code converters
Serial to parallel
C341S101000
Reexamination Certificate
active
06583737
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and a device for compensating for propagation delay differences between n serial data streams (n=2, 3, . . . ), which are each transmitted via parallel optical lines, with data which can be transmitted by means of the n serial data streams being in the form of m-bit-words (m=1, 2, . . . ).
Cables which have a number of optical lines can be used for optical transmission of information and data. The lines are in this case in the form of individual glass fibers. When data is transmitted in parallel form and optically via a number of glass fibers, which are combined to form a cable, the signals to be transmitted have different delays in the individual glass fibers. These delays are due to physical effects and relate, in particular, to propagation delay scatters owing to wavelength differences or manufacturing tolerances, which occur during the production of the glass fibers. This places a major restriction on the maximum length of the glass fibers that can be used for transmission. For example, the maximum length for transmission of data rates of 1.3 GBd is less than 100 m.
In order to avoid propagation delay differences resulting from manufacturing tolerances in the production of the glass fibers, the glass fibers that are produced are measured individually and are then selected such that only glass fibers with similar transmission characteristics are used together in one cable.
U.S. Pat. No. 5,426,644 (European patent 533 091) describes a method for parallel transmission of data, with a large number of 1 to P parallel data channels at the transmission end being in each case converted by means of a multiplexing apparatus as a serial data stream and then being transmitted to the receiver end, where the serial data is once again demultiplexed in an appropriate manner. This system has a propagation delay compensation apparatus, which synchronizes the serial data.
In the article “Long Distance Parallel Data Link Using WDM Transmission with Bit-Skew Compensation”, from the Journal of Lightwave Technology, Vol. 14, No. 5, May 1996, G. Jeong, et al. describe, as an alternative to pure serial data transmission systems for long distances (>>10 km), a parallel WDM data transmission system with a propagation delay compensation apparatus. The disclosed methods for compensating for propagation delay between the parallel optical data channels have the disadvantage that it is necessary to measure the propagation delay differences between the various parallel transmission channels individually.
SUMMARY OF THE IVNENTION
It is accordingly an object of the invention to provide a device and method for compensating for propagation delay, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which compensates for the described propagation delay scatters, which, in particular, does not require separate propagation delay characterization of the parallel transmission channels.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for compensating for propagation delay differences between n serial data streams transmitted via parallel optical lines, wherein the data transmitted via the n serial data streams are formed as m-bit words, the device comprising:
n regeneration apparatus each having an input connected to one of the parallel optical lines, a data output and a clock output, the input receiving a data stream from the respective optical line, each the regeneration apparatus being configured to regenerate data and a clock from the respective data stream;
propagation delay control apparatus each having a data input and a clock input respectively connected to the data output and the clock output of the regeneration apparatus, the data input receiving the regenerated data and the clock input receiving the regenerated clock; and
each of the propagation delay control apparatus having a demultiplexer for dividing the regenerated data and the regenerated clocks in a ratio 1:(x·m) and an alignment apparatus for distributing the divided, regenerated data between in each case x·m parallel data outputs of the propagation delay control apparatus, wherein a divided, regenerated clock that is synchronized to the divided, regenerated data is emitted at a clock output of a least one of the propagation delay control apparatus.
In other words, the objects of the invention are achieved:
in that data and a clock for the respective data stream are regenerated by means of the respective regeneration apparatus, with the data stream being transmitted via the parallel optical lines to the respective input;
in that one data output and one clock output of the regeneration apparatus are in each case connected to propagation delay control apparatus, so that the regenerated data and the regenerated clock are respectively passed to a data input and a clock input of the propagation delay control apparatus; and
in that the propagation delay control apparatus each have a demultiplexer for dividing the regenerated data and the regenerated clocks in the ratio 1:(x·m) (x=1, 2, . . . ) and an alignment apparatus for distributing the divided, regenerated data between in each case x·m parallel data outputs of the propagation delay control apparatus, wherein a divided, regenerated clock which is synchronized to the divided, regenerated data can be emitted at a clock output of a least one of the propagation delay control apparatus.
It is a primary advantage of the invention that it provides the capability to compensate for the propagation delay scatters which occur during transmission by means of parallel optical lines. In comparison to known transmission paths, this allows considerably longer transmission paths to be used. This opens up novel application options for the use of optical signals for information transmission.
A further advantage is that there is no need for measurement and selection of glass fibers which have been produced and are intended to be used together in one glass fiber, since any propagation delay differences that occur can be compensated for by means of the device according to the invention.
In accordance with an added feature of the invention, the n regeneration apparatus are a clock regeneration apparatus.
In accordance with an alternative feature of the invention, one of the n regeneration apparatus is a clock regeneration apparatus, and a number n−1 of the regeneration apparatus are each formed as a phase regeneration apparatus, and the clock output of the clock regeneration apparatus is connected to a respective clock input of the n−1 phase regeneration apparatus.
In accordance with another feature of the invention, the device further comprises:
n multiplexer apparatus for converting the divided, regenerated data to a respective serial, regenerated data stream, the n multiplexer apparatus having x·m parallel data inputs respectively connected to the x·m parallel data outputs of the propagation delay control apparatus; and
a synthesizer having an input connected to a respective clock input of the multiplexer apparatus and to the clock output of the at least one propagation delay control apparatus, and the synthesizer having an output connected to a respective further clock input of the multiplexer apparatus.
In accordance with an additional feature of the invention, at least one of the n multiplexer apparatus has a serial clock output for outputting a further serial clock signal matched to the serial regenerated data stream and delayed with respect to a serial clock signal generated by the synthesizer.
In accordance with a concomitant feature of the invention, decoder apparatus are provided. Each of the decoders is coupled between a respective propagation delay control apparatus and multiplexer apparatus.
That is, one expedient refinement of the invention provides that the n regeneration apparatus are each in the form of a clock regeneration apparatus, thus allowing separate clock regeneration for each
Greenberg Laurence A.
Jean-Pierre Peguy
Locher Ralph E.
Stemer Werner H.
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