Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-06-03
2001-10-30
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200, C359S199200, C359S199200, C375S130000
Reexamination Certificate
active
06310706
ABSTRACT:
TECHNICAL FIELD
The present invention relates to two transmitting/receiving facilities and a method for transmitting broadband signals, and to two transmitting/receiving facilities for receiving broadband signals.
BACKGROUND OF THE INVENTION
Broadband signals are, for example, request signals or data signals which are transmitted from a subscriber to a center in the upstream frequency band of a distribution network with a return (upstream) channel. EP 0 422 032 B1 discloses a data transmission apparatus for a cable television distribution network with a return channel by means of which data of a subscriber is transmitted to a center (head end) in the upstream frequency band using spread-spectrum techniques. Stationary interference signals caused by broadcasts may enter a cable television distribution network and may adversely affect the transmission of the data in the upstream frequency band, since they lie in the same frequency band. The return channel uses the frequency band 5-30 MHz, for example. For error-free tansmission of data at a high bit rate, e.g., 2 Mb/s, no sufficiently large interference-free frequency range is available in the return channel because of the great number of stationary interference signals. During despreading, however, the stationary interference signals are also multiplied by the spreading function and thus spread. As a result, portions of the interference signals appear in the frequency band of the broadband signals and cause a degradation in signal-to-noise performance.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to transmit broadband signals in such a way that they are less susceptible to stationary interference signals.
This object is attained by a transmitting/receiving facility for optically transmitting broadband signals using spread-spectrum techniques, comprising: a receiving unit for receiving frequency values of stationary interference signals occurring on an optical link; a memory for storing the received frequency values; a broadband optical source; an electrooptic modulator for modulating the optical output signals from the broadband optical source with the broadband signals to be transmitted; and an optical filter with variable stop frequencies which are varied, at least in part, as a function of the stored frequency values.
It is further attained by a transmitting/receiving facility for receiving broadband signals modulated using spread-spectrum techniques, comprising: a detection unit for detecting frequency values of stationary interference signals; a transmitting unit for transmitting the detected frequency values; a memory for storing the detected frequency values; at least one optical filter with variable stop frequencies which are varied, at least in part, as a function of the stored frequency values; and at least one optical-to-electrical transducer following the at least one optical filter and serving to convert the signals passed by the at least one optical filter from optical to electrical form.
A particular advantage of the invention is that the transmission of the broadband signals is very insensitive to discrete-frequency interference signals. The bit errors that would be caused by the interference signals are reduced.
Furthermore, the invention can be used for transmission over both coaxial cables and fiber optic cables and for radio transmission.
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H1702, Wideband Fiber-Optic Signal Processor, by Esman et al., Jan. 06, 1998. United States Statutory Invention Registration.
Heidemann Rolf
Krimmel Heinz
Alcatel
Nguyen Chau Minh
Pascal Leslie
Ware Fressola Van der Sluys & Adolphson LLP
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