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Coherent optical multi-channel arrangement

  • US 5,365,361 A
  • Filed: 06/10/1993
  • Issued: 11/15/1994
  • Est. Priority Date: 06/17/1992
  • Status: Expired due to Fees
First Claim
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1. A coherent optical multi-channel arrangement comprising a plurality of spatially distributed optical transmitters for transmitting optical information signals,, each transmitter having means for frequency modulating said optical information signals with a modulation frequency within a predetermined modulation frequency range, each of the transmitters transmitting its frequency-modulated optical information signal on a respective channel at a respective carrier frequency, the respective channel carrier frequencies of said channels differing from one another by such small frequency spacings that a risk of crosstalk between the channels may be present given frequency changes of the carrier frequencies caused by instability during operation of one or more transmitters, each of the transmitters having means for additionally frequency-modulating its frequency-modulated optical information signal with a periodic identification signal, each periodic identification signal having a unique fixed repetition frequency individually allocated to its transmitter for identification of the respective transmitter;

  • means for tapping the additionally frequency modulated, frequency-modulated optical information signals from each transmitter to obtain a plurality of tapped signals;

    means for forming an optical frequency comb spectrum having components respectively at a plurality of reference frequency lines at respective fixed reference frequencies, said fixed reference frequencies respectively coinciding with said carrier frequencies at said small frequency spacings from one another;

    coherent optical heterodyning means supplied with the tapped signal of each transmitter, for generating a heterodyned signal by respectively superimposing said tapped signals with the components of the optical frequency comb spectrum;

    filter means, supplied with said heterodyned signal from the heterodyning means, for transmitting the repetition frequencies of the identification signals and any frequency changes of the channel carrier frequencies contained in the heterodyned signal, and for blocking higher frequencies that are otherwise obtained in the heterodyned signal including the channel carrier frequencies of the transmitters and the modulation frequencies of the frequency-modulated optical information signals, said filter means having a filter output signal that contains the information about the repetition frequencies, said frequency changes and an allocation of the frequency changes to the repetition frequencies; and

    control means, supplied with said filter output signal and connected to each transmitter, for generating a respective control signal for every transmitter for controlling the channel carrier frequency of each transmitter, dependent on said information contained in the filter output signal for cancelling any existing frequency change of the carrier frequency of the transmitter.

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