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EP0564075A1 Expired / Lapsed EP ⏱️ 0.0 years remaining

Continuous phase FSK modulated optical transmission system with local osciallator control

Assignee: Nortel Networks Ltd
•
Filing: 1993-02-04
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Granted: —
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Expires: 2013-02-04
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Abstract

Abstract An optical transmission system utilising at a transmitter (100) continuous phase frequency shift keyed modulation of a laser (14) and a coherent heterodyne receiver (200) therefor, the system including at the transmitter means for imposing (18,12) a low frequency modulation on the transmitter optical power and frequency deviation and at the receiver means for extracting (28) from the receiver AGC control signal a replica of the low frequency modulation, means for demodulating (32) the modulated frequency deviation of the received optical signal synchronously with respect to the extracted low frequency signal, means for deriving (34) from the demodulated signal an error signal and a control system responsive to the error signal to control the receiver local oscillator (22) frequency.

Inventors

  • 👤 Ian Hardcastle

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-09 00:00
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/60; H04B10/61; H04B10/64

Claims Analysis

Total Claims: 5
Claim 1
Independent Claim 121 words
An optical transmission system utilising at a transmitter (100) continuous phase frequency shift keyed modulation of a laser (14) and a coherent heterodyne receiver (200) therefor, the system including at the transmitter means for imposing (18,12) a low frequency modulation on the transmitter optical power and frequency deviation characterised in that the receiver includes means for extracting (28) from the receiver AGC control signal a replica of the low frequency modulation, means for demodulating (32) the modulated frequency deviation of the received optical signal synchronously with respect to the extracted low frequency signal, means for deriving (34) from the demodulated signal an error signal and a control system responsive to the error signal to control the receiver local oscillator (22) frequency.
Claim 2
Dependent Claim 36 words
An optical transmission system according to claim 1, characterised in that the means for demodulating the modulated frequency deviation comprises means for multiplying the modulated frequency deviation with the replica of the local oscillator frequency modulation.
Claim 3
Dependent Claim 61 words
An optical transmission system according to claim 1, characterised in that means for imposing a low frequency modulation on the transmitter optical frequency deviation comprises a reference oscillator the output of which is applied to cause further modulation of the transmitter laser drive current during data modulation of the laser drive current for one significance only of a binary data input.
Claim 4
Independent Claim 72 words
A method of controlling local oscillator frequency in a receiver for a continuous phase frequency shift keyed modulation optical transmission system including the steps of superimposing at the system transmitter a low frequency reference modulation on the transmitter optical power and optical frequency and in the receiver demodulating the low frequency deviation variation synchronously with respect to the reference modulation to form an error signal for controlling the receiver local oscillator frequency.
Claim 5
Dependent Claim 14 words
A method according to claim 4 wherein the reference frequency is less than 100KHz.

References Cited (Backward Citations)

EP0142427A2 Cited
EP0247738A2 Cited
EP0298484A1 Cited
EP0401557A2 Cited

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