Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1990-07-31
1991-09-03
Eisenzopf, Reinhard J.
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
H04B 900
Patent
active
050461400
ABSTRACT:
An automatic frequency control system, for an optical coherent communication system, in which an output frequency of a local oscillator is swept by a frequency sweep signal FM-modulated with a frequency shift signal. The FM-modulated local frequency is combined with an input optical signal and heterodyne-detected. A frequency shift signal component derived from a heterodyne detection output is compared with the frequency shift signal to verify whether or not the local oscillation frequency is in a predetermined range with respect to the input signal frequency. When it is in the predetermined range, the system operates to terminate the frequency sweep signal and remove the frequency shift signal and is switched to oscillation frequency control of the local oscillator by using a d.c. component of the hterodyne detection output.
REFERENCES:
patent: 4903342 (1990-02-01), Yamazaki
S. D. Lowney et al., "Frequency Acquisition and Tracking for Optical Heterodyne Communication Systems", Journal of Lightwave Technology, vol. LT-5, No. 4, Apr. 1987, pp. 538-550.
Eisenzopf Reinhard J.
NEC Corporation
Sutcliffe Geoff
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