Optical wavelength monitoring apparatus
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United States of America Patent
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Apr 27, 1999
Grant Date -
N/A
app pub date -
Jun 19, 1997
filing date -
Jun 21, 1996
priority date (Note) -
Expired
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Abstract
In an optical wavelength monitoring apparatus for easily monitoring wavelength deviation, light introduced from a laser source 10 to an optical transmission line 12 is divided by directional couplers 14, 20. Optical output of the directional coupler 14 is converted into an electrical signal by a photodiode 16, and logarithmic-amplified by a logarithmic amplifier 18. Optical output of the directional coupler 20 is introduced to a photodiode 26 via an optical filter 24. The optical filter 24 is an optical element whose transmittance decreases as the incident light deviates from a specific wavelength .lambda.a. Optical output from the optical filter 24 is converted into an electrical signal by a photodiode 26, and logarithmic-amplified by a logarithmic amplifier 28. A differential amplifier 30 outputs a difference between outputs of the amplifiers 18, 28. A comparator 32 compares the output of the differential amplifier 30 with an alarm threshold Vref, and outputs an alarm-on signal when the difference is Vref or higher.
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