Optics: measuring and testing – By shade or color – With color transmitting filter
Patent
1997-06-19
1999-04-27
Evans, F. L.
Optics: measuring and testing
By shade or color
With color transmitting filter
356419, 250226, 372 32, H04B11008, G01J 351
Patent
active
058985026
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.
REFERENCES:
patent: 4821273 (1989-04-01), Hori
patent: 4998043 (1991-03-01), Unami et al.
Horiuchi Yukio
Yamamoto Shu
Evans F. L.
KDD Submarine Cable Systems Inc.
Kokusai Denshin Denwa Kabushiki Kaisha
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