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US 4,732,469 AGranted
Low noise optical time domain reflectometer
AssigneeIwatsu Electric Co., Ltd.
InventorMasafumi Souma
Life of this patent
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Abstract
A time domain reflectometer includes a combined a pulse generator for generating a pulse which is fed to an object under test such as a optical fiber and a sampler for sampling a reflection signal such as a back scattering signal. The pulse generator is controlled by analog delay means and the sampler is controlled by digital delay means. It, therefore, is possible to sample the small back scattering signal and to measure a very long fiber without influences of undesirable signals.
Claims6
A low noise optical time domain reflectometer comprising:
- clock means for generating clock edges at a predetermined frequency;
- digital delay means for generating a sampling signal upon receipt a predetermined number of the clock edges according to delay data;
- analog delay means for generating a pulse trigger at the end of a predetermined period according to the delay data after receipt of the first clock edge;
- pulse generating means for generating a pulse upon receipt of said pulse trigger;
- coupling means for sending said pulse to an object under test and taking out a reflection signal from the object;
- sampling means for sampling said reflection signal upon the instant of receipt of said sampling signal without being affected by noise which comes from said analog delay means;
- analog to digital converting means for converting an analog output of said sampling means to a digital value;
- and
- control means which includes,
- memory means for memorizing output data of said analog to digital converting means, and
- processing means for processing the delay data being sent out to said digital delay menas and said analog delay means, and for processing the output data memorized in said memory means,
- whereby data of said object under test are obtained.
9 more elements
Dependencies are inferred from the claim text.