Fiber optic dispersion method and apparatus

Claim 1

Transmission dispersion measuring means for an optic fiber under test comprising receiving means for receiving light through the fiber and producing an electrical signal in response thereto, the fiber under test having a characteristic wherein there is a one-to-one correspondence between a time delay produced therein and value of the transmissive parameter, first means for providing a coherently varying light signal for response thereto by said receiving means resulting from said time delay, a first time detector means for measuring said time delay and providing an ac signal indicative thereof, said first time detector means having a first input responsive to said receiving means and a second input, said second input comprising a first reference signal indicative of a modulating signal undelayed by the fiber, said measuring means further comprising means for modulating the value of the transmissive parameter in accordance with the frequency of a second reference signal at a second reference frequency alternately to first and second values of said transmissive parameter, whereby said ac signal is at said second reference signal frequency and second detector means for responding to the output of said first time detector means and to said second reference signal to produce an output indicative of said dispersion proportional to a component of said ac signal in phase with the second reference signal.

Claim 13

A method for measuring transmissive dispersion of an optic fiber comprising the steps of providing a light source providing light having selected values of a transmissive parameter with respect to which dispersion is being measured, imposing from a source of variation a coherent variation on the light, transmitting the light through said fiber under test whereby a time delay is produced in said fiber having a magnitude whose value for said fiber has a one-to-one correspondence with the value of the transmissive parameter, producing a first output indicative of the time delay by detecting the coherent variation of the light transmitted through the fiber and comparing the detected variation to the source of variation, modulating the value of the transmissive parameter to and from a first and a second value respectively during successive half cycles in accordance with a modulation frequency from a modulation frequency source, whereby the first output comprises a time difference signal at the modulation frequency, and measuring a component of the first output in phase with the modulation frequency source to provide an output indicative of transmissive dispersion.

Claim 14

A method for measuring transmissive dispersion of an optic fiber comprising the steps of providing a light source providing light having selected values of a transmissive parameter with respect to which dispersion is being measured, imposing from a source of variation a coherent variation on the light, transmitting the light through said fiber under test whereby a time delay is produced in said fiber having a magnitude whose value for said fiber has a one-to-one correspondence with the value of the transmissive parameter, producing a first output indicative of the time delay by detecting the coherent variation of the light transmitted through the fiber and comparing the detected variation to the source of variation, modulating the value of the transmissive parameter to and from a first and a second value respectively during successive half cycles in accordance with a modulation frequency from a modulation frequency source, whereby the first output comprises a time difference signal at the modulation frequency, and measuring a component of the first output in phase with the modulation frequency source to provide an output indicative of transmissive dispersion.