Patent ID: 6912046
Filing Date: 2005-06-28
Classification: D04B,G01M

Abstract:
1. An instrument for measuring chromatic dispersion in a subject optical fiber including an optical source and a receiver, wherein: the optical source for connection to an input end of the subject optical fiber, includes (a) a first pulse producing circuit which drives a laser that produces a laser pulse, the pulse entering the input end of the subject fiber, said laser pulse being used as a timing reference; and (b) a second pulse producing circuit which drives a light emitting diode (LED) which emits a short light pulse with a broad spectrum, which is also coupled to the subject optical fiber; the receiver including (a) a photodetector, connected at the output end of the subject optical fiber for detecting the laser pulse; (b) a wavelength-selection element connected to the output end of the subject optical fiber and thus optically connected to the LED, which filters one or several wavelengths out of the LED spectrum of the light pulse and transmits them to photon-counting detector; (c) the photon-counting detector, connected at the output end of the subject optical fiber, for detection of the filtered LED pulses; and (d) a high resolution timing circuit for measuring the time delay between the laser pulse and the LED pulse, connected to the photodetector at a receiving end of the timing circuit and, connected to the photo-counting detector at a feedback end of the high resolution timing circuit, and, connected to an analysis circuit and an output end of the high resolution timing circuit wherein the analysis circuit is a counting circuit which records the time delays for a large number of pulses.