Mixer-based time domain reflectometer and method
An apparatus to measure optical characteristics of a fiber optic transmission line or other optical medium may include a source to generate a bipolar pulse signal waveform. The apparatus may also include a mixer to mix the bipolar pulse signal waveform and an optical pulse and reflected signal waveform from the fiber optic transmission line or other optical medium to form a mixed product waveform, wherein the reflected signal is responsive to the optical pulse being transmitted into the fiber optic transmission line or optical medium.
1. A method to measure optical characteristics from a selected segment of a fiber optic transmission line or other optical medium divided into a predetermined number of segments, the method comprising:
determining an average value or voltage of an optical pulse and reflected signal waveform without any modulation on a local oscillator;
applying a bipolar pulse on the local oscillator at a time delay corresponding to the selected segment of the fiber optic transmission line or other optical medium;
mixing the bipolar pulse and the optical pulse and reflected signal waveform to form a mixed product waveform; and
determining an average value or voltage of the mixed product waveform to detect an anomalies in the fiber optic transmission line or other optical medium.
2. The method of claim 1 , wherein applying the bipolar pulse comprises applying a negative-going bipolar pulse to the local oscillator.
3. The method of claim 1 , further comprising detecting any reflections in the fiber optic transmission line or other optical medium at the selected segment based on a value or voltage at the selected segment.
4. The method of claim 1 , further comprising determining a value or voltage at the selected segment to detect any reflections at the selected segment.
5. The method of claim 4 , wherein determining the value or voltage at the selected segment comprises determining a difference between the average value or voltage of the optical pulse and reflected signal waveform without any modulation and the average value or voltage of the mixed product signal.
6. The method of claim 5 , further comprising amplifying the difference between the average value or voltage of the optical pulse and reflected signal waveform without any modulation and the average value or voltage of the mixed product signal by a predetermined factor.
7. The method of claim 5 , further comprising amplifying the difference between the average value or voltage of the optical pulse and reflected signal waveform without any modulation and the average value or voltage of the mixed product signal by a predetermined factor that is a function of the predetermined number of segments.
8. The method of claim 1 , further comprising detecting any reflections at any other segments along the fiber optic transmission line or other optical medium by time delaying the bipolar pulse to correspond to any of the other segments.