Optical time domain reflectometer with high resolution and high sensitivity

1. An optical time domain reflectometry (OTDR) apparatus, comprising:

a splitter/combiner, the splitter/combiner configured to couple an optical pulse signal to one end of an optical fiber under test;

an optical modulator, the optical modulator configured to receive a reflected optical pulse signal from the one end of the optical fiber under test and to output a gated version of the reflected optical pulse signal;

a photodetector coupled to an output of the optical modulator, the photodetector configured to receive the gated version of the reflected optical pulse signal;

wherein the optical pulse signal is generated by at least one light source that is driven by a clocked signal; and

wherein a gating signal is time synchronized to the clocked signal.

2. The apparatus of claim 1 , wherein the gated version of the reflected optical pulse signal is based on a gating signal to the optical modulator that controls the optical modulator to block the reflected optical pulse signal except during a time window defined by the gating signal.

3. The apparatus of claim 1 , wherein the light source is at least one of: a) a laser, b) a vertical cavity surface emitting laser, and c) an edge emitting semiconductor device.

4. The apparatus of claim 1 , wherein the clocked signal operates at approximately 5 GHz.

5. The apparatus of claim 1 , wherein the at least one light source comprises a plurality of light sources.

6. The apparatus of claim 1 , wherein the optical modulator receives the reflected optical pulse signal through a coupling with the splitter/combiner.

7. The apparatus of claim 6 , further comprising an attenuator coupled between the splitter/combiner and the optical modulator.

8. The apparatus of claim 1 , further comprising:

a first ASIC that controls the optical pulse signal and measures an output of the photodetector that is based on the receiving of the gated version of the reflected optical pulse signal; and

a second ASIC, in time synchronization with the first ASIC, that controls the optical modulator for outputting of the gated version of the reflected optical pulse signal.

9. The apparatus of claim 8 , further comprising a third ASIC that provides clocking to the first and second ASICs for the time synchronization of the first and second ASICs.

10. The apparatus of claim 9 , further comprising a user control module that controls OTDR measurement parameters.

11. A method for optical time domain reflectometry (OTDR) apparatus, comprising:

coupling, via a splitter/combiner, an optical pulse signal to one end of an optical fiber under test;

based on the coupling, receiving, via an optical modulator, a reflected optical pulse signal from the one end of the optical fiber under test; p 1 generating, via the optical modulator, a gated version of the reflected optical pulse signal;

wherein the generating, via the optical modulator, of the gated version of the reflected optical pulse signal comprises:

providing, to the optical modulator, a gating signal;

based on the providing, blocking the reflected optical pulse signal except during a time window defined by the gating signal;

further comprising driving, via a clocked signal, at least one light source, thereby generating the optical pulse signal;

wherein the gating signal is time synchronized to the clocked signal;

detecting, via a photodetector, the gated version of the reflected optical pulse signal; and

based on the detecting, measuring an output of the photodetector to determine a time difference from the optical pulse signal to obtain an OTDR measurement.

12. The method of claim 11 , wherein the optical modulator receives the reflected optical pulse signal through a coupling with the splitter/combiner.

13. The method of claim 12 , further comprising:

coupling an attenuator between the splitter/combiner and the optical modulator.