In-service optical time domain reflectometry utilizing raman pump source

Patent metadata

Field	Value
Publication number	US-9494484-B2
Application number	US-201514630988-A
Country	US
Kind code	B2
Filing date	Feb 25, 2015
Priority date	Mar 9, 2014
Publication date	Nov 15, 2016
Grant date	Nov 15, 2016

Abstract

An arrangement for providing real-time, in-service OTDR measurements in an optical communication system utilizing distributed Raman amplification. One or more of the laser diodes used to provide the pump light necessary to create optical gain is modified to also generate short duration pulses that ride above or below the conventional pump light. These short duration pulses (which co-exist with the pump light within the optical fiber) are used in performing OTDR measurements, with a conventional processing system used to evaluate reflected pulses and create the actual OTDR measurements.

First claim

What is claimed is:

1. An arrangement for performing optical time reflectometry (OTDR) within a communication system utilizing distributed Raman amplification, the arrangement comprising
a Raman pump source for supplying continuous power pump light to generate optical gain in a propagating signal
a pulse generator coupled to the Raman pump source, the pulse generator for injecting pulses of a predetermined polarity, duration, modulation depth and repetition interval onto the continuous power pump light such that the injected pulses co-propagate with the continuous power pump light along a span of optical waveguide to be measured while generating optical gain, the injected pulses propagating along the optical waveguide and creating a plurality of reflected pulses as a function of conditions along the optical waveguide; and
a monitoring module responsive to the plurality of reflected optical pulses, the monitoring module including a photodetector for converting the reflected optical signals into an electrical reflection signal and a signal processing component for determining OTDR measurements from the electrical reflection signal.

2. The arrangement of claim 1 wherein the pulse generator is coupled to a single Raman pump laser diode in the Raman pump source.

3. The arrangement as defined in claim 2 wherein the pulse generator is coupled to the single Raman pump laser diode operating at a longest wavelength within the Raman pump source.

4. The arrangement of claim 1 wherein the pulse generator is coupled to a plurality of separate Raman pump laser diodes within the Raman pump source.

5. The arrangement as defined in claim 4 wherein the pulse generator utilizes a separate set of polarity, duration, modulation depth and repetition interval parameters for each Raman pump laser diode in the plurality of separate Raman pump laser diodes.

6. The arrangement as defined in claim 4 wherein the pulse generator creates pulses upon more than Raman pump laser diode at the same time.

7. The arrangement as defined in claim 4 wherein the pulse generator creates pulses upon separate Raman pump laser diodes at different times.

8. The arrangement of claim 1 further comprising an optical filter disposed at the input of the monitoring module, the optical filter configured to pass only reflected optical pulses at the wavelengths of the one or more pulsed Raman laser diode sources.

9. The arrangement of claim 1 further comprising a pulse controller coupled to the pulse generator, the pulse controller providing command inputs to adjust one or more of the polarity, duration, modulation depth and repetition interval of the generated pulses.

10. The arrangement of claim 9 wherein the output from the monitoring module signal processing component is applied as an input to the pulse control and utilized to determine one or more of the generated command inputs.

11. The arrangement of claim 1 wherein the monitoring module comprises
a transimpedance amplifier coupled to the output of the photodetector and providing an amplified electrical output signal;
an A/D converter responsive to the amplified electrical output signal for creating a digital version thereof; and
a signal processor responsive to the digital output of the A/D converter for performing processing of the digital data and creating OTDR measurements therefrom.

12. The arrangement of claim 1 wherein the optical waveguide is a section of optical fiber.

13. A distributed Raman amplifier system including in-service optical time domain reflectometry (OTDR) measurement capabilities, the distributed Raman amplifier system comprising:
a transmission fiber for supporting the propagation of an optical signal;
a Raman pump source coupled to the transmission fiber for injecting continuous power pump light into the transmission fiber and generating optical gain within the propagating optical input signal;
a pulse generator coupled to the Raman pump source, the pulse generator injecting pulses of a predetermined polarity, duration, modulation depth and repetition interval upon the supplied pump light such that the pulses propagate with the continuous power pump light along the transmission fiber, the injected pulses propagating along the optical waveguide and creating a plurality of reflected pulses as a function of conditions along the transmission fiber; and
a monitoring module responsive to the plurality of reflected pulses, the monitoring module including a photodetector for converting the reflected optical signals into an electrical reflection signal and a signal processing component for determining OTDR measurements from the electrical reflection signal.

14. The distributed Raman amplifier system as defined in claim 13 wherein the Raman pump source is disposed to provide counter-propagating pump light with respect to the propagation direction of the optical input signal.

15. The distributed Raman amplifier system as defined in claim 13 wherein the Raman pump source is coupled to the transmission fiber through a wavelength division multiplexer, wherein the wavelength division multiplexer also functions to direct the returning reflected pulses out of an amplified optical signal output path and toward the monitoring module.

16. The distributed Raman amplifier system as defined in claim 15 wherein the system further comprises an optical coupling component for redirecting the reflected pulses from the wavelength division multiplexer into the monitoring module, output of a signal path associated with the Raman pump source.

17. The distributed Raman amplifier system as defined in claim 16 wherein the optical coupling component comprises an optical circulator.

18. The distributed Raman amplifier system as defined in claim 15 wherein the system further comprises an optical filter disposed between the optical coupling component and the monitoring module, the optical filter configured to pass only reflected optical pulses at the wavelengths of the one or more pulsed Raman laser diode sources.

19. The distributed Raman amplifier system of claim 15 further comprising a pulse controller coupled to the pulse generator, the pulse controller providing command inputs to adjust one or more of the polarity, duration, modulation depth and repetition interval of the generated pulses.

20. The distributed Raman amplifier system of claim 19 wherein the output from the monitoring module signal processing component is applied as an input to the pulse control and utilized to determine one or more of the generated command inputs.

Assignees

• Ii Vi Inc

Inventors

• Gurusami Aravanan
• Zahnley Timothy K
• Dahl Scott
• Williams Martin R
• Mcclean Ian P

Classifications

• G01M11/319

  Reflectometers using stimulated back-scatter, e.g. Raman or fibre amplifiers · CPC title

• G01M11/3127 Primary

  using multiple or wavelength variable input source · CPC title

• H01S3/302

  in an optical fibre · CPC title

• H01S3/094076

  Pulsed or modulated pumping (H01S3/1024 takes precedence) · CPC title

• H01S3/0014

  Monitoring arrangements not otherwise provided for (photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003) · CPC title