In-line forward/backward fiber-optic signal analyzer

• US 8,755,649 B2
• Filed: 08/11/2010
• Issued: 06/17/2014
• Est. Priority Date: 10/19/2009
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Yilmaz, Tolga, Brar, Khush, Lemaire, Charles A.
• Primary Examiner(s): Kianni, Kaveh C.
• Assistant Examiner(s): LAM, HUNG Q
• Application Number:
  US12/854,868
• Publication Number:
  US 20110091155A1
• Time in Patent Office: 1,406 Days
• Field of Search: 385/18, 385/27, 385/31, 385/38, 385/42, 385/47, 385/48, 385/122, 385/30, 359/333, 359/341.1, 359/341.2, 359/341.3, 359/341.31, 359/341.33
• US Class Current: 385/31
• CPC Class Codes: G02B 6/2817 using reflective elements to split or combine optical signals
• CPC Class Codes: G02B 6/2835 formed or shaped by thermal treatment, e.g. couplers
• CPC Class Codes: G02B 6/4207 with optical elements reducing the sensitivity to optical feedback anti-reflection devices specially adapted for lasers, see H01S3/0064
• CPC Class Codes: G02B 6/4287 Optical modules with tapping or launching means through the surface of the waveguide G02B6/2852, G02B6/4286 take precedence
• CPC Class Codes: G02B 6/4291 by accessing the evanescent field of the light guide
• CPC Class Codes: H01S 2301/02 ASE (amplified spontaneous emission), noise; Reduction thereof
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/094003 the pumped medium being a fibre
• CPC Class Codes: H01S 3/094053 Fibre coupled pump, e.g. delivering pump light using a fibre or a fibre bundle
• CPC Class Codes: H01S 3/09408 Pump redundancy
• CPC Class Codes: H01S 3/10015 by monitoring or controlling, e.g. attenuating, the input signal
• CPC Class Codes: H01S 3/13013 by controlling the optical pumping
• CPC Class Codes: H01S 3/2308 Amplifier arrangements, e.g. MOPA

Abstract

An optical connector having a plurality of directional taps and connecting between a plurality of optical waveguides (e.g., such as a connector between a waveguide that is part of, or leads from, a seed laser and/or an initial optical-gain-fiber power amplifier, and a waveguide that is part of, or leads to, an output optical-gain-fiber power amplifier and/or a delivery fiber), wherein one of the directional taps extracts a small amount of the forward-traveling optical output signal from the seed laser or initial power amplifier (wherein this forward-tapped signal is optionally monitored using a sensor for the forward-tapped signal), and wherein another of the directional taps extracts at least some of any backward-traveling optical signal that may have been reflected (wherein this backward-tapped signal is optionally monitored using a sensor for the backward-tapped signal).

Claims

1. A method comprising:

generating a seed-signal laser beam;

propagating the seed-signal laser beam in a forward-traveling direction in a core of an input optical fiber;

splitting the forward-traveling seed-signal laser beam from the core of the input optical fiber into a plurality of portions including a first portion having majority of the forward-traveling seed-signal laser beam and a second portion having a minority of the forward-traveling seed-signal laser beam;

directing the first portion of the forward-traveling seed-signal laser beam into a core of a first output optical gain fiber and directing the second portion of the forward-traveling seed-signal laser beam into a core of a second output optical fiber;

amplifying the first portion of the forward-traveling seed-signal laser beam in the first output optical gain fiber;

directing at least a first portion of a backward-traveling laser beam from the core of the first output optical gain fiber into a third output optical fiber; and

analyzing the second portion of the forward-traveling seed-signal laser beam and analyzing at least the first portion of the backward-traveling laser beam.

2. The method of claim 1, further comprising:

opto-isolating the forward-traveling seed-signal laser beam before the splitting of the forward-traveling seed-signal laser beam from the core of the input optical fiber into the plurality of portions.

3. The method of claim 2, further comprising:

providing a sealed enclosure having a plurality of fittings including a first fitting for accepting the first output optical fiber, a second fitting for accepting the second output optical fiber, a third fitting for accepting the third output optical fiber, and a fourth fitting for accepting the input optical fiber, and

performing, inside the sealed enclosure, the opto-isolating of the forward-traveling seed-signal laser beam from the input optical fiber, and the splitting of the forward-traveling seed-signal laser beam from the core of the input optical fiber into a plurality of portions.

4. The method of claim 1, further comprising:

providing a sealed enclosure having a plurality of fittings including a first fitting for accepting the first output optical fiber, a second fitting for accepting the second output optical fiber, a third fitting for accepting the third output optical fiber, and a fourth fitting for accepting the first input optical fiber, and

performing, inside the sealed enclosure, the splitting of the forward-traveling seed-signal laser beam from the core of the input optical fiber into the plurality of portions.

5. The method of claim 1, wherein the splitting of the forward-traveling seed-signal laser beam from the core of the input optical fiber into the plurality of portions includes reflecting the first portion of the forward-traveling seed-signal laser beam and transmitting the second portion of the forward-traveling seed-signal laser beam.

6. The method of claim 1, wherein the splitting of the forward-traveling seed-signal laser beam from the core of the input optical fiber into a plurality of portions includes evanescently coupling the second portion of the forward-traveling seed-signal laser beam from the core of the input optical fiber into the core of second output optical fiber, and wherein the directing of at least the first portion of the backward-traveling laser beam from the core of the first output optical fiber into the third output optical fiber includes evanescently coupling at least the first portion of the backward-traveling laser beam from the core of first output optical fiber into the third output optical fiber.

7. The method of claim 1, further comprising:

fusing a middle portion of a first source fiber to a middle portion of a second fiber to form an evanescent coupler, wherein the input optical fiber and the first output optical fiber are two end portions of the first source fiber at opposite sides of the middle portion of the first source fiber, and the second output fiber and the third output fiber are two end portions of the second fiber at opposite sides of the middle portion of the second fiber,

wherein the splitting of the forward-traveling seed-signal laser beam from the core of the input optical fiber into a plurality of portions includes evanescently coupling the second portion of the forward-traveling seed-signal laser beam from the core of the input optical fiber into the core of second output optical fiber using the evanescent coupler, and

wherein the directing of at least the first portion of the backward-traveling laser beam from the core of first output optical fiber into the third output optical fiber includes evanescently coupling at least the first portion of the backward-traveling laser beam from the core of first output optical fiber into the third output optical fiber using the evanescent coupler.

8. The method of claim 1, further comprising:

applying pump light to the first output optical gain fiber; and

controlling, based on results of the analyzing, at least one of the generating of the forward-traveling seed-signal laser beam and the amplifying of the laser beam.

9. An apparatus comprising:

a source of a seed-signal laser beam;

a signal-input optical fiber optically coupled to the source to propagate the seed-signal laser beam in a forward-traveling direction in a core of the input optical fiber;

a signal-output optical gain fiber;

a forward-tap output fiber;

a backward-tap output fiber;

a beam splitter optically coupled to the input fiber, the signal-output gain fiber, the forward-tap fiber, and the backward tap fiber, and configured to split the forward-traveling seed-signal laser beam from the core of input optical fiber into a plurality of portions including a first portion having a majority of the forward-traveling seed-signal laser beam directed into a core of the signal-output optical gain fiber and a second portion having a minority of the forward-traveling seed-signal laser beam directed into the forward-tap output fiber and to direct at least a portion of any backward-propagating light from the signal-output gain fiber into the backward-tap output fiber; and

an analyzer functionally coupled to the second portion of the forward-traveling seed-signal laser beam and at least the portion of a backward-traveling laser beam and that generates an analysis signal.

10. The apparatus of claim 9, further comprising:

an opto-isolator to optically isolate the forward-traveling seed-signal laser beam before the beam splitter.

11. The apparatus of claim 10, further comprising:

a sealed enclosure having a plurality of fittings including a first fitting for the signal-input fiber, a second fitting for the signal-output optical gain fiber, a third fitting for the forward-tap output fiber, and a fourth fitting for the backward-tap output fiber, and wherein the beam splitter and opto-isolator are enclosed within the sealed enclosure.

12. The apparatus of claim 9, further comprising:

a sealed enclosure having a plurality of fittings including a first fitting for the signal-input fiber, a second fitting for the signal-output optical gain fiber, a third fitting for the forward-tap output fiber, and a fourth fitting for the backward-tap output fiber, and wherein the beam splitter is enclosed inside the sealed enclosure.

13. The apparatus of claim 9, wherein the beam splitter reflects the first portion of the forward-traveling seed-signal laser beam and transmits the second portion of the forward-traveling seed-signal laser beam, in order to split the forward-traveling seed-signal laser beam from the input optical fiber into the plurality of portions.

14. The apparatus of claim 9, wherein the beam splitter includes an evanescent coupler that evanescently couples the second portion of the forward-traveling seed-signal laser beam from the input optical fiber to direct the minority of the forward-traveling seed-signal laser beam into the forward-tap output fiber, and wherein the beam splitter evanescently couples the portion of any backward-propagating light from the signal-output optical gain fiber into the backward-tap output fiber.

15. The apparatus of claim 9, wherein the beam splitter further comprises:

a middle portion of a first source fiber that is fused to a middle portion of a second fiber to form an evanescent-coupler beam splitter such that the input optical fiber and the signal-output optical gain fiber are two end portions of the first source fiber at opposite sides of the middle portion of the first source fiber, and the second output fiber and the third output fiber are two end portions of the second fiber at opposite sides of the middle portion of the second fiber.

16. The apparatus of claim 9, further comprising:

a source of pump light operative coupled to the signal-output optical gain fiber; and

a controller that is operatively coupled to receive the analysis signal from the analyzer and that, based on the analysis signal by the analyzer, controls at least one of the source of the seed-signal laser beam and the source of the pump light.

17. An apparatus comprising:

means for generating a seed-signal laser beam;

input optical-fiber core means for propagating the seed-signal laser beam in a forward-traveling direction;

means for splitting the forward-traveling seed-signal laser beam from the input optical-fiber core means into a plurality of portions including a first portion having majority of the forward-traveling seed-signal laser beam and a second portion having a minority of the forward-traveling seed-signal laser beam;

first output optical-fiber gain means for propagating and amplifying a first forward laser signal output beam, second output optical fiber means for propagating a first forward laser beam tap signal, and third output optical fiber means for propagating a first backward-traveling laser beam tap signal;

means for directing the first portion of the forward-traveling seed-signal laser beam into the first output optical-fiber gain means;

means for directing the second portion of the forward-traveling seed-signal laser beam into the second output optical-fiber means;

means for directing at least a first portion of a backward-traveling laser beam from the first output optical fiber gain means into the third output optical-fiber means; and

means for analyzing the first forward seed-signal laser beam tap signal and means for analyzing at least the first portion of a backward-traveling laser beam.

18. The apparatus of claim 17, further comprising:

means for opto-isolating the forward-traveling seed-signal laser beam before the means for splitting the forward-traveling seed-signal laser beam from the input optical-fiber means into the plurality of portions.

19. The apparatus of claim 17, wherein the means for splitting the forward-traveling seed-signal laser beam from the input optical-fiber means into the plurality of portions includes means for evanescently coupling the second portion of the forward-traveling seed-signal laser beam from a core of the input optical fiber into a core of the second output optical fiber means, and wherein the means for directing of at least the first portion of the backward-traveling laser beam from the core of the first output optical fiber means into the third output optical fiber means includes means for evanescently coupling at least the first portion of the backward-traveling laser beam from the core of the first output optical-fiber gain means into a core of the third output optical fiber means.

20. The apparatus of claim 17, further comprising:

means for applying pump light to the fiber means for propagating and amplifying; and

means for controlling, based on results of the analyzing, at least one of the means for generating of the seed-signal laser beam and the optical-fiber gain means for propagating and amplifying of the seed-signal laser beam.