Optical sensor for circumferential interior surface of turbomachine casing, and related method

1. An optical sensor for a rotating blade stage of a turbomachine, the optical sensor comprising:

a housing configured to be mounted relative to a circumferential interior surface of a casing of the turbomachine;

at least one optical fiber operatively coupled to the housing for communicating: an optical signal for sending toward the rotating blade stage and a return optical signal reflected by the rotating blade stage, through the casing;

an optical signal redirecting element configured to redirect the optical signal from the at least one optical fiber inwardly toward the rotating blade stage relative to the casing, and redirect the return optical signal reflected by the rotating blade stage into the at least one optical fiber,

wherein the at least one optical fiber has a longitudinal shape configured to follow the circumferential interior surface of the casing; and

wherein the optical signal redirecting element redirects the optical signal from the at least one optical fiber inwardly at a substantially perpendicular angle relative to an axis of the turbomachine and substantially radially relative to the circumferential interior surface of the casing toward the rotating blade stage, and redirects the return optical signal reflected by the rotating blade stage into the at least one optical fiber extending along the circumferential interior surface of the casing.

2. The optical sensor of claim 1 , wherein the at least one optical fiber includes a single optical fiber.

3. The optical sensor of claim 1 , wherein the at least one optical fiber includes a send optical fiber for the optical signal, and a receive optical fiber for the return optical signal,

wherein the optical signal redirecting element is operatively coupled to the send optical fiber and the receive optical fiber.

4. The optical sensor of claim 1 , wherein the optical signal redirecting element includes:

a first optical signal redirecting element for the optical signal and a second optical redirecting element for the return optical signal, and

wherein the first optical signal redirecting element is distanced circumferentially from the second optical signal redirecting element along the circumferential interior surface of the casing.

5. The optical sensor of claim 4 , wherein at least one of the first and second optical signal redirecting elements includes a mirror.

6. The optical sensor of claim 4 , wherein at least one of the first and second optical signal redirecting elements includes a prism.

7. The optical sensor of claim 4 , wherein at least one of the first and second optical signal redirecting elements includes a cleaved end of the at least one optical fiber.

8. The optical sensor of claim 1 , wherein the housing and the at least one optical fiber have a radial height of no greater than 2 centimeters.

9. A method of performing an optical analysis of a rotating blade stage of a turbomachine, the method comprising:

mounting an optical sensor to a circumferential interior surface of a casing of the turbomachine, the optical sensor including:

a housing configured to be mounted relative to the circumferential interior surface of the casing of the turbomachine;

at least one optical fiber operatively coupled to the housing for communicating: an optical signal for sending toward the rotating blade stage and a return optical signal reflected by the rotating blade stage, through the casing;

a first optical signal redirecting element configured to redirect the optical signal from the at least one optical fiber and inwardly toward the rotating blade stage relative to the casing; and

a second optical signal redirecting element configured to redirect the return optical signal reflected by the rotating blade stage into the at least one optical fiber,

wherein the mounting includes routing the at least one optical fiber to follow the circumferential interior surface of the casing; and

performing optical analysis of the rotating blade stage using the optical sensor, and

wherein the first optical signal redirecting element redirects the optical signal from the send optical fiber toward the rotating blade stage at a first non-perpendicular angle relative to the circumferential interior surface of the casing, and

wherein the second optical signal redirecting element redirects the return optical signal reflected by the rotating blade stage received at a second non-perpendicular angle relative to the circumferential interior surface of the casing into the at least one optical fiber that extends along the circumferential interior surface of the casing.

10. The method of claim 9 , wherein the at least one optical fiber includes a send optical fiber for the optical signal, and a receive optical fiber for the return optical signal,

wherein the first optical signal redirecting element is operatively coupled to the send optical fiber and the second optical signal redirecting element is operatively coupled to the receive optical fiber.

11. The method of claim 10 , wherein the first optical signal redirecting element is distanced circumferentially from the second optical signal redirecting element along the circumferential interior surface of the casing.

12. The method of claim 9 , wherein the first and second non-perpendicular angles are different.

13. The method of claim 9 , wherein performing the optical analysis includes a clearance test for the rotating blade stage relative to the circumferential interior surface of the casing.

14. The method of claim 9 , wherein at least one of the first and second optical signal redirecting elements includes a mirror.

15. The method of claim 9 , wherein at least one of the first and second optical signal redirecting elements includes a prism.

16. The method of claim 9 , wherein at least one of the first and second optical signal redirecting elements includes a cleaved end of the at least one optical fiber.

17. The method of claim 9 , wherein the optical analysis performing includes a time-of-arrival testing for the rotating blade stage.