Image conduit for fuel nozzle assemblies

1. A fuel nozzle for a gas turbine engine, comprising:

a feed arm including a fuel passage for issuing a spray of fuel;

a nozzle assembly fixed at an upstream end of the feed arm having a fuel inlet in fluid communication with the fuel passage; and

a fiber optic cable configured to collect burner radiation for a pyrometer input having a first end centered within an optical connector of the nozzle assembly and a second end exposed from the spray outlet, wherein the fiber optic cable fitted within the feed arm and nozzle assembly has a permanent bend radius preformed in the fiber optic cable,

wherein the bend radius is equal to or greater than the minimum bend radii for the fiber optic cable to serve as a waveguide for wavelengths for monitoring combustion,

wherein the fiber optic cable includes a rigid metal sheath enclosing a plurality of individual wave guides,

wherein each wave guide is 0.017 inches in diameter such that the metal sheath has a minimum bend radius of three times a wave guide diameter.

2. The fuel nozzle of claim 1 , wherein each wave guide is spaced apart from the other wave guides.

3. The fuel nozzle of claim 1 , wherein interstitial sites between each wave guide are filled with compacted alumina powder.

4. The fuel nozzle of claim 1 , wherein the metal sheath has bend radius of 0.5 inches.

5. The fuel nozzle of claim 1 , wherein the fiber optic cable includes seven wave guides with a center wave guide and six wave guides circumferentially spaced around the center wave guide.

6. The fuel nozzle of claim 5 , wherein each of the wave guides are the same diameter such that a 1/7th reduction in expected signal strength indicates breakage of one of the wave guides.

7. The fuel nozzle of claim 1 , wherein wavelengths of light passed through each wave guide are within the range of 430 nm to 1400 nm.

8. The fuel nozzle of claim 1 , wherein each wave guide is made up of fibers coated and bonded to adjacent fibers.