Overview examples
The following are examples of Fiber Bragg Gratings written with the NORIA including their original Sol Photonics design
EXAMPLE Fiber Bragg gratings in hydrogen loaded and non-hydrogen loaded SMF-28 fiber
Hydrogen loading significantly improves the photosensitivity of a fiber. As an example case, below are the results of an FBG designed for a sensing application written in a standard SMF-28 telecom fiber with and without hydrogen loading.
Grating design:
- Uniform grating
- Reflectivity >90%
- Physical length 4 mm
- Central wavelength: between 1510 – 1590 nm
Used phase mask:
- Ibsen +/- first order
- pitch 1066.41 nm
- no Chirp
- Optimized for 193 nm illumination
The following graphs show the difference in photosensitivity of the SMF-28 fiber. The enhancement in photosensitivity is a 100 fold:
A total of 5 gratings are written consecutively using the NORIA. Grating spectra given below show the performance in repeatability of writing a set grating design.
EXAMPLE High reflective long chirp gratings centered at 1650 nm
Gratings centered in the monitoring band of the ITU grid can be used for diagnostic purposes. Sol Photonics has made the grating design using GDS. Manufacturing of the gratings was done with the NORIA and an Ibsen phase mask.
Grating design:
- Uniform grating
- Reflectivity: 90%
- Physical length 10 mm
- Central wavelength: 1650 nm
- Full Width Half Maximum: >10 nm
Sol Photonics GDS simulation result
The Sol Photonics GDS software indicates which phase mask (pitch and chirp rate) is needed. After purchasing a phase mask the designed grating is manufactured. Results are given below. (left; reflection spectrum, right: transmission spectrum)
EXAMPLE High Reflective (HR) grating and Output Coupler (OC) grating in Large Mode Area (LMA) fiber
High power fiber lasers use Fiber Bragg Gratings as cavity mirrors. 2 different grating designs are used to comprise a laser cavity; an HR grating with a typical reflectivity >97% and a bandwidth of several nm (e.g. 3 to 5 nm) and an OC grating which is used for feedback with a typical reflectivity between 4 - 20 % and a bandwidth of 0.5 - 1 nm. The fiber type used in a fiber laser cavity is typically a Large Mode Area (LMA) fiber having a small NA (0.06 - 0.08) and large core (e.g. 20µm).
Using GDS the following design was made (left: HR grating, right OC grating).
Phase masks are ordered based on the GD simulations and gratings written using the NORIA. Both HR and OC results are given in the figures below.
