A grating is an optical element composed of a large number of parallel slits (or reflective surfaces) of equal width and spacing.
Classification of gratings
Geometry Classification: Planar Gratings and Stereo Gratings
Action type classification: reflection grating and transmission gratingfiber optic splitter box
The role of grating
Dispersive spectroscopy, the most basic application, uses the optical path difference to achieve the effect of spectral separation. The technology is the most sophisticated, with a wide variety and mature technology;
optical filter;
In information optics, optical imaging, gratings are used for filtering, encoding and wave selection and holographic imaging;
In the field of optical fiber communication and optical fiber sensing, fiber gratings are also widely used.
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grating diffraction
When the parallel light hits the grating plane perpendicularly, the light wave will diffract at each slit, and the diffracted light interferes and then converges on the screen through the lens, so that fine and bright equal-spaced fringes appear on the screen.
is the combined effect of single-slit diffraction and interference between individual slits.fibconet.com
Definition of Fiber Grating
Fiber grating: On a certain length of fiber, the refractive index is periodically changed in the core or cladding of the fiber. The essence of fiber grating is a transmission or reflection filter, and the spectral characteristics and time delay characteristics can be flexibly designed. It has the advantages of small size, light weight, anti-electromagnetic interference, chemical stability and electrical insulation. fiber optic passive components.fibconet.comfiber optic splitter box
Classification of fiber gratings
Divided by cycle size into
Bragg grating (FBG: Fiber Bragg Grating, period less than 1 micron)
Long Period Gating (LPG: Long Period Gating, period greater than 10 microns)
When referring to grating, unless otherwise specified, it is generally short period grating fiber optic splitter box
According to the uniformity of the modulation period:
Uniform and Chirped Gratings
Sampling raster is divided into sampling method:
phase sampling grating
Amplitude sampling grating
Phase-shift grating: The phase-shift fiber grating is formed because the refractive index modulation of the grating produces a phase mutation at a certain position, which is reflected in its reflection spectrum and opens a transmission window with a very narrow bandwidth.fibconet. com fiber optic splitter box
Blazed grating
The refractive index modulation fringes are inclined at a certain angle to the fiber axis
According to the intensity of UV exposure
Class I grating
Refractive index changes due to localized defect formation in fibers with lower UV exposure and lower doping concentration
Refractive index change ⊿n～10-5—10-3>0 Poor temperature stability (300℃); pulse or continuous laser can be used, the former is more effective fiber optic splitter box
Class IIA (III) grating
Higher UV exposure (> 500J/cm2), the formation of structural reconstruction in the fiber with higher doping concentration causes the refractive index change, the refractive index change ⊿n<0; the temperature stability is better (500 ℃); the pulse can be used or continuous laser
Class II grating
Extremely high UV exposure, instantaneous local temperature can reach thousands of degrees; physical damage causes refractive index change; refractive index change ⊿n can reach 10-2; good temperature stability (800 ° C); only pulsed laser can be used
Classification by materials used: single-mode fiber grating, multi-mode fiber grating, optical fiber grating
Subcrystal fiber grating, polarization maintaining fiber grating, ….fibconet.com
