Optical component with spectral separation
The invention relates to an optical component comprising at least one input monomode fiber ( 1 - 4 ), at least one output monomode fiber ( 5 ) and a diffractive element ( 7 ) which is disposed between the input fiber or fibers ( 1 - 4 ) and the output fiber or fibers ( 5 ). The inventive component is characterized in that at least one of the input or output fibers ( 1 - 5 ) comprises a fiber ( 1 - 5 ) containing a portion ( 21 - 25 ) which is designed to increase the radius of the mode field it guides. According to the invention, the portion which is designed to increase the mode field radius can comprise a portion with a graded index, a portion having a core or cladding refractive index which varies transversely and/or longitudinally.
1. An optical component comprising at least one input monomode fiber ( 1 - 4 ), at least one output monomode fiber ( 5 ), a diffractive element ( 7 ) positioned between the input fiber or fibers ( 1 - 4 ) and the output fiber or fibers ( 5 ), and a focusing element ( 6 ) placed, between the ends of the fibers ( 1 - 5 ) and the diffractive element ( 7 ), characterized in that at least one of the input or output fibers ( 1 - 5 ) comprises a graded-index portion ( 21 - 25 ) designed to increase the radius of the mode field it guides for an enhancement of the FWHM/Δλ ratio and that the focusing element ( 6 ) is separated from the fibers.
2. The component as claimed in claim 1 , wherein the portion ( 21 - 25 ) designed to increase the mode field radius is formed of a segment(s) of fiber added and spliced to the end of the fiber ( 1 - 5 ).
3. The component as claimed in claim 1 , wherein the component forms a wavelength multiplexer/demultiplexer.
4. The component as claimed in claim 3 , wherein the diffractive element ( 7 ) receives the incident beams from a plurality of input fibers ( 1 - 4 ), the diffractive element ( 7 ) combines those incident beams into a single beam and sends this single beam to at least one output fiber ( 5 ).
5. The component as claimed in claim 3 , wherein the diffractive element ( 7 ) receives an incident beam containing different wavelengths from at least one input fiber ( 5 ), the diffractive element ( 7 ) separates the incident beam angularly and sends the beams separately to output fibers ( 1 - 4 ).
6. The component as claimed in claim 1 , wherein the fiber or fibers ( 1 - 5 ) also comprise a pure silica portion positioned between the end of the fiber ( 31 ) and the fiber portion ensuring the increase in the mode field radius ( 21 - 25 ).
7. The component as claimed in claim 1 , wherein each fiber ( 1 - 5 ) comprising a portion designed to increase the mode field radius has at its end a protective silica portion connected to the fiber portion ensuring the increase of the mode field radius ( 21 - 25 ), said protective silica portions can be polished without the risk of modifying the length of the fiber portion ensuring the increase of the mode field radius ( 21 - 25 ).
8. The component as claimed in claim 1 , wherein the diameter of the end of the fiber or fibers ( 1 - 5 ) comprising at least one fiber portion ensuring the increase of the mode field radius ( 21 - 25 ) is reduced by chemical attack of the external surfaces of the fibers.
9. The component as claimed in claim 1 , wherein the diffractive element ( 7 ) is chosen from the group consisting of echelle gratings, volume-phase holographic gratings, prisms or a combination of these elements.
10. The component as claimed in claim 1 , wherein the focusing element is a lens spatially separated from the input and output fibers.