Optical device comprising a compact dispersing system
A fibre optic transmission application, in particular, an optical device that can be incorporated into telecommunications equipment as well as into test and measurement equipment with reduced insertion loss, reduced crosstalk effects and reduced height, with increased versatility in the implementation of optical functions other than multiplexers and demultiplexers. Relates to components, modules, equipments and instruments such as multiplexers, demultiplexers, routers, channel monitors, and tunable filters that encompass such optical devices.
1. An optical device ( 100 , 500 ) comprising:
a) a single fibre array ( 120 , 220 , 320 , 520 ) comprising a single end face ( 125 );
i) the single fibre array ( 120 , 220 , 320 , 520 ) being a mounting assembly that comprises M input elements ( 122 ) with beam emitting end faces positioned on a first straight emission line ( 112 ), and N output elements ( 121 ) with beam receiving end faces positioned on a second straight reception line ( 111 ) which is parallel to the first straight emission line ( 112 ) and separated from the first straight emission line ( 112 ) by a distance D chosen such that at least the input elements ( 122 ) do not affect the output elements ( 121 ) and vice versa, where the beam emitting end faces of the input elements ( 122 ) and the beam receiving end faces of the output elements ( 121 ) are positioned such that they substantially coincide with the single end face ( 125 ) of the fibre array ( 120 , 220 , 320 , 520 ); and
b) a compact dispersing system ( 130 , 530 );
c) the compact dispersing system ( 130 , 530 ) ensuring wavelength selective conjugation of signals between the end faces of the input elements ( 122 ) and the end faces of the output elements ( 121 ) based on beam propagation and comprising:
i) an aperture-less plane mirror ( 140 , 540 );
ii) a single concave mirror ( 60 ) having a focus, a focal plane and an axis ( 63 ) that intersects the end face ( 125 ) of the fibre array ( 120 , 220 , 320 , 520 ) half way between the two said parallel straight lines ( 111 , 112 ) while being perpendicular to the end face ( 125 ) of the fibre array ( 120 , 220 , 320 , 520 ); and
iii) a plane diffraction grating ( 50 ) having a dispersion plane that is parallel with respect to the two said parallel straight lines ( 111 , 112 ) while the diffraction grating ( 50 ) makes an angle of ′π° -φ with respect to the end face ( 125 ) of the fibre array ( 120 , 220 , 320 , 520 ) where the angle φ is chosen such that the position of the grating ( 50 ) does not affect beam propagation in the compact dispersing system ( 130 , 530 );
d) the end face ( 125 ) of the fibre array ( 120 , 220 , 320 , 520 ) being located in the vicinity of the focal plane of the concave mirror ( 60 ) such that the diverging beams coming from the end faces of the input elements ( 122 ) become collimated by reflection on the mirror ( 60 ) while being directed towards the plane mirror ( 140 , 540 );
e) the plane mirror ( 140 , 540 ) reflecting the collimated beams coming from the concave mirror ( 60 ) to the grating ( 50 ) and, inversely, reflecting the diffracted collimated beams coming from the grating ( 50 ) to the concave mirror ( 60 ), being firstly located between the end face ( 125 ) of the fibre array ( 120 , 220 , 320 , 520 ) and the concave mirror ( 60 ), being secondly perpendicular to the dispersion plane, and making thirdly an angle ‘α’ with respect to the axis ( 63 ) of the concave mirror ( 60 ) such that the diffraction grating ( 50 ) is located in the vicinity of the focus of the concave mirror ( 60 ), the angle α being chosen such that the diffraction grating ( 50 ) is operated near Littrow;
f) the concave mirror ( 60 ) reflecting the dispersed collimated beams coming from the plane mirror ( 140 , 540 ) and said dispersed collimated beams passing by the plane mirror ( 140 , 540 ) without being affected by said plane mirror such that the beams are focused on the reception line ( 111 ) of the fibre array ( 120 , 220 , 320 , 520 ), about linearly distributed over the line with respect to wavelength, and entering end faces of the output elements ( 121 ) where they are present; and
g) the optical device ( 100 , 500 ) being characterised in that the size of the plane mirror ( 140 , 540 ) is limited with respect to the two said parallel straight lines ( 111 , 112 ) such that beams propagating from the end faces of the input elements ( 122 ) to the concave mirror ( 60 ) and beams propagating from the concave mirror ( 60 ) to the end faces of the output elements ( 121 ) are not affected by the presence of the plane mirror ( 140 , 540 ).
2. The optical device ( 100 , 500 ) of claim 1 , wherein the plane mirror ( 140 , 540 ) has a rotation mechanism for tuning the angle α which enables wavelength tuning of the device.
3. The optical device ( 100 , 500 ) of claim 1 , wherein the diffraction grating ( 50 ) has a rotation mechanism for tuning the angle φ which enables wavelength tuning of the device.
4. The optical device ( 100 , 500 ) of claim 1 , wherein the fibre array ( 120 , 220 , 320 , 520 ) has a translation mechanism for simultaneously tuning the position of the end faces of the input elements ( 122 ) and the output elements ( 121 ) over the said parallel straight lines ( 111 , 112 ) which enables wavelength tuning of the device.
5. The optical device ( 100 , 500 ) of claim 1 , wherein the concave mirror ( 60 ) has a translation mechanism for tuning the position of the concave mirror ( 60 ) parallel along the said parallel straight lines ( 111 , 112 ), which enables wavelength tuning of the device.
6. The optical device ( 100 , 500 ) of claim 1 , wherein each input element ( 122 ) is a single mode fibre.
7. The optical device ( 100 , 500 ) of claim 6 , wherein each single mode fibre ( 122 ) is terminated with collimating means.
8. The optical device ( 100 , 500 ) of claim 7 , wherein each collimating means consists of a graded-index lens ( 128 ) spliced to the end of said single mode fibre ( 121 , 122 ).
9. The optical device ( 100 , 500 ) of claim 1 , wherein each output element ( 121 ) is a single mode fibre.
10. The optical device ( 100 , 500 ) of claim 9 , wherein each single mode fibre ( 121 ) is terminated with collimating means.
11. The optical device ( 100 , 500 ) of claim 10 , wherein each collimating means consists of a graded-index lens ( 128 ) spliced to the end of said single mode fibre ( 121 , 122 ).
12. The optical device ( 100 , 500 ) of claim 1 , wherein each input element ( 122 ) is a multimode fibre terminated with collimating means.
13. The optical device ( 100 , 500 ) of claim 1 , wherein each output element ( 121 ) is a multimode fibre terminated with collimating means.
14. The optical device ( 100 , 500 ) of claim 1 , wherein each output element ( 121 ) is a photodiode.
15. The optical device ( 100 , 500 ) of claim 14 , wherein each photodiode ( 121 ) is terminated with collimating means.
16. The optical device ( 100 , 500 ) of claim 1 , wherein each input element ( 122 ) is a laser diode terminated with collimating means.
17. The optical device ( 100 , 500 ) of claim 1 , wherein each input element ( 122 ) and output element ( 121 ) is terminated with collimating means consisting of a microlens ( 228 ).
18. A single mode wavelength router comprising the optical device ( 100 , 500 ) of claim 1 , wherein each input element ( 122 ) is a single mode fibre, and wherein each output element ( 121 ) is a single mode fibre.
19. A single mode wavelength router comprising the optical device ( 100 , 500 ) of claim 1 , wherein each input element ( 122 ) is a single mode fibre terminated with collimating means, and wherein each output element ( 121 ) is a single mode fibre terminated with collimating means.
20. A single mode wavelength multiplexer comprising the optical device ( 100 , 500 ) of claim 1 , wherein each input element ( 122 ) is a single mode fibre, and wherein there is only one output element ( 121 ) that is a single mode fibre.
21. A single mode wavelength multiplexer comprising the optical device ( 100 , 500 ) of claim 1 , wherein each input element ( 122 ) is a single mode fibre terminated with collimating means, and wherein there is only one output element ( 121 ) that is a single mode fibre terminated with collimating means.
22. A single mode wavelength demultiplexer comprising the optical device ( 100 , 500 ) of claim 1 , wherein there is only one input element ( 122 ) that is a single mode fibre, and wherein each output element ( 121 ) is a single mode fibre.
23. A single mode wavelength demultiplexer comprising the optical device ( 100 , 500 ) of claim 1 , wherein there is only one input element ( 122 ) that is a single mode fibre terminated with collimating means, and wherein each output element ( 121 ) is a single mode fibre terminated with collimating means.
24. A single mode wavelength filter comprising the optical device ( 100 , 500 ) of claim 1 , wherein there is only one input element ( 122 ) that is a single mode fibre, and wherein there is only one output element ( 121 ) that is a single mode fibre.
25. A single mode wavelength filter comprising the optical device ( 100 , 500 ) of claim 1 , wherein there is only one input element ( 122 ) that is a single mode fibre terminated with collimating means, and wherein there is only one output element ( 121 ) that is a single mode fibre terminated with collimating means.
26. A single mode optical channel monitor comprising the optical device ( 100 , 500 ) of claim 1 , wherein each output element ( 121 ) is a photodiode, and wherein there is only one input element ( 122 ) that is a single mode fibre.
27. A single mode optical channel monitor comprising the optical device ( 100 , 500 ) of claim 1 , wherein each output element ( 121 ) is a photodiode terminated with collimating means, and wherein there is only one input element ( 122 ) that is a single mode fibre.
28. A multimode wavelength router comprising the optical device ( 100 , 500 ) of claim 1 , wherein each input element ( 122 ) is a multimode fibre terminated with collimating means and wherein each output element ( 121 ) is a multimode fibre terminated with collimating means.
29. A multimode wavelength multiplexer comprising the optical device ( 100 , 500 ) of claim 1 , wherein each input element ( 122 ) is a multimode fibre terminated with collimating means and wherein there is only one output element ( 121 ) that is a multimode fibre terminated with collimating means.
30. A multimode wavelength demultiplexer comprising the optical device ( 100 , 500 ) of claim 1 , wherein there is only one input element ( 122 ) that is a multimode fibre terminated with collimating means and wherein each output element ( 121 ) is a multimode fibre terminated with collimating means.
31. A multimode wavelength filter comprising the optical device ( 100 , 500 ) of claim 1 , wherein there is only one input element ( 122 ) that is a multimode fibre terminated with collimating means and wherein there is only one output element ( 121 ) that is a multimode fibre terminated with collimating means.
32. A multimode optical channel monitor comprising the optical device ( 100 , 500 ) of claim 1 , wherein each output element ( 121 ) is a photodiode, and wherein there is only one input element ( 122 ) that is a multimode fibre terminated with collimating means.
33. A multimode optical channel monitor comprising the optical device ( 100 , 500 ) of claim 1 , wherein each output element ( 121 ) is a photodiode terminated with collimating means, and wherein there is only one input element ( 122 ) that is a multimode fibre terminated with collimating means.