Network for distributing signals to a plurality of user equipment
View Patent ↗A network for distributing signals to a plurality of user having a distribution unit and a plurality of optical cables adapted to make the distribution unit communicate with the plurality of user equipment. In turn, each optical cable has an optical fibre having a core, a cladding and a predetermined simple refractive index profile Δn(r). Each optical fibre is adapted to guarantee a single-mode propagation at higher wavelengths than about 1260 nm and a few-mode propagation at about 850 nm, and each optical fibre has such refractive index profile Δn(r) as to guarantee macro-bending losses at 1550 nm that are less than about 0.5 dB and an intermodal delay Δτ at 850 nm that is less than or equal to, about 1 ns/Km.
1. A network for distributing signals to a plurality of user equipment comprising
a distribution unit; and
a plurality of optical cables adapted to make said distribution unit communicate with said plurality of user equipment, each optical cable comprising an optical fibre having a core, a cladding and a predetermined simple refractive index profile Δn(r), where Δn(r) refers to the refractive index difference between the core and the cladding as a function of the radial distance r, each optical fibre being adapted to provide a single-mode propagation at higher wavelengths than about 1260 nm and a few-mode propagation at about 850 nm;
the refractive index profile Δn(r) of each optical fibre being such as to provide macro-bending losses at 1550 nm that are less than about 0.5 dB after 100 turns on a mandrel having a 60-mm diameter; and
an intermodal delay Δτ at 850 nm that is less than or equal to, about 1 ns/Km.
2. The distribution network according to claim 1 , wherein the intermodal delay Δτ at 850 nm is less than about 0.5 n ns/Km.
3. The distribution network according to claim 2 , wherein the intermodal delay Δτ at 850 nm is less than about 0.05 ns/Km.
4. The distribution network according to claim 1 , wherein macro-bending losses at 1550 nm after 100 turns on a mandrel having a 60-nm diameter are less than about 0.2 dB.
5. The distribution network according to claim 1 , wherein micro-bending losses at 1550 nm of the optical fibres are less than about 15 [(dB/Km)/(g/mm)].
6. The distribution network according to claim 5 , wherein micro-bending losses at 1550 nm of the optical fibres are less than about 10 [(dB/Km)/(g/mm)].
7. The distribution network according to claim 1 , wherein each optical fibre has a normalized frequency value V at 850 nm between about 3.0 and 3.6.
8. The distribution network according to claim 7 , wherein each optical fibre has a normalized frequency value V at 850 nm between about 3.2 and 3.6.
9. The distribution network according to claim 7 or 8 , wherein the optical fibre is produced with an outside vapour deposition (OVD) method.
10. A distribution network according to claim 7 or 8 , wherein the optical fibre is produced with a vapour axial deposition (VAD) method.
11. The distribution network according to claim 1 , wherein each optical fibre has a value of Δn 0 between about 5*10 −3 and 7*10 −3 .
12. The distribution network according to claim 1 , wherein a semi-area subtended by the refractive index profile is more than about 0.017 μm.
13. The distribution network according to claim 12 , wherein the semi-area subtended by the refractive index profile is more than about 0.018 μm.
14. The distribution network according to claim 1 , wherein the core radius of each optical fibre is between about 3 μm and 6 μm.
15. The distribution network according to claim 1 , wherein each optical fibre, outside the cladding, is provided with an external protective coating made of a polymeric material.
16. The distribution network according to claim 15 , wherein a portion of said external coating in contact with the cladding, has a higher refractive index than that of the cladding in a temperature range between 10° C. and 60° C.
17. The distribution network according to claim 15 , wherein the external protective coating consists of a material capable of strongly absorbing the electromagnetic radiation.
18. The distribution network according to claim 1 , wherein each optical cable further comprises a second optical fibre.
19. The distribution network according to claim 1 , further comprising a plurality of opto-electronic conversion devices in communication with the plurality of optical cables.
20. The distribution network according to claim 19 , wherein each opto-electronic conversion device comprises a photodetector.
21. The distribution network according to claim 19 or 20 , wherein each opto-electronic conversion device comprises a light source.
22. The distribution network according to claim 21 , wherein said light source is adapted to operate at a wavelength between about 820 and 870 nm.
23. The distribution network according to claim 22 , wherein said light source is adapted to operate at a wavelength between about 830 and 860 nm.
24. The distribution network according to claim 22 , wherein the light source of at least part of the opto-electronic conversion devices is adapted to operate at a wavelength between about 1300 nm and 1625 nm.
25. The distribution network according to claim 22 , adapted to transmit, in the few-mode propagation condition, optical signals at bit rates that are higher than or equal to, 2.5 Gbit/s on a link of about 300-m length.
26. The distribution network according to claim 1 , wherein the distribution unit is adapted to multiplex a plurality of signals at different wavelengths in a single WDM optical signal and to send said WDM signal along at least one of said optical cables.
27. The distribution network according to claim 1 , further comprising, on a user side, at least one domestic network connected to a corresponding optical cable and adapted to send signals coming from the optical cable to a plurality of user equipment.
28. The distribution network according to claim 27 , wherein the domestic network is of the start type.
29. The distribution network according to claim 27 , wherein the domestic network is of the bus type.
30. The distribution network according to claim 27 , wherein the domestic network comprises a wavelength selective optical coupler adapted to wavelength demultiplex an incoming WDM optical signal at its input.
31. The distribution network according to claim 27 , wherein the domestic network comprises an optical coupler adapted to split the power of an incoming WDM optical signal at its input.
32. The distribution network according to claim 1 , wherein each optical fibre has a chromatic dispersion value at 1550 nm lower than or equal to one of the following values 20, 19, 18, 17 or 16 ps/(nm*Km).
33. The distribution network according to claim 1 , wherein each optical fibre has a chromatic dispersion value at 1550nm lower than or equal to 15.4 ps(nm*Km).
34. An optical fibre having a core, cladding and a predetermined simple refractive index profile Δn(r), where Δn(r) refers to the refractive index difference between the core and the cladding as a function of the radial distance r, said optical fibre being adapted to provide a single-mode propagation at higher wavelengths than about 1260 nm and a few-mode propagation at about 850 nm,
the predetermined refractive index profile Δn(r) being adapted to provide macro-bending losses at 1550 nm that are less than about 0.5 dB after 100 turns on a mandrel having a 60-mm diameter; and
an intermodal delay Δτ at 850 nm that is less than or equal tp about 1 ns/Km.
35. The optical fibre according to claim 34 , having a chromatic dispersion value at 1550 nm lower than or equal to one of the following values 20, 19, 18, 17 or 16 ps/(nm*Km).
36. The optical fibre according to claim 34 , having a chromatic dispersion value at 1550 nm lower than or equal to 15.4 ps/(nm*Km).
37. The optical fibre according to claim 34 , wherein the intermodal delay Δτ at 850 nm is less than about 0.5 ns/Km.
38. The optical fibre according to claim 37 , wherein the intermodal delay Δτ at 850 nm is less than about 0.05 ns/Km.
39. The optical fibre according to claim 34 , wherein macro-bending losses at 1550 nm after 100 turns on a mandrel having a 60-nm diameter are less than about 0.2 dB.
40. The optical fibre according to claim 34 , wherein micro-bending losses at 1550 nm of the optical fibres are less than about 15 [(dB/Km)/(g/mm)].
41. The optical fibre according to claim 40 , wherein micro-bending losses at 1550 nm of the optical fibres are less than about 10 [(dB/Km)/(g/mm)].
42. The optical fibre according to claim 34 , wherein the optical fibre has a normalized frequency value V at 850 nm between about 3.0 and 3.6.
43. The optical fibre according to claim 42 , wherein the optical fibre has a normalized frequency value V at 850 nm between about 3.2 and 3.6.
44. The optical fibre according to claim 42 or 43 , wherein the optical fibre is produced with an outside vapour deposition (OVD) method.
45. The optical fibre according to claim 42 or 43 , wherein the optical fibre is produced with a vapour axial deposition (VAD) method.
46. The optical fibre according to claim 34 , wherein the optical fibre has a value Δn 0 between about 5*10 −3 and 7*10 −3 .
47. The optical fibre according to claim 34 , wherein semi-area subtended by the refractive index profile is more than about 0.017 μm.
48. The optical fibre according to claim 47 , wherein a semi-area subtended by the refractive index profile is more than about 0.018 μm.
49. The optical fibre according to claim 34 , wherein the core radius of the optical fibre is between about 3 μm and 6 μm.
50. The optical fibre according to claim 34 , wherein the optical fibre, outside the cladding, is provided with an external protective coating made of a polymeric material.
51. The optical fibre according to claim 50 , wherein a portion of said external coating in contact with the cladding, has a higher refractive index than that of the cladding in a temperature range between 10° C. and 60° C.
52. The optical fibre according to claim 50 , wherein the external protective coating consists of a material capable of strongly absorbing the electromagnetic radiation.
53. A method for the transmission of optical signals at about 850 nm, comprising transmitting said optical signals through at least one optical fibre having a core, a cladding and a predetermined simple refractive index profile Δn(r), where Δn(r) refers to the refractive index difference between the core and the cladding as a function of the radial distance r, said optical fibre being adapted to provide a single-mode propagation at higher wavelengths than about 1260 nm and a few-mode propagation at about 850 nm,
the predetermined refractive index profile Δn(r) being adapted to provide macro-bending losses at 1550 nm that are less than about 0.5 dB after 100 turns on a mandrel having a 60-mm diameter; and
an intermodal delay Δt at 850 nm that is less than or about 1 ns/Km.
54. A method according to claim 53 , comprising transmitting the optical signals at a wavelength between about 820 and 870 nm.