EP0458256A1
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EP
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Unit for amplifying signals of light in optical fiber transmission lines
Assignee: Pirelli and C SpA
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Filing: 1991-05-21
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Granted: —
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Expires: 2011-05-21
Abstract
Abstract The present invention relates to a optical fiber telecommunication line comprising active-fiber (10) optical amplifiers (5, 6) in which the reflectivity towards the amplifiers' active fiber is limited below a critical value lower by at least 10 dB than the reflectivity due to the Rayleigh scattering within the line fibres; this reflectivity value is obtained by arranging optical isolators (11a, 11b) having a limited inner reflectivity upstream and downstream of the amplifier (6) and by disposing reflection limiting means on all fibres (12) converging towards the amplifier's active fiber (10).
Inventors
- 👤 Giorgio Grasso
- 👤 Aldo Righetti
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 16:19
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/04; H03F3/08; H04; H04B; H04B10/00; H04B10/29; H04B10/291; H01; H01S; H01S3/00; H01S3/05; H01S3/06; H01S3/063; H01S3/067; H01S3/06754; H04B10/2912; H01S2301/00; H01S2301/02
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
122 words
An optical fiber telecommunication line, in which an optical transmission signal is brought from one end of the line to the other end without regenerations, along which line at least an optical fiber amplifier (6a, 6b, 6c) is present comprising an active optical fiber length (10) having a doped core in which the doping is carried out by fluorescent substances, characterised in that all fibres connected to the amplifier's active fiber (10) or belonging to each amplifier (6a, 6b, 6c) have reflection limiting means (11a, 11b, 13) the reflectivity of which, seen from the faced end of the active fiber, is lower by at least 10 dB than the reflectivity corresponding to the Rayleigh scattering in the fiber at the transmission wavelength.
Claim 2
Dependent Claim
54 words
An optical fiber telecommunication line according to claim 1, characterised in that the reflection limiting means (11a, 11b, 13) cause reflectivities of the fibres converging towards the active fiber (10) which are equal to or lower by 15 dB than the reflectivity corresponding to the Rayleigh scattering in the fiber at the transmission wavelength.
Claim 3
Dependent Claim
69 words
An optical fiber telecommunication line according to claim 1, characterised in that all fibres connected to the amplifier's active fiber or belonging to each amplifier (6a, 6b, 6c) are provided with reflection limiting means having a reflectivity, seen from the faced end of the active fiber, the absolute value of which is higher by at least 10 dB and preferably at least 15 dB than the expected amplifier gain.
Claim 4
Dependent Claim
39 words
An optical fiber telecommunication line according to claim 1 or 3, characterised in that the reflection limiting means comprises polarisation control optical isolators (11a, 11b) located upstream and downstream of the optical active fiber (10) of the amplifier (6).
Claim 5
Dependent Claim
29 words
An optical fiber telecommunication line according to claim 4, characterised in that the optical isolators (11a, 11b) are of a type insensitive to the polarisation of the transmission signal.
Claim 6
Dependent Claim
78 words
An optical fiber telecommunication line according to claim 1, characterised in that the fibres connected to the amplifier's active fiber, devoid of optical isolators, have antireflection coatings and/or an oblique cut of the surface(s) (13) passed through by the transmission signal giving rise to a reflectivity at the transmission signal wavelength lower by at least 10 dB and preferably at least 15 dB than the reflectivity corresponding to the Rayleigh scattering in the fiber at the transmission wavelength.
Claim 7
Dependent Claim
76 words
An optical fiber telecommunication line according to claim 3, characterised in that the fibres connected to the amplifier's (6) active fiber (10), devoid of optical isolators, have antireflection coatings and/or an oblique cut of the surface(s) (13) passed through by the transmission signal giving rise to a reflectivity at the transmission signal wavelength the absolute value of which is higher by at least 10 dB and preferably at least 15 dB than the expected amplifier gain.
Claim 8
Dependent Claim
125 words
An optical amplifier for optical fiber telecommunication lines of the active fiber type comprising an active optical fiber (10) having a doped core in which the doping is carried out by a fluorescent substance, connected at the ends thereof to the optical fibres of a telecommunication line, to which active optical fiber (10) being also connected, through respective coupling means (7), at least an optical fiber (12) connected to a source of an optical pumping signal (9), characterised in that all fibres connected to the active fiber (10) exhibit reflection limiting means causing a reflectivity, seen from the faced end of the active fiber, lower by at least 10 dB than the reflectivity corresponding to the Rayleigh scattering in the fiber at the transmission wavelength.
Claim 9
Dependent Claim
44 words
An optical amplifier according to claim 8, characterised in that the reflection limiting means cause reflectivities of the fibres converging towards the active fiber (10) which are lower by at least 15 dB than the reflectivity due to the Rayleigh scattering in the fiber.
Claim 10
Dependent Claim
58 words
An optical amplifier according to claim 8, characterised in that all fibres connected to the active fiber (10) have reflection limiting means exhibiting a reflectivity, seen from the faced end of the active fiber, the absolute value of which is higher by at least 10 dB and preferably by at least 15 dB than the expected amplifier gain.
Claim 11
Dependent Claim
31 words
An optical amplifier according to claim 8, characterised in that the reflection limiting means comprises polarisation control optical isolators (11a, 11b) located upstream and downstream of the active optical fiber (10).
Claim 12
Dependent Claim
25 words
An optical amplifier according to claim 8, characterised in that the optical isolators (11a, 11b) are of the type insensitive to the transmission signal polarisation.
Claim 13
Dependent Claim
49 words
An optical amplifier according to claim 11, characterised in that each optical isolator (11a, 11b) has a reflectivity towards the active fiber at the wavelength of the transmission signal lower by 10 dB and preferably 15 dB than the reflectivity given by the Rayleigh scattering in the line fiber.
Claim 14
Dependent Claim
53 words
An optical amplifier according to claim 11, characterised in that each optical isolator (11a, 11b) has a reflectivity towards the active fiber (10) at the wavelength of the transmission signal the absolute value of which is higher by at least 10 dB and preferably at least 15 dB than the expected amplifier gain.
Claim 15
Dependent Claim
104 words
An optical amplifier according to claim 8, characterised in that the fiber (12) connected to the optical pumping source (9) is devoid of optical isolators and at the end (13) thereof connected to said source (9) is provided with reflection limiting means comprising antireflection coating layers and/or an oblique cut of the surface(s) passed through by the transmission signal, said reflection limiting means supplying a reflectivity which is lower by 10 dB and preferably by 15 dB than the reflectivity resulting from the Rayleigh scattering, the attenuations due to the passage of the transmission signal and reflected signal through the coupling means being included.
Claim 16
Dependent Claim
106 words
An optical amplifier according to claim 15, characterised in that the fiber (12) connected to the optical pumping source (9) is devoid of optical isolators and at the end thereof connected to said source is provided with reflection limiting means comprising antireflection coating layers and/or an oblique cut of the surface(s) passed through by the transmission signal, said reflection limiting means supplying a reflectivity the absolute value of which is higher by at least 10 dB and preferably at least 15 dB than the expected amplifier gain, the attenuations due to the passage of the transmission signal and reflected signal through the coupling means being included.
Claim 17
Dependent Claim
45 words
An optical amplifier according to claim 15, characterised in that the end (13) of the optical fiber (12) connected to the pumping signal source (9) is cut at an angle ranging between 5° and 10° with respect to the plane normal to the fiber axis.
Claim 18
Dependent Claim
85 words
An optical amplifier according to claim 15, characterised in that the fiber (12) connected to the source (9) of the optical pumping signal is connected to the active fiber (10) through a dichroic coupler (7) and the optical isolators (11a, 11b) are interposed between the active fiber (10) and the optical line fiber (3), at one end thereof, and between the line fiber (3) and the optical coupler (7) immediately contiguous to the active fiber (10), at the other end of the active fiber itself.
Claim 19
Dependent Claim
54 words
An optical amplifier according to claim 15, characterised in that the fiber (12) the fiber connected to the source (9) of the optical pumping signal is connected to the active fiber (10) through a dichroic coupler (7) and an optical isolator (11a) is interposed between the active fiber (10) and the dichroic coupler (7).
Claim 20
Dependent Claim
76 words
An optical amplifier according to claim 8, characterised in that in case of power amplifiers (5) operating with a power transmission signal higher than the saturation power of the amplifier and connected at a position contiguous to the the transmission signal emitting laser (4), equipped with a respective protection optical isolator (15), an optical isolator (11b) is present only at the downstream end of the active fiber (10) in the running direction of the transmission signal.
References Cited (Backward Citations)
GB2220789A
Cited
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