Amplifier for optical fiber telecommunication lines and optical fiber telecommunication lines incorporating said amplifier

Claim 2

An amplifier (3) for signal-transmitting optical fiber telecommunication lines, which can be interposed between one portion (2) of the optical fiber of the line and a second portion (4) of the optical fiber of the line comprising an optical pumping radiation source (7), a dichroic coupler (6) adapted to be connected to said first optical fiber portion (2) of the line and connected to the optical pumping radiation source (7), and a length (8) of active-core optical fiber, single-mode to both optical signal radiation and optical pumping radiation, having one end connected to the dichroic coupler (6) and the other end susceptible of being connected to said second optical fiber portion (4) of the line, said amplifier (3) being characterized in that the dichroic coupler (6) is of the type comprising two lengths (9, 10) of nonactive-core optical fiber disposed in side by side relation over a portion (11) of their length where they are optically coupled to each other by fusion of the respective claddings and substantial setting in common of the respective cores by stretching the lengths themselves, both said optical fiber lengths (9, 10) forming the dichroic coupler (6) being single-mode both for the optical signal radiation and optical pumping radiation.

Claim 3

An amplifier (3) according to claim 1, characterized in that the optical fiber lengths (9, 10) forming the dichroic coupler (6), in their respective claddings and cores have a distribution of nonactive dopants substantially identical to the distribution of nonactive dopants in the cladding and core of the length (8) of active-core optical fiber of the amplifier itself.

Claim 4

An amplifier (3) according to claim 1, characterized in that in the dichroic coupler (6) the ratio between the diameter of the substantially common core of the two optical fiber component lengths (9, 10) and the diameter of the core of said lengths at their ends is in the range of 0.3 to 0.5.

Claim 5

An amplifier (3) according to claim 1, characterized in that the mode diameter to the signal wavelength in the optical fiber lengths (9, 10) forming the amplifier (3) is substantially equal to the mode diameter to said signal wavelength in the optical fiber portions (2, 4′) forming the line for which the amplifier (3) is designed.

Claim 6

An amplifier (3) according to claim 1, characterized in that in the dichroic coupler (6) the diameter of the substantially common core of the two optical fiber component lengths (9, 10) is in the range of 1.56 to 2.8 for 1536-pm and 980-nm signal and pumping wavelengths respectively.

Claim 7

An optical fiber telecommunication line comprising at least one portion (2) of signal transmitting optical fiber and at least a second portion (4) of signal transmitting optical fiber optically connected to each other through an optical amplifier (3) interposed therebetween, said optical amplifier (3) comprising an optical pumping radiation source (7), a dichroic coupler (6) optically associated with said optical pumping radiation source (7) and to the first optical fiber transmission portion (2) of the line, one length (8) of active-core optical fiber, single-mode to both optical signal and pumping radiations downstream of the dichroic coupler (6) and optically connected thereto, said length (8) of active-core optical fiber being also optically connected to the second portion (4) of the signal transmitting optical fiber of the line, said line being characterized in that the dichroic coupler (6) is of the type comprising two lengths (9, 10) of nonactive-core optical fiber disposed in side by side relation over a portion (11) of their length where they are optically coupled to each other by fusion of the respective claddings and substantial setting in common of the respective cores by stretching the lengths themselves, both optical fiber lengths (9, 10) of the dichroic coupler (6) being single-mode to both optical signal and pumping radiations.

Claim 8

An optical fiber telecommunication line comprising at least one portion (2) of signal transmitting optical fiber and at least a second portion (4) of signal transmitting optical fiber optically connected to each other through an optical amplifier (3) interposed therebetween, said optical amplifier (3) comprising an optical pumping radiation source (7), a dichroic coupler (6) optically associated with said optical pumping radiation source (7) and to the first optical fiber transmission portion (2) of the line, one length (8) of active-core optical fiber, single-mode to both optical signal and pumping radiations downstream of the dichroic coupler (6) and optically connected thereto, said length (8) of active-core optical fiber being also optically connected to the second portion (4) of the signal transmitting optical fiber of the line, said line being characterized in that the dichroic coupler (6) is of the type comprising two lengths (9, 10) of nonactive-core optical fiber disposed in side by side relation over a portion (11) of their length where they are optically coupled to each other by fusion of the respective claddings and substantial setting in common of the respective cores by stretching the lengths themselves, both optical fiber lengths (9, 10) of the dichroic coupler (6) being single-mode to both optical signal and pumping radiations.

Claim 9

An optical fiber telecommunication line according to claim 6, characterized in that the optical fiber lengths (9, 10) forming the dichroic coupler (6) have in their respective claddings and cores a nonactive-dopant distribution substantially identical to the distribution of the nonactive dopants present in the cladding and core of the length (8) of active-core optical fiber of the amplifier (3) itself.

Claim 10

An optical fiber telecommunication line according to claim 6, characterized in that in the dichroic coupler (6) the ratio between the substantially common core of the two optical fiber component lengths (9, 10) and the diameter of the core of said lengths at the ends thereof is in the range of 0.3 and 0.5.

Claim 11

An optical fiber telecommunication line according to claim 6, characterized in that the mode diameter to the signal wavelength of the optical fiber lengths (9, 10) forming the amplifier (3) is substantially equal to the mode diameter to said signal wavelength of the optical fiber transmission portions (2, 4) of the line.

Claim 12

An optical fiber telecommunication line according to claim 6, characterized in that in the dichroic coupler (6) of the amplifier (3) the diameter of the substantially common core of the two optical fiber component lengths (9, 10) is in the range of 1.56 to 2.8, the optical signal and measurement radiations being 1536 and 980 nm respectively.