Double core, active fiber optical amplifier having a wide band signal wavelength

Claim 2

An active fiber optical amplifier for amplifying telecommunication signals at a predetermined wavelength, said amplifier comprising: at least one portion of two side-by-side optical fibers, at least one of said fibers containing a fluorescing dopant which has a peak emission at a wavelength different from said predetermined wavelength and having an input and an output and the other of said fibers being optically coupled to said one of said fibers at a coupling wavelength different from said predetermined wavelength, being open ended and having a length such that energy at the wavelength of said peak emission is absorbed therein; a source of pumping energy for pumping said one of said fibers and thereby raising the energy of the ions of said dopant; and an optical coupler coupled to said input of said one of said optical fibers and to said source and for coupling to a source of said telecommunication signals for providing both said telecommunication signals and said pumping energy to said input of said one of said optical fibers whereby energy at at least one wavelength different from said predetermined wavelength is absorbed and said telecommunication signals are amplified.

Claim 3

An active fiber optical amplifier as set forth in claim 1 wherein said optical coupler is a dichroic coupler having a coupler output and two coupler inputs and wherein said coupler output is coupled to said input of said one fiber, one of said coupler inputs is coupled to said pumping energy source and the other of said coupler inputs is adapted for connection to said source of telecommunication signals.

Claim 4

An active fiber optical amplifier as set forth in claim 1 wherein there are a plurality of the portions of said two optical fibers in series with a single one of said one of said fibers interconnecting the output of said one of said fibers of one of said portions with the input of said one of said fibers of the next adjacent portion.

Claim 5

An active fiber optical amplifier as set forth in claim 1 wherein said other of said fibers contains an absorbing dopant which absorbs energy at said wavelength different from said predetermined wavelength.

Claim 6

An active fiber optical amplifier as set forth in claim 4 wherein the content of said absorbing dopant and the coupling of said one fiber and said other fiber are selected so that said other fiber has a length less than one-tenth of the beating length between said one fiber and said other fiber at the coupling wavelength.

Claim 7

An active fiber optical amplifier as set forth in claim 4 wherein said absorbing dopant is the same as the first-mentioned said dopant.

Claim 8

An active fiber optical amplifier as set forth in claim 6 wherein both said absorbing dopant and said first-mentioned said dopant are erbium.

Claim 9

An active fiber optical amplifier as set forth in claim 4 wherein said absorbing dopant is selected from the group consisting of titanium, vanadium, chromium, iron and mixtures thereof, part of the selected absorbing dopant being present in its lower valency state.

Claim 10

An active fiber optical amplifier as set forth in claim 1 wherein the first-mentioned dopant is erbium.

Claim 11

An active fiber optical amplifier as set forth in claim 9 wherein said wavelength at which said one fiber is coupled to said other fiber is in the range from 1530 nm to 1540 nm.

Claim 12

An active fiber optical amplifier as set forth in claim 1 wherein the length of said one fiber and said length of said other fiber within a said portion is at least equal to the beating length between said one fiber and said other fiber at the coupling wavelength.

Claim 13

An active fiber optical amplifier as set forth in claim 11 wherein said other fiber is without an absorbing dopant and the lengths of said one fiber and said other fiber within a portion are within 10% of a whole multiple of a beating length between said one fiber and said other fiber.

Claim 14

An active fiber optical amplifier as set forth in claim 1 wherein said fiber and said other fiber are within a common cladding, said one fiber is co-axial with the external surface of said cladding and said other fiber is offset with respect to the axis of said cladding.

Claim 15

An active fiber optical amplifier as set forth in claim 1 wherein said at least one fiber is monomodal at said predetermined wavelength and at the wavelength of said pumping energy.

Claim 16

An active fiber optical amplifier as set forth in claim 1 wherein there are a plurality of the portions of said two optical fibers in series, the output of said one of said fibers of one portion being connected to the input of said one of said fibers of the next adjacent section by a length of said one fiber without said other of said fibers, the last-mentioned said length being selected to provide a gain of not more than 15 dB at said wavelength of coupling between the first-mentioned said one of said fibers and said other of said fibers.

Claim 17

An active fiber optical amplifier as set forth in claim 15 wherein one of said plurality of portions is at at least one end of said series of portions.

Claim 18

An active fiber optical amplifier as set forth in claim 1 wherein said portion is constrained in an arc to provide said coupling wavelength.

Claim 19

An active optical fiber amplifier as set forth in claim 1 wherein said source of pumping energy provides energy at a wavelength lower than said predetermined wavelength and said wavelength different from said predetermined wavelength and said optical coupler is coupled to said input of said one one of said fibers by a portion of optical fiber containing a fluorescent dopant which emits radiation in a wavelength range which includes said predetermined wavelength and said wavelength different from said predetermined wavelength.

Claim 20

An active fiber optical amplifier for amplifying telecommunication signals at a first predetermined wavelength, said amplifier having a telecommunication signal input and a telecommunication signal output and comprising: an optical coupler having a telecommunication signal first input, a second input and an output; a first portion of optical fiber comprising an active optical fiber having a first core with a cladding therearound, said first active optical fiber being connected to said output of said optical coupler and said core being doped with a fluorescent dopant which emits energy in a wavelength range which includes said first predetermined wavelength and which has a maximum energy emission at a second wavelength different from said first predetermined wavelength; a source of pumping energy at a third wavelength different from, and lower than, said first predetermined wavelength and said second wavelength connected to said second input of said optical coupler for providing pumping energy to said first portion of optical fiber and raising the energy of the ions of said fluorescent dopant; a second portion of optical fiber having a first core and a second core within a cladding, said first core of said second portion of optical fiber being connected to said first core of said first portion so that optical signals at both said first predetermined wavelength and said second wavelength in said first core of said first portion are transmitted to said first core of said second portion, said first core and said second core of said second portion being optically coupled at said second wavelength to cause energy at said second wavelength to be transferred from said first core of said second portion to said second core of said second portion and said second core of said second portion being open-ended and having a length such that energy at said second wavelength transferred to said second core is absorbed at said second core whereby said energy at said second wavelength is prevented from returning to said first core of said second portion.

Claim 21

An active fiber optical amplifier for amplifying telecommunication signals at a first predetermined wavelength, said amplifier having a telecommunication signal input and a telecommunication signal output and comprising: an optical coupler having a telecommunication signal first input, a second input and an output; a first portion of optical fiber comprising an active optical fiber having a first core with a cladding therearound, said first active optical fiber being connected to said output of said optical coupler and said core being doped with a fluorescent dopant which emits energy in a wavelength range which includes said first predetermined wavelength and which has a maximum energy emission at a second wavelength different from said first predetermined wavelength; a source of pumping energy at a third wavelength different from, and lower than, said first predetermined wavelength and said second wavelength connected to said second input of said optical coupler for providing pumping energy to said first portion of optical fiber and raising the energy of the ions of said fluorescent dopant; a second portion of optical fiber having a first core and a second core within a cladding, said first core of said second portion of optical fiber being connected to said first core of said first portion so that optical signals at both said first predetermined wavelength and said second wavelength in said first core of said first portion are transmitted to said first core of said second portion, said first core and said second core of said second portion being optically coupled at said second wavelength to cause energy at said second wavelength to be transferred from said first core of said second portion to said second core of said second portion and said second core of said second portion being open-ended and having a length such that energy at said second wavelength transferred to said second core is absorbed at said second core whereby said energy at said second wavelength is prevented from returning to said first core of said second portion.

Claim 22

An active fiber optical amplifier as set forth in claim 19 wherein said optical coupler is a dichroic coupler.

Claim 23

An active fiber optical amplifier as set forth in claim 19 wherein said second core contains an absorbing dopant which absorbs energy at said second wavelength.

Claim 24

An active fiber optical amplifier as set forth in claim 21 wherein said dichroic coupler has said output and said first input and said second input, said first portion of optical fiber as an input, said output is coupled to said input of said first portion of optical fiber, and said first input is adapted for connection to said source of telecommunication signals.

Claim 25

An active fiber optical amplifier as set forth in claim 19 wherein said second core is without an absorbing dopant and the lengths of said first core of said second portion of optical fiber and said second core of said second portion of optical fiber are within 10% of a whole multiple of a beating length between said first core of said second portion and said second core of said second portion.

Claim 26

An active fiber optical amplifier as set forth in claim 19 wherein said first core of said second portion of said optical fiber comprises said fluorescent dopant.

Claim 27

An active fiber optical amplifier as set forth in claim 19 wherein said first core of said second portion of optical fiber is connected to said first core of said first portion of optical fiber by a single optical fiber.

Claim 28

An active fiber optical amplifier as set forth in claim 19 wherein said second core of said second portion of optical fiber contains an absorbing dopant which absorbs energy at said wavelength different from said predetermined wavelength.

Claim 29

An active fiber optical amplifier as set forth in claim 26 wherein the content of said absorbing dopant and the coupling of said first core of said second portion of optical fiber and said second core of said second portion of optical fiber are selected so that said second core of said second portion of optical fiber has a length less than one-tenth of the beating length between said first core of said second portion of optical fiber and said second core of said second portion of optical fiber at the coupling wavelength.

Claim 30

An active fiber optical amplifier as set forth in claim 26 wherein said absorbing dopant is the same as the first-mentioned said dopant.

Claim 31

An active fiber optical amplifier as set forth in claim 28 wherein both said absorbing dopant and said first-mentioned said dopant are erbium.

Claim 32

An active fiber optical amplifier as set forth in claim 26 wherein said absorbing dopant is selected from the group consisting of titanium, vanadium, chromium, iron and mixtures thereof, part of the selected absorbing dopant being present in its lower valency state.

Claim 33

An active fiber optical amplifier as set forth in claim 19 wherein the first-mentioned dopant is erbium.

Claim 34

An active fiber amplifier as set forth in claim 31 wherein said wavelength at which said second core of said second portion of optical fiber is coupled to said first core of said second portion of optical fiber is in the range from 1530 nm to 1540 mn.

Claim 35

An active fiber optical amplifier as set forth in claim 19 wherein the length of said first core and said length of said second fiber within said second portion of optical fiber are at least equal to the beat length between said first core and said second core of said second portion of optical fiber at the coupling wavelength.

Claim 36

An active fiber optical amplifier as set forth in claim 33 wherein said second core of said second portion of optical fiber is without an absorbing dopant and the lengths of said second core and said first core of said second portion of optical fiber are within 10% of a whole multiple of a beat length between said second core and said first core of said second portion of optical fiber.

Claim 37

An active fiber optical amplifier as set forth in claim 19 wherein said first core and said second core of said second portion of optical fiber are within a common cladding, the last-mentioned said first core is co-axial with the external surface of said cladding and the last-mentioned said second core is offset with respect to the axis of said cladding.

Claim 38

An active fiber optical amplifier as set forth in claim 19 wherein at least said first portion of optical fiber is monomodal at said predetermined wavelength and at the wavelength of said pumping energy.

Claim 39

An active fiber optical amplifier as set forth in claim 19 wherein there are a plurality of sections of said second portion of optical fiber in series, the first core of one said plurality of sections being connected to the first core of the next adjacent section by a length of the last-mentioned said first core without said second core, the last-mentioned said length being selected to provide a gain of not more than 15 dB at said wavelength of coupling between the said first core of said second portion of optical fiber and said second core of said second section of optical fiber.

Claim 40

An active fiber optical amplifier as set forth in claim 37 wherein one of said plurality sections is at at least one end of said series of sections.

Claim 41

An active fiber optical amplifier as set forth in claim 19 wherein said second portion of optical fiber is constrained in an arc to provide said coupling wavelength.