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WO1995010868A1 - A high power optical fiber amplifier pumped by a multi-mode laser source - Google Patents

A high power optical fiber amplifier pumped by a multi-mode laser source Download PDF

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Publication number
WO1995010868A1
WO1995010868A1 PCT/IT1993/000107 IT9300107W WO9510868A1 WO 1995010868 A1 WO1995010868 A1 WO 1995010868A1 IT 9300107 W IT9300107 W IT 9300107W WO 9510868 A1 WO9510868 A1 WO 9510868A1
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WO
WIPO (PCT)
Prior art keywords
mode
optical fiber
fiber
core
fiber amplifier
Prior art date
Application number
PCT/IT1993/000107
Other languages
French (fr)
Inventor
Valentin P. Gapontsev
Igor Samartsev
Original Assignee
Italtel Società Italiana Telecomunicazioni S.P.A.
Ire-Polus Co.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Italtel Società Italiana Telecomunicazioni S.P.A., Ire-Polus Co. filed Critical Italtel Società Italiana Telecomunicazioni S.P.A.
Priority to RU96108614A priority Critical patent/RU2142184C1/en
Priority to AU58221/94A priority patent/AU5822194A/en
Priority to EP94903981A priority patent/EP0723714A1/en
Priority to PCT/IT1993/000107 priority patent/WO1995010868A1/en
Publication of WO1995010868A1 publication Critical patent/WO1995010868A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/0915—Processes or apparatus for excitation, e.g. pumping using optical pumping by incoherent light
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/0915—Processes or apparatus for excitation, e.g. pumping using optical pumping by incoherent light
    • H01S3/0933—Processes or apparatus for excitation, e.g. pumping using optical pumping by incoherent light of a semiconductor, e.g. light emitting diode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
    • H01S3/094007—Cladding pumping, i.e. pump light propagating in a clad surrounding the active core
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
    • H01S3/094011—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre with bidirectional pumping, i.e. with injection of the pump light from both two ends of the fibre
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
    • H01S3/094019—Side pumped fibre, whereby pump light is coupled laterally into the fibre via an optical component like a prism, or a grating, or via V-groove coupling
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094069—Multi-mode pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/1601—Solid materials characterised by an active (lasing) ion
    • H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
    • H01S3/1608—Solid materials characterised by an active (lasing) ion rare earth erbium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/1601—Solid materials characterised by an active (lasing) ion
    • H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
    • H01S3/1618—Solid materials characterised by an active (lasing) ion rare earth ytterbium

Definitions

  • the invention relates to an improved high power optical fiber amplifier pumped by a multi-mode laser source.
  • a fiber optic amplifier for telecommunications is constituted by a single-mode optical fiber which core is doped with rare earths like Erbium. Pump power coupled into the fiber provides gain in the active medium for the information signal propagating along the fiber.
  • US-A- 4 829 529 to Kafka discloses a double core fiber structure for pumping the inner single-mode core doped with a rare earth like Neodymium or Erbium in order to obtain lasing action.
  • This patent shows a double core laser structure, but does not provide for any simultaneous doping with different rare earths, nor suggests that the arrangement could be suitable for producing a fiber optic amplifier and further the coupling of the pump radiation to the fiber is performed through its end faces, using bulk optics.
  • AU-A-10374/92 discloses an optical fiber amplifier comprising an Erbium doped fiber length, a single-mode coupler for coupling to a pump light source, and a length of Yb doped fiber spliced to the output end of the amplifying fiber for absorbing the residual pump light.
  • DE-OS 4 005 867 discloses an optical fiber amplifier comprising a Lanthanid doped length of fiber each end of which is coupled to a pump light source to achieve a high amplification of the incoming signal.
  • EP-A-0 509 577 discloses a two stage optical amplifier with the downstream amplifier comprising a length of active fiber doped with a fluorescent dopant, a coupler for supplying a pump light from a laser diode and a pair of optical insulators.
  • the present invention aims to overcome the above mentioned limitations and drawbacks.
  • a first object of the present invention is to provide a fiber optic amplifier with high gain and high output power.
  • a second object of the present invention is to provide a fiber optic amplifier that effectively suppresses the pumping light outside the lenght of amplifying fiber.
  • a third object of the present invention is to provide a fiber optic amplifier with an uniform gain profile across the amplifying core of the active fiber.
  • a further object of the present invention is to provide a fiber optic amplifier capable to make possible the use of pump sources emitting in a broad wavelength range and not requiring accurate thermal stabilization.
  • an optical fiber amplifier comprising: a lenght of double-clad fiber with: i. a co-doped single-mode core of amplifying material; ii. a multi-mode core surrounding the single-mode core and acting as guide for pump radiation; iii. an outer cladding; - a pump source coupled to said lenght of double clad fiber, characterized in that: said inner core is of an Erbium-Ytterbium doped material; - said pump power source comprises at least a multi-mode diode source supplying multi-mode pumping radiation to said lenght of double-clad fiber, transversally with respect to the optical axis of the fiber.
  • the first object is attained by means of said multi- mode diode source with associated multi-mode/high power pumping radiation;
  • the second and third object are attained by means of said transverse pumping and consequent transverse path of the pumping radiation with respect to the axial path of the information signal propagating along said lenght of optical fiber: thanks to said transverse path, the pumping radiation does not superimpose the information signal and no absorbing means are needed;
  • the fourth object is attained by means of said inner core of an Erbium-Ytterbium doped materials thanks to the broad absorption spectrum of said materials.
  • multi-mode couplers for high efficient coupling of pump multi-mode radiation into the active fiber in order to perform said transverse pumping.
  • at least two multi-mode couplers and two multi-mode diode sources are provided.
  • Fig. 1 is a schematic view of a fiber amplifier according to the invention.
  • Fig. 2 is a cross-sectional side view schematically illustrating the active fiber and the coupler to the pumping source.
  • the amplifier according to the invention comprises a length of optical fiber 1 made by a double concentrical core 2 and 3. With reference in particular to Fig. 1 it is assumed that an optical signal carrying information is propagating along the fiber in the direction shown by arrow S.
  • the inner core 2 is a single-mode core, with size analogous to those of the standard telecommunications fibers, and is doped with both Ytterbium and Erbium i.e. is Yb/Er co-doped.
  • the active material of the inner core 2 exhibits a broad absorption spectrum and is suitable for providing gain at optical communications wavelengths.
  • codoping with Ytterbium and Erbium of the active core allows for a broad pump wavelength range, between 900 nm and 1000 nm, so that within this range pump sources do not require wavelength selection and accurate temperature stabilization.
  • the sorrounding core 3 is a multi-mode core used for pumping by coupling pump radiation from a laser diode 4a through a multi-mode fiber 6a and a multi-mode coupler 5a.
  • An outer cladding 8 surrounds the multi-mode core 3.
  • the pump light from the pump source is injected transversally with respect to the optical axis of said fiber length 1 through the multi-mode couplers - that, according to a preferred embodiment of the invention are non-symmetrical type - and through multiple reflections (as schematically shown for a beam a in Fig. 2), penetrates into the inner core 2 and is absorbed therein without to superimpose to the optical signal to be amplified.
  • the multi-mode coupler can be formed, as an example, by a length of multi-mode fiber and a length of double core fiber. According to a preferred embodiment of the invention the multi-mode coupler is formed directly on the active fiber twisting, heating an subsequently pulling the two fibers.
  • an additional laser diode 4b is connected to the active fiber 1 through a multi-mode fiber 6b and a second multi-mode coupler 5b for increasing the pump power and in order to achieve a more uniform power distribution along the amplifying fiber which in turn results in improved amplifying characteristics.
  • Isolators INS1 and INS2 can be further provided along the fiber 1. Thanks to the fact that the pump radiation does not couple into the amplifying core 2 along the signal direction, no output filter is needed.
  • the gain profile is uniform across the active core, which thus can be made similar in dimensions to standard single-mode telecommunications fibers.
  • the outer cladding provides optical confinement for pump radiation.
  • the use of multi- mode fibers allows for much higher pump powers and the double core pumping scheme together with said transverse pumping makes possible placing several sources along a single active fiber; therefore high gain and output power are achievable.
  • the (each) pump source is a multi-mode laser diode and the pumping radiation is a coherent radiation.
  • the pumping radiation can be an incoherent radiation, such as that generated, e.g. by a superfluorescent diode.
  • the single-mode amplifying fiber 1 is preferably made by Erbium-Ytterbium doped glass.
  • the diameters of the multi-mode pump core and the single-mode amplifying core are in a ratio of about 10:1 and the length of the optical fiber 1 is between 2 and 20m.
  • the best mode for carrying out the invention is the one shown in fig. 2 and comprising two multi-mode fiber optic couplers 6a and 6b in order to obtain high output power and, thanks to the transverse pumping the pump radiation is not superimposed to the optical signal to be amplified, and consequently no filter is required at the output of the amplifier to eliminate residual pump radiation.
  • the high power optical fiber amplifier is applicable in telecommunication transmission systems and in particular in long haul transmission lines and in distribution networks.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)

Abstract

A fiber optic amplifier is made by a fiber (1) with two concentrical cores (2 and 3), the innermost one (2) constituted by amplifying material, the other one (3) used for pumping. Pump radiation is provided by multi-mode sources (4) and coupled, transversally with respect to the optical axis of said fiber (1), to the outer core (3) through multi-mode fibres (6) and multi-mode optical couplers (5). Pump radiation propagates through the outer core (3) and couples to the amplifying core (2), thus pumping the active material. The composition of the amplifying material is chosen in such a way that pumping can take place in a broad range of wavelengths. Coherent or incoherent pump sources can be used.

Description

"A HIGH POWER OPTICAL FIBER AMPLIFIER PUMPED BY A MULTI- MODE LASER SOURCE"
Technical Field
The invention relates to an improved high power optical fiber amplifier pumped by a multi-mode laser source.
A fiber optic amplifier for telecommunications is constituted by a single-mode optical fiber which core is doped with rare earths like Erbium. Pump power coupled into the fiber provides gain in the active medium for the information signal propagating along the fiber.
Background Art
Currently 980 nm and 1480 nm single-mode laser diodes are used as pump sources for fiber optic amplifiers that are directly coupled to a single-mode fiber and, through a single-mode multiplexer, to the active fiber. The use of single-mode fibers and the narrow range allowed for the source wavelength require sophisticated packaging techniques, narrow wavelength selection and an accurate thermal stabilization, achieved currently by power consuming Peltier coolers. Important characteristics of the fiber optic amplifiers such as the gain and saturation power thereof depend on pump intensity. Presently laser diodes with single-mode pigtail are available, at wavelengths suitable for pumping Erbium, with coupled power less than 100 m , and pump radiation is coupled directly to the end-face of the fiber and particularly into the core of the amplifying fiber through single-mode couplers. This has limited the maximum output power achievable from a single amplifier to about 17 dBm (50 mW) and the maximum gain to about 35 dB. Pumping directly into the core of the active fiber causes the pump radiation to propagate together with the optical signal to be amplified, therefore a filter may be required at the output of the amplifier to eliminate residual pump radiation from the transmission line. Counter-propagating pumping schemes have been developed to avoid this problem, by making the pump radiation propagating backwards with respect to the signal, but such configurations increase the noise generated by spontaneous emission, thus degrading the noise figure of the amplifier. Single-mode pumping, moreover, creates a non flat gain profile across the active medium thus requiring for example the realization of very small core and high numerical aperture active fiber to avoid signal absorption on the tails of the pump beam profile.
In summary the realization of high output power, high gain, low noise, low cost fiber optic amplifiers is limited by the availability and the cost of suitable pump sources which have to be coupled into single-mode fibers and by the pumping method which causes the coexistence of pump and signal radiation propagating along the amplifying core. Moreover single-mode pumping through single-mode couplers may result in polarization dependence and other losses due to the change in shape of the fiber cores inside the couplers.
US-A- 4 829 529 to Kafka discloses a double core fiber structure for pumping the inner single-mode core doped with a rare earth like Neodymium or Erbium in order to obtain lasing action. This patent shows a double core laser structure, but does not provide for any simultaneous doping with different rare earths, nor suggests that the arrangement could be suitable for producing a fiber optic amplifier and further the coupling of the pump radiation to the fiber is performed through its end faces, using bulk optics.
A work of Minelly et. al. reports amplification by a double core Ytterbium-Erbium doped fiber, but again the pumping is made through the end faces by bulk optics. Moreover in both works the pump sources are preferably diode arrays.
AU-A-10374/92 discloses an optical fiber amplifier comprising an Erbium doped fiber length, a single-mode coupler for coupling to a pump light source, and a length of Yb doped fiber spliced to the output end of the amplifying fiber for absorbing the residual pump light.
DE-OS 4 005 867 discloses an optical fiber amplifier comprising a Lanthanid doped length of fiber each end of which is coupled to a pump light source to achieve a high amplification of the incoming signal.
EP-A-0 509 577 discloses a two stage optical amplifier with the downstream amplifier comprising a length of active fiber doped with a fluorescent dopant, a coupler for supplying a pump light from a laser diode and a pair of optical insulators.
The present invention aims to overcome the above mentioned limitations and drawbacks.
Objects of the Invention
A first object of the present invention is to provide a fiber optic amplifier with high gain and high output power.
A second object of the present invention is to provide a fiber optic amplifier that effectively suppresses the pumping light outside the lenght of amplifying fiber.
A third object of the present invention is to provide a fiber optic amplifier with an uniform gain profile across the amplifying core of the active fiber. A further object of the present invention is to provide a fiber optic amplifier capable to make possible the use of pump sources emitting in a broad wavelength range and not requiring accurate thermal stabilization.
Disclosure of Invention Accordingly these and other objects are realized in the present invention concerning an optical fiber amplifier comprising: a lenght of double-clad fiber with: i. a co-doped single-mode core of amplifying material; ii. a multi-mode core surrounding the single-mode core and acting as guide for pump radiation; iii. an outer cladding; - a pump source coupled to said lenght of double clad fiber, characterized in that: said inner core is of an Erbium-Ytterbium doped material; - said pump power source comprises at least a multi-mode diode source supplying multi-mode pumping radiation to said lenght of double-clad fiber, transversally with respect to the optical axis of the fiber. According to the invention: - the first object is attained by means of said multi- mode diode source with associated multi-mode/high power pumping radiation; the second and third object are attained by means of said transverse pumping and consequent transverse path of the pumping radiation with respect to the axial path of the information signal propagating along said lenght of optical fiber: thanks to said transverse path, the pumping radiation does not superimpose the information signal and no absorbing means are needed; - the fourth object is attained by means of said inner core of an Erbium-Ytterbium doped materials thanks to the broad absorption spectrum of said materials.
Additional characteristics of the present invention will be better understood from the depending claims and in particular the use of multi-mode couplers for high efficient coupling of pump multi-mode radiation into the active fiber in order to perform said transverse pumping. In addition, in order to increase the pump power, at least two multi-mode couplers and two multi-mode diode sources are provided.
Further features and advantages of an optical amplifier according to the invention will become more clearly apparent from the following detailed description of a preferred embodiment of the device illustrated - only as non limiting examples - in the attached drawings, in which:
Brief Description of the Drawings
Fig. 1 is a schematic view of a fiber amplifier according to the invention; and
Fig. 2 is a cross-sectional side view schematically illustrating the active fiber and the coupler to the pumping source.
With reference to the Figures, the amplifier according to the invention comprises a length of optical fiber 1 made by a double concentrical core 2 and 3. With reference in particular to Fig. 1 it is assumed that an optical signal carrying information is propagating along the fiber in the direction shown by arrow S.
The inner core 2 is a single-mode core, with size analogous to those of the standard telecommunications fibers, and is doped with both Ytterbium and Erbium i.e. is Yb/Er co-doped. Thus the active material of the inner core 2 exhibits a broad absorption spectrum and is suitable for providing gain at optical communications wavelengths.
More particularly the codoping with Ytterbium and Erbium of the active core allows for a broad pump wavelength range, between 900 nm and 1000 nm, so that within this range pump sources do not require wavelength selection and accurate temperature stabilization.
The sorrounding core 3 is a multi-mode core used for pumping by coupling pump radiation from a laser diode 4a through a multi-mode fiber 6a and a multi-mode coupler 5a. An outer cladding 8 surrounds the multi-mode core 3.
The pump light from the pump source is injected transversally with respect to the optical axis of said fiber length 1 through the multi-mode couplers - that, according to a preferred embodiment of the invention are non-symmetrical type - and through multiple reflections (as schematically shown for a beam a in Fig. 2), penetrates into the inner core 2 and is absorbed therein without to superimpose to the optical signal to be amplified.
The multi-mode coupler can be formed, as an example, by a length of multi-mode fiber and a length of double core fiber. According to a preferred embodiment of the invention the multi-mode coupler is formed directly on the active fiber twisting, heating an subsequently pulling the two fibers.
In the diagram of Fig. 1 an additional laser diode 4b is connected to the active fiber 1 through a multi-mode fiber 6b and a second multi-mode coupler 5b for increasing the pump power and in order to achieve a more uniform power distribution along the amplifying fiber which in turn results in improved amplifying characteristics.
Isolators INS1 and INS2 can be further provided along the fiber 1. Thanks to the fact that the pump radiation does not couple into the amplifying core 2 along the signal direction, no output filter is needed. The gain profile is uniform across the active core, which thus can be made similar in dimensions to standard single-mode telecommunications fibers. The outer cladding provides optical confinement for pump radiation. The use of multi- mode fibers allows for much higher pump powers and the double core pumping scheme together with said transverse pumping makes possible placing several sources along a single active fiber; therefore high gain and output power are achievable. According to a preferred embodiment the (each) pump source is a multi-mode laser diode and the pumping radiation is a coherent radiation. Alternatively the pumping radiation can be an incoherent radiation, such as that generated, e.g. by a superfluorescent diode.
The single-mode amplifying fiber 1 is preferably made by Erbium-Ytterbium doped glass.
As for what concerns the preferred values,the diameters of the multi-mode pump core and the single-mode amplifying core are in a ratio of about 10:1 and the length of the optical fiber 1 is between 2 and 20m.
Best Mode for Carrying Out the Invention
The best mode for carrying out the invention is the one shown in fig. 2 and comprising two multi-mode fiber optic couplers 6a and 6b in order to obtain high output power and, thanks to the transverse pumping the pump radiation is not superimposed to the optical signal to be amplified, and consequently no filter is required at the output of the amplifier to eliminate residual pump radiation.
Industrial Applicability
The high power optical fiber amplifier is applicable in telecommunication transmission systems and in particular in long haul transmission lines and in distribution networks.
It will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the scope and spirit thereof.

Claims

1. An optical fiber amplifier comprising: a lenght of double-clad fiber with: i. a co-doped single-mode core of amplifying material; ii. a multi-mode core surrounding the single-mode core and acting as guide for pump radiation; iii. an outer cladding; a pump source coupled to said lenght of double clad fiber, characterized in that: said inner core (2) is of an Erbium-Ytterbium doped material; - said pump power source (4) comprises at least a multi- mode diode source supplying multi-mode pumping radiation to said lenght of double-clad fiber (1) , transversally with respect to the optical axis of the fiber (1) .
2. An optical fiber amplifier as claimed in claim 1, characterized in that said transverse pumping is performed by means of at least a multi-mode fiber optic coupler (5) associated to said lenght of double-clad fiber (1) .
3. An optical fiber amplifier as claimed in claims 1 and 2, characterized in that said multi-mode coupler (5) is formed directly on the double-clad fiber (1).
4. An optical fiber amplifier as claimed in claims 1 and 2, characterized in that includes two multi-mode diode sources (4a, 4b) and two multi-mode fiber optic couplers (5a, 5b).
5. An optical fiber amplifier as claimed in claims 1 to 4, characterized in that said pumping radiation is a coherent radiation.
6. An optical fiber amplifier as claimed in claims 1 to 4, characterized in that said pumping radiation is an incoherent radiation.
7. An optical fiber amplifier as claimed in claims 1 to 6, characterized in that said pump source is a superluminescent diode.
8. An optical fiber amplifier as claimed in claim 1, characterized in that the single-mode amplifying fiber is made by Erbium-Ytterbium doped glass.
9. An optical fiber amplifier as claimed in the preceding claims, characterized in that the diameters of the multi-mode pump core and the single-mode amplifying core are in a ratio of about 10:1.
10. An optical fiber amplifier as claimed in the preceding claims, characterized in that the length of the optical fiber is between 2 and 20 m.
11. An optical fiber amplifier as claimed in claim 2, characterized in that said multi-mode optic coupler (5) is non-symmetrical type.
PCT/IT1993/000107 1993-10-13 1993-10-13 A high power optical fiber amplifier pumped by a multi-mode laser source WO1995010868A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
RU96108614A RU2142184C1 (en) 1993-10-13 1993-10-13 High-power optical fiber amplifier pumped with multimode laser source
AU58221/94A AU5822194A (en) 1993-10-13 1993-10-13 A high power optical fiber amplifier pumped by a multi-mode laser source
EP94903981A EP0723714A1 (en) 1993-10-13 1993-10-13 A high power optical fiber amplifier pumped by a multi-mode laser source
PCT/IT1993/000107 WO1995010868A1 (en) 1993-10-13 1993-10-13 A high power optical fiber amplifier pumped by a multi-mode laser source

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IT1993/000107 WO1995010868A1 (en) 1993-10-13 1993-10-13 A high power optical fiber amplifier pumped by a multi-mode laser source

Publications (1)

Publication Number Publication Date
WO1995010868A1 true WO1995010868A1 (en) 1995-04-20

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EP0899837A1 (en) * 1997-08-23 1999-03-03 PIRELLI CAVI E SISTEMI S.p.A. Unequal couplers for multimode pumping optical amplifiers
US5920582A (en) * 1996-12-19 1999-07-06 Northern Telecom Limited Cladding mode pumped amplifier
EP0989638A1 (en) * 1998-09-22 2000-03-29 PIRELLI CAVI E SISTEMI S.p.A. Pump device for pumping an actice fiber of an optical amplifier and corresponding optical amplifier
WO2000030223A1 (en) * 1998-11-13 2000-05-25 Alliedsignal Inc. High-power cladding-pumped broadband fiber source and amplifier
FR2789813A1 (en) * 1999-02-15 2000-08-18 Cit Alcatel OPTICAL AMPLIFIER
WO2000049686A1 (en) * 1999-02-19 2000-08-24 Alcatel Doped fibre optical amplifier for 1600 nm band
US6181466B1 (en) 1997-08-23 2001-01-30 Pirelle Cavi E Sistemi S.P.A. Unequal couplers for multimode pumping optical amplifiers
FR2799054A1 (en) * 1999-09-24 2001-03-30 Cit Alcatel OPTICAL FIBER OPTICAL AMPLIFIER
DE19953871A1 (en) * 1999-11-09 2001-05-17 Siemens Ag Multi-clad fibre amplifier pumping circuit e.g. for submarine cable transmission systems
DE19961515A1 (en) * 1999-12-20 2001-06-28 Siemens Ag Arrangement for the transmission of pump light of high power
DE10009379A1 (en) * 2000-02-29 2001-09-13 Schneider Laser Technologies Fiber optical amplifier, has multimode dual core fiber with transversal mode selection element on it or in it near one end that suppresses higher modes than fundamental mode
US6327279B1 (en) 1998-07-23 2001-12-04 Robert Bosch Gmbh Device for pump light supply for laser active and amplifying fibers
US6359728B1 (en) 1998-09-22 2002-03-19 Pirelli Cavi E Sistemi S.P.A. Pump device for pumping an active fiber of an optical amplifier and corresponding optical amplifier
EP1241744A1 (en) * 2001-03-12 2002-09-18 Alcatel Double-clad optical fiber and fiber amplifier
US6477295B1 (en) * 1997-01-16 2002-11-05 Jds Uniphase Corporation Pump coupling of double clad fibers
US6525760B1 (en) * 1997-11-10 2003-02-25 Fujifilm Electronic Imaging Limited Method and apparatus for exposing an image recording medium
US6556346B1 (en) 1998-09-22 2003-04-29 Corning O.T.I.Spa Optical amplifying unit and optical transmission system
US6603598B1 (en) 1999-09-29 2003-08-05 Corning O.T.I. Inc. Optical amplifying unit and optical transmission system
US6603905B1 (en) 2000-03-03 2003-08-05 Hrl Laboratories, Llc Launch port for pumping fiber lasers and amplifiers
US6795611B2 (en) 2003-01-29 2004-09-21 Institut National D'optique Light coupling between a light source and an optical waveguide
US6941053B2 (en) 1999-12-24 2005-09-06 Institut National D'optique Triple-clad rare-earth doped optical fiber and applications
US7068900B2 (en) 1999-12-24 2006-06-27 Croteau Andre Multi-clad doped optical fiber
US7161966B2 (en) * 2003-01-24 2007-01-09 Trumpf, Inc. Side-pumped fiber laser
CN1330117C (en) * 2002-07-12 2007-08-01 俄罗斯A.M.普洛科霍洛娃普通物理研究所光纤科学中心 Device for protecting fibre lines against destruction by laser radiation
DE102007036701A1 (en) 2007-08-01 2009-02-05 Laserinstitut Mittelsachsen E.V. Production of fiber laser, comprises arranging glass cylinder with active medium of the fiber laser and glass tubes in pipe, placing pumping fibers in the pipe to partly overlap the glass cylinder, and pulling preform in multi-stage manner
US7542488B2 (en) 2003-01-24 2009-06-02 Trumpf, Inc. Fiber laser
EP1873874A3 (en) * 1999-04-30 2010-07-21 SPI Lasers UK Limited An optical fibre arrangement
DE19619983B4 (en) * 1995-05-19 2011-02-24 IMRA America, Inc., Ann Arbor High performance fiber optic amplifier system with time proportional frequency modulation based on rare earth doped cladding pump light optical fibers
WO2012047218A1 (en) * 2010-10-07 2012-04-12 Ipg Photonics Corporation High power neodymium fiber lasers and amplifiers
WO2012109400A1 (en) * 2011-02-10 2012-08-16 Soreq Nuclear Research Center High power planar lasing waveguide
US8873593B2 (en) 1998-11-25 2014-10-28 Imra America, Inc. Mode-locked multi-mode fiber laser pulse source
EP3190388A1 (en) * 2009-07-23 2017-07-12 Fotech Solutions Limited Distributed optical fibre sensing

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US7130111B2 (en) * 2001-12-13 2006-10-31 Intel Corporation Optical amplifier with transverse pump
JP7107935B2 (en) * 2016-12-01 2022-07-27 アイピージー フォトニクス コーポレーション High-power rare-earth-doped crystal amplifiers based on ultra-low quantum defect pumping schemes utilizing single-mode or low-mode fiber lasers

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DE19619983B4 (en) * 1995-05-19 2011-02-24 IMRA America, Inc., Ann Arbor High performance fiber optic amplifier system with time proportional frequency modulation based on rare earth doped cladding pump light optical fibers
US5920582A (en) * 1996-12-19 1999-07-06 Northern Telecom Limited Cladding mode pumped amplifier
US6477295B1 (en) * 1997-01-16 2002-11-05 Jds Uniphase Corporation Pump coupling of double clad fibers
US6263003B1 (en) 1997-02-14 2001-07-17 Alliedsignal Inc. High-power cladding-pumped broadband fiber source and amplifier
US6181466B1 (en) 1997-08-23 2001-01-30 Pirelle Cavi E Sistemi S.P.A. Unequal couplers for multimode pumping optical amplifiers
EP0899837A1 (en) * 1997-08-23 1999-03-03 PIRELLI CAVI E SISTEMI S.p.A. Unequal couplers for multimode pumping optical amplifiers
US6525760B1 (en) * 1997-11-10 2003-02-25 Fujifilm Electronic Imaging Limited Method and apparatus for exposing an image recording medium
US6327279B1 (en) 1998-07-23 2001-12-04 Robert Bosch Gmbh Device for pump light supply for laser active and amplifying fibers
US6359728B1 (en) 1998-09-22 2002-03-19 Pirelli Cavi E Sistemi S.P.A. Pump device for pumping an active fiber of an optical amplifier and corresponding optical amplifier
EP0989638A1 (en) * 1998-09-22 2000-03-29 PIRELLI CAVI E SISTEMI S.p.A. Pump device for pumping an actice fiber of an optical amplifier and corresponding optical amplifier
US6556346B1 (en) 1998-09-22 2003-04-29 Corning O.T.I.Spa Optical amplifying unit and optical transmission system
WO2000030223A1 (en) * 1998-11-13 2000-05-25 Alliedsignal Inc. High-power cladding-pumped broadband fiber source and amplifier
US9570880B2 (en) 1998-11-25 2017-02-14 Imra America, Inc. Multi-mode fiber amplifier
US8873593B2 (en) 1998-11-25 2014-10-28 Imra America, Inc. Mode-locked multi-mode fiber laser pulse source
US9153929B2 (en) 1998-11-25 2015-10-06 Imra America, Inc. Mode-locked multi-mode fiber laser pulse source
US9595802B2 (en) 1998-11-25 2017-03-14 Imra America, Inc. Multi-mode fiber amplifier
EP1030412A1 (en) * 1999-02-15 2000-08-23 Alcatel Optical amplifier
FR2789813A1 (en) * 1999-02-15 2000-08-18 Cit Alcatel OPTICAL AMPLIFIER
FR2790109A1 (en) * 1999-02-19 2000-08-25 Cit Alcatel OPTICAL AMPLIFIER WITH DOPED FIBER FOR THE BAND AT 1600 nm
WO2000049686A1 (en) * 1999-02-19 2000-08-24 Alcatel Doped fibre optical amplifier for 1600 nm band
EP1873874A3 (en) * 1999-04-30 2010-07-21 SPI Lasers UK Limited An optical fibre arrangement
EP1089402A1 (en) * 1999-09-24 2001-04-04 Alcatel Optical fiber amplifier
FR2799054A1 (en) * 1999-09-24 2001-03-30 Cit Alcatel OPTICAL FIBER OPTICAL AMPLIFIER
US6603598B1 (en) 1999-09-29 2003-08-05 Corning O.T.I. Inc. Optical amplifying unit and optical transmission system
DE19953871A1 (en) * 1999-11-09 2001-05-17 Siemens Ag Multi-clad fibre amplifier pumping circuit e.g. for submarine cable transmission systems
DE19961515C2 (en) * 1999-12-20 2002-04-25 Siemens Ag Arrangement for the transmission of pump light of high power for remote feeding of a fiber amplifier
EP1111740A3 (en) * 1999-12-20 2003-04-02 Siemens Aktiengesellschaft Transmission method of high power optical pumping
DE19961515A1 (en) * 1999-12-20 2001-06-28 Siemens Ag Arrangement for the transmission of pump light of high power
US7068900B2 (en) 1999-12-24 2006-06-27 Croteau Andre Multi-clad doped optical fiber
US6941053B2 (en) 1999-12-24 2005-09-06 Institut National D'optique Triple-clad rare-earth doped optical fiber and applications
DE10009379A1 (en) * 2000-02-29 2001-09-13 Schneider Laser Technologies Fiber optical amplifier, has multimode dual core fiber with transversal mode selection element on it or in it near one end that suppresses higher modes than fundamental mode
DE10009379C2 (en) * 2000-02-29 2002-04-25 Schneider Laser Technologies Fiber optic amplifier
US6603905B1 (en) 2000-03-03 2003-08-05 Hrl Laboratories, Llc Launch port for pumping fiber lasers and amplifiers
EP1241744A1 (en) * 2001-03-12 2002-09-18 Alcatel Double-clad optical fiber and fiber amplifier
CN1330117C (en) * 2002-07-12 2007-08-01 俄罗斯A.M.普洛科霍洛娃普通物理研究所光纤科学中心 Device for protecting fibre lines against destruction by laser radiation
US7542488B2 (en) 2003-01-24 2009-06-02 Trumpf, Inc. Fiber laser
US7161966B2 (en) * 2003-01-24 2007-01-09 Trumpf, Inc. Side-pumped fiber laser
US6795611B2 (en) 2003-01-29 2004-09-21 Institut National D'optique Light coupling between a light source and an optical waveguide
DE102007036701A1 (en) 2007-08-01 2009-02-05 Laserinstitut Mittelsachsen E.V. Production of fiber laser, comprises arranging glass cylinder with active medium of the fiber laser and glass tubes in pipe, placing pumping fibers in the pipe to partly overlap the glass cylinder, and pulling preform in multi-stage manner
EP3190388A1 (en) * 2009-07-23 2017-07-12 Fotech Solutions Limited Distributed optical fibre sensing
JP2013522928A (en) * 2010-10-07 2013-06-13 アイピージー フォトニクス コーポレーション High power neodymium fiber laser and amplifier
WO2012047218A1 (en) * 2010-10-07 2012-04-12 Ipg Photonics Corporation High power neodymium fiber lasers and amplifiers
WO2012109400A1 (en) * 2011-02-10 2012-08-16 Soreq Nuclear Research Center High power planar lasing waveguide

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AU5822194A (en) 1995-05-04
EP0723714A1 (en) 1996-07-31

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