Reducing photo-induced losses in optical fibers

Abstract

An ultrashort supercontinuum light source includes a pump source and a supercontinuum generator configured to receive electromagnetic radiation from the pump source and generate supercontinuum radiation. The supercontinuum generator includes a nonlinear microstructured optical fiber having a core region comprising silica. The core region includes a dopant selected to reduce photo-induced non-bridging oxygen hole center losses in the nonlinear microstructured optical fiber.

Description

[0001] This application is a divisional application of Chinese patent application No. 201880048880.6, entitled "Reducing Optical Loss in Optical Fibers". Technical Field

[0002] This manual relates to reducing optical loss in optical fibers. Background Technology

[0003] At high power levels, photodarkening can occur in optical fibers due to photoinduced defects, particularly in the visible light region of the electromagnetic spectrum. One mechanism of photodarkening is the generation of non-bridged oxygen hole centers (NBOHC) defects in the fiber. NBOHCs generate significant losses in the visible light wavelength region of the spectrum, centered at approximately 615 nm. Since NBOHCs are generated by light propagating through the fiber, the resulting losses increase with the use of the fiber, thus limiting its lifespan. Summary of the Invention

[0004] This specification provides a supercontinuum light source comprising a pump source and a supercontinuum generator configured to receive light from the pump source and generate supercontinuum light. The supercontinuum generator may comprise a nonlinear microstructured optical fiber having a core region comprising silica. At least a portion of the core region is doped with a dopant selected to reduce photoinduced nonbridged oxygen hole center loss in the nonlinear microstructured optical fiber. The dopant concentration is sufficient to provide resistance to supercontinuum power degradation in the visible region of the spectrum.

[0005] It should be noted that, in this art, the term “doped” is used to distinguish it from “undoped” optical fiber (where the amount of dopant is negligible (e.g., at levels below 1000 ppm)).

[0006] Dopant may include aluminum. Alternatively or in addition, dopant may include cerium, phosphorus and / or boron.

[0007] By reducing the attenuation of supercontinuum power in the visible region of the spectrum, the lifespan of supercontinuum light sources can be extended for applications requiring higher power in the visible region of the spectrum.

[0008] The concentration of the dopant may be sufficient to improve the transmission loss at 615 nm after 1200 hours of pumping (compared to the case where the fiber is undoped and pumped in the same cycle). The improvement (i.e. reduction) in transmission loss (e.g., after 1200 hours of pumping) can be greater than 0.1 dB / km, greater than 0.5 dB / km, greater than 1 dB / km, greater than 5 dB / km, greater than 10 dB / km, greater than 50 dB / km, greater than 100 dB / km, greater than 200 dB / km, greater than 500 dB / km, or greater than 600 dB / km.

[0009] Dopant can be provided in doped regions of the fiber core region. These doped regions can be the entire fiber core region, a single portion of the fiber core region (e.g., a single longitudinally extending portion of the fiber core region), or multiple portions of the fiber core region (e.g., independent portions that are discontinuous with each other). In various embodiments, the dopant concentration in the doped regions is greater than 1000 ppm. The number of dopant atoms in the doped regions can be greater than 0.05%, greater than 0.1%, greater than 1%, greater than 3%, greater than 8%, or greater than 20% of the number of silicon atoms in the doped regions.

[0010] In some embodiments, there is a “trade-off” regarding the reduction in supercontinuum power attenuation occurring in the visible region of the spectrum; in particular, the presence of dopants can also increase losses in the blue and / or ultraviolet (UV) regions of the spectrum. In some embodiments, the transmission loss of the doped fiber at 400 nm can be greater than 600 dB / km, greater than 750 dB / km, greater than 1000 dB / km, greater than 1500 dB / km, greater than 2000 dB / km, greater than 2500 dB / km, or greater than 3000 dB / km.

[0011] The core region can have a generally circular cross-section. The core diameter can be less than 10 μm (e.g., about 8 μm), less than 5 μm, less than 4 μm, less than 3 μm, or less than 2 μm. The core region can include the core of the optical fiber.

[0012] The core region may include additional dopant selected to control the refractive index of the core region to compensate for at least a portion of refractive index variations that would otherwise be caused by the presence of the dopant. Alternatively or additionally, additional dopant may be combined with the dopant to further improve lifetime, for example, by further reducing photoinduced nonbridged oxygen hole center loss in the nonlinear microstructure fiber. The additional dopant may include fluorine. In some embodiments, the additional dopant may include cerium.

[0013] Therefore, in some embodiments, the core region may be co-doped, for example, the core region may be doped with: aluminum and fluorine; cerium and fluorine; phosphorus and fluorine; boron and fluorine; or aluminum and cerium.

[0014] The core region may include a first longitudinally extending region and a second longitudinally extending region, wherein the first longitudinally extending region includes a first doped region containing a dopant, and the second longitudinally extending region includes a second doped region containing an additional dopant. The second longitudinally extending region may be doped with an additional dopant, but may not be doped with the aforementioned dopant.

[0015] In some embodiments, the second longitudinal extension region is disposed around (e.g., surrounding) the first longitudinal extension region. For example, the second longitudinal extension region may have an annular cross-section surrounding the first longitudinal extension region.

[0016] The second longitudinal extension region may include multiple different longitudinal extension regions, each having a substantially circular cross-section.

[0017] The first longitudinally extending region can have a substantially circular cross-section.

[0018] The first and second longitudinally extending regions can be configured such that the core region has a desired average refractive index, for example, equal to the refractive index of silicon dioxide. For example, the concentration of the dopant and / or other dopant can be selected to give the core region a target average refractive index, for example, equal to the refractive index of silicon dioxide. Alternatively or otherwise, the position and / or shape of the first and / or second regions can be selected to give the core region a target average refractive index, for example, equal to the refractive index of silicon dioxide.

[0019] The core region of a microstructured optical fiber may contain hydrogen and / or deuterium. In one example, the microstructured optical fiber comprises molecular hydrogen and / or deuterium in gaseous form. Hydrogen and / or deuterium can be bound within the core region of the microstructured optical fiber. In some examples, hydrogen and / or deuterium can be chemically bound within the core region, thereby forming OH and / or OD.

[0020] The concentrations of hydrogen and / or deuterium can be greater than one part per billion, greater than ten parts per billion, greater than one hundred parts per billion, greater than one part per million, greater than one hundred parts per million, greater than one thousand parts per million, greater than two thousand parts per million, or greater than ten thousand parts per million. Among these, parts per million (ppm) and parts per billion (ppb) are considered to be the molar ratio of OH and / or OD to SiO2 (or H2 and / or D2 to SiO2).

[0021] Microstructured optical fibers may include a coating that acts as a hydrogen / deuterium diffusion barrier. The diffusion barrier prevents the diffusion of free molecules of hydrogen and / or deuterium.

[0022] Microstructured optical fibers may further include a cladding region, wherein the difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 10. -4 or less than 10 -5 .

[0023] The length of microstructured optical fibers can be less than 5m, approximately 5m, or greater than 5m.

[0024] A supercontinuum generator may include additional microstructured optical fibers located upstream or downstream of the microstructured optical fiber. The microstructured optical fiber and the additional microstructured optical fiber may have different waveguide (e.g., dispersion) properties and / or different material (e.g., absorption) properties.

[0025] Compared to microstructured optical fibers, other microstructured optical fibers can exhibit lower loss in the blue region of the spectrum. This microstructured optical fiber, and other microstructured optical fibers, can have substantially circular cores, each with a different diameter.

[0026] In some embodiments, at least a portion of the core region of a microstructured optical fiber and / or other microstructured optical fibers may taper gradually along its length. For example, the input region of the core region of a microstructured optical fiber may be tapered.

[0027] This specification also provides a passive optical fiber having a core region comprising silicon dioxide, wherein the core region is doped with aluminum. As those skilled in the art will understand, the term "passive" is a technical term used to distinguish it from so-called "active" optical fibers; "active" optical fibers are fibers doped with gain materials, such as ytterbium or erbium, to provide optical gain when pumped at an appropriate pump wavelength; passive optical fibers do not contain such "active" fiber dopants.

[0028] Passive optical fibers can be supercontinuum fibers and / or large mode area fibers. Supercontinuum fibers can include nonlinear fibers. Large mode area fibers can include core regions with a diameter greater than 5 μm. In some embodiments, passive optical fibers (e.g., supercontinuum fibers and / or large mode area fibers) are microstructured fibers.

[0029] The core region may include the core of the optical fiber. The core region of a passive optical fiber may include at least one co-doperb selected to control the refractive index of the core region to compensate for at least a portion of a change in refractive index that would otherwise be caused by the presence of aluminum. In some embodiments, the core region is co-doped with fluorine.

[0030] The core region may include a first longitudinally extending region and a second longitudinally extending region, wherein the first longitudinally extending region is doped with aluminum and the second longitudinally extending region is doped with at least one co-doperant.

[0031] Aluminum can be provided in doped regions of the fiber core region. These doped regions can be the entire fiber core region, a single continuous portion of the fiber core region (e.g., a single longitudinally extending portion of the fiber core region), or multiple portions of the fiber core region (e.g., independent portions that are not connected to each other). The number of aluminum atoms in the doped region can be greater than 0.1%, greater than 1%, greater than 3%, greater than 8%, or greater than 20% of the number of silicon atoms in the doped region.

[0032] As will be understood by those skilled in the art, the term “light” as used herein is not limited to visible light, but includes any suitable electromagnetic radiation, such as infrared light (including near-infrared and far-infrared light), visible light, and ultraviolet light. Attached Figure Description

[0033] Various embodiments will now be described with reference to the accompanying drawings, in which:

[0034] Figure 1 This is a schematic diagram of a supercontinuum light source.

[0035] Figures 2(a) and 2(b) show the experimental results, in which two different fiber under test (FUT) were pumped and the output power and spectrum were measured.

[0036] Figure 3 The formation of aluminum oxide vacancy centers is schematically illustrated.

[0037] Figure 4 This is a cross-sectional view of the AL:F-doped core region of an example microstructured optical fiber.

[0038] Figure 5 An example cascaded configuration is shown, which includes a first microstructure fiber and a second microstructure fiber downstream of the first microstructure fiber.

[0039] Figure 6 Illustrative trend lines are shown, indicating how the D2 load mitigates the attenuation of visible supercontinuum power in doped and undoped microstructured nonlinear fibers (NLF) in different ways.

[0040] Figure 7 Experimental results showing the variation of visible light output power over time for two different fiber under test (FUT) are presented. Detailed Implementation

[0041] Figure 1A supercontinuum light source 100 according to an example is shown. As shown, the supercontinuum light source 100 includes a pump source 102 and a supercontinuum generator 104.

[0042] The generation of supercontinuum is known in itself and will not be described in detail here. See “Visible continuum generation in air silica microstructure optical fibres with anomalous dispersion at 800 nm”, J.K. Ranka, R.S. Windeler, and A.J. S. Tentz, Optics Letters, 2000, Vol. 25: pp. 25-27.

[0043] Pump source 102

[0044] The pump source can be configured to generate short optical pulses. For example, the pump source can be configured to generate optical pulses with a full width at half maximum (FWHM) duration of less than 100 ns, less than 10 ns, less than 1 ns, less than 100 ps, ​​less than 10 ps, ​​less than 1 ps, less than 500 fs, or less than 100 fs.

[0045] In some examples, the pump source can be configured to produce a pulsed output at a wavelength in the ytterbium gain bandwidth (e.g., about 1 micrometer, such as about 1.064 micrometers) or alternatively, a continuous wave output.

[0046] In embodiments where the pulse sequence is generated by a pump source, the pulse sequence can be generated at a repetition frequency greater than 10 kHz, greater than 100 kHz, greater than 1 MHz, greater than 10 MHz, greater than 20 MHz, greater than 50 MHz, or greater than 100 MHz.

[0047] In various examples, the pump source can be configured to produce an average power greater than 1mW, greater than 10mW, greater than 100mW, greater than 1W, greater than 2W, greater than 5W, greater than 10W, greater than 20W, or greater than 50W.

[0048] The pump source may include a seed source and one or more optical amplifiers. The seed source may include an oscillator, such as a gain-switching diode or a mode-locked fiber laser. The output from the seed source may be amplified by one or more amplifiers, which may include an amplifier chain comprising a preamplifier and one or more additional amplifiers. Suitable systems for obtaining power, wavelength, pulse duration, and repetition frequency characteristics appropriate for generating supercontinuum in microstructured optical fibers are known in themselves and will not be described in detail here. References are made to European Patent EP2081074B1 and the documents and commercial products referenced therein.

[0049] Supercontinuum Generator 104

[0050] The supercontinuum generator 104 may include a microstructured optical fiber 104, which is "pumped" by a pump source 102 to form a supercontinuum. The microstructured optical fiber includes a core region and a cladding region. The core region may be substantially circular and may have a core diameter, for example, less than 10 μm, less than 5 μm, less than 4 μm, less than 3 μm, or less than 2 μm. The cladding region includes longitudinally extending features (e.g., pores) disposed around the cladding region, wherein the refractive index of the feature is different from the refractive index of the material surrounding the feature. This feature facilitates light guidance via one or more mechanisms, such as refractive index guidance or guidance via the generation of a photonic bandgap. The microstructured optical fiber includes so-called porous fiber, photonic crystal fiber, and air-clad fiber.

[0051] As those skilled in the art will understand, longitudinal extension features in the cladding region can produce an “effective refractive index” for the cladding region as defined by the basic space-filling pattern. In some examples described herein, the difference between the refractive index of the core region and the effective refractive index of the cladding region can be less than 10. -4 or less than 10 -5 The solid regions of microstructured optical fibers can be formed from doped or undoped silicon dioxide.

[0052] The supercontinuum generator 104 may include a microstructured optical fiber having a core region comprising silicon dioxide, the core region including a first dopant selected to reduce photoinduced non-bridged oxygen hole center loss in the microstructured optical fiber. The first dopant may include aluminum. The number of aluminum atoms may be greater than 0.05%, greater than 0.1%, greater than 1%, greater than 3%, greater than 8%, or greater than 20% of the number of silicon atoms in the aluminum-doped region.

[0053] The core region may also include a second dopant, selected to control the refractive index of the core region to compensate for at least a portion of the refractive index variation that would otherwise be caused by the presence of the first dopant. Therefore, the second dopant prevents undesirable waveguide effects (which might otherwise be caused by the presence of the first dopant). For example, due to the LP of optical fibers... 11 In the absence of a second dopant, if the mode undergoes an undesirable change at the cutoff wavelength, the first dopant might alter the refractive index in such a way that the fiber becomes multimode at the wavelength where single-mode operation is desired. A second dopant can be included to prevent this by at least partially compensating for the refractive index change (which would otherwise be introduced by the first dopant). Alternatively or additionally, co-dopersive agents can have a positive impact on lifetime; for example, they can further reduce optically induced non-bridged oxygen hole center losses in microstructured fibers.

[0054] The second dopant may contain fluorine. Co-doping with aluminum and fluorine may be referred to herein as Al:F doping. Fibers with Al:F-doped core regions may be referred to herein as "Al:F-doped fiber".

[0055] Figures 2(a) and 2(b) show the experimental results, in which two different optical fibers were pumped and the output power and spectra were recorded. The dashed line in Figure 2(a) shows the change in average visible light power over time for a 10 m long pure silica microstructure fiber pumped at a constant pump power. The solid line shows the change in average visible light power over time for a 4.5 m long microstructure fiber with an Al:F doped core region pumped at a constant pump power. Figure 2(b) shows the loss measurements performed after 1200 hours of pumping the pure silica fiber (dashed line) and the Al:F doped fiber (solid line).

[0056] Figure 2(b) clearly shows the NBOHC absorption peak (dashed line) at 615 nm for pure silica microstructure fiber. In contrast, for Al:F doped fiber (solid line), Figure 2(b) shows significantly less absorption at 615 nm, indicating that the NBOHC loss has been reduced due to the presence of the dopant. Therefore, this experiment indicates that the attenuation of supercontinuum power in at least a portion of the visible region of the spectrum is mitigated due to the presence of the dopant. The trade-off is a larger ultraviolet (UV) loss tail in the Al:F doped case, as shown in Figure 2(b).

[0057] NBOHC forms in pure silica when silica bonds break to form NBOHC and e' defects. Not wanting to be bound by theory, a possible explanation for reduced NBOHC formation in Al:F-doped silica is that, in Al:F-doped silica, NBOHC formation can be replaced by a process where photons break Si-O-Al bonds to form aluminum-oxygen hole centers (AlOHC) and e'. Therefore, the reduced peak at 615 nm in Figure 2(b) can be attributed to the different optical properties of AlOHC and NBOHC defects. The formation of AlOHC... Figure 3 The diagram is shown schematically.

[0058] Figure 4 This is a cross-sectional view of the Al:F-doped core region of the example microstructured optical fiber 400. As shown, the core region 402 of the example optical fiber 400 comprises multiple individual regions 404, 406, and 408. Some regions 404 are doped with aluminum. Other regions 406 are doped with fluorine. Other regions 408 are undoped. Including doped and / or undoped regions as separate longitudinally extending regions within the core region of the microstructured optical fiber facilitates fabrication and allows for improved control over the total refractive index of the core region.

[0059] Alternatively, the central region 408 may be doped with aluminum, and some or all of the surrounding regions 404, 406 may be doped with additional dopants (e.g., fluorine). In some embodiments, the core region doped with additional dopants (e.g., fluorine) may form a circular ring around the central region doped with the first dopant.

[0060] In various embodiments, the doped regions are configured to provide a target average refractive index, for example, equal to the refractive index of silicon dioxide. For example, the concentration of aluminum and / or the concentration of other dopants can be selected such that the core as a whole (or a region of the core) has a target average refractive index, for example, equal to the refractive index of silicon dioxide. Alternatively or additionally, the location and / or shape of the aluminum-doped regions (and / or the location and / or shape of the regions doped with other dopants) can be selected such that the core as a whole (or a region of the core) has a target average refractive index, for example, equal to the refractive index of silicon dioxide.

[0061] In some embodiments, the supercontinuum generator 104 comprises a single microstructured optical fiber. In other embodiments, the supercontinuum generator may comprise more than one microstructured optical fiber. For example, the supercontinuum generator may comprise two or more optical fibers coupled in series (e.g., fused together). Thus, an optical fiber “cascade” can be formed. The optical fibers in the cascade may have different waveguide properties and / or different material properties.

[0062] Figure 5An example cascaded configuration is shown, comprising a first microstructured fiber and a second microstructured fiber downstream of the first microstructured fiber. The first and second fibers have different material properties but share the same waveguide characteristics. For example, the first fiber may have an Al:F-doped core region for more efficient supercontinuum generation and reduced NBOHC formation. The material properties of the second fiber can be optimized to reduce absorption at blue and / or UV wavelengths. The reduced blue and / or UV absorption of the second fiber compensates for the increased UV loss tail that may occur in the first fiber due to Al:F doping in the core region. Thus, this configuration leverages the benefits of Al:F doping while mitigating its drawbacks.

[0063] In one variation, the waveguide (e.g., dispersion) characteristics of the first and second optical fibers can differ, in addition to material properties. For example, the waveguide characteristics of the first fiber can be optimized to generate a red supercontinuum, and the waveguide characteristics of the second fiber can be optimized to generate a blue supercontinuum. Although in some embodiments the microstructured fiber of the supercontinuum generator may be non-tapered, in other embodiments the supercontinuum generator may include one or more tapered fibers. For example, the supercontinuum generator may include two non-tapered microstructured fiber sections of different diameters, and a tapered fiber "mode adapter" between the two non-tapered fibers. Alternatively, the microstructured fiber may include a tapered input region.

[0064] Although the first dopant preferably comprises aluminum, in any embodiment described herein, the first dopant may alternatively (or in addition to) comprise cerium, boron, or phosphorus, or another suitable dopant selected to reduce photoinduced nonbridged oxygen hole center loss in nonlinear microstructured optical fibers.

[0065] Hydrogen / deuterium loading

[0066] It is known to incorporate hydrogen and / or deuterium into the microstructure of a supercontinuum light source to extend its lifetime. Hydrogen and / or deuterium can be chemically confined within the fiber core and / or exist as free molecules within the quartz glass. See European patent application EP2111564.

[0067] It has also been found that hydrogen and / or deuterium loading in Al:F doped fibers has a positive impact on loss rate. However, for Al:F doped fibers, hydrogen / deuterium may interact with the AlOHC defects mentioned above, thereby reducing loss that would otherwise be caused by the presence of these defects. Therefore, the presence of aluminum dopant works synergistically with hydrogen and / or deuterium loading to provide improvement in loss rate, thereby extending lifetime.

[0068] Although hydrogen can be loaded into Al:F doped optical fibers, deuterium is preferred because hydrogen may combine with oxygen in the fiber to form OH bonds, resulting in absorption peaks at approximately 1380 nm and 2210 nm. Figure 6 Illustrative trend lines are shown, indicating how D2 loading mitigates the attenuation of visible supercontinuum power in standard and Al:F fibers in different ways.

[0069] Figure 7 The results of the experiment are shown, in which two different deuterium-loaded optical fibers were pumped, and the monitored output power of visible light was observed to change over time. The pump power was kept constant. The dashed line shows the change of visible light output power over time for a 10 m long deuterium-loaded silica microstructure optical fiber. The solid line shows the change of output power over time for a 4.5 m long Al:F-doped microstructure optical fiber.

[0070] In various embodiments, the concentrations of hydrogen and / or deuterium can be higher than one part per billion, higher than ten parts per billion, higher than one hundred parts per billion, higher than one million, higher than one hundred million, higher than one thousand million, higher than two thousand million, or higher than ten thousand million. In some embodiments, the concentration of deuterium can typically be reduced to between 60 ppm and 220 ppm, which is considered to be the molar ratio of OD to SiO2 (or D2 to SiO2). This concentration can be obtained via spectral absorption measurements performed during fiber stretching, and the OD absorption in silica can be converted to ppm by taking into account the values ​​given in “Analysis of OH absorption bands in synthetic silica” by O. Hubach et al., Journal of Non-Crystalline Solids 203 (1996) 19-26 (note that the values ​​given in this reference are in weight ppm; we convert them to molar ppm).

[0071] In some examples, the microstructured optical fiber may include a coating to act as a diffusion barrier layer for hydrogen and / or deuterium.

[0072] Other optical fibers

[0073] While the above discussion focuses on nonlinear microstructured fibers, in some embodiments, the core region of other silica-based fibers may be doped with aluminum (and / or other suitable dopants). For example, large-mode-area fibers (e.g., large-mode-area microstructured fibers) used to transmit high-power supercontinuum from one location to another may be doped with aluminum to reduce photoinduced nonbridged oxygen hole center loss in large-mode-area fibers.

[0074] In some embodiments, a passive optical fiber may be provided having a core region comprising silica, wherein the core region is doped with aluminum. It should be noted that, in the art, the term "passive" is used to distinguish it from so-called "active" optical fibers; "active" optical fibers are fibers doped with gain materials, such as ytterbium or erbium, to provide optical gain when pumped at a suitable pump wavelength; passive optical fibers do not contain such "active" fiber dopants. Passive optical fibers may include microstructured fibers or other supercontinuum fibers or large mode area fibers.

[0075] Many other modifications and variations will be apparent to those skilled in the art, and fall within the scope of the following claims.

Claims

1. A supercontinuum light source, comprising: Pump source; as well as A supercontinuum generator configured to receive electromagnetic radiation from a pump source and to generate supercontinuum radiation, the supercontinuum generator comprising a passive nonlinear microstructure optical fiber having a hydrogen and / or deuterium-loaded core region comprising silicon dioxide. At least a portion of the core region of the microstructured fiber is doped with aluminum, wherein aluminum reduces the photoinduced nonbridged oxygen hole center loss in the nonlinear microstructured fiber, and wherein aluminum is provided in the doped region, and wherein the number of aluminum atoms in the doped region is greater than 0.05% of the number of silicon atoms in the doped region.

2. The supercontinuum light source according to claim 1, wherein, At least a portion of the doped region is co-doped with an additional dopant, which is selected to control the refractive index of the core region to compensate for at least a portion of the refractive index change that would otherwise be caused by the presence of aluminum.

3. The supercontinuum light source according to claim 2, wherein, The number of aluminum atoms in the doped region is greater than 0.1% of the number of silicon atoms in the doped region.

4. The supercontinuum light source according to claim 2, wherein, The number of aluminum atoms in the doped region is greater than 1% of the number of silicon atoms in the doped region.

5. The supercontinuum light source according to claim 2, wherein, The number of aluminum atoms in the doped region is greater than 3% of the number of silicon atoms in the doped region.

6. The supercontinuum light source according to claim 2, wherein, The number of aluminum atoms in the doped region is greater than 8% of the number of silicon atoms in the doped region.

7. The supercontinuum light source according to claim 2, wherein, The additional dopant includes fluorine, wherein the core region includes a first longitudinally extending region and a second longitudinally extending region, wherein the first longitudinally extending region includes aluminum and the second longitudinally extending region includes fluorine.

8. The supercontinuum light source according to claim 7, wherein the second longitudinally extending region is doped with fluorine but not with aluminum.

9. The supercontinuum light source according to claim 7 or 8, wherein, The second longitudinal extension region is arranged around the first longitudinal extension region.

10. The supercontinuum light source according to claim 9, wherein, The second longitudinally extending region has an annular cross-section.

11. The supercontinuum light source according to claim 7, wherein, The second longitudinal extension region includes a plurality of different longitudinal extension regions, each of which has a circular cross-section.

12. The supercontinuum light source according to claim 7, wherein, The first longitudinally extending region has a circular cross-section.

13. The supercontinuum light source according to claim 7, wherein, The first longitudinal extension region and the second longitudinal extension region are configured such that the core region has a desired average refractive index.

14. The supercontinuum light source according to claim 13, wherein the desired average refractive index is equal to the refractive index of silicon dioxide.

15. The supercontinuum light source according to claim 1, wherein, The concentration of hydrogen and / or deuterium is greater than one part per billion.

16. The supercontinuum light source according to claim 1, wherein, The concentration of hydrogen and / or deuterium is greater than 10 parts per billion.

17. The supercontinuum light source according to claim 1, wherein, The concentration of hydrogen and / or deuterium is greater than 100 parts per billion.

18. The supercontinuum light source according to claim 1, wherein, The concentration of hydrogen and / or deuterium is greater than one part per million.

19. The supercontinuum light source according to claim 1, wherein, The concentration of hydrogen and / or deuterium is greater than 100 parts per million.

20. The supercontinuum light source according to claim 1, wherein, The concentration of hydrogen and / or deuterium is greater than one thousand parts per million.

21. The supercontinuum light source according to claim 1, wherein, The concentration of hydrogen and / or deuterium is greater than 2,000 parts per million.

22. The supercontinuum light source according to claim 1, wherein, The concentration of hydrogen and / or deuterium is greater than 10,000 parts per million.

23. The supercontinuum light source according to claim 1, wherein, The microstructured optical fiber includes a coating that serves as a hydrogen / deuterium diffusion barrier.

24. The supercontinuum light source according to claim 1, wherein, The core region has a core diameter of less than 10 μm.

25. The supercontinuum light source according to claim 1, wherein, The core region has a core diameter of less than 5 μm.

26. The supercontinuum light source according to claim 1, wherein, The core region has a core diameter of less than 4 μm.

27. The supercontinuum light source according to claim 1, wherein, The core region has a core diameter of less than 3 μm.

28. The supercontinuum light source according to claim 1, wherein, The core region has a core diameter of less than 2 μm.

29. The supercontinuum light source according to claim 1, wherein, The supercontinuum generator includes additional microstructured optical fibers located upstream or downstream of the microstructured optical fiber.

30. The supercontinuum light source according to claim 29, wherein, The microstructured optical fiber and the other microstructured optical fiber have different waveguide properties.

31. The supercontinuum light source according to claim 29 or 30, wherein, The microstructured optical fiber and the other microstructured optical fiber have different dispersion characteristics.

32. The supercontinuum light source according to claim 29, wherein, The microstructured optical fiber and the other microstructured optical fiber have different material properties.

33. The supercontinuum light source according to claim 29, wherein, The microstructured optical fiber and the other microstructured optical fiber have different absorption characteristics.

34. The supercontinuum light source according to claim 29, wherein, The additional microstructured optical fiber is located downstream of the microstructured optical fiber.

35. The supercontinuum light source according to claim 34, wherein, Compared to the microstructured optical fiber, the additional microstructured optical fiber has lower loss in the blue region of the spectrum.

36. The supercontinuum light source according to claim 29, wherein, The microstructured optical fiber and the other microstructured optical fiber have circular cores, each of which has a different diameter.

37. The supercontinuum light source according to claim 1, wherein, At least a portion of the core region of the microstructured optical fiber gradually tapers along its length.

38. The supercontinuum light source according to claim 37, wherein, The input region of the core area of ​​the microstructured optical fiber is tapered.

39. A passive optical fiber having a hydrogen and / or deuterium-loaded core region comprising silicon dioxide, wherein at least a portion of the core region of the optical fiber is doped with aluminum, wherein aluminum reduces photoinduced non-bridged oxygen hole center loss in the optical fiber, and wherein, Aluminum is provided in the doped region, wherein the number of aluminum atoms in the doped region is greater than 0.1% of the number of silicon atoms in the doped region.

40. The passive optical fiber according to claim 39, wherein, The passive optical fiber is a large mode area optical fiber.

41. The passive optical fiber according to claim 39 or 40, wherein, The passive optical fiber further includes a cladding region, wherein the difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 10. -2 .

42. The passive optical fiber according to claim 41, wherein, The difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 6 × 10⁻⁶. -3 .

43. The passive optical fiber according to claim 41, wherein, The difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 5 × 10⁻⁶. -3 .

44. The passive optical fiber according to claim 41, wherein, The difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 4 × 10⁻⁶. -3 .

45. The passive optical fiber according to claim 41, wherein, The difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 3 × 10⁻⁶. -3 .

46. ​​The passive optical fiber according to claim 41, wherein, The difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 10. -3 .

47. The passive optical fiber according to claim 41, wherein, The difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 3 × 10⁻⁶. -4 .

48. The passive optical fiber according to claim 41, wherein, The difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 2 × 10⁻⁶. -4 .

49. The passive optical fiber according to claim 41, wherein, The difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 10. -4 .

50. The passive optical fiber according to claim 41, wherein, The difference between the refractive index of the core region and the effective refractive index of the cladding region is less than 10. -5 .

51. The passive optical fiber according to claim 41, wherein, The passive optical fiber is a supercontinuum optical fiber.

52. The passive optical fiber according to claim 39, wherein, The passive optical fiber is a microstructure optical fiber.

53. The passive optical fiber according to claim 39, wherein, The fiber core region includes a first longitudinally extending region and a second longitudinally extending region, wherein the first longitudinally extending region is doped with aluminum and the second longitudinally extending region is doped with fluorine.

54. The passive optical fiber according to claim 53, wherein, The second longitudinally extended region is doped with fluorine but not with aluminum.

55. The passive optical fiber according to claim 53 or 54, wherein, The second longitudinal extension region is arranged around the first longitudinal extension region.

56. The passive optical fiber according to claim 55, wherein, The second longitudinally extending region has an annular cross-section.

57. The passive optical fiber according to claim 53, wherein, The second longitudinal extension region includes a plurality of different longitudinal extension regions, each of which has a circular cross-section.

58. The passive optical fiber according to claim 53, wherein, The first longitudinally extending region has a circular cross-section.

59. The passive optical fiber according to claim 53, wherein, The first longitudinal extension region and the second longitudinal extension region are configured such that the core region has a desired average refractive index.

60. The passive optical fiber according to claim 59, wherein, The desired average refractive index is equal to the refractive index of silicon dioxide.

61. The passive optical fiber according to claim 53, wherein, The first longitudinal extension region and the second longitudinal extension region have the same cross-sectional shape.

62. The passive optical fiber according to claim 39, wherein, At least a portion of the doped region is co-doped with an additional dopant, which is selected to control the refractive index of the core region to compensate for at least a portion of the refractive index change that would otherwise be caused by the presence of aluminum.

63. The passive optical fiber according to claim 39, wherein, The number of aluminum atoms in the dopant is greater than 1% of the number of silicon atoms in the aluminum-doped region.

64. The passive optical fiber according to claim 39, wherein, The number of aluminum atoms in the dopant is greater than 3% of the number of silicon atoms in the aluminum-doped region.

65. The passive optical fiber according to claim 39, wherein, The number of aluminum atoms in the dopant is greater than 8% of the number of silicon atoms in the aluminum-doped region.

66. The passive optical fiber according to claim 39, wherein, The number of aluminum atoms in the dopant is greater than 20% of the number of silicon atoms in the aluminum-doped region.

67. The passive optical fiber according to claim 62, wherein, The additional dopants include fluorine.

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