FR2768143A1 - ERBIUM DOPED FLUOROPHOSPHATE GLASS AND OPTICAL AMPLIFIER INCLUDING THIS GLASS - Google Patents

Abstract

The invention relates to a family of erbium-doped fluorophosphate glasses for use in optical signal amplification. The composition, based on 100 parts by weight, is constituted by: P2O5 15-40, A12O3 0-5, MgO 0-9, CaO 0-9, SrO 0-9, BaO 0-45, AlF3 5-25, MgF2 0-10, CaF2 0-25, SrF2 0-25, BaF2 0-20, KHF2 0-2, K2TiF6 0-2, with up to 10 parts by weight of erbium oxide. The glasses according to the present invention exhibit a high gain and a very flat spectrum over the 1550 nm bandwidth, as compared to the glasses of the figure. These glass compositions are particularly well suited for use in fiber or planar optical amplification in WDM and similar applications.

Description

The present invention relates generally to the field of

  optical signal amplifiers and in particular fluorophosphate glass compositions for use in signal amplifiers

  optics operating at wavelengths in the vicinity of 1.55 gm.

  Optical signal amplifiers are now widely used in optical telecommunications networks, particularly in networks that use optical fibers over long distances. even though

  modern silica-based optical fibers generally exhibit relative losses

  tively low in the 1.55 µm window, these losses are not zero and accumulate with distance. To reduce the resulting attenuation, opto-electronic devices were used to regenerate the signal strength. These devices require that the optical signal be converted into an electronic signal which is then amplified using known amplification techniques in a way

  general to be converted back to an optical signal for retrans-

mission.

  Optical signal amplifiers amplify optical signals without the need for opto-electronic signal conversion. In optical amplifiers, the weakened light signal is caused to pass through an amplifying medium which has been doped with ions of a rare earth element. Light from an external source, typically a semiconductor laser, is pumped into the amplifying medium to stimulate the rare earth atoms to a higher energy level. The light entering the amplifying medium at the signal wavelength further stimulates the excited rare earth ions so that they emit their energy from excess photons as light at the wavelength of the phase signal. with the signal pulses, which amplifies the light signal. One type of optical amplifier uses a certain length of erbium-doped optical fiber. Erbium doped fiber amplifiers (EDFA) are usually doped with erbium ions at about -500 ppm. Typical EDFA fiber lengths are in the range of 10-30m and depend on the final gain required for a particular application. In some applications, it is not possible to use a fiber length of 10 to 30 m. Planar-type optical amplifiers have been developed for use in more confined spaces. The useful length of a planar amplifier device does not generally exceed 10 cm. To reach the same amplification levels as in an EDFA with a length of 10 to 30 m, a planar amplifier requires an amplifying medium whose concentration in

  erbium ions is higher, on the order of up to 4 to 7% by weight.

  However, in known types of optical amplifying media, there are several mechanisms of loss of gain at high levels of erbium ion concentrations, such as ion aggregation and homogeneous cooperative conversion (concentration relaxation). Because erbium ions do not dissolve well in a silica matrix, they aggregate allowing energy transfer to the aggregated region. In addition, at higher erbium concentrations, ion-ion interactions become more sensitive. The resulting energy conversion relaxes the inverted population. The energy of erbium ions is used in the aggregation and relaxation processes so that it is not available for the necessary amplifier phonon process. As a result, the quantum yield of the amplifying medium decreases rapidly when the concentration of erbium ions increases, which is accompanied by a decrease in the

amplifier gain.

  In addition, known silica-based erbium-doped amplifiers exhibit clear spectral gain non-uniformity. The absence of a flat gain spectrum over a large bandwidth poses several problems. For example, extremely short optical pulses have a relatively wide energy spectrum and are not precisely amplified if the gain spectrum is not flat. In addition, in higher bandwidth applications, such as wavelength multiplexing (WDM), the fiber receives data-modulated optical signals from multiple optical transmitters, each of which uses a different optical carrier frequency. If the gain spectrum of the optical amplifier is not flat in the operating wavelength range, the carrier frequencies may be saturated at the gain maxima while they may not be sufficiently amplified at the level sides and minimum gain. Previous efforts to make the gain flat were based primarily on passive or active filtering of the higher characteristics of the gain spectrum. However, this requires close adaptation of the particular amplifier and filter and must take account of variations

gain spectrum.

  The present invention relates to a family of glasses which can be advantageously used in particular in the production of optical signal amplifiers. These glasses are doped with high concentrations (up to almost 10% by weight) of erbium oxide while exhibiting a weak concentration relaxation behavior. These glasses also allow a higher fluorescence yield and more uniform gain characteristics.

  as the media constituted by known silicate and fluorosirconate glasses.

  These glasses have high and flat gain characteristics which are particularly useful for optical amplification in the window of 1.55 µm optical frequencies and are particularly suitable for optical systems.

  wavelength multiplexing (WDM).

  In one of its aspects, the present invention relates to a family of

  glasses, especially fluorophosphate glasses, which are particularly suitable

  lie well for high levels of rare earth ion concentrations. The pre-

  sente invention aims to provide a fluorophosphate glass medium doped with erbium oxide ions and intended for use in an optical amplifier to produce a flat and high gain in a wavelength window

  optics located near 1.55, utm. Glasses of fluorophosphate from pre-

  sente invention include high concentrations of erbium ions (i.e.

  say up to almost 10% by weight) and give a more uniform gain from the spectral point of view, in the same way as the fluorinated glasses ZBLAN (that is to say fluorinated glasses for optical fibers containing the fluorides ZrF4 , BaF2, LaF3, AIF3 and NaF), and are significantly improved compared to the glass compositions of

typical silicate and phosphate.

  The present invention relates to a family of glasses for amplification.

  optical cation comprising a doped fluorophosphate glass medium substantially free of silica, per 100 parts by weight consisting of: P205 15-40 MgF2 0-10 A1203 0-5 CaF2 0-25 MgO 0-9 SrF2 0-25 CaO 0 -9 BaF2 0-20 SrO 0-9 KHF2 0-2 BaO 0-45 K2TiF6 0-2

AIF3 5-25

  with up to 10, preferably between 0.01 and 10, parts by weight of erbium oxide.

4 2768143

  Preferably, the doped fluorophosphate glass according to the present invention has a composition comprising in parts by weight: P205 16.9-24.0 MgF2 0-7.5 A1203 1.6-3.2 CaF2 0-18.7 MgO 0-5, 0 SrF2 0-19.7 CaO 0-5.1 BaF2 1.5-11.3 SrO 0-8.5 KHF2 0-1.3 BaO 2.7-43.2 K2TiF6 0-0, 6

AIF3 9.5-19.3

  The fluorophosphate glass according to the present invention can also be co-doped with up to 15 parts by weight of Yb203 as a sensitizer to increase the pumping efficiency at around 980 nm. The fluorophosphate glass according to the invention preferably has a refractive index of between approximately 1.48 and 1.58. Preferably, the fluoride content (s) of the fluorophosphate glass according to the

  The present invention is in the range of 7 to 88 parts by weight.

  In another aspect, the present invention relates to an optical amplifier doped with erbium for a band of wavelengths of about 1.55 µm, comprising a medium for optical amplification comprising a substantially free fluorophosphate glass composition of silica which comprises, in addition to the 100 parts by weight of the other components of the glass, about 0.01 to 10 parts by weight of Er 2 O 3. The optical amplifier according to the present invention can be an amplifier

  planar type optical amplifier or a single mode fiber optic amplifier.

  The optical amplifier according to the present invention comprises a glass of fluorophosphate comprising, per 100 parts by weight consisting of:

2768143

  P205 15-40 MgF2 0-10 A1203 0-5 CaF2 0-25 MgO 0-9 SrF2 0-25 CaO 0-9 BaF2 0-20 SrO 0-9 KHF2 0-2 BaO 0-45 K2TiF6 0-2

A1F3 5-25

  up to 10, and preferably between 0.01 and 10, parts by weight of erbium oxide.

  The fluorophosphate glass used for the optical amplifier according to the present invention can also be doped with up to 15 parts by weight of Yb203 as a sensitizer to increase the pumping efficiency at around 980 nm, and it preferably has an index of refraction between about 1.48 and 1.58. The optical amplifiers according to the present invention are particularly useful in

  wavelength multiplexing (WDM) systems.

  Preferably, the fluoride (s) content of the fluorophosphate glass used for the optical amplifier according to the present invention is in the range of 7

to 88 parts by weight.

  In the optical amplifier according to the invention, the optical amplification medium can constitute an active optical medium having an input and an output, said active optical medium receiving on its input optical signals whose wavelength is included in the range from approximately 1525 to 1570 nanometers; and there is provided a pumping source providing said active optical medium with a pumping light power at a wavelength of approximately 980 nm, the pumping light being adapted to excite the erbium in order to cause photons to be emitted to said erbium. said optical signals in a wavelength range of width approximately 20 to 30 nm with a substantially flat gain spectrum whose variation is less than approximately 13% in the spectral range from 1525 to approximately 1565 nanometers, o the quantum efficiency of said active optical medium

6 2768143

  exceeds about 65%, said quantum yield being the ratio between lifetime

  fluorescence of the active optical medium and the lifetime of radiation.

  Other characteristics and advantages of the invention will appear better in

  the detailed description which follows and refers to the appended drawings, given only to

  By way of example, and in which: FIGS. 1 and 2 are graphs representing a typical behavior of concentration relaxation over the lifetime of fluorescence and the yield of a binary silicate glass; Figures 3 and 4 are graphs showing the fluorescence lifetime and the yield of fluorophosphate glasses according to the present invention; FIG. 5 is a graph showing the shape of the gain as a function of the wavelength for a typical silicate-based glass; FIG. 6 is a graph showing the shape of the gain as a function of the wavelength for a typical ZBLAN glass; Figures 7 to 9 are graphs showing the shape of the gain as a function

  wavelength for fluorophosphate glasses according to the present invention.

  The present invention relates to a family of glasses useful in particular in lighting, optical and electronic applications. Glasses have unique characteristics that make them particularly useful for production

  optical signal amplifiers.

  A feature of these glasses is that they are substantially free of SiO2. Erbium ions do not dissolve well in a silica matrix, which promotes ion aggregation and degradation of gain yield, so removal of the silica matrix helps prevent ion aggregation and to conserve for the amplification the excess energy in photons of the ions. The glasses according to the present invention contain a relatively high concentration of P205. The present invention relates to a family of glasses for optical amplification comprising a fluorophosphate glass medium substantially free of silica, doped, per 100 parts by weight of the other components, with up to 10 parts by weight of erbium oxide . Table 1 indicates the essential composition domains for the fluorophosphate glass according to the present invention. Table 1 - (parts by weight) P205 15-40 MgF2 0-10 AI203 0-5 CaF2 0-25 MgO 0-9 SrF2 0- 25 CaO 0-9 BaF2, 0-20 SrO 0-9 KHF2 0-2 BaO 0-45 KTiF6 0-2

AIF3 5-25

  The family of erbium doped glasses according to the invention can include

  additionally take about 0.01 to 15 parts by weight of Yb203 which is intended to be

  used as a sensitizer to increase the pumping efficiency in the vicinity

  980nm swim. Table 2 defines narrower preferred domains of the consti-

  glass oxide killers according to the present invention. These narrower areas

  provide optimal properties for sigrt 'amplifiers.

optics and their production.

  Table 2 - (parts by weight) P205 16.9-24.0 MgF2 0-7.5 AI203 1.6-3.2 CaF2 0-18.7 MgO 0-5.0 SrF2 0-19.7 CaO 0 -5.1 BaF2 1.5-11.3 SrO 0-8.5 KHF2 0-1.3 BaO 2.7-43.2 K: TiF6 0-0.6

AIF3 9.5-19.3

  Another characteristic of the glasses according to the present invention is their ability to be doped with relatively high concentrations of erbium oxide (Er203). In the absence of a silica-based glass, high concentrations of doping with Er203 give excellent fluorescence effects which are important for the amplification of optical signals by laser pumping due to

  reduction of ion aggregation and positive conversion relaxation.

  This property provides an excellent amplification medium for use in optical amplifiers for the 1,550 nm wavelength. In another aspect, the present invention relates to an erbium-doped optical amplifier comprising a medium for optical amplification which comprises a fluorophosphate glass composition. Preferably, the fluorophosphate glass composition is doped per 100 parts by weight consisting of: Table 3 - (parts by weight) P205 15- 40 MgF2 0-10 A1203 0-5 CaF2 0-25 MgO 0-9 SrF2 0- 25 CaO 0-9 BaF2 0-20 SrO 0-9 KHF, 0- 2 BaO 0-45 K2TiF6 0-2

AIF3 5-25

  with approximately 0.01 to 10 parts by weight of Er2O03 According to another embodiment of the present invention, the optical amplifier medium doped with erbium comprises, as regards the components in addition to erbium oxide, 100 parts by weight made up, as

  shown in Table 4 below.

  Table 4 - (parts by weight) P205 16.9-24.0 MgF2 0-7.5 AL203 1.6-3.2 CaF2 0-18.7 MgO 0-5.0 SrF2 0-19.7 CaO 0 -5.1 BaF2 1.5-11.3 SrO 0-8.5 KHF2 0-1.3 BaO 2.7-43.2 K2TiF6 0-0.6

4AIF3 9.5-19.3

  The optical amplifier doped with erbium scion the invention can include

  additionally takes about 0.01 to 15 parts by weight of Yb2O3 which is intended to be used as a sensitizer to increase the pumping rate in the vicinity of 980 nm. The optical amplifier according to the present invention can take a number of forms provided that the medium can be doped with erbium ions. The optical amplifier can be an optical amplifier of the single-mode fiber type. Alternatively, the optical amplifier can also be a planar type optical amplifier. The effects of concentration relaxation

  on beaker glasses of typical binary silicates are shown in Figure 1.

  At low Er: O3 concentration levels, below 5E19 ions / cm3 (which is equivalent to less than 0.5 parts by weight), the fluorescence lifetime is constant. Beyond this concentration level, the fluorescence lifetime decreases rapidly when the concentration increases. Two characteristic concentrations can be defined to differentiate the glasses. The Cqb concentration corresponds to the triggering of the concentration relaxation. The Cq concentration corresponds to the concentration level at which the fluorescence lifetime is divided by 2. As shown in Figure 1, the concentration relaxation begins in typical binary silicate glasses when Cqb = 7E19 ions / cm3 (or about 0 , 9 parts by weight). At this point, the fluorescence lifetime is approximately 13 ms. When C, = 3E20 ions / cm3 (or approximately

  3 parts by weight), the fluorescence lifetime is approximately 7.5 ms.

  FIG. 2 is a graph showing the effects of concentration relaxation on the fluorescence yield of typical silicate-based glasses. The fluorescence yield is defined as being fluorescence at 1.55 μm per Er ion as a function of the Er concentration. For the concentration levels of ions of interest, that is to say between 3 and 5 E20 Er ions / cm3 (approximately 4-7 parts by weight), the fluorescence yield of glasses based on

  silicates is between 0.5 and 2 E-19nW / ion.

  FIG. 3 is a graph showing the effects of concentration relaxation on the fluorescence lifetime of three types of fluorophosphate-based glasses according to the present invention. FIG. 4 is a graph showing the effects of concentration relaxation on the fluorescence yield of three types of fluorophosphate-based glasses according to the present invention. As shown in Figures 3 and 4, Cqb and Cq are both an order of magnitude higher than the corresponding values of glasses based on silicates. This indicates that the concentration relaxation behavior at high levels of Er ion concentrations is relatively weak in the fluorophosphate glasses according to the invention, and that these glasses are very good candidates for short optical length amplifiers. wave and high gain. Table 5 presents a comparison of the compositions and associated measured and calculated properties of three types of fluorophosphate glasses according to the

  present invention, a typical borosilicate glass and a ZBLAN glass.

  The compositions indicated in Table 5 are expressed in quantity per batch.

  The actual ingredients of the batches may consist of any type of raw materials oxides, fluorides or phosphates, which, when melted together, are converted into the desired oxides and fluorides in the appropriate proportions. Non-limiting examples of raw materials are: Ca (PO3) 2, Ba2P207, A4 (P207) 3,

  Al (PO, 3) 3, NaPO3, K2TiF6, X2Oy, XFy, X representing the metal ion of valence y.

  The values quoted in Table 5 (like the values quoted everywhere else in this text) represent the theoretical values of the various components in the final glass, according to the usual practice in this field. In the case of

  oxides, the theoretical values remain very close to the actual quantities (i.e.

  say that the "batch yield" is very close to 100% for oxides). In the case of fluorides, which are more volatile, the recllcs values are slightly lower than the theoretical values (the batch yield is 90% to 95%,

about).

Board

  Glass type code Example 1 Example 2 Example 3 borosilicate ZBLAN2 parts by weight molar% SiO2 66.6

B203 11.6

P205 16.9 24.0 30.9

AI, 203 3.2 2.7 1.6

  MgF2 5.8 7.5 0.0 CaF2 18.7 0.5 0.0 SrF2 19.7 17.9 0.0 BaF2 11.3 14.4 1.5 i 22

AIF3 19.3 11.3 9.5 4

  Table 5 (continued) Glass type code Example 1 Excmplc 2 Example 3 borosilicate ZBLAN2 parts in% molar weight ZrF4 48 InF3 LaF3 3.2 NaF '22

KHF2 1.3 0.0 0.0

  KJTiF6 0.6 0.5 0.0 'Na2O 0.5 0.0 0.0 10

K20 9

  CaO 0.0 5.1 0.0 SrO 0.0 2.4 8.5 BaO 2.7 13.7 43.2 0.6 MgO 0.0 0.0 4.9 ErF3 0.8 Er203 6, 0 4.0 1.5 2 Er203 5.84 + 20 4.64 + 20 1.60 + 20 1.6E + 20 1.5E + 20 (ions / cm3) Index 1.49 1.54 1.59 1 , 52 Density 3.62 3.83 3.976 2.552 Duration of 6, 8 7.6 7 6.3

fluo- life

  rescence Fluorescent lifetime 9,5 8 7 16 rescence with low Er content (ms) Table 5 (suitel Glass Code from Example 1 Example Example 3 type ZBLAN2 2 borosilicate

QE (%) 68 95 100 39

  Fluorescent efficiency 2.3 2.7 3.2 1.3 rescence (nW / Er ion) * lE-19 Effective sections (cm2) * 1E-21 Pumping absorption 975 nm 1.9 2.3 (980 nm ) 0.8 2.6 1 480nm 3.3 3.9 1.2 4.7 Signal absorption (Cab (X)) 1,533 nm 4.9 5.9 (1,527 nm) 5.6 Width at mid -height 65 64 15 (nm) Emission signal (, em (3.)) 1,522 nm 5.3 6.5 (1,537 nm) 7.2 6 Width at mid-height 51 49 17 (nm) Emission / absorption 1.1 1.1 1, 3 1.1 Radiative lifetime 10 8 16 8 (ms) The ingredients of the batch are mixed to obtain a homogeneity, placed inside a platinum crucible and heated by effect Joule at around 1000 C. When the fusion is complete, the temperature is raised to a value

  between 1050 and 1350 C to obtain homogeneity and refinement of the glass.

  The melt is then cooled and mixed simultaneously in the desired form, then transferred to a quenching oven which operates at about 400 C. Another melting process consists in forming the glass from the ingredients of the batch and in melting this glass with the desired proportion of raw materials Er and / or Yb. This

  process can in some cases increase the homogeneity of the glass.

  As shown in Table 5, the tod / rtd quantum yield is in the range of 70 to 100% for fluorophosphate glasses according to the present invention at desired levels of Er concentrations, while the quantum yield for basc glasses of silica at the same level of concentration is

  included in the range of 20 to 35%.

  The spectral non-uniformity of the gain observed in EDFA in silica-based glass constitutes a limitation of the total use of the bandwidth in wavelength multiplexing systems. Another feature

  important compositions of fluorophosphate doped with Er at high concentration

  tration according to the present invention, compared to silica-based glasses, is that fluorophosphate glasses have a very flat gain spectrum over a range of about 28 to 30 nm in the bandwidth of 1550 nm. This is comparable to ZBLAN glass fibers doped with Er. To get this look

  flat gain between 1,528 and 1,563 nm, the glass medium according to the present invention

  tion preferably has a fluorine content of at least 18 parts by weight. It is possible to obtain a good representation of the spectral shape of the gain as a function of the wavelength using the following formula g (crm-ri {'re (X)' N2-ab (X ( ) * N,} (1) in which: c <m (k) is the emission cross section in cm2, cb (X.) Is the absorption cross section in cm2, N2 is the population of ions at the level higher (4I] 3.2) (length-averaged), N1 is the population of ions in the ground state (4I, 5) (length-averaged), and

  N, is the total concentration of Er ions (in ions per cm3).

  If the percentage of inversion is defined as being D = (N2-N1) / N ,, equation (1) can be rewritten as follows G (dB / cm) = 2.15 * N, * {ccm (X) * (l + D) -ab (X) * (1-)} (2) o: D = -1: 0% inversion, and

D = + 1: 100% inversion.

  Equation 2 was used to calculate the shape of the gain as a function of the wavelength of the different glass compositions, and the results obtained.

  are shown in Figures 5 to 9.

  Figure 5 shows the gain pattern of a typical borosilicate glass used in optical signal amplifiers. It is clear that the

  gain spectrum in the bandwidth of 1550 nm which is used in multi-

  wavelength plexing is non-uniform in character. The amplification between about 1,530 nm and 1,560 nm, a typical domain used in wavelength multiplexing, is non-uniform. The variation between maximum gain and gain

minimum can reach 250%.

  FIG. 6 represents the shape of the gain of a ZBLAN glass intended to be used in an optical signal amplifier. Compared to borosilicate glass, ZBLAN glass provides a flattened gain appearance in a range of

  wavelengths of width approximately 30 nm.

  FIG. 7 represents the shape of the gain for a first glass of fluorophosphate type according to the present invention. This glass, called example 1, has an Er concentration greater than 7 parts by weight per 100 parts by weight of the other components while still having a substantially flat gain appearance.

  over a spectrum of 28 nm in the bandwidth of 1,530 - 1,560 nm.

  FIG. 8 represents the gain pattern for a second type of fluorophosphate glass according to the present invention. This glass, called Example 2, has an Er concentration greater than 4 parts by weight per 100 parts by weight of the other components, and has a flattened gain appearance over a spectrum of approximately

26 nm.

  Figure 9 shows the gain pattern of a phosphate-based glass.

  This glass, called example 3, has an Er concentration slightly less than 3 parts by weight, per 100 parts by weight of the other components, and has two relatively flat gain domains, of which lc prcmiecr has a width of approximately

  nm and the second a width of about 9 nm.

  Another aspect of the present invention is the ability to achieve efficient pumping of the amplification medium at 980 nm while maintaining relatively low noise levels. Optical amplification requires the excitation of

  erbium ions in the glass medium at a higher energy level then the relaxa-

  tion of ions. This process causes the emission of photons when the erbium ions undergo relaxation down to the fundamental level. The photons emitted during this process have a wavelength such that the optical signals are amplified

at the same wavelength.

  If we consider the first three energy levels of erbium, a useful emission occurs between level 2 (the metastable level) and level 1 (the fundamental level). To present a population inversion (population at level 2 greater than or equal to 50%) and therefore a gain, the gain medium must be pumped by means of an external source. Generally, for the amplification of the optical signals, the gain medium is pumped with a laser diode at 980 or 1480 nm. When a lascr diode at 980 nm is used, the electrons reach the third level (I,), then undergo relaxation at the second level and then at the fundamental level by emitting a photon at 1.55, um. When a laser diode at 1480 nm is used, the electrons come directly to level (2) and then to the fundamental level by emitting a photon of 1.55 µm. The most pumping

  efficient and most reliable for optical amplification is pumping at 980 nm.

  However, since the pumping process at 980 nm moves the electrons to the third level, the lifetime at level 3 must be very short, preferably of the order of a microsecond, because otherwise the electrons can be excited to higher levels and therefore reduce pumping performance. This actually occurs in the case of a glass medium similar to ZBLAN glass when it undergoes pumping at 980 nm, due to the relatively long lifetime at level 3 (approximately 9 ms). Thus, an amplification medium analogous to ZBLAN glass cannot be pumped as efficiently as the fluorophosphate glass medium according to the invention, with a pump constituted by a laser diode with

980 nm.

  The glass of fluorophosphate doped with Er according to the present invention,

  as an amplification medium with a pump at 980 nm, has advantages

  compared to other fluorides doped with Er. The compositions similar to ZBLAN glass (100% fluoride, 0% oxygen), due to the high fluorescence lifetime (9 ms) at pumping level 41, lose in yield of

  pumping. As a result, compositions analogous to ZBLAN vcrre are usual-

  pumped at 1,480 nm. However, pumping at such long wavelengths has a drawback. For example, the ion population cannot be completely reversed at this level and the noise increases in the amplifier. On the contrary, the fluorophosphate glass medium according to the present invention can be pumped efficiently at 980 nm since the lifetime of [u

is in the range of 10 to 70, us.

  FIGS. 5 to 9 show that the fluorophosphate glasses according to the present invention exhibit characteristics of flattening of the gain with a

  pumping at 980 nm in a similar way to ZBLAN glass, and that they are sensitive-

  compared to silicates and phosphates. The glass compositions according to the present invention give high gain and flattened characteristics in short optical amplifiers, and they can be used for the manufacture of planar and / or short single mode fiber amplifiers having a gain similar to ZBLAN glass which are useful in wavelength multiplexing and

  in other similar applications.

Claims (13)

  1. Glass of fluorophosphate intended for use in amplifiers   high and flat gain 1.55 µm optical sensors, characterized in that it comprises, per 100 parts by weight consisting of: P205 15-40 MgF2 0-10 A1203 0-5 CaF2 0-25 MgO 0-9 SrF2 0-25 CaO 0-9 BaF2 - 0-20 SrO 0-9 KHF2 0-2 BaO 0-45 K2TiF6 0-2 AlF3 5-25   0.01 to 10 parts by weight of Er203.   2. Glass of fluorophosphate according to claim 1, characterized in that   that it also comprises 0.01 to 15 parts by weight of Yb203.   3. Glass of fluorophosphate according to claim 1 or 2, characterized in that it has a chemical composition comprising in parts by weight: P205 16.9-24.0 MgF2 0-7.5 Al203 1.6-3.2 CaF2 0-18.7 MgO 0- 5.0 SrF2 0-19.7 CaO 0-5.1 BaF2 1.5-11.3 SrO 0-8.5 KHF2 0-1.3 BaO 2.7-43.2 K2TiF6 0-0.6 AIF, 9.5-19.3   4. Glass of fluorophosphate according to any one of claims   1 to 3, characterized in that its fluoride (s) content is in the range of 7 to 88 parts by weight.   5. Glass of fluorophosphate according to claim 4, characterized in that   that its fluoride (s) content is equal to or greater than 18 parts by weight.   6. Erbium-doped optical amplifier comprising a medium for   optical amplification, characterized in that said medium comprises a composition   tion of fluorophosphate glass comprising, per 100 parts by weight consisting of: P205 15-40 MgF2 0-10 A1203 0-5 CaF2 0-25 MgO 0-9 SrF2 0-25 CaO 0-9 BaF2 0-20 SrO 0- 9 KHF2 0-2 BaO 0-45 KITiF6 0-2 AIF3 5-25   0.01 to 10 parts by weight of Er203 7. An optical amplifier doped with erbium according to claim 6, characterized in that said medium has a chemical composition comprising in parts by weight: P205 16.9-24.0 MgF2 0-7.5 AI203 1.6-3 .2 CaF2 0-18.7 MgO 0-5.0 SrF2 0-19.7 CaO 0-5.1 BaF2 1.5-11.3 SrO 0-8.5 KHF2 0-1.3 BaO 2.7 -43.2 K2TiF6 0-0.6 AIF3 9.5-19.3   8. An optical amplifier doped with erbium according to claim 6 or 7,   characterized in that it further comprises 0.01 to 15 parts by weight of Yb203.   9. An erbium doped optical amplifier according to claim 6, 7 or   8, characterized in that it is an optical amplifier of the planar type.   10. An optical amplifier doped with erbium according to claim 6, 7 or 8, characterized in that it is an optical amplifier of the fiber type. single-mode. 19 2768143   11. An optical amplifier doped with erbium according to any one of   Claims 6 to 10, characterized in that its fluoride (s) content is found in the range from 7 to 88 parts by weight.   12. An optical amplifier doped with erbium according to claim 11, characterized in that its fluoride content (s) is equal to or greater than 18 parts by weight. 13. An optical amplifier doped with erbium according to any one of   Claims 6 to 12, characterized in that:   said medium for optical amplification constitutes an active optical medium having an input and an output, said active optical medium receiving on its input optical signals whose wavelength is in the range from 1525 to 1570 nanometers approximately; and in that there is provided a pumping source providing to said active optical medium a pumping light power at a wavelength of approximately 980 nm, the pumping light being adapted to excite erbium in order to cause said erbium to emit photons for amplifying said optical signals in a wavelength range of width about 20 to 30 nm with a substantially flat gain spectrum whose variation is less than about 13% in the spectral range from about 1525 to 1565 nanometers, o the quantum yield of said active optical medium exceeds approximately 65%, said quantum yield being the ratio between the lifetime   fluorescence of the active optical medium and the lifetime of radiation.