JP3514203B2 - Optical fiber amplifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber amplifier having an amplification band at 1440 to 1520 nm, which is a low loss region of an optical fiber, and a broadband optical fiber amplifier including the same.

[0002]

2. Description of the Related Art The demand for increasing the transmission capacity represented by the Internet is 1550, which is a low loss wavelength of an optical fiber.
nm single-channel transmission to transmit a plurality of channels to the amplification band (1528 to 1570 nm) of an erbium-doped fiber amplifier (EDFA).
The optical transmission system was transformed into lexing (WDM) transmission. Further, at present, it is in the stage of studying expansion of the signal band outside the amplification band of the erbium-doped optical fiber amplifier.

As an optical fiber amplifier for amplifying a wavelength band outside the amplification band of an erbium-doped optical fiber amplifier,
1560 to 1650 nm band gain-shifted erbium-doped optical fiber amplifier in which gain band of erbium-doped optical fiber amplifier is shifted to long wavelength, ultra-wideband erbium-doped optical fiber amplifier capable of amplifying 50 nm or more out of 1528 to 1610 nm, 1440 to 1480 nm Amplifiable thulium-doped fiber amplifier
ber amplifer (TDFA) has been developed so far.

By utilizing these, particularly in the wavelength band of 1450 to 1650 nm, which is the ultra-low loss region of the optical fiber, 1440 to 1480 and 1528 to 1620 are limited.
This means that 132 nm of 132 nm can be used for wavelength division multiplexing transmission. This means that signals of nearly 200 channels can be actually transmitted by wavelength division multiplexing transmission having a channel spacing of 100 GHz, for example. The present invention is 1
The present invention relates to a Tm-doped optical fiber amplifier having a gain band at 400 nm.

FIG. 14 shows the energy level of Tm. Optical amplification of 1400nm band, ³ H ₄ of Tm - based on stimulated emission between ³ F _4. Since the fluorescence lifetime of this level is shorter than that of the lower level, it is generally not easy to form a population inversion and high efficiency amplification cannot be expected. To efficiently form a population inversion, 980 to 1080n
Upconversion excitation using the excitation light of m is performed (for example, T. Komukai et al., "Upconversion
pumped Thulium-Doped Fluoride Fiber Amplifier and
Laser Operating at 1.47 μm ", IEEE Journal of Quant
umn Electronics Vol. 31, No. 11, (1995) 1880-1889)
.

When this method is used, it is the final level of amplification.
^Since excitation from ³ F ₄ is performed, a high population inversion distribution can be achieved in spite of the long fluorescence lifetime of ³ F ₄ , and using this method, as shown in FIG. 15, 1440 nm to 1480 nm.
High gain can be achieved in the wavelength range of nm. In addition to this, the gain band of the thulium-doped optical fiber amplifier is set to 148
A method of extending to 0 to 1530 nm has been proposed.
In addition to the excitation light of 980 to 1080 nm, this is 10
80-1250 nm, 1510-2000 nm, 770
This is a method of shifting the gain to a long wavelength by using dual wavelength pumping using pumping light of any wavelength of ˜840 nm.

In general, in a three-level rare-earth-doped optical fiber amplifier, the gain band can be shifted to a long wavelength region by using the fiber for a long time in a state where the population inversion is not good (for example, H. Ono et. al., "1.58 μm band Gain
Flattened Erbium-doped Fiber Amplifiers for WDM tr
ansmission Systems ", IEEE Journal of Lightwave Tec
hnology, Vol. 17, (1999), pp.490-496). ³ H of Tm ³⁺
_{The 4} to ³ F ₄ level is a 4-level system, but as described above, ³ F ₄
Has a longer fluorescence lifetime than ³ H ₄ , it can be regarded as a pseudo three-level system by exciting to ³ F ₄ by using the excitation light having the above wavelength, which is a long wavelength region of 1480 to 1530n
Gain can be obtained with m.

The present invention is realized by a method different from the method described above, and has a gain shift thulium-doped optical fiber amplifier (GS-TDFA) having a gain in the long wavelength region of 1480 to 1530 nm, and this gain shift. The present invention relates to a 1400 nm band wide band optical fiber amplifier by connecting a thulium-doped optical fiber amplifier and a conventional thulium-doped optical fiber amplifier.

[0009]

As described above, in order to shift the gain to the long wavelength band, the method proposed so far requires a pumping light source of two wavelengths. For this reason, the construction method becomes complicated as compared with the conventional thulium-doped optical fiber amplifier, and the number of optical components for multiplexing the pumping light increases, so that the pumping efficiency or the noise figure (NF) deteriorates. There are drawbacks such as Also, when adjusting the output with respect to the input fluctuation, it is necessary to control the pumping lights of the two wavelengths, respectively, so that the control method becomes complicated.

The problem to be solved by the present invention is to realize a thulium-doped optical fiber amplifier having a long wavelength gain by pumping one wavelength. Another object is to realize a broadband 1400 nm band thulium-doped optical fiber amplifier by combining this long wavelength gain-shifted thulium-doped optical fiber amplifier with a conventional thulium-doped optical fiber amplifier.

[0011]

In order to solve these problems, the present invention relates to an amplification optical fiber in which rare earth ion thulium (Tm ³⁺ ) is added to either the core or the clad, an optical isolator, and a pump. In an optical fiber amplifier equipped with a light source, pumping light / signal light multiplexing / demultiplexing coupler, optical filter, etc., the concentration of Tm added is 3000 ppmwt or more ,
That is, by adding Tm ³⁺ in a high concentration, Tm ³⁺ −
Using the cross relaxation between Tm ³⁺ , gain spectrum
The feature is that the peak is shifted to a long wavelength.

FIG. 1 shows a conceptual diagram of cross relaxation. Cross relaxation interacts with Tm ³⁺ in Tm ³⁺ and the ground level ³ H ₆ excited in ³ H _4, a phenomenon in which two ion are both ³ F ₄ level state. As a result, even when a pumping light source with a wavelength of around 1.0 μm is used, a state with a poor population inversion state can be created, and as a result, the gain can be shifted to a long wavelength. Cross relaxation between the Tm ³⁺ -Tm ³⁺ appears as a phenomenon that the short lifetime of the fluorescence lifetime of ³ H _4.

FIG. 2 shows the fluorescence lifetime Tm ^{3+ of 3} H ₄ and ³ F _4.
Depends on the added concentration. Since the fluorescence lifetime of ³ H ₄ becomes shorter as the concentration of Tm ³⁺ added becomes higher, Tm ³⁺ −Tm ³⁺
It can be seen that inter-cross relaxation has certainly occurred. Tm
It is expected that the population inversion will deteriorate and the gain will shift to longer wavelengths by increasing the ³⁺ addition concentration. As for the concentration of addition, the effect of cross relaxation is remarkable, and the fluorescence lifetime is 9
3000 ppm or more, which is reduced to 0% or less, is effective. In addition, the upper limit of high concentration is several wt% considering the current glass or fiber manufacturing technology, and the maximum is 10 wt%.
it is conceivable that.

[0014] Also, in 1480~1530nm,
To achieve high gain and flat gain spectrum,
It has a bidirectional structure in which pumping light is input from both ends of the amplification fiber, and the power of pumping light (forward pumping light) input in the same direction as the signal light is converted into pumping light (backward pumping) input in the opposite direction to the signal light. It is effective to make it larger than the power of light). In particular, the power ratio of the forward pump light and the backward pump light is 100:
When set in the range of 0 to 65:35, 1480 to 1
The deviation of the gain spectrum becomes small at 530 nm. In addition, in the production of the amplification fiber, the addition accuracy of the thulium concentration is at most about one digit. Therefore, in this specification, the thulium concentration is described only in the first digit.

Thus, the concentration of Tm added is 3000 ppm
The above thulium-doped optical fiber amplifier has high gain characteristics in the long wavelength region. The invention according to claims 3 to 7 of the present invention
Is the amplifier and a different amount of amplification optical fiber
The optical amplification unit including the fiber is connected in series, in parallel, or a mixture thereof.
It is characterized by having a configuration. This allows for a different increase
Wide bandwidth can be adjusted and wide band amplification is possible
It

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical fiber amplifier according to the present invention will be described in detail below with reference to the embodiments shown in the drawings. [Embodiment 1] FIG. 3 shows an optical fiber amplifier according to the first embodiment of the present invention. This optical fiber amplifier has 3 cores
Rare Earth Ion Thulium (T
An amplification optical fiber 1 to which m) is added, an optical isolator 2, a wavelength division multiplexing coupler 3 that multiplexes pump light with signal light of 1400 to 1520 nm, a pump light source 4, and the like.

The amplifier is configured as a forward pump configuration in which pump light is input in the same direction as the traveling direction of the signal light, as shown in FIG. 3A, and as shown in FIG. A backward pumping configuration in which pumping light is input in a direction opposite to the traveling direction, FIG.
As shown in FIG. 3C, two pumping lights are used, and bidirectional pumping structure in which the pumping light is pumped from both ends of the amplification optical fiber, FIG.
As shown in, there is a hybrid pump configuration in which forward pump, backward pump, and bidirectional pump configurations are mixed and connected in series.

In order to enable highly efficient amplification, the material (host) glass of the amplification optical fiber 1 has a higher probability of emitting multiple sounds than silica glass, which is usually used as an optical fiber material for transmission lines. Low glass is used. A typical glass is a fluoride glass (a typical glass is ZB containing ZrF ₄ , BaF ₂ , LaF ₃ or the like as a main component).
LAN glass, an In-Pb glass composed mainly of _{InF 2, BaF 2, PbF 2} ) and, GaS, chalcogenide glass (sulfide glass as a main component, etc. AsS), TeO ₂ main component and tellurite glass, and so on.

In FIG. 4, the concentration of Tm added is 2000 pp.
The fiber length dependence of the gain spectrum in the case of m and the case of 6000 ppm is shown. The configuration of the amplifier is the forward pumping shown in FIG. Zr-based fluoride glass (ZBLAN glass) was used as the host glass. The relative refractive index difference of the amplification optical fiber was 3.7%, and the core diameter was 1 to 8 μm.
The excitation light source is Nd: YL with an oscillation wavelength of 1.047 μm.
An F laser was used. The excitation light power was 500 mW.

As shown in FIG. 4, as the fiber length is lengthened, the gain peak shifts to longer wavelengths, and the peak gain decreases. The peak wavelength is 1 at 2000ppm.
146 when 460 to 1468 nm and 6000 ppm
It moves in the range of 0 to 1510 nm. Especially the addition concentration is 6
At 000 ppm, as the fiber length increases,
An increase in gain was observed in the long wavelength region (1480 to 1520 nm).

FIG. 5 shows the additive concentration dependence of the moving range of the peak of the gain spectrum. The higher the concentration of Tm added, the more the peak can be shifted to a longer wavelength. In particular, it is possible to shift the peak to a wavelength longer than 1480 nm, at which a large gain cannot be obtained with a thulium-doped optical fiber amplifier, when Tm is added in an amount of 3000 ppm or more. It is effective in constructing a thulium-doped optical fiber amplifier having a gain spectrum.

[Embodiment 2] Also in this embodiment, an optical fiber amplifier having the same configuration as in FIG. 3 is used. This optical fiber amplifier is an amplification optical fiber 1 in which 3000 ppmwt or more of rare earth ion thulium (Tm) is added to a core,
An optical isolator 2, a wavelength division multiplexing coupler 3 for multiplexing pumping light and signal light of 1400 to 1520 nm, a pumping light source 4, and the like are provided. A forward pump configuration, a backward pump configuration, a bidirectional pump configuration, a hybrid pump configuration, or the like is used for the amplifier configuration.

In this embodiment, the wavelength of the excitation light is 98
Light having a wavelength of 0 to 1080 nm is used. This wavelength is ³ F ₄ to ³ H ₄ in the up-conversion excitation method of FIG.
Since the pumping efficiency is extremely high, particularly when the pumping light is input in the same direction as the traveling direction of the signal light (forward pumping configuration, bidirectional pumping configuration, etc.), good noise figure amplification can be realized. In this wavelength range, there are several commercially available compact, high-power light sources. Examples include semiconductor LDs, optical fiber lasers in which Yb is added to the core, Nd-doped solid-state lasers (Nd: YLF laser, Nd: YAG laser), and the like.

[Embodiment 3] In this embodiment, FIG.
The optical fiber amplifier of the bidirectional pumping configuration of (c) is used.
The optical fiber amplifier includes an amplification optical fiber 1 in which 3000 ppmwt or more of rare earth ion thulium (Tm) is added to the core, an optical isolator 2, pumping light 1400 to 15
A wavelength division multiplexing coupler 3 that multiplexes a signal light of 20 nm, a pumping light source 4, and the like are provided. As the wavelength of the excitation light, 98
Light having a wavelength of 0 to 1080 nm is used.

In this embodiment, the power of pumping light (forward pumping light) in the same direction as the traveling direction of the signal light is set higher than that of pumping light in the opposite direction (backward pumping light). This amplifier can greatly change the gain spectrum by changing the power ratio of the forward pumping light and the backward pumping light. In particular, in order to realize an amplifier having an amplification band in the long wavelength range of 1480 to 1530 nm. Therefore, it is necessary to set the forward pump power high.

Even if the input power changes and the gain spectrum changes, the gain spectrum can be controlled to a desired state by changing the ratio of the forward pumping light and the backward pumping light. . Thus, in the thulium-doped optical fiber amplifier, the spectrum changes depending on the doping concentration, fiber length, front-to-back pumping light power ratio, and the like. By optimizing these parameters, high gain in the wavelength range of 1480 to 1530 nm can be obtained even when one wavelength is excited.
It can be seen that a flat gain characteristic can be realized.

[Embodiment 4] FIG. 6 shows an optical fiber amplifier according to a fourth embodiment of the present invention. The amplifier has two amplifying unit A, and a two-stage configuration and consisting of B, the amplifying unit A and the amplifying fiber 1,5 of different Tm doping concentration in B are arranged in series. The pumping light from the pumping light source 4 is input from both ends of each amplification fiber through the wavelength division multiplexing coupler 3.

Although each amplifying section in this embodiment has a bidirectional pumping structure, the structure of each stage may be forward pumping, backward pumping, or hybrid pumping as shown in FIG. Since the doping concentrations of the amplification optical fibers 1 and 5 are different,
Each has a spectrum in a different band, and as a result, the amplifiers connected in series as described above are capable of wideband optical amplification as shown in FIG.

In the thulium-doped optical fiber amplifier in which the gain is shifted to a long wavelength by adding Tm in a high concentration, the noise figure deteriorates in the short wavelength region (wavelength region shorter than 1480 nm). Therefore, in an amplifier in which amplifying fibers having different concentrations are connected in series, it is effective to arrange an amplifier having a low doping concentration in the preceding stage in order to suppress noise figure deterioration particularly in the short wavelength region.

[Embodiment 5] FIG. 8 shows an optical fiber amplifier according to a fifth embodiment of the present invention. The amplifier has a two-stage configuration including two amplifying units A and B, and amplifying fibers 1 and 5 having different Tm-doped concentrations are arranged in series in the amplifying units A and B, respectively. A gain equalizer 6 is provided between the two amplification optical fibers.
Are sandwiched by isolators.

The pumping light from the pumping light source 4 is inputted from both ends of each amplification fiber through the wavelength division multiplexing coupler 3. Although each amplification section in the present embodiment has a bidirectional pumping configuration, the configuration of each stage may be forward pumping, backward pumping, or hybrid pumping as shown in FIG.

Since the amplifying optical fibers 1 and 5 have different doping concentrations, each has a spectrum in a different band, and the sum is the gain spectrum of the amplifiers connected in series. By inserting a gain equalizer between the amplification optical fibers 1 and 5, as shown in FIG. 9, 1450 to 1520 nm is obtained.
It becomes possible to perform optical amplification with a flat gain characteristic in a very wide range.

[Embodiment 6] FIG. 10 shows an optical fiber amplifier according to a sixth embodiment of the present invention. The amplifier has optical amplifiers C and D arranged in parallel. The optical amplification sections C and D include amplification fibers 1 and 5 having different Tm-doped concentrations. In each of the amplifiers C and D, the pumping light from the pumping light source 4 is input from both ends of the amplifying fiber through the wavelength division multiplexing coupler 3. A band multiplexer / demultiplexer 7 that multiplexes the amplification bands of the amplification units including the respective amplification optical fibers is arranged.

The input wavelength division multiplexed signal is first demultiplexed by the band multiplexer / demultiplexer 7, amplified individually in each band, and then multiplexed by the band multiplexer / demultiplexer 7 and output. It Although each amplification section in the present embodiment has a bidirectional pumping configuration, the configuration of each stage may be forward pumping, backward pumping, or hybrid pumping as shown in FIG. Since the amplification optical fibers 1 and 5 have different doping concentrations, the amplification units C and D have spectra in different bands. Therefore, the amplification characteristic of the entire amplifier has a gain spectrum that is the sum of the amplification units.

As a result, 1450 as shown in FIG.
Optical amplification having a gain characteristic in a very wide range of ˜1520 nm is possible. This method has an advantage that it is simple because the amplification characteristic of each amplification section may be controlled independently. However, (1) since the band multiplexer / demultiplexer 7 is arranged before and after each amplification unit, the noise figure of the insertion loss of the band multiplexer / demultiplexer 7 installed on the signal input side increases or the signal output side is increased. The output for the insertion loss of the band multiplexer / demultiplexer 7 installed in (2) has a gap in each band for multiplexing / demultiplexing of the band multiplexer / demultiplexer 7, and the wavelength range of this part is There are drawbacks such as the inability to use.

[Embodiment 7] FIG. 12 shows an optical fiber amplifier according to a seventh embodiment of the present invention. The amplifier is composed of three amplifying sections E, F and G. The input signal is amplified by the pre-optical amplifying section E, then divided into two bands by the band multiplexer / demultiplexer 7, and F and G respectively. After amplifying the respective bands by the two optical amplifying sections, the band combiner 7 combines and outputs.

The pumping light from the pumping light source 4 is input to each amplifier through the isolator 1 and the signal light / pumping light multiplexing wavelength division multiplexing coupler 3. The amplification optical fibers 1 and 5 forming the amplification units F and G have different Tm doping concentrations. For each amplifier, in addition to bidirectional pumping as shown in FIG. 12, forward pumping, backward pumping, hybrid pumping, etc. as shown in FIG. 3 can be used.

Since the amplifying optical fibers 1 and 5 have different doping concentrations, the amplifying sections F and G have spectra in different bands, and the sum is the gain spectrum of the amplifiers connected in parallel. As a result, as shown in FIG.
It is possible to perform optical amplification having a gain characteristic in a very wide range of 50 to 1520 nm.

In this method, both bands are simultaneously amplified by the amplifying section E arranged in the preceding stage. As a result, it is possible to suppress an increase in noise figure caused by the insertion loss of the band multiplexer 7. However, there is a drawback that the wavelength range of the gap existing between the bands of the band multiplexer / demultiplexer 7 cannot be used.

[Embodiment 8] In this embodiment, the case where the gain spectrum becomes flat at the used wavelength of 1480 nm to 1510 nm will be described. As an optical fiber amplifier,
When the bidirectional pumping configuration shown in FIG. 3C, which is the same as that of the third embodiment, is used, the gain spectrum can be changed by optimizing the power ratio of the forward pumping light and the backward pumping light. FIG. 16 shows a gain spectrum in the case where the total pumping light power is 720 mW, the front and rear pumping light powers are optimized, and the gains at 1480 nm and 1510 nm are adjusted to be the same. As shown in FIG. 16, by controlling the front and rear pumping light powers in this way, 148
W with a relatively small gain deviation in the range of 0 to 1510 nm
An amplifier suitable for DM transmission can be realized.

The concentration of thulium added to the core is 2000-
The conditions under which such a gain spectrum can be realized were measured by changing the value to 10000 ppm. In FIG. 17, the fiber length is changed for each thulium concentration, and the pumping light powers in the front and the back are optimized so that the gains of 1480 nm and 1510 nm match (total pumping light amount 500 mW is constant), and When a gain spectrum like this is realized,
The gain is shown at 1480 nm or 1510 nm.
The gain increases to 6000p when the concentration of thulium added is increased.
It becomes maximum in the case of pm addition, and the gain tends to decrease even if the concentration of addition is further increased.

When the concentration of thulium added is 3,000 ppn or less, it is 148 even when the front and rear pumping light power ratios are changed.
The condition that the gains of 0 nm and 1510 nm match could not be found. From this, in order to realize a gain of 10 dB or more in the band of 1480 to 1510 nm, it is effective to set the doping concentration to 4000 to 8000 ppm. Here, the reason why the gain of 10 dB or more is effective is that the required gain is about 10 dB in the submarine transmission with the smallest required gain among various transmission modes to which the optical fiber amplifier is applied.

The same examination as above was conducted with a total pumping light power of 250 m.
FIG. 18 shows the results of the maximum gain and the optimum ratio of the forward pumping light power and the backward pumping light power at that time, which were also obtained when W and 750 mW. As shown in FIG. 18, for any total pumping light power, the gain is
It is 10 dB or more in the case of 8000 ppm. Further, the pumping light at this time always has a front pumping light power higher than a rear pumping light power. It can be seen that the optimum values of the front and rear pumping light powers are in the range of about 100: 0 to 65:35.

[0044]

As described above in detail with reference to the embodiments, the optical fiber amplifier of the present invention contains Tm at a high concentration of 3000 ppmwt or more, which has not been used so far, and therefore thulium is added. It is possible to shift the amplification band of the optical fiber amplifier to the long wavelength side. Furthermore, a broadband thulium-doped optical fiber amplifier can be realized by combining thulium-doped optical fiber amplifiers having different amplification bands. Therefore, according to the present invention, it is possible to provide a new optical fiber amplifier that meets the demand for expanding the amplification band of the optical amplifier, which is required with the development of wavelength division multiplexing transmission.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of cross relaxation.

FIG. 2 is a graph showing the dependence of fluorescence lifetimes of ³ H ₄ and ³ F ₄ levels on Tm ³⁺ addition concentration.

FIG. 3 is a configuration diagram of an optical fiber amplifier according to claims 1, 2, 3, and 4 of the present invention, wherein (a) forward pumping, (b) backward pumping, (c) bidirectional pumping, (d) hybrid pumping. Regarding

FIG. 4 is a graph showing the fiber length dependence of the gain spectrum of a thulium-doped optical fiber amplifier, and FIG.
Is about Tm of 1000 ppmwt, and FIG.
Each is shown for 00 ppmwt.

FIG. 5 is a graph showing a wavelength range in which a peak moves at each Tm addition concentration.

FIG. 6 is a configuration diagram of an optical fiber amplifier according to a fourth embodiment of the present invention.

FIG. 7 is a graph showing a gain spectrum of the optical fiber amplifier according to the fourth embodiment of the present invention.

FIG. 8 is a configuration diagram of an optical fiber amplifier according to a fifth embodiment of the present invention.

FIG. 9 is a graph showing a gain spectrum of the optical fiber amplifier according to the fifth embodiment of the present invention.

FIG. 10 is a configuration diagram of an optical fiber amplifier according to a sixth embodiment of the present invention.

FIG. 11 is a graph showing a gain spectrum of the optical fiber amplifier according to the sixth embodiment of the present invention.

FIG. 12 is a configuration diagram of an optical fiber amplifier according to a seventh embodiment of the present invention.

FIG. 13 is a graph showing a gain spectrum of the optical fiber amplifier according to the seventh embodiment of the present invention.

FIG. 14 is a graph showing an energy level diagram of thulium ions.

FIG. 15 is a graph showing a fluorescence spectrum and an excitation level absorption spectrum of ³ H ₄ − ³ F ₄ of Tm ³⁺ .

FIG. 16 is a graph showing an example of a flattened gain spectrum.

FIG. 17 is a graph showing a flattened gain (1480 nm: solid line) and a pump ratio (pump ratio: broken line) at that time.

FIG. 18 is a graph showing the maximum gain (white) and the excitation ratio (filled) at the time of gain flattening.

[Explanation of symbols]

1 Optical fiber for amplification with Tm concentration of 3000 ppmwt or more 2 Optical isolator 3 Wavelength division multiplexing coupler for pumping light / signal light 4 Pumping light source 5 Optical fiber for amplification 6 with different concentration from optical fiber for amplification 6 Gain equalizer 7 band multiplexer / demultiplexer 8 optical fiber for amplification A optical amplification section B constituting a serial connection type optical fiber amplifier B optical amplification section C constituting a series connection type optical fiber amplifier C optical amplification section constituting a parallel connection type optical fiber amplifier D Optical amplification unit constituting a parallel connection type optical fiber amplifier E Optical amplification unit F constituting an optical fiber amplifier F Optical amplification unit G constituting an optical fiber amplifier G Optical amplification unit constituting an optical fiber amplifier

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Makoto Shimizu 2-3-1, Otemachi, Chiyoda-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (56) Reference JP-A-6-90055 (JP, A) JP-A-7-142806 (JP, A) JP-A-8-18129 (JP, A) JP-A-11-233864 (JP, A) JP-A-2000-332320 (JP, A) US Patent 5388110 (US, A) (US Pat. 58) Fields surveyed (Int.Cl. ⁷ , DB name) H01S 3/00-3/30

Claims (10)

(57) [Claims] 1. An optical fiber amplifier comprising at least an amplification optical fiber in which rare earth ion thulium is added to at least one of a core and a clad, and an optical isolator, a pumping light source, and a pumping light / signal light multiplexing / demultiplexing coupler.
In at least one of the core and the clad, the concentration of the rare earth ion / thulium added is 3000 ppmw.
Since it is t or more, the peak of the gain spectrum becomes a long wave.
An optical fiber amplifier characterized by shifting to a long length . 2. A wavelength band of 1480 to 1530 nm, which is provided with at least an amplifying optical fiber in which at least one of core and clad is doped with rare earth ion thulium, an optical isolator, a pumping light source, and a pumping light / signal light multiplexing / demultiplexing coupler.
In an optical fiber amplifier having an amplification band in the long range,
In at least one of the core or the clad, the
The concentration of rare earth ions and thulium added is 3000ppmw
Since it is t or more, the peak of the gain spectrum becomes a long wave.
An optical fiber amplifier characterized by shifting to a long length . 3. The concentration of the rare earth ions and thulium added.
Is 3000ppmwt or more and 10wt% or less
The optical fiber amplifier according to claim 1 or 2, which is characterized. 4. A rare earth ion, thulium, at least
Amplifying optical fiber added to either
And optical isolator, pump light source, pump light / signal light combined amplification
Two optical fiber amplifiers equipped with at least demultiplexing coupler
Amplification in the wavelength range of 1450 to 1520 m, using one or more
An optical fiber amplifier having a band, each optical fiber amplifier
The amplifier is at least one other optical fiber amplifier
Connected in series or in parallel using two optical multiplexers / demultiplexers
And at least one of the plurality of optical fibers
The optical fiber amplifier according to claim 2, and
Concentrations of the plurality of amplification optical fibers are two or more
An optical fiber amplifier characterized by the above. 5. At least two optical fiber amplifiers.
Includes a part connected in series, and said part connected in series
At least one gain equalizer between optical fiber amplifiers
The optical fiber according to claim 4, characterized in that
amplifier. 6. A band multiplexer / demultiplexer is used on the signal input side to obtain the signal.
At least the part where the optical fiber amplifiers are connected in parallel is included.
The optical fiber addition according to claim 4 or 5,
Breadth. 7. Optical amplification on the signal input side of said band multiplexer / demultiplexer
7. The device according to claim 6, wherein the containers are connected in series.
Optical fiber amplifier. 8. The additive concentration of the rare earth ion thulium.
Is 4000ppmwt or more and 8000ppmwt or less
The optical fiber according to claim 1 or 2, wherein
amplifier. 9. The amplifier is located at both ends of an optical fiber for amplification.
The same direction as the signal
Input pump light power in the opposite direction to the signal.
The contract is characterized in that it is higher than the excitation light applied.
The optical fiber amplifier according to claim 1 or 2. 10. The power of the forward pumping light and the power of the backward pumping light
Specially, the work ratio should be between 100: 0 and 65:35.
The optical fiber amplifier according to claim 1, which is a characteristic of the optical fiber amplifier.