WO2001071863A1

WO2001071863A1 - Optical amplifier

Info

Publication number: WO2001071863A1
Application number: PCT/JP2001/002374
Authority: WO
Inventors: Takamasa Yamashita; Hisashi Sawada; Minoru Yoshida
Original assignee: Mitsubishi Cable Industries, Ltd.
Priority date: 2000-03-24
Filing date: 2001-03-26
Publication date: 2001-09-27
Also published as: JP2001274494A; TW493305B

Abstract

An optical amplifier amplifies signal light in L band (wavelength of 1560 nm to 1610 nm) efficiently with a large gain. The optical amplifier comprises a source of exciting radiation, an optical multiplexer for multiplexing incident signal light and exciting radiation to produce output, and an erbium-doped fiber connected to the output of the optical multiplexer to produce amplified signal light. The wavelength of exciting radiation is 1.50 microns to 1.56 microns, and the wavelength of signal light to be amplified is 1560 nm to 1610 nm. The product of erbium concentration and fiber length is selected to provide a large gain.

Description

Optical amplification equipment

The present invention relates to an optical amplifier for amplifying an optical signal used for communication. Background art

2. Description of the Related Art An amplifier that amplifies an optical signal using an optical fiber as an amplification medium is known. The erbium-doped fiber (EDF) using the erbium-doped fiber (EDF) as the optical fiber shows excellent performance as an optical amplifier in the 1.55 m band. -doped fiber amplifier).

In EDFA, the wavelength 1. 48 m or 0. 98 / xm absorption is relatively large in _c EDF the excitation light has been used for, 1. 55 mu m band (1 530 nm which has been used in the optical communication up to now (1560 nm), and the advantage that the absorption characteristics of the EDF are small with respect to the wavelength and the amplification characteristics do not change significantly even if the excitation wavelength shifts. m excitation light has often been used.

On the other hand, a method called wavelength division multiplexing (WDM) transmission, in which light of multiple wavelengths is transmitted through a single optical fiber, has attracted attention. In WDM transmission, the transmission capacity can be increased by increasing the number of signal lights having different wavelengths that propagate in an optical fiber. For this reason, a signal wavelength (1560 ηπ! ~ 1610 nm) called L band or 1.58 m band, which has not been used until now, has come to be used.

Solution 1

However, the peak of the absorption spectrum of EDF is around 1.53 μπι, and 1.48 μm is not the peak of the absorption spectrum. For this reason, the wavelength 1. When the pump light of 48 / im is used, the L-band signal light cannot be spread very efficiently, and the EDF, which is much longer than when amplifying the 1.55 / m band signal light, cannot be obtained. Was needed. Disclosure of the invention

The present invention provides an optical amplifying device that efficiently amplifies L-band signal light and obtains a large gain by using excitation light having a wavelength around 1.53 / zm, which is the peak of the absorption spectrum of EDF. The purpose is to do.

An optical amplifying device of the present invention includes: a pump light source that outputs pump light; an optical multiplexer that multiplexes and outputs the input signal light and the pump light; and an output of the optical multiplexer, An erbium-doped fiber for amplifying and outputting the signal light, wherein the wavelength of the pump light is 1.50 / im to 1.56 μm.

According to the present invention, since a wavelength near the peak of the absorption spectrum of the EDF is used as the excitation light, even if the excitation light has the same intensity, the EDF is more effective than when the excitation light of another wavelength is used. The number of erbium ions at the excitation level in F can be increased, and the amplification efficiency and gain of EDFA can be increased.

In the optical amplifying device, the wavelength of the signal light is 1560 ηπ! Preferably, it is 11610 nm.

According to this, a larger gain and a higher power conversion efficiency can be obtained as compared with the case where the pumping light with a wavelength of 48 ^ um is used.

Further, in this optical amplifying device, the relationship between the concentration-length product CL of the erbium-doped fiber and the intensity PP of the pumping light is CL> (1 / α) · In (P _P / j3) and] 3. , A constant determined by the wavelength of the pump light and the intensity of the signal light).

According to this, it is possible to surely obtain a large gain as compared with the case where the pumping light having the wavelength of 1.48 is used.

Further, another optical amplifying device according to the present invention comprises: an excitation light source for outputting excitation light; An optical multiplexer that multiplexes the obtained signal light and the pump light and outputs the multiplexed light, and an erbium-doped fiber that receives the output of the optical multiplexer as an input, amplifies the signal light, and outputs the amplified signal light. Wavelength is 1.54 / 54! 1.1.55 μm, and the concentration product of the erbium-doped fiber is 6 O kp pm 'n! 9090 kp pm, m.

According to the present invention, it is possible to obtain a large gain and to reduce the fluctuation of the gain with respect to a change in the signal wavelength, as compared with a case where pumping light having a wavelength of 1.48 μm is used.

Further, still another optical amplifier according to the present invention includes: an excitation light source that outputs excitation light; an optical multiplexer that multiplexes and outputs an input signal light and the excitation light; and an optical multiplexer. And an erbium-doped fiber for amplifying the signal light and outputting the amplified signal light, wherein the intensity of the signal light is 10 dBm or more, and the wavelength of the pump light is 1.54 // m. 55 / xm, and the concentration length product of the erbium-doped fiber is 60 kp pm · π! ~ 90 kppm · m.

According to the present invention, when the intensity of the signal light is relatively large, a larger gain can be obtained as compared with the case where the pumping light having the wavelength of 1.48 μπι is used.

Effect of one invention

As described above, according to the present invention, the wavelength of EDFA is 1.50 μπ! Using a pump light with a wavelength of ~ 1.56 μπι provides a larger gain when amplifying L-band signal light than using a pump light with a wavelength of 1.48 μm, and the wavelength of the signal light. Fluctuation of the gain with respect to the fluctuation of can be suppressed. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram illustrating a configuration of an optical amplifying device according to an embodiment of the present invention. FIG. 2 is a graph showing the gain of the EDFA (erbium-doped fiber amplifier) of FIG. 1 with respect to the concentration length product at a signal wavelength of 1600 nm.

Figure 3 shows the concentration profile product at a signal wavelength of 1600 nm and a signal input of 10 dBm. FIG. 2 is a diagram showing the gain of the EDFA of FIG.

FIG. 4 is a diagram showing the gain of the EDF A of FIG. 1 versus the concentration-length product when the signal wavelength is 1600 nm and the signal input is 40 dBm.

FIG. 5 is a diagram illustrating an example of the power conversion efficiency of the EDFA of FIG. 1 with respect to the concentration length product when the signal input is 10 dBm and the signal wavelength is 1600 nm.

FIG. 6 is a diagram showing the power conversion efficiency of the EDF A of FIG. 1 with respect to the excitation wavelength at the concentration-length product at which the highest power conversion efficiency was obtained at each excitation wavelength. FIG. 7 is a diagram showing the power conversion efficiency of the EDF A of FIG. 1 with respect to the excitation input. Fig. 8 shows the combination of the concentration-length product and the pump input in the EDFA of Fig. 1 such that the gain is larger at the pump wavelength of 1.54 μm than at the pump wavelength of 1.48 μπι. It is a figure for obtaining.

FIG. 9 is a diagram showing a condition where the gain is larger at an excitation wavelength of 1.5 X μm than at an excitation wavelength of 1.48 when the signal input is 10 dBm.

FIG. 10 is a diagram showing a condition where the gain is larger at an excitation wavelength of 1.5 x / m than at an excitation wavelength of 1.48 / zm when the signal input is 40 dBm. FIG. 11 is a diagram showing the gain of the EDFA of FIG. 1 with respect to the signal wavelength when the signal input is 10 dBm, the pump input is 9 OmW, and the pump wavelength is 1.48 m.

FIG. 12 is a diagram showing the gain of the EDF A of FIG. 1 with respect to the signal wavelength when the signal input is 10 dBm, the pump input is 85.5 mW, and the pump wavelength is 1.535 μm.

Fig. 13 is a diagram showing the gain of the EDFA in Fig. 1 with respect to the signal wavelength when the signal input is 10 dBm, the pump input is 85.5 mW, and the pump wavelength is 1.54 µm.

Fig. 14 is a diagram showing the gain of the EDFA of Fig. 1 with respect to the signal wavelength when the signal input is 10 dBm, the pump input is 85.5 mW, and the pump wavelength is 1.554 µm.

FIG. 15 is a diagram illustrating the gain of the EDFA of FIG. 1 with respect to the signal wavelength when the signal input is −10 dBm, the pump input is 85.5 mW, and the pump wavelength is 1.55 μm.

FIG. 16 is a diagram illustrating the gain of the EDF A of FIG. 1 with respect to the signal wavelength when the signal input is 40 dBm, the pump input is 90 mW, and the pump wavelength is 1.48 / zm. Figure 17 shows the gain of the EDFA of Figure 1 versus signal wavelength when the signal input is 40 dBm, the pump input is 85.5 mW, and the pump wavelength is 1.535 μm.

Fig. 18 is a diagram showing the gain of the EDFA of Fig. 1 with respect to the signal wavelength when the signal input is 40 dBm, the pump input is 85.5 mW, and the pump wavelength is 1.54 µm.

Fig. 19 is a diagram showing the gain of the EDF A of Fig. 1 with respect to the signal wavelength when the signal input is 40 dBm, the pump input is 85.5 mW, and the pump wavelength is 1.554 µm.

FIG. 20 shows the gain of the EDFA of FIG. 1 with respect to the signal wavelength when the signal input is 40 dBm, the pump input is 85.5 mW, and the pump wavelength is 1.55 μm.

Fig. 21 is a diagram showing the gain of the EDF A of Fig. 1 with respect to the signal input when the signal wavelength is 1600 nm, the pump input is 90 mW, and the pump wavelength is 1.48 µm.

Fig. 22 shows the gain of the EDF A of Fig. 1 with respect to the signal input when the signal wavelength is 1600 nm, the pump input is 85.5 mW, and the pump wavelength is 1.535 µm.

FIG. 23 is a diagram showing the gain of the EDFA of FIG. 1 with respect to the signal input when the signal wavelength is 1600 nm, the pump input is 85.5 mW, and the pump wavelength is 1.54 μm.

FIG. 24 is a diagram showing the gain of the EDF of FIG. 1 with respect to the signal input when the signal wavelength is 1600 nm, the pump input is 85.5 mW, and the pump wavelength is 1.554 μπι.

FIG. 25 is a diagram showing the gain of the EDFA of FIG. 1 with respect to the signal input when the signal wavelength is 1600 nm, the pump input is 85.5 mW, and the pump wavelength is 1.55 μm. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an optical amplifying device according to an embodiment of the present invention. The optical amplifier (hereinafter referred to as EDFA) in FIG. 1 includes isolators 12 and 15, an optical multiplexer 13, an EDF 14, and a 1.5 X xm pump light source 21. In the following, 1.5 x / nil.50 / zm to l.56 .mu.m will be expressed.

The isolator 12 receives the signal light as an input to its input terminal, and outputs this signal light from its output terminal to the optical multiplexer 13. Optical multiplexer 13 outputs isolator 12 The signal light to be applied and the 1.5 × m pump light having a wavelength of 1.50 m to 1.56 μm output from the 1.5 X m pump light source 21 are multiplexed and output to the EDF 14. The EDF 14 amplifies the signal light by the stimulated emission phenomenon of erbium ions excited by the excitation light, and outputs the amplified signal light to the isolator 15. The isolator 15 receives the amplified signal light as an input to its input terminal, and outputs this signal light from its output terminal as the output of the EDF A in FIG. The isolators 12 and 15 do not allow signal transmission from the output terminal to the input terminal.

The EDFA shown in Fig. 1 has isolators 12 and 15 to remove laser oscillation and reflected return light from the EDF 14. However, even if there are no isolators 12 and 15, the optical amplifying device is not required. Is possible.

The EDFA shown in Fig. 1 has a configuration in which pumping light and signal light enter the EDF 14 in the same direction by forward pumping, but the pumping light and signal light enter the EDF 14 from the opposite direction. It is also possible to use backward pumping or bidirectional pumping in which pump light is incident from both ends of the EDF14.

In the EDF 14, the erbium ions are excited by the excitation light, and stimulated emission amplifies the input signal light. Therefore, the gain can be increased as the number of erbium ions in the excitation level increases. The absorption in EDF 14 is 1.50 μπ near the peak of the absorption spectrum! Since the light of ~ 1.56 / zm is larger than the light of wavelength 1.48 μm, even if the excitation light has the same intensity, the wavelength is 1.50) um ~ l.56 jum Can increase the number of erbium ions in the excitation level compared to when the wavelength is 1.48 μm, and can increase the amplification efficiency and gain of the EDFA in Fig. 1.

In other words, in the EDFA of Fig. 1, the wavelength 1.50 μπ! Using a pump light of ~ 1.56 m has the same effect as increasing the intensity of the pump light at a wavelength of 1.48 / m, and also requires a pump input ( Excitation light intensity) can be reduced. Further, the excitation light having a wavelength of 1.50 / m to l.56 / im is absorbed by EDF14. EDF 14 can be shortened.

The characteristics of the EDFA in FIG. 1 under various conditions are shown below. For comparison, a 1.48 μm excitation light source (not shown) was used to provide 1.48 μππ excitation light to the optical multiplexer 13 instead of the 1.5 X μm excitation light source 21. The characteristics in the case of the above are also shown. The product of the erbium concentration [p pm] of EDF 14 and its fiber length [m] is referred to as the concentration strip product. The unit of the concentration product is p pm · m, and 1000 p pm-m is expressed as 1 k p pm · m. The erbium concentration of EDF 14 is about 900 ppm.

FIG. 2 is a diagram showing the gain of the EDF A of FIG. 1 with respect to the concentration length product when the signal wavelength (wavelength of the signal light) is 1600 nm. In Fig. 2, ▲ indicates the excitation wavelength (wavelength of the excitation light) 1.53 μπι, signal input (intensity of the signal light)-10 dBm, and the image indicates the excitation wavelength 1.53 ^ m, signal input 1 4 0 d Bm and △ show the case of the pump wavelength 1.48 / zm, signal input—10 dBm, and the mouth shows the case of the pump wavelength 1.48 μηι, signal input—40 dBm. The excitation input is 31.8 mW.

According to Fig. 2, when the concentration-length product is optimized, the excitation wavelength is 1.53 μπι more than 1.48 tm regardless of the signal input size. It can be seen that a large gain can be obtained.

FIGS. 3 and 4 are graphs showing the gain of the EDFA of FIG. 1 with respect to the concentration length product at a signal wavelength of 160 nm. FIG. 3 shows the signal input—10 dBm, and FIG. 4 shows the gain. Signal input

It is a figure about the case of 40 dBm.

Figures 3 and 4 show that the excitation wavelength is 1.48 zm, 1.535 μm, 1.54 m, 1.

The data for the cases of 5 4 5 111 and 1.55 μm are shown. Excitation input: 9 OmW for excitation wavelength 1.48 μm, excitation wavelength 1.535 m to 85.5 mW for 1.55 m, excitation wavelength 1.48 μm In the case of m, the excitation input is about 0.2 dB larger than in the other cases, but it is considered that there is almost no problem if this difference in the excitation input is ignored. In the following figure, the excitation wavelength _1. 4 8 μ πι, and data in the case of the excitation input 9 0 mW, excitation wavelength 1. 5 0 X m~:. I 5 6 μ m, the excitation input When the data for the case of power 85.5 mW is shown in the same figure, the excitation input shall be simply indicated as 85.5 mW.

According to Figures 3 and 4, when the concentration-length product is optimized, regardless of the size of the signal input, the excitation wavelength is 1.48 μm when the excitation wavelength is 1.553 μπι to 1.55 m. It can be seen that a larger gain is obtained than in the case of m.

Therefore, when the wavelength of the signal light is in the L band (1560 nm to 1610 nm), the wavelength of the pump light is 1.50DFπ! By setting the wavelength to 1.56 μm, preferably 1.53 / m to 1.55 μm, a larger gain can be obtained than when the wavelength of the pump light is 1.48 μπι.

FIG. 5 is a diagram illustrating an example of the power conversion efficiency of the EDFA of FIG. 1 with respect to the concentration length product when the signal input is 10 dBm and the signal wavelength is 1600 nm. The power conversion efficiency is represented by (signal output / excitation input from EDF) XI00. The larger this value is, the more efficiently the pump light can be used for amplifying the signal light.

FIG. 5 shows data for the excitation wavelengths of 1.48 ^ m, 1.535 / zm, 1.54m, 1.545545111 and 1.55 μm. The excitation input is 85.5 mW for an excitation wavelength of 1.535; um to 1.55111, and 9 OmW for an excitation wavelength of 1.48 μm.

From Fig. 5, it can be seen that the concentration length product having the highest power conversion efficiency differs depending on the excitation wavelength. The excitation input was varied from 9.5 mW to 85.5 mW, and a graph similar to Fig. 5 was drawn.For each excitation wavelength, the concentration at which the highest power conversion efficiency was obtained from the data obtained When the product of the strip length is obtained, when the excitation wavelength is 1.48 / m,

30 kppmm, 60 kp pm * m for an excitation wavelength of 1 535 μm, 80 kppmm for an excitation wavelength of 1.54 μm, 70 kp for an excitation wavelength of 1.545 μm It was 70 kp pm 'm when ρ m · m and the excitation wavelength was 1.55.

FIG. 6 is a diagram showing the power conversion efficiency of the EDF A of FIG. 1 with respect to the excitation wavelength at the concentration strip product at which the highest power conversion efficiency was obtained at each excitation wavelength. The signal wavelength is 1600 nm and the signal input is 10 dBm. However, Due to the limited data obtained in the measurement, the concentration length product is smaller than 30 kppmm for the excitation wavelength of 1.48 μπι, and 60 kppmm for the excitation wavelength of 1.535 μm. It is possible that the highest power conversion efficiency can be obtained at the concentration product with the largest concentration.

From Fig. 6, the power conversion efficiency obtained at an excitation wavelength of 1.48 m is up to about 10%, whereas the excitation wavelength is 1.54 / ζπ! The power conversion efficiency obtained at ~ 1.55 µm is up to about 20%. Also, even at an excitation wavelength of 1.535 μπι, the maximum power conversion efficiency is about 15%.

Therefore, when the wavelength of the signal light is that of the L band, the wavelength of the pump light is set to 1.50 μπ! By setting the wavelength to 光 1.56 μm, preferably 1.535 μπι to 1.55 μπι, a greater power conversion efficiency can be obtained than when the wavelength of the pump light is 1.48 μπι.

FIG. 7 is a diagram showing the power conversion efficiency of the EDF of FIG. 1 with respect to the excitation input. The concentration length product at each excitation wavelength is the same as in Fig. 6, the signal wavelength is 1600 ηm, and the signal input is 10 dBm. Excitation input is 1.53 5 μπ! 85.5 mW for ~ 1.55 / xm, 90 mW for an excitation wavelength of 1.48 µm. From Fig. 7, the power conversion efficiency at an excitation wavelength of 1.48 m is up to about 10%, while the power conversion efficiency at an excitation wavelength of 1.54; im to 1.5 m is up to about 10%. In the case of an excitation wavelength of 1.54 / zm to 1.55 μm, it can be expected that the power conversion efficiency will be further increased by making the excitation input larger than 85.5 mW.

Figure 8 shows the combination of the concentration-length product and the excitation input in the EDFA of Fig. 1 so that the gain is greater at the excitation wavelength of 1.54 m than at the excitation wavelength of 1.48 μm. It is an example of a diagram for obtaining. The signal input is one 10 dBm and the signal wavelength is 1600 nm.

From Fig. 8, for example, when the concentration-length product is 40 kppm · m, the gain at an excitation wavelength of 1.48 μm and the gain at an excitation wavelength of 1.54 μm are approximately 34 It is the same when mW is set, and it can be seen that when the pump input is smaller than this, the gain is larger at the pump wavelength of 1.54 μm. Similarly, for other pump wavelengths (1.535 jum, 1.545 m, 1.55 μm), the pump gain becomes larger than when the pump wavelength is 1.48 / m. The range of the input can be determined.

FIGS. 9 and 10 are diagrams showing the conditions thus obtained in which the gain is larger at the excitation wavelength of 1.5 x / im than at the excitation wavelength of 1.48 μπι. FIG. 9 shows the case where the signal input is 10 dBm, and FIG. 10 shows the case where the signal input is 40 dBm. The region where the excitation input is smaller than the data points shown in FIGS. 9 and 10, that is, the region where the concentration product is larger than these data points, is closer to the excitation wavelength of 1-5 X μππι. Is the region where the gain is larger and the characteristics are better than when the pump wavelength is 1.48 μm.

Here, for each case of the excitation wavelength of 1.5 X m, the area where the gain is larger than that of the case of the excitation wavelength of 1.48 / zm is obtained by an approximate expression based on the data shown in Fig. 9. When the concentration length product of EDF is CL and the excitation input is PP, the excitation wavelengths are 1.535 μm, 1.54 μm, 1, 545 μm, and 1.55 μm, respectively. ,

C L> (1/0. 0 8 8)-1 n (P P / 0.93 5),

C L> (1/0. 1 0 8) 1 η (P P / 0.44 7),

C L> (1 / 0. 1 2 2)-1 n (P P / 0.26 1),

CL> (1 /0.0 9 7) 1 η (Ρ _Ρ Ό. 6 0 8)

Becomes When the same equation is calculated based on the data shown in Fig. 10, the excitation wavelengths are 1.535 μm, 1.54 ^ m, 1, 545 m and 1.55 μm. In the case of ιη,

C L> (1/0. 0 5 5) 1 η (Ρ Ρ / 2.44 4),

C L> (1/0. 0 5 5) 1 η (Ρ Ρ / 2.5 4 3),

C L> (1 / 0.05 8) 1 η (Ρ Ρ / 2.25 1),

C L> (1/0 .0 5 8) 1 η (Ρ ρ / 2.24 6)

Becomes Therefore, when the conditions in such a region are expressed as CL〉 (1s α) · In (Pβ), a and β can be constants determined by the excitation wavelength and the magnitude of the signal input. it can. The value of α increases as the magnitude of the signal input increases. When the signal input is _10 dBm and the signal input is in the range of 0.08 to 0.13 and 0.2 to 1.0, respectively, and the signal input is 14 dBm , Respectively, in the range of 0.05 to 0.06 and 2.2 to 2.6.

FIGS. 11 to 15 are diagrams showing the gain of the EDFA in FIG. 1 with respect to the signal wavelength when the signal input is 10 dBm and the excitation input is 85.5 mW (FIG. 11 is 90 mW). Figure 1:! To 15 are for the excitation wavelengths of 1.48 μπι, 1.535 m, 1.554 m, 1.545 μιη and 1.55 μm, respectively. FIG.

Figure 1: From ~ 15, signal input-10 dBm, excitation input 85.5 mW (9 O mW for excitation wavelength 1.48 μππι): I understand. That is, the signal wavelength is 1578 nm to 1615 nm, the concentration product is 60 kppm · n! In the case of 990 kppm · m, the gain is larger when the excitation wavelength is 1.535 μΐη11.55 μm than when the excitation wavelength is 1.48 μm. In addition, when the signal wavelength is 157 nm to 160 nm and the concentration is 70 kppmm to 90 kppmm, the excitation wavelength is 1.54 than when the excitation wavelength is 1.48 m. When μ πι ~ 1.55 μ πι, the gain is larger and the gain flatness is better. In other words, the dependence of the gain on the signal wavelength is small, and the gain fluctuation is small. Excitation wavelength 1.55 μπ within the signal wavelength range of 1756 nm to 1605 nm! The gain variation at ~ 1.55 μm is about 1 dΒ.

In order to obtain a characteristic with the same small gain fluctuation at an excitation wavelength of 1.48 / zm, an EDF with a concentration-length product of 100 kppmm or more is required. , Literature, H. Sawada, et.al., Broadband and gain-flattened erbium- doped fiber amplifier with + 20dBra output power for 1580nra band amplification, "Proc.EC0C 99, Nice, France, Sep. 1999, TuD3. Is shown in

Figures 16 to 20 show signal input of 40 dBm, excitation input of 85.5 mW (Figure 16 shows 9 FIG. 2 is a diagram illustrating a gain of the EDFA of FIG. 1 with respect to a signal wavelength at the time of 0 mW). Figures 16 to 20 show the cases where the excitation wavelength is 1.48 μπι, 1.535 jum, 1.554 μm, 1.545 / zm and 1.55 μm, respectively. FIG.

From Figures 16 to 20, from the signal input of 40 dBm and the excitation input of 85.5 mW (90 mW for an excitation wavelength of 1.48 μm), Understand. That is, the signal wavelength 1 5 7 0 η π! ~ 1620 nm, concentration length product 70 kppm · n! In the case of · 90 kppm · m, the gain is larger when the excitation wavelength is 1.54 / z rn to 1.55 m than when the excitation wavelength is 1.48 m. In addition, when the signal wavelength is 157 nm to 160 nm, and the concentration-length product is 70 kppmm to 90 kppmm, the excitation wavelength is 1 more than when the excitation wavelength is 1.48 μm. . 5 4 μπ! The gain flatness is better at ~ 1.55 μηι. Within the scope of signal wavelengths 1 5 7 0 nm~ 1 6 0 0 nm, the excitation wavelength 1. 5 4 / im~:. I 5 when ₅ μ πι, especially if the concentration length product is 8 0 kppm · m The gain variation is about 2 dB.

If the gain flatness is excellent, the level difference between the wavelengths of the signal output by the EDFA can be reduced, so that the effects of waveform distortion occurring during transmission and the reception characteristics at the receiver are improved. To improve the gain flatness, there is a method using a gain equalizer, but the loss caused by the gain equalizer degrades the performance of the EDFA. Figures 21 to 25 show the gain of the EDFA of Figure 1 with respect to the signal input when the signal wavelength is 1600 nm and the excitation input is 85.5 mW (Figure 21 is 9 O mW). . Figures 21 to 25 show the cases where the excitation wavelength is 1.48 μπι, 1.535 μm, 1.554 μm, 1.545111 and 1.55 μm, respectively. FIG.

From Figures 21 to 25, under the conditions of a signal wavelength of 160 nm and an excitation input of 85.5 mW (9 O mW for an excitation wavelength of 1.48 / xm), Understand.

That is, if the signal input is between −40 dBm and 20 dBm, the concentration product is 70 k ρ ρ m · π! When the excitation wavelength is 1.54 μm to 1.55 μm, the gain is larger than when the excitation wavelength is 1.48. If the signal input is greater than 10 dBm, the concentration product is 60 kppm · π! ~ 90 kppm In the case of m, the gain is larger when the excitation wavelength is 1.54 / im to 1.55 m than when the excitation wavelength is 1.48 μm.

From the trends in Figs. 23 to 25, even when the concentration-length product is greater than 90 kppmm, the excitation is more pronounced when the excitation wavelength is 1.54 zm to 1.55 μm. It can be expected that the gain is greater than at a wavelength of 1.48 / m. Also, from Figs. 21 to 25, 30 kppm · π! Up to 60 kppmm, when the excitation wavelength is 1.535 μm to 1.55 μm, the signal input is in the range of _40 dBm to 110 dBm. It can be seen that there is little decrease in the gain due to the increase in the wavelength, so that even if the signal input is more than 10 dBm, a larger gain can be expected than when the pump wavelength is 1.48 μπι.

Referring to FIGS. 3 and 4 in addition to FIGS. 21 to 25, the signal wavelength is 1600 nm, the pump input is 85.5 mW (9 O mW for the pump wavelength of 1.48 / im). Under the condition), the following can be seen.

In other words, when the signal input is 10 dBm and the concentration product is 55 kppmm or more, the excitation wavelength is 1.535 μπι to 1.55 / Xm, and the excitation wavelength is 1.4. The gain is larger than at 8 μπι. When the signal input is between 40 dBm and 20 dBm and the concentration product is 65 kppm · m or more, the excitation wavelength is 1.535 μπ! At 1.55 πι, the gain is larger than at the excitation wavelength of 1.48 / im. Industrial applicability

As described above, the optical amplifying device according to the present invention is useful for amplifying an optical signal used for communication, and is particularly suitable for amplifying an L-band optical signal.

Claims

The scope of the claims

1. an excitation light source that outputs excitation light;

An optical multiplexer that multiplexes and outputs the input signal light and the pump light,

An erbium-added fiber that receives an output of the optical multiplexer as an input, amplifies the signal light, and outputs the amplified signal light;

The wavelength of the excitation light is 1.50 μπι to 1.56 μπι

Optical amplifier.

2. The optical amplifying device according to claim 1,

The wavelength of the signal light is 1560 nm to 1610 nm

An optical amplifying device characterized by the above-mentioned.

3. In the optical amplifying device according to claim 2,

The relationship between the concentration-length product CL of the erbium-doped fiber and the intensity P _{P of the} pump light is

CL> (1 / a) In (P _P / i3)

( _α and) 3 are constants determined by the wavelength of the pump light and the intensity of the signal light)

An optical amplifying device characterized by the above-mentioned.

4. an excitation light source that outputs excitation light;

The wavelength of the excitation light is 1.54 μπι to 1.55 μπι,

The concentration-length product of the rubidium-doped fiber is 60 kppm · π! ~ 90 kppm • m

An optical amplifying device characterized by the above-mentioned.

5. an excitation light source that outputs the excitation light;

The intensity of the signal light is −10 dBm or more;

The excitation light has a wavelength of 1.54 m to l.55 im;

The concentration-length product of the erbium-doped fiber is 60 kppm.m to 90 kppm.

♦ m

An optical amplifying device characterized by the above-mentioned.