JP3392284B2 - Evaluation method of optical amplifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention evaluates multi-wavelength collective amplification characteristics in an optical amplifier such as an erbium-doped optical fiber amplifier (hereinafter referred to as "EDFA") which directly amplifies light by stimulated emission. The present invention relates to an evaluation method of an optical amplifier.

[0002]

2. Description of the Related Art Gain characteristics and noise characteristics of an optical fiber amplifier to which a rare earth element such as erbium is added vary greatly depending on the optical power value and wavelength of an input optical signal. Therefore, for example, when measuring the characteristics of the EDFA, it is necessary to use the light source of the input optical signal actually used. Conventionally, especially in an EDFA that collectively amplifies optical signals of many wavelengths, the characteristics have been measured using the same number of light sources with the same wavelength as that actually used. FIG. 2 is a measurement system diagram used for evaluation of a conventional optical amplifier. Signal light sources 1-1, 1 such as a plurality of laser diodes (hereinafter, LD)
-2, ..., 1-n are optical attenuators 2-1, 2-2, ..., 2 respectively.
It is connected to the input side of the optical coupler 3 via -n. The output side of the optical coupler 3 is the EDF to be measured.
It is connected to the input side of A4. Furthermore, this EDFA4
The output side of is connected to the measurement terminal of the optical spectrum analyzer 5.

FIGS. 3 and 4 are optical spectrum distribution diagrams of the input and output of the EDFA 4 measured by the optical spectrum analyzer 5 of FIG. 2, respectively. In these distribution charts,
The horizontal axis shows the wavelength λ of light, and the vertical axis shows the optical power P.
Next, processing procedures (A) to (E) of a conventional optical amplifier evaluation method will be described with reference to FIGS.

(A) Processing procedure i: The measurement terminal of the optical spectrum analyzer 5 is connected to the output side of the optical coupler 3, and the signal light sources 1-1 to 1-n are connected to the EDFA 4.
, And outputs the lights of wavelengths λ1, λ2, ..., λn actually used. Then, while measuring the optical power P of each wavelength λ1 to λn with the optical spectrum analyzer 5, the optical attenuators 2-1 to 2-n are adjusted to adjust the input optical signal power Pin (λ1 in the normal use state of the EDFA 4). ), Pin (λ2),
..., Pin (λn) is adjusted. (B) Processing procedure ii Each of the signal light sources 1-1 to 1 by the optical spectrum analyzer 5
-n spontaneous emission light component (SSE: Signal Spontaneous Emi
ssion) power Psse (λ1), Psse (λ2), ..., P
Measure sse (λn). Here, the spontaneous emission light component is
As shown in FIG. 3, it is an optical signal level when it is assumed that there is no optical signal of a specific wavelength λi by each signal light source 1-i (i = 1 to n).

(C) Processing procedure iii The output side of the optical coupler 3 is connected to the input side of the EDFA 4 to be measured, and the output side of the EDFA 4 is connected to the measurement terminal of the optical spectrum analyzer 5. Then, the output powers Pout (λ1), P of the EDFA 4 for the respective wavelengths λ1 to λn
out (λ2), ..., Pout (λn) are measured. (D) Processing procedure iv The spontaneous emission light component (ASE: Amplified Spontane) after amplification of each wavelength λ1 to λn by the optical spectrum analyzer 5
light power Pase (λ1), Pase (λ
2), ..., Pase (λn) is measured. Here, the amplified spontaneous emission light component means each signal light source 1 as shown in FIG.
Near a specific wavelength λi by -i (± number n from wavelength λi
It is the level of the spontaneous emission light after amplification at the wavelength λi, which is interpolated by the quadratic function approximation from the amplified spontaneous emission light component of m).

(E) Processing procedure v The gain G (λi) and noise figure NF (λi) at each wavelength λi are calculated by a computer or the like using the following equations. G (λi) = {Pout (λi) -Pase (λi)} / Pin
(Λi) NF (λi) = {Pase (λi) −Psse (λi) · G (λ
i)} / {hνnΔνG (λi)} where h 1; Planck's constant (6.626 × 10 ⁻³⁴ ) νn; Signal light frequency (c / λi) c; Light velocity (2.998 × 10 ⁸ [m / s]) Δν; Measurement bandwidth of optical spectrum analyzer 5 [Hz]

[0007]

However, in the conventional evaluation method of the optical amplifier such as the EDFA 4, the number of the light sources 1-i and the optical attenuators 2-corresponding to the optical signal power Pin (λi) of the wavelength λi to be measured are used. Since i is required, the wavelength λi
There is a problem that the measurement system becomes complicated when the number of is large. Further, the number of components such as the optical coupler 3 increases, and the coupling loss and the like increase accordingly, which causes a problem that the input optical signal power Pin (λi) to the EDFA 4 decreases. In particular, as the band of the EDFA 4 becomes wider, the number of input optical signals to be collectively amplified also increases. For example, when the wavelength λi becomes 32 waves or more, the conventional method has a limit. SUMMARY OF THE INVENTION The present invention provides an optical amplifier evaluation method for easily and accurately measuring the characteristics of an optical amplifier for a plurality of signals in a wide band, as a problem that the above-mentioned conventional technique has.

[0008]

In order to solve the above-mentioned problems, the first invention is formed by pumping light when the total of a plurality of input optical signals having uniform power and different wavelengths is defined as the specified input optical power. An input optical signal having a predetermined energy range that changes the state of the population inversion is input, the input optical signal is directly amplified by stimulated emission by the input optical signal, and a plurality of optical signals in the wavelength band of the amplified optical signal are input. In an optical amplifier that outputs an output optical signal having a peak gain with respect to the wavelength, the characteristics are evaluated by the following procedure. First, the wavelength distribution of the amplified spontaneous emission light component in the output optical signal is measured, and a peak gain wavelength measurement process for detecting a peak gain wavelength corresponding to the plurality of peak gains is performed. An input optical signal wavelength setting process is performed to set the wavelength to each of the plurality of peak gain wavelengths.

Next, the wavelength-switchable probe light in the wavelength band and the plurality of input optical signals are multiplexed to generate a multiplexed optical signal, and the multiplexed optical signal is input to the optical amplifier. Performing an optical multiplexing process to, among the plurality of input optical signals and probe light in the optical multiplexed signal,
The total optical power of the plurality of input optical signals is adjusted so as to be substantially equal to the value of the specified input optical power, and the optical power of the probe light is a predetermined light that does not affect the population inversion and can be measured. Optical power adjustment processing for adjusting to a power value is performed. Then, the wavelength of the probe light before the optical multiplexing process is sequentially switched, and the input optical power of the probe light in the multiplexed optical signal before being amplified by the optical amplifier for each of these wavelengths, and the optical amplifier. After performing the input / output optical power measurement process for measuring the output optical power of the probe light and the amplified optical power of the spontaneous emission component in the multiplexed optical signal amplified by The optical amplifier is evaluated by calculating the amplification factor / noise figure of the optical amplifier based on the measured value of.

In the second invention, in adjusting the optical powers of the plurality of input optical signals in the optical power adjusting process of the first invention, the optical powers of the respective input optical signals are adjusted to be substantially equal. To do. In the third invention, the plurality of input optical signals to be the targets of the optical power adjustment of the second invention are
Two input optical signals. Then, in the input optical signal wavelength setting process, the wavelengths of the two input optical signals are set to the wavelengths having the first and second peak gains obtained in the peak gain wavelength measurement process, respectively, and further, these 2 The optical power values of the two input optical signals are adjusted to be substantially equal. According to the present invention, since the optical amplifier evaluation method is configured as described above, it operates as follows.

By inputting a plurality of input optical signals matching the peak gain wavelength of the optical amplifier to be measured to the optical amplifier, wavelength characteristics similar to those in the case of multi-wavelength input during actual use can be obtained. . Further, the total of these input optical powers is made equal to the total of a plurality of input optical signals having different wavelengths, as in the actual use. For this reason,
The population inversion equivalent to that in the used state is formed, and the gain characteristic of the optical amplifier becomes equal to the gain characteristic in the actually used state. The optical amplifier is set in such a state, the probe light that does not affect the population inversion in the optical amplifier is input to the optical amplifier, the wavelength of the probe light is sequentially switched, and the probe light for each wavelength is changed. By measuring the input / output level of, the optical amplifier can be evaluated when multiple signals are input.

[0012]

1 is a measurement system diagram used for evaluation of an optical amplifier showing an embodiment of the present invention. In this measurement system, signal light sources 10-1 and 10-2 formed of LDs or the like for generating input optical signals Lin (λ1) and Lin (λ2) and probe light Lpr (λ) in a wavelength band to be measured are provided. It has a probe light source 20 composed of an output variable wavelength LD or the like. These signal light sources 10-1 and 10-2 may have variable wavelengths whose wavelengths can be adjusted, or may have fixed wavelengths. Each signal light source 10-1, 10-2 and probe light source 2
Optical attenuators 30-1, 30-2, and 40 capable of adjusting the attenuation rate of optical power are connected to the output side of 0, respectively.
A three-input optical coupler 50 is connected to the output sides of the optical attenuators 30-1, 30-2 and 40. This optical coupler 50 is
The optical inputs of three different wavelengths are multiplexed, and the EDFA 60 to be measured is connected to the output side. ED
The FA 60 directly amplifies the input optical signal by stimulated emission by the input optical signal Lin (λ) input from the signal light source 10-1 or the like, and outputs the output optical signal Lout (λ). The side is connected to the optical spectrum analyzer 70. The optical spectrum analyzer 70 is a measuring device for measuring the distribution of the optical signal power with respect to the wavelength of the light in the measurement band. With this measurement system, the EDFA 60 is evaluated, for example, by the following processing procedures (a) to (k).

(A) Processing procedure 1 The outputs of the signal light sources 10-1 and 10-2 and the probe light source 20 are turned off, and the spectral distribution of the amplified spontaneous emission component ASE appearing on the output side of the EDFA 60 is measured. It is measured by the spectrum analyzer 70. FIG. 5 is a diagram showing an example of the spectral distribution of the amplified spontaneous emission (ASE) component on the output side of the EDFA 60 measured by the optical spectrum analyzer 70 of FIG. In this spectrum distribution diagram,
The horizontal axis shows the wavelength λ of light, and the vertical axis shows the optical power P.
The optical signal Lin (λ) is not input to the EDFA 60 in the state of FIG. Therefore, the spontaneous emission light component SSE having a uniform spectrum distribution is amplified by the EDFA 60, and the amplified spontaneous emission light component ASE is output from the EDFA 60. Due to the wavelength characteristic of the EDFA 60, the spontaneous emission light component ASE after amplification is not uniform and has a spectral distribution having peak characteristics for a plurality of wavelengths (for example, λa and λb) as shown in FIG.

(B) Processing procedure 2 Based on the spectral distribution of the spontaneous emission light component ASE measured in processing procedure 1, the wavelength λa at which the optical power P shows the maximum peak value and the wavelength λb at which the light power P has the second largest peak value are determined. It is obtained from the measurement output of the optical spectrum analyzer 70. (C) Processing procedure 3 The EDFA 60 is removed from the measurement system, and the output side of the optical coupler 50 is directly connected to the optical spectrum analyzer 70. (D) Processing procedure 4 While observing with the optical spectrum analyzer 70, the output wavelengths λ of the signal light sources 10-1 and 10-2 are set to be substantially equal to λa and λb, respectively. Signal light sources 10-1, 10
-2 may use a signal light source whose wavelength is adjustable,
A signal light source having a fixed wavelength of a or λb may be used.

(E) Processing procedure 5 While observing with the optical spectrum analyzer 70, the optical signal powers Pin (λa) and Pin (λb) input from the signal light sources 10-1 and 10-2 to the optical spectrum analyzer 70 are The attenuation factors of the optical attenuators 30-1 and 30-2 are adjusted so that they are approximately 50% of the value of the specified input optical power Ptot of the EDFA 60. (F) Processing procedure 6 The output of the probe light source 20 is turned on. And
Probe light L input to the optical spectrum analyzer 70
The optical power Pprin (λ) of pr (λ) is a value that can be measured without affecting the population inversion formed in the EDFA 60,
For example, the optical power Pin (λa) of the signal light source 10-1 is 100
The attenuation rate of the optical attenuator 40 is adjusted so that it becomes one-half.

(G) Processing procedure 7 The output wavelength λ of the probe light source 20 is swept over the measurement wavelength band, the input probe light power Pprin (λ) is uniform with respect to the wavelength, and the light of the signal light source 10-1 is emitted. Power Pin
Confirm that the value does not exceed 1/100 of (λa). If it exceeds, readjust the attenuation factor of the optical attenuator 40. (H) Processing procedure 8 After the adjustment of the optical attenuator 40 is completed, the output wavelength λ of the probe light source 20 is swept over the measurement wavelength band, and the probe light Lpr (λ) at each wavelength λ is transferred to the optical spectrum analyzer 70. The input probe light power Pprin (λ) is measured. FIG. 6 shows the optical spectrum analyzer 7 during this measurement.
2 is a spectrum distribution diagram of input light of the EDFA 60 of FIG. 1 displayed at 0. FIG.

(I) Processing procedure 9 The output side of the optical coupler 50 is connected to the input side of the EDFA 60, and the output side of the EDFA 60 is connected to the optical spectrum analyzer 7.
0 to configure the measurement system of FIG. (J) Processing procedure 10 With the signal light sources 10-1 and 10-2 turned on, the output wavelength λ of the probe light source 20 is swept over the measurement wavelength band, and the probe light Lpr (λ) amplified by the EDFA 60 is used. Of the output probe light power Pprout (λ) at each wavelength λ and the optical power Pprase (λ) of the amplified spontaneous emission light component ASE at each wavelength λ of the optical spectrum analyzer 70
To measure. FIG. 7 is a spectrum distribution diagram of the output light of the EDFA 60 of FIG. 1 displayed on the optical spectrum analyzer 70 during the measurement.

(K) Processing procedure 11 The gain G (λ) and the noise figure NF (λ) at each wavelength λ are calculated by a computer or the like using the following equations. G (λ) = {Pprout (λ) -Pprase (λ)} / Pprin
(Λ) NF (λ) = Pprase (λ) / {h ・ νn ・ Δν ・ G
(Λ)} where h is Planck's constant (6.626 × 10 ⁻³⁴ ) νn; Signal light frequency (c / λ) c is the speed of light (2.998 × 10 ⁸ [m / s]) Δν; Optical spectrum analyzer 70 measurement bandwidth [H
z] Through the processing procedures 1 to 11 as described above, the amplification operation and characteristics of the EDFA 60 have the following contents, as shown in FIGS.

FIG. 8 is a block diagram showing an example of the EDFA 60 of FIG. 1, and FIG. 9 is an energy level diagram for explaining the amplification mechanism in the EDFA 60 of FIG.
The EDFA 60 of FIG. 8 has an input optical signal Lin to be amplified.
It has an input terminal 61 to which (λ) is input, and an optical isolator 62 is connected to this input terminal 61. The optical isolator 62 prevents an optical signal from propagating in the opposite direction due to reflection at an optical connector (not shown) and Rayleigh scattering in the optical fiber of the optical propagation path. The output side of the optical isolator 62 is connected to the first side of the wavelength multiplexer 63.
Is connected to the input side of the
The LD 64 that outputs the excitation light Lpump having a wavelength of 980 nm is connected to the input side of the LD. The output side of the wavelength multiplexer 63 is connected to one end of an erbium-doped optical fiber (hereinafter referred to as EDF) 65, and the other end of the EDF 65 is
It is connected via an optical isolator 66 to an output terminal 67 which outputs an output optical signal Pout (λ).

The input optical signal Lin (λ) input to the input terminal 61 of the EDFA 60 and the pumping light Lpump output from the LD 64 are wavelength-multiplexed by the wavelength multiplexer 63, and EDF is added.
65 is input. The erbium ion (hereinafter simply referred to as ion) Er ^{3+ in the} EDF 65 absorbs the input excitation light Lpump, and as shown in FIG.
The energy level of 1 transits to the energy level of E2. When the input excitation light Lpump exceeds a certain value, a so-called energy level inversion distribution state in which the number of ions N2 in the upper level E2 exceeds the number N1 of ions in the ground level E1 is formed. When the input optical signal is propagated in the EDF 65 with this population inversion formed, the optical signal being propagated is amplified by stimulated emission. The gain coefficient g (λ) by the EDF 65 at this time is expressed by the following equation. g (λ) = σe (λ) · N2-σa (λ) · N1 = σe (λ) {N2- (σa (λ) / σe (λ)) N1} where σe (λ) is the induced emission interruption The area, σa (λ), is the stimulated absorption cross section and depends on the wavelength λ of the optical signal.

FIG. 10 is a characteristic diagram showing wavelength characteristics of the stimulated emission cross section σe (λ) and the stimulated absorption cross section σa (λ) in the EDF 65 of FIG. In this characteristic diagram, the horizontal axis shows the wavelength λ and the vertical axis shows the respective cross-sectional areas σe and σa. Figure 1
As shown in FIG. 0, the stimulated emission cross section σe (λ) has a wavelength λ =
Since it becomes maximum at 1530 nm, when the number of ions N1 of the ground level E1 is small, the gain coefficient g (λ) is the wavelength λ.
It becomes maximum at = 1530 nm. When the optical power Pin (λ) of the input optical signal Lin (λ) is small, the number of ions N2 in the upper level E2 is large, and the wavelength dependence of the gain coefficient g (λ) is the stimulated emission cross section σe (λ). The influence increases, and the wavelength λ =
Gain peaks occur near 1530 nm and λ = 1550 nm. At this time, the state of the gain coefficient g (λ) is the wavelength λ
The input optical signal power Pin
Even if (λ) is equal, depending on the wavelength λ, for example, 1530n
The gain coefficient g (λ) greatly differs between m and 1550 nm. In the EDFA 60 that amplifies a wavelength band of 1530 nm to 1560 nm, wavelengths corresponding to two peak gains of 1530 nm band and 1550 nm band, for example, λa and λb.
When the multiplexed light of is used, the gain coefficient g (λ) in the EDF 65 is
Is close to the actual multi-wavelength optical amplification characteristic.

On the other hand, the induced absorption cross section σa (λ) is large when the wavelength λ is around 1530 nm. Therefore, the ground level E1
When the number N1 of ions is large, the peak near 1530 nm decreases, and thus the wavelength dependence of the gain coefficient g (λ) is small. When the input optical signal power Pin (λ) increases,
N1 increases, and the influence of the induced absorption cross section σa (λ) on the gain coefficient g (λ) increases. Therefore, the wavelength dependence of the gain coefficient g (λ) is reduced by increasing the input optical signal power Pin (λ) and adjusting the signal light power such that N1 is equal to N2, that is, a saturated state. can do. In the present embodiment, the spontaneous emission light component AS on the output side of the EDFA 60 is processed by the processing procedures 1 and 2 described above.
The wavelengths λa and λb of the two peak gains are obtained by measuring the distribution of E. In the processing procedure 4, the wavelengths λ of the signal light sources 10-1 and 10-2 are set to two wavelengths λa and λb corresponding to the peak gain, respectively. Further, in processing procedure 5, the sum of the input optical signal powers Pin (λa) and Pin (λb) from the signal light sources 10-1 and 10-2 is adjusted so as to be the value of the specified input optical power Ptot of the EDFA 60.
As a result, a state close to the population inversion of energy levels formed when the input optical signals Lin (λi) of a plurality of wavelengths are actually input to the EDF 65 in the EDFA 60 is formed.

After forming such a state, in processing steps 6 and 7, the input probe light power Pprin (λ) from the probe light source 20 is set to a low level that does not affect the population inversion formed in the EDFA 60. And it is adjusted to a measurable level. Then, in processing steps 8 and 10, the probe light Lpr (λ) thus adjusted is used to amplify the input probe light power Pprin (λ) for each wavelength λ of the probe light Lpr (λ) in the EDFA 60. The spontaneous emission light component Pprase (λ) and the output probe light power Pprout (λ) are measured. As described above, the evaluation method of the optical amplifier of the present embodiment is similar to the case where the two signal light sources 10-1 and 10-2 are similar to the case where the actual multiple wavelengths are input over the amplification wavelength band of the EDFA 60. A distribution state is formed, and in such a state, the input / output characteristic for the probe light Lpr (λ) is measured.
Therefore, there is an advantage that evaluation can be easily and highly accurately performed over the amplification band of the EDFA 60 without requiring many signal light sources 10-i and complicated measurement systems. The present invention is not limited to the above embodiment, and various modifications can be made. Examples of this modification include the following (1) to (7).

(1) The measured optical amplifier shown in FIG.
However, the present invention is not limited to the EDFA, but is also applicable to optical fiber amplifiers doped with other rare earth elements such as praseodymium-doped optical fiber amplifiers and neodymium-doped optical fiber amplifiers, or semiconductor amplifiers. In addition, it can be applied to an optical amplifier having an amplification principle similar to these. (2) In the measurement system of FIG. 1, two signal light sources 10-1 and 10 are used.
Although -2 is used, the number of signal light sources 10-i according to the number of peak gain wavelengths is not limited to this and can be used.
As a result, a population inversion that is closer to the actual state of use is formed in the optical amplifier, which enables accurate evaluation. (3) In the processing procedure 5, the input optical signal powers Pin (λa) and Pin (λb) from the plurality of signal light sources 10-1 and 10-2 are adjusted to be equal, but the EDFA 60 is actually used. If the optical power Pin (λ) of the input optical signal at this time is different for each wavelength, the input optical signal power Pin (λ) is distributed so as to be close to the actual use state, and the evaluation is performed more accurately. You can

(4) In the processing procedure 5, a plurality of signal light sources 10
-1, 10-2 input optical signal power Pin (λa), Pin
Although (λb) is adjusted to be equal to each other, the plurality of signal light sources may be added so as to reproduce the population inversion when the optical amplifier is used. (5) The probe light source 20 of FIG. 1 uses the variable wavelength LD to sweep the wavelength λ within the measurement band for measurement, and sequentially switches the required wavelength λj (j = 1 to N). Other types of light sources may be used if possible. (6) In the measurement system of FIG. 1, the input / output optical signal power Pin
Optical spectrum analyzer 7 for measuring (λ) and Pout (λ)
Although 0 is used, it is not limited to the optical spectrum analyzer and may be any one capable of measuring the optical power in each wavelength band. (7) In the measurement system of FIG. 1, the optical attenuators 30-1, 30-1, 40 are provided for each of the signal light sources 10-1, 10-2 and the probe light source 20.
However, these optical attenuators are not necessary if a light source whose output power can be adjusted is used.

(8) The measurement system shown in FIG.
1, 10-2, and an optical attenuator 30-for each probe light source 20
1, 30-1 and 40, each signal light source 10-1,
If a certain level difference can be maintained between the output level of 10-2 and the output level of the probe light source 20, one optical attenuator may be provided after the optical coupler 50. As a result, the configuration and adjustment can be simplified. (9) In the processing procedure 11, the gain G (λ) and the noise figure NF
Although (λ) is calculated and the EDFA 60 is evaluated,
Others can also be evaluated.

[0027]

As described in detail above, according to the first and second inventions, a plurality of input optical signals are used, and the wavelengths of the respective input optical signals are measured by a plurality of optical amplifiers. The sum of the optical power of each input optical signal is adjusted to the value of the specified input optical power of the optical amplifier by adjusting to the peak gain wavelength. This brings the optical amplifier into a state similar to that in actual use. In this state, probe light that does not affect the population inversion in the optical amplifier is input, the wavelength of the probe light is sequentially switched, and the characteristics of the optical amplifier for each wavelength are measured. Therefore, there is an effect that the evaluation over the amplification band of the optical amplifier can be performed easily and with high accuracy without requiring many light sources and complicated measurement systems.
In the third invention, the first and second optical amplifiers to be measured are included.
Since only two input optical signals having a wavelength corresponding to the peak gain of 1 are used, the same effects as those of the first and second inventions are obtained, and the configuration is further simplified.

[Brief description of drawings]

FIG. 1 is a measurement system diagram of an optical amplifier according to an embodiment of the present invention.

FIG. 2 is a measurement system diagram of a conventional optical amplifier.

FIG. 3 is a distribution diagram of an input light spectrum of the EDFA of FIG.

4 is an output light spectrum distribution chart of the EDFA of FIG.

5 is a distribution diagram of amplified spontaneous emission (ASE) components on the output side of the EDFA of FIG. 1. FIG.

FIG. 6 is a distribution diagram of an input light spectrum of the EDFA of FIG.

7 is an output light spectrum distribution chart of the EDFA of FIG.

8 is a configuration diagram of the EDFA of FIG.

FIG. 9 is an energy level diagram in the EDF of FIG.

10 is a wavelength characteristic diagram of a stimulated emission cross section and a stimulated absorption cross section of the EDF of FIG.

[Explanation of symbols]

10-1, 10-2 signal light source 20 probe light source 30-1, 30-2, 40 optical attenuator 50 optical coupler 60 EDFA 70 optical spectrum analyzer Lin (λ) input optical signal Lout (λ) output optical signal Lpr ( λ) Probe light Pin (λ) Input light signal power Pout (λ) Output light signal power Pprin (λ) Input probe light power Pprout (λ) Output probe light power Pprase (λ) Probe light ASE component power Ptot Specified input light power

Claims (3)

(57) [Claims] 1. An input optical signal having a predetermined energy range for changing a state of population inversion formed by pumping light when a prescribed input optical power is defined as a total of a plurality of input optical signals having uniform power and different wavelengths. Is input, and the input signal is directly amplified by stimulated emission by the input optical signal,
In an optical amplifier that outputs an output optical signal having a peak gain for a plurality of wavelengths within the wavelength band of this amplified optical signal, measuring the wavelength distribution of the amplified spontaneous emission light component in the output optical signal, Peak gain wavelength measurement processing for detecting peak gain wavelengths corresponding to the plurality of peak gains, input optical signal wavelength setting processing for setting the wavelengths of the plurality of input optical signals to the plurality of peak gain wavelengths, respectively, the wavelength An optical multiplexing process of generating a multiplexed optical signal by multiplexing a probe light whose wavelength is switchable within a band and the plurality of input optical signals, and inputting the multiplexed optical signal to the optical amplifier, Of the plurality of input optical signals and the probe light in the optical multiplexed signal, the total of the optical powers of the plurality of input optical signals should be approximately equal to the value of the specified input optical power. And the optical power adjustment process of adjusting the optical power of the probe light to a predetermined optical power value that does not affect the population inversion and can be measured, and the wavelength of the probe light before the optical multiplexing process is sequentially performed. Input light power of the probe light in the multiplexed optical signal before being amplified by the optical amplifier for each of these wavelengths, and output of the probe light in the multiplexed optical signal amplified by the optical amplifier. Input / output optical power measurement processing for measuring the optical power and the optical power of the amplified spontaneous emission light component, and calculating the amplification factor / noise figure of the optical amplifier based on the measured values of the input / output optical power measurement processing. An evaluation method of an optical amplifier, characterized in that: 2. The adjustment of the optical power of the plurality of input optical signals in the optical power adjustment processing is performed so that the optical power values of the respective input optical signals are substantially equal to each other. 1. The optical amplifier evaluation method described in 1. 3. A plurality of input optical signals for which the optical power is to be adjusted are two input optical signals, and the input optical signal wavelength setting process is performed by setting the wavelengths of the two input optical signals to the peak gain wavelength. 3. The optical amplifier evaluation method according to claim 2, wherein the wavelengths having the first and second peak gains obtained by the measurement process are set respectively.