JP2001308421A - Method and device for evaluating characteristics of optical fiber amplifier, wavelength multiplexing optical amplifier and wavelength multiplexing optical transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluating method for the intensity characteristics of input and output light during multiple amplification of wavelength which enables to apply even for EDFA which is structured to module together with light parts with exception of an erbium-doped fiber. SOLUTION: Each wave length of signal light used in wavelength multiplexing optical transmission system is inputted one by one during the state without EDFA excitation, and the parameter deciding the characteristics of an erbium- doped fiber of the signal light wavelength is calculated from the intensity dependency of the input light of the intensity of output light at the time. Then, one wave of the signal light wavelength is inputted with EDFA excited, and the parameter deciding the characteristics of an erbium-doped fiber of the excitation light wavelength is calculated from the intensity dependency of the input light of the intensity of output light at the time. The relation between input light intensity and the output light intensity during multiple amplification of wavelength is calculated using those parameters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical fiber amplifier for collectively amplifying a plurality of optical signals having different wavelengths, and a wavelength division multiplexing optical transmission system using the optical fiber amplifier.

[0002]

2. Description of the Related Art In the field of optical transmission, wavelength multiplexing technology has been widely introduced in order to cope with an increase in demand for transmission capacity in recent years. The introduction of wavelength multiplexing has been studied or implemented not only in newly installed systems, but also in existing systems that have not conventionally performed wavelength multiplexing.

On the other hand, in an optical transmission system, an optical fiber amplifier, particularly an erbium-doped fiber amplifier (hereinafter, referred to as EDFA) is generally used for compensating transmission loss. The EDFA supplies pump light (wavelength 0.98 μm or 1.48) shorter in wavelength than signal light (wavelength 1.55 μm band) in order to supply energy necessary for amplification in addition to signal light.
μm) is input to an erbium-doped fiber, which is an amplification medium, to amplify signal light. It is known that the output light intensity characteristic of an EDFA changes according to the intensity and wavelength of input light, and many studies have been made in the past, and the relationship between input light intensity, wavelength, and output light intensity has been formulated. I have.
Above all, A. A model based on the two-level system proposed by SALEH et al. (IEEE PHOTONICS TECHNO
LOGYLETTERS, VOL2, No. 10, p
p. 714-717) is the actual E
It is known that the characteristics match well with those of DFA. When this model is used, a steady state in which an n-wavelength wavelength multiplexed optical signal is amplified (a state in which the input light intensity is constant regardless of time)
The relationship between the input light intensity and the output light intensity of the erbium-doped fiber in the above is expressed by the following equation.

[0004]

(Equation 4)

The meaning of each parameter is as follows.

P _k ⁱⁿ : signal light (wavelength λ _k , k = 1, 2,
, The input light intensity of n) P _k ^out: signal light (wavelength lambda _k, k = 1, 2,, the output light intensity of n) _{P p} ^in: the input light intensity of the excitation light (wavelength λ _p) τ: upper level Σ _sk : stimulated emission cross section at signal light wavelength λ _k σ _sp : stimulated emission cross section at excitation light wavelength λ _p σ _ak : absorption cross section at signal light wavelength λ _k σ _ap : Absorption cross section at excitation light wavelength λ _p ρ: Erbium ion density S: Cross section of core of erbium-doped fiber Γ _k : Confinement coefficient at wavelength λ _k L: Length of erbium-doped fiber (Equation 4) is (Equation 5) It is transformed as follows.

[0007]

(Equation 5)

The parameters A _j and P _j ^IS (j = p,
1, 2,..., N) are defined as follows.

[0009]

(Equation 6)

[0010]

(Equation 7)

The correlation between the input light intensity and the output light intensity can be known by ^obtaining the values of these parameters A _j and P _j ^IS in advance.

Conventionally, the values of the parameters A _j and P _j ^IS have been determined from the measurement results of the input light intensity dependence of the output light intensity of the erbium-doped fiber alone. The method will be described below.

First, light having a signal light wavelength λ ₁ is input to an erbium-doped fiber, and the output light intensity at this time is measured.
This measurement is performed by changing the input light intensity (two or more measurement points). When light of wavelength λ ₁ is input, (Equation 5) is modified as follows.

[0014]

(Equation 8)

Accordingly, the values of the parameters A ₁ and P ₁ ^IS are obtained by substituting the measured values (two or more points) of the input light intensity and the output light intensity into (Equation 8). Remaining signal light wavelength λ ₂
For λ _n , the values of the parameters A ₂ ＡA _n and P ₂ ^IS ＰP _n ^IS are obtained by the same procedure. Also, for the excitation light wavelength λ _p , the values of A _p and P _p ^IS are obtained by the same procedure.

The parameters A ₁ -A obtained in this way
_{A n, A p, P 1} IS ~P n IS, by substituting the values of P _p ^IS to (5), obtaining the relationship between the input light intensity output light intensity. If these parameters are obtained in advance, the input light intensity necessary to obtain a desired output light intensity can be obtained by calculation even when the number of input wavelengths fluctuates during wavelength multiplexing. FIG. 16 is a flowchart summarizing the above procedure.

[0017]

The above-described method is intended for evaluating the characteristics of a newly manufactured EDFA, and it is necessary to measure and extract the parameters of the erbium-doped fiber alone. However, when applying wavelength division multiplexing to an already installed optical transmission system, it is necessary to evaluate the characteristics of an already operated EDFA.

As shown in FIG. 17, the EDFA device is generally modularized with optical components other than the erbium-doped fiber. The pumping lasers 52 and 55 output pumping light, and the output pumping light is multiplexed with signal light in WDM couplers 53 and 56. Also, the optical isolator 51,
Reference numeral 57 is provided to prevent noise characteristics from deteriorating due to multiple reflection. Each port of the WDM couplers 53 and 56 has wavelength selectivity, the port a transmits light of a signal light wavelength, and the port b transmits only light of a pump light wavelength. Therefore, the path from the input port to the output port of the EDFA module can transmit light of the signal light wavelength, but cannot transmit light of the excitation light wavelength.

Therefore, it is impossible to input the light of the excitation light wavelength to the EDFA module to measure the output light intensity, that is, it is impossible to obtain the parameters A _p and P _p ^IS. Thus, it was impossible to obtain and set the input light intensity from the desired value of the output light intensity.

Therefore, the present invention is applicable to a modularized EDFA that is already in operation, and a method for setting the input light intensity corresponding to the fluctuation in the number of wavelengths at the time of wavelength multiplex amplification, and a wavelength based on the method. It is an object to provide a multiplex optical amplifier.

[0021]

According to a first aspect of the present invention, there is provided a method for evaluating characteristics of an optical fiber amplifier for evaluating characteristics of an optical fiber amplifier used in a wavelength division multiplexed optical transmission system. Light of each signal light wavelength used in the wavelength division multiplexing optical transmission system is inputted one by one, and a predetermined first parameter of the amplification medium at the signal light wavelength is obtained from the input light intensity dependency of the output light intensity, In the pumping state, one wave of the signal light wavelength is input, and a predetermined second parameter of the amplification medium at the pumping light wavelength is obtained from the input light intensity dependence of the output light intensity, and the first and second parameters are used as the first and second parameters. It is characterized in that a relationship between the input light intensity and the output light intensity is obtained based on the input light intensity.

The method for evaluating characteristics of an optical fiber amplifier according to the second invention is used for evaluating characteristics of an optical fiber amplifier used in a wavelength division multiplexing optical transmission system in the first invention.
Light of each signal light wavelength used in the wavelength division multiplexing optical transmission system is input one by one in an unexcited state, and output light intensity under the three or more input light intensity conditions is extracted,

[0023]

(Equation 9)

According to the above, predetermined parameters A _k , P _k ^IS and L _k of the amplification medium at the signal light wavelength are obtained, and then one light of the signal light wavelength is input in the excited state, and the two or more input light intensities are obtained. Extract the output light intensity under the condition,

[0025]

(Equation 10)

The values of the predetermined parameters A _p and P _p ^IS of the amplification medium at the pumping light wavelength are calculated according to

[0027]

[Equation 11]

[0028] and obtains the relationship between the input light intensity P _k ⁱⁿ the output light intensity P _k ^out of each signal light at the time of wavelength multiplexing based on.

A wavelength division multiplexing optical amplifying device according to a third aspect of the present invention is used in a wavelength division multiplexing optical transmission system, and detects a presence or absence of an optical signal of each wavelength, and a light intensity adjustment for adjusting the signal light intensity of each wavelength. Unit, an optical fiber amplifier for amplifying an optical signal output from the light intensity adjustment unit, and a desired output light intensity from the optical fiber amplifier and an amplification medium determined by the method of the first or second invention. A control unit that calculates a required value of the input light intensity to the optical fiber amplifier based on a predetermined parameter and controls the intensity of the signal light output from the light intensity adjustment unit.

A wavelength division multiplexing optical amplifying device according to a fourth aspect of the present invention comprises
The invention according to claim 1, further comprising a plurality of optical fiber amplifiers connected in cascade, wherein the control unit determines a desired output light intensity from the last-stage optical fiber amplifier and an amplification medium determined by the method of the first or second invention. And calculating a required value of the input light intensity to the optical fiber amplifier based on the predetermined parameters.

An apparatus for evaluating characteristics of an optical fiber amplifier according to a fifth aspect of the present invention is an apparatus used for evaluating characteristics of an optical fiber amplifier used in a wavelength division multiplexing optical transmission system, and is used in the wavelength division multiplexing optical transmission system. A light source unit that can output light having an arbitrary signal light wavelength, a light intensity measuring unit that measures light intensity output from the optical fiber amplifier, and a wavelength and intensity of output light from the light source unit and the optical fiber amplifier. A control unit for controlling the presence or absence of excitation;
A calculating unit for calculating the relationship between the input light intensity and the output light intensity of the optical fiber amplifier according to the method of the invention.

A wavelength division multiplexing optical transmission apparatus according to a sixth aspect of the present invention provides
Alternatively, a wavelength division multiplexing optical amplifying device according to the fourth invention is provided.

A wavelength division multiplexing optical transmission apparatus according to a seventh aspect of the present invention includes a light source unit for outputting optical signals having wavelengths different from each other and having variable intensity, and an optical fiber amplifier for amplifying the wavelength multiplexed optical signal. The method is characterized in that the output light intensity from the light source unit is determined by using the method for evaluating the characteristics of the optical fiber amplifier according to the first or second aspect.

The wavelength division multiplexing optical transmission apparatus according to an eighth aspect of the present invention is the
A plurality of optical fiber amplifiers connected in cascade, and a light source using the characteristic evaluation method of the optical fiber amplifier according to the first or second invention based on a desired output light intensity from the last stage optical fiber amplifier. Determining the output light intensity from the unit.

According to a ninth aspect of the present invention, there is provided a wavelength division multiplexing optical transmission apparatus comprising:
Alternatively, in the eighth invention, a plurality of light source units for outputting optical signals having different wavelengths and variable intensities, a wavelength multiplexing unit for wavelength multiplexing the optical signals output from the plurality of light source units, An optical fiber amplifier that amplifies an optical signal output from the optical fiber amplifier, a branching unit that branches the optical signal output from the optical fiber amplifier, and an optical intensity measuring unit that measures the intensity of one of the optical signals output from the branching unit. And calculating and controlling required output light intensities from the plurality of light source units based on a desired output light intensity from the optical fiber amplifier according to the method of the first or second invention, and determining whether the optical fiber amplifier is excited. And a control unit for controlling the

[0036]

Embodiments of the present invention will be described below with reference to the drawings. However, a case where an EDFA is used as an optical fiber amplifier will be described below.

(Embodiment 1) FIG. 1 is a flowchart showing a procedure of a method for evaluating characteristics of an optical fiber amplifier according to Embodiment 1 of the present invention. The procedure of the method for evaluating the characteristics of the optical fiber amplifier according to the present embodiment will be described with reference to FIG.

It is assumed that an n-wavelength wavelength multiplexed optical signal is input to the EDFA module shown in FIG. This EDFA
The module is modularized by adding an optical component such as a WDM coupler in addition to the erbium-doped fiber as an amplification medium. Here, the wavelength of the optical signal is λ ₁ to λ _n . The relationship between the input light intensity and the output light intensity in this case is represented by (Equation 11). Where L _k is the wavelength λ _k (k
= 1, 2,..., N) are optical losses due to optical components other than the erbium-doped fiber.

Also, it is assumed that the magnitudes of the optical loss before and after the erbium-doped fiber are equal. If the values of the parameters A _p , P _p ^IS , A _k , P _k ^IS, and the optical loss L _k are all obtained, the output light intensity is obtained from the input light intensity using Expression (11), or the input light is obtained from the output light intensity. It is possible to determine the strength. Hereinafter, a method of extracting each parameter will be described.

First, in a state where the EDFA module is not pumped, that is, the pumping light is not input to the erbium-doped fiber, the light of the signal light wavelength λ ₁ is input to the EDFA module, and the output light intensity depends on the input light intensity. Measure gender. FIG. 3 shows an example of the measurement result. (Equation 11) can be transformed into (Equation 9) when only one wave of the wavelength λ ₁ is input. From the measured values of the input light intensity and the output light intensity and (Equation 9), the values of the parameters A _k , P _k ^IS and the optical loss L _k are calculated. The calculation is performed by fitting (Equation 9) with the measurement result or selecting three measurement points and using the following (Equation 12)
(Expression 14) (see FIG. 3).

[0041]

(Equation 12)

[0042]

(Equation 13)

[0043]

[Equation 14]

The other signal light wavelengths λ _i (i = 1, 2,...,
Regarding n), the values of the parameters A _i , P _i ^IS and the optical loss L _i are obtained by the same procedure.

Subsequently, with the EDFA module pumped, that is, with the pumping light input to the erbium-doped fiber, one light having an arbitrary signal light wavelength λ _k is input, and the dependency of the output light intensity on the input light intensity is determined. Measure. FIG. 4 shows an example of the measurement result. At this time, (Equation 11) is transformed as (Equation 10). Using the measured values of the input light intensity and the output light intensity of the EDFA module and the values of A _k , P _k ^IS , and L _k obtained previously, the parameter A _{p at} the wavelength λ _p of the excitation light is obtained from (Equation 10). , P _p ^IS are calculated. However, the input light intensity _{P p} ⁱⁿ of the excitation light is assumed to be known. The calculation is
The fitting is performed between (Equation 10) and the measurement result, or by selecting two measurement points and substituting them into the following (Equation 15) and (Equation 16) (see FIG. 4).

[0046]

(Equation 15)

[0047]

(Equation 16)

Here, C _a and C _b in (Equation 15) and (Equation 16) are expressed as follows.

[0049]

[Equation 17]

[0050]

(Equation 18)

By substituting the values of the parameters A _k , P _k ^IS , L _k , A _p , and P _p ^IS obtained by the above procedure into (Equation 11), the input light intensity of the EDFA module at the time of wavelength multiplex amplification is obtained. And the output light intensity can be obtained.

Also, in the case where wavelengths are multiplexed by combining arbitrary wavelengths from λ _{1 to} λ _n , the relationship between the input light intensity and the output light intensity can be obtained.

As described above, in the present embodiment, all the parameters necessary for calculating the relationship between the input light intensity and the output light intensity are obtained using only the light of the signal light wavelength.
It is also possible to calculate the relationship between the input and output light intensities for an EDFA that is modularized with optical components other than the erbium-doped fiber and does not transmit light of the excitation light wavelength. If the parameters are obtained for all the wavelengths that are assumed to be used, the relationship between the input and output light intensities can be calculated even when wavelengths are multiplexed by combining arbitrary wavelengths among them.

(Embodiment 2) FIG. 5 is an example of a block diagram of a wavelength division multiplexing optical amplifying apparatus according to Embodiment 2 of the present invention. This wavelength division multiplexing optical amplifying device includes a wavelength separation unit 31, detection units 321 to 32n, a control unit 35, and a light intensity adjustment unit 3
71 to 37n, a multiplexing unit 38, and an EDFA 39.

Next, the operation of each part of the wavelength division multiplexing optical amplifying device according to this embodiment will be described with reference to FIG.

The wavelength separation unit 31 separates the input wavelength multiplexed optical signal for each wavelength. Detectors 321 to 32n
Corresponds to the optical signal of each wavelength, and detects whether each optical signal is actually input. Light intensity adjustment unit 371-
37n adjusts the intensity of the optical signal separated for each wavelength in the wavelength separation unit 31. The multiplexing unit 38 multiplexes the optical signals output from the light intensity adjustment units 371 to 37n.
The EDFA 39 amplifies the wavelength multiplexed optical signals multiplexed in the multiplexing unit 38 at a time. The EDFA 39 has the function of an optical amplifier by itself, and as shown in FIG. 2, is composed of an erbium-doped fiber and accompanying optical components such as a pumping laser. The control unit 35 calculates the required input light intensity to the EDFA 39 from the parameters that determine the characteristics of the erbium-doped fiber stored in advance and the desired output light intensity of the optical signal of each wavelength, and obtains the obtained value. The light intensity adjusters 371 to 37n are adjusted based on the light intensity.

Next, the specific operation of the present apparatus will be described in more detail. First, the values of the parameters A _k , P _k ^IS , L _k , A _p , and P _p ^IS that determine the characteristics of the erbium-doped fiber are determined in advance by the method described in the first embodiment. At the time of actual operation, the detecting units 321 to 3
2n, the wavelength actually input is detected, and from the result, the values of the parameters A _k , P _k ^IS , L _k , A _p , P _p ^IS , and the desired output light intensity, using (Equation 11) The input light intensity of each wavelength to the EDFA 39 is calculated, and the light intensity adjustment unit 37 is adjusted so that the input light intensity to the EDFA 39 becomes a value obtained by the calculation.
The light intensity of each wavelength is adjusted in 1 to 37n.

If the number of optical signals actually input fluctuates due to a light source failure or the like, the presence or absence of an optical signal of each wavelength is detected by the detection unit, and the input light of each wavelength to the EDFA 39 is newly detected. Calculate the intensity, and adjust the light intensity
Adjust n.

FIG. 5 shows a case where each signal light wavelength is separated by the wavelength separation unit 31 and the detection units 321 to 32n and the light intensity adjustment units 371 to 37n are provided for each wavelength. It is not always necessary to provide -32n for each wavelength as long as the presence or absence of optical signals of a plurality of wavelengths can be detected collectively, and the light intensity adjustment units 371 to 37n are not necessarily provided if the intensities of a plurality of optical signals can be adjusted collectively. It is not necessary to provide for each wavelength.

As described above, in the present embodiment, even when the number of optical signals fluctuates due to a failure of the light source or the like, the input light intensity of each wavelength is set again, so that the output light intensity of each wavelength can be set to a desired value. Value can be maintained. Also, EDFA
Even in the case of replacing 39, the input light intensity can be optimally controlled only by changing the parameters stored in the control unit 35.

As another example of the present embodiment,
There is a wavelength division multiplexing optical transmission device using the wavelength division multiplexing optical amplification device described above. This wavelength division multiplexing optical transmission device has the same advantages as the wavelength division multiplexing optical amplification device described above.

(Embodiment 3) FIG. 6 is a block diagram of an apparatus for evaluating characteristics of an optical fiber amplifier according to Embodiment 3 of the present invention. This characteristic evaluation device for an optical fiber amplifier includes a light source unit 11, a control unit 13, a light intensity setting unit 14, and a calculation unit 15.

Next, the operation of each unit of the optical fiber amplifier characteristic evaluation apparatus according to this embodiment will be described with reference to FIG.

The light source unit 11 is an EDFA 1 to be evaluated.
It is possible to output light having the same arbitrary wavelength as the signal light in the wavelength division multiplexing optical transmission system using 0, and to make the intensity of the output light variable. The control unit 13 determines the wavelength and intensity of the light output from the light source unit 11 and whether or not the EDFA 10 is in an excited state, that is, ON / OFF of the excitation light inside the EDFA 10.
Control OFF. The light intensity measurement unit 14 measures the output light intensity from the EDFA 10. The calculation unit 15 is the first embodiment.
The relationship between the input light intensity and the output light intensity at the time of wavelength multiplexing is calculated by the same method as described above.

Next, the specific operation of the evaluation apparatus will be described.
This will be described in detail. First, the control unit 13 controls the EDFA 1
0 is a state controlled to be the excitation OFF, that is, E
When the DFA 10 is not excited and exits the light source 11
The wavelength of the light to be input is set to each signal light wavelength, and the EDFA 1
The input light intensity dependency of the output light intensity from 0 is measured. Profit
From the measurement results obtained, the method was performed in the same manner as in Embodiment 1.
Parameter A₁~ A_n, P ₁ ^IS~ P_n ^ISAnd light loss L₁~ L_nof
Find the value.

Next, a state in which the control unit 13 controls the EDFA 10 to turn on the excitation, that is, the EDFA 1
0 is set to the excited state, the wavelength of the light output from the light source unit 11 is set to an arbitrary signal light wavelength λ _k , and the EDFA 10
Of the output light intensity from the input light intensity is measured. From the obtained measurement results, the values of the parameters A _p and P _p ^IS at the wavelength λ _p of the excitation light are determined in the same manner as in the first embodiment.

The parameters A ₁ -A _n , A _p ,
The values of P ₁ ^{IS to} P _n ^IS , P _p ^IS and the optical losses L _{1 to} L _n are given by (Equation 1)
By substituting into 1), the relationship between the input light intensity and the output light intensity at the time of wavelength multiplexing can be calculated.

As the configuration of the light source section 11, the configurations shown in FIGS. 7 to 11 can be mainly considered. First, as shown in FIG. 7, there is a configuration using only the wavelength variable light source 21 in which both the wavelength and the intensity are variable. Further, as shown in FIG. 8, a configuration may be adopted in which a light intensity adjusting unit 23 for adjusting the light intensity is provided on the output side of the variable wavelength light source 21. As the light intensity adjustment unit 23, any device whose light intensity can be adjusted, such as an optical attenuator, an optical amplifier, and an optical modulator, may be used.

Next, as shown in FIG. 9, it is also possible to adopt a configuration comprising a plurality of light sources 211 to 21n whose output light intensity is variable and a multiplexing section 22. This configuration is effective when it is difficult to output light of all signal light wavelengths with one variable wavelength light source. Also in this case,
It is good also as composition which adjusts light intensity in a place different from light sources 211-21n. That is, the light intensity adjusting unit 23 is provided on the output side of the multiplexing unit 22 as shown in FIG. 10, or the light intensity adjusting unit 23 is provided between the light sources 211 to 21n and the multiplexing unit 22 as shown in FIG. May be provided.

The configuration of the light source unit 11 may be a configuration other than the above example as long as the wavelength and the light intensity are variable.

As described above, in the present embodiment, as in the first embodiment, all parameters necessary for calculating the relationship between the input light intensity and the output light intensity are obtained by using only the light of the signal light wavelength. Therefore, the relationship between the input and output light intensities can be evaluated even for an EDFA that is modularized with optical components other than the erbium-doped fiber and does not transmit light of the excitation light wavelength. If parameters are obtained for all wavelengths that are assumed to be used, it is possible to cope with a case where wavelength multiplexing is performed by combining arbitrary wavelengths.

(Embodiment 4) FIG. 12 is a block diagram of a wavelength division multiplexing optical transmission apparatus according to Embodiment 4 of the present invention.
This wavelength division multiplexing optical transmission device includes light source units 411 to 41n,
It has a wavelength multiplexing unit 42 and an EDFA 43.

Next, the operation of the wavelength division multiplexing optical transmission apparatus according to this embodiment will be described with reference to FIG.

The light sources 411 to 41n output a plurality of optical signals having different wavelengths. In addition, the light source units 411 to 411
41n also has a function of adjusting the intensity of the output optical signal. The wavelength multiplexing unit 42 wavelength multiplexes the optical signals output from the light source units 411 to 41n. The EDFA 43 collectively amplifies the wavelength-multiplexed optical signal.

The output light intensity from the light source units 411 to 41n is set as follows. First, the input light intensity to the EDFA 43 is determined from the desired output light intensity from the EDFA 43 by the method described in the first embodiment. Next, based on the intensity of light input to the EDFA 43, the light source 41
The output light intensity from 1 to 41n is obtained.

In this embodiment, the light source units 411 to 4
Since the output light intensity from 1n is directly adjusted, there is no need to provide a light intensity adjustment unit in the middle of the transmission path, and the configuration can be simplified as compared with the third embodiment. Other advantages are the same as in the third embodiment.

(Embodiment 5) FIG. 13 is a block diagram of a wavelength division multiplexing optical transmission apparatus according to Embodiment 5 of the present invention.
The configuration of FIG. 13 is the same as that of FIG. 12 except that the number of EDFAs 431 to 43m is plural. In this case,
EDFA of the number of stages and m, the output light intensity from the light source unit _{^{411~41n P 1 0 ~P n 0,}} j -th E at wavelength lambda _k
The input light intensity and the output light intensity of the DFA are P _k ^{in (j)} , P _k ^{out (j)} , and the EDFA and j of the (j−1) stage, respectively.
When the loss of the optical transmission path between the stage of the EDFA and X _k ^j (see FIG. 13, provided that X _k ¹ denotes a light source portion 41k and the first stage E
Loss with the DFA 431), and the following relationship holds.

[0078]

[Equation 19]

Thus, the desired output light intensity of the final stage EDFA 43m is set, and the relationship between the input light intensity and the output light intensity of each EDFA is obtained by using the method described in the first embodiment. it can be obtained an output light intensity P ₁ ⁰ ~P _n ⁰ from the light source unit 411 to 41n.

As the configuration of this embodiment, the configuration shown in FIG. 14 is also possible. In FIG. 14, the wavelength separation unit 31,
Detecting units 321 to 32n, control unit 35, light intensity adjusting unit 37
The functions 1 to 37n are the same as those described in the third embodiment. Each of the EDFAs 391 to 39m independently has a function as an optical amplifier. For example, as shown in FIG.
It consists of erbium-doped fiber and associated optical components such as a pumping laser. The control unit 35 calculates the output light intensity of the light intensity adjustment units 371 to 37n from the desired value of the output light intensity of the final stage EDFA 39m using (Equation 19).

As described above, this embodiment corresponds to the first embodiment.
In the case where EDFAs are connected in multiple stages, the output light intensity from the final stage EDFA can be maintained at a desired value only by adjusting the input light intensity to the first stage EDFA. it can.

(Embodiment 6) FIG. 15 is a block diagram of a wavelength division multiplexing optical transmission apparatus according to Embodiment 6 of the present invention.
This wavelength division multiplexing optical transmission device includes light source units 411 to 41n,
It has a wavelength multiplexing unit 42, an EDFA 43, a branching unit 45, a light intensity measuring unit 46, and a control unit 47.

Next, the operation of each part of the wavelength division multiplexing optical transmission apparatus according to the present embodiment will be described with reference to FIG.

The functions of the light source units 411 to 41n, the wavelength multiplexing unit 42 and the EDFA 43 are the same as those described in the fourth embodiment. The branching unit 45 branches the optical signal output from the EDFA 43 into output light to be output to a transmission path and monitor light used for intensity measurement. The control unit 47 includes light source units 411 to 41
n switches the wavelength and intensity of the light output and the excitation / non-excitation of the EDFA 43. The light intensity measuring unit 46 measures the intensity of the monitor light and obtains the intensity of the output light from the EDFA 43. The calculation unit 47 calculates the input light intensity from the desired value of the output light intensity of each wavelength of the EDFA 43 at the time of wavelength multiplexing in the same manner as in the first embodiment.

Next, a specific operation of the wavelength division multiplexing optical transmission device will be described in detail. Prior to actual operation, EDFA
The extraction of parameters for determining the characteristics of 43 is performed. First, in a state where the EDFA 43 is not excited, the light source 41
Only 1 (wavelength λ ₁ ) is turned on, and the input light intensity dependency of the output light intensity of the EDFA 10 is measured. From the obtained measured values, the values of the parameters A ₁ , P ₁ ^IS and the optical loss L ₁ are obtained by the same method as in the first embodiment. Other light source unit 4
12 to 41n (wavelengths λ _{2 to} λ _n )
Each of them is turned on, and parameters and light loss values are obtained in the same procedure. Next, with the EDFA 43 excited,
Only one of the light source units 411 to 41n is turned on, and the input light intensity dependency of the output light intensity of the EDFA 10 at this time is measured. From the obtained measured values, the values of the parameters A _p and P _p ^IS at the wavelength λ _p of the excitation light are determined by the same method as in the first embodiment.

Next, at the time of actual operation, the control unit 4
7, the input light intensity at the time of wavelength multiplexing is calculated from the parameters obtained in step 7 and the desired output light intensity from the EDFA 10, and the input light intensity from the light source units 411 to 41n is set so that the input light intensity to the EDFA 43 becomes a value obtained by the calculation. Adjust the output light intensity.

As described above, in this embodiment, since the function for extracting the parameters necessary for calculating the relationship between the input and output light intensities is provided internally, special preparation is required even when the EDFA 43 is replaced. Without light sources 411-41
n can be set appropriately. Other advantages are the same as in the first embodiment.

(Other Embodiments) As another embodiment of the present invention, in each of the above-described embodiments, the ED
A configuration in which the FA is replaced with another type of optical fiber amplifier having similar characteristics is also possible.

[0089]

As described above, according to the present invention, it is necessary to calculate the input light or output light intensity characteristics at the time of wavelength multiplexing from the output light intensity characteristics when only the light of the signal light wavelength is input to the optical fiber amplifier. Since all the parameters are obtained, the relationship between the input and output light intensities can be calculated also for the optical fiber amplifier modularized together with the optical components other than the amplification medium. In addition, if parameters are obtained for all wavelengths that are assumed to be used, it is possible to calculate the case where wavelengths are multiplexed by combining arbitrary wavelengths among them. Further, even when the number of optical signals fluctuates due to a failure of the light source or the like, it is possible to optimally set the input light intensity.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a procedure according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a configuration of an EDFA module;

FIG. 3 is a diagram showing an example of an output light intensity characteristic in a state where the EDFA module is not excited.

FIG. 4 is a diagram illustrating an example of output light intensity characteristics in a state where the EDFA module is excited;

FIG. 5 is a block diagram showing a configuration of a second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a third embodiment of the present invention.

FIG. 7 is a block diagram illustrating an example (1) of a configuration of a light source unit according to Embodiment 3 of the present invention.

FIG. 8 is a block diagram illustrating an example (2) of a configuration of a light source unit according to Embodiment 3 of the present invention.

FIG. 9 is a block diagram illustrating an example (3) of a configuration of a light source unit according to Embodiment 3 of the present invention.

FIG. 10 is a block diagram illustrating an example (4) of a configuration of a light source unit according to Embodiment 3 of the present invention.

FIG. 11 is a block diagram illustrating an example (5) of a configuration of a light source unit according to Embodiment 3 of the present invention.

FIG. 12 is a block diagram illustrating an example of a configuration according to a fourth embodiment of the present invention.

FIG. 13 is a block diagram illustrating an example (1) of a configuration according to a fifth embodiment of the present invention;

FIG. 14 is a block diagram showing an example (2) of the configuration according to the fifth embodiment of the present invention;

FIG. 15 is a block diagram showing a configuration of a sixth embodiment of the present invention.

FIG. 16 is a flowchart showing the procedure of a conventional method for calculating the relationship between the input light intensity and the output light intensity of an EDFA during wavelength multiplexing.

FIG. 17 illustrates an example of a configuration of an EDFA module.

[Explanation of symbols]

10,39,391-39m, 43,431-43m
EDFA 11, 411 to 41n Light source unit 13, 35, 47 Control unit 14, 46 Light intensity measurement unit 15 Calculation unit 21 Wavelength variable light source 211 to 21n Light source 22, 38 Combining unit 23, 231 to 23n, 371 to 37n Light intensity Adjustment unit 31, wavelength separation unit 321 to 32n detection unit 42 wavelength multiplexing unit 45 branch unit 51, 57 optical isolator 52, 55 excitation laser 53, 56 WDM coupler 54 erbium-doped fiber

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04J 14/02 H04B 9/00 J H04B 10/17 10/16 (72) Inventor Yu Fudo Kadoma, Osaka 1006 Oji Kadoma Matsushita Electric Industrial Co., Ltd. F term (reference) 2G086 BB01 EE12 5F072 AB09 AK06 HH02 HH08 JJ20 KK30 PP10 YY17 5K002 AA06 CA09 CA13 DA02

Claims (9)

[Claims] 1. A method for evaluating the characteristics of an optical fiber amplifier used in a wavelength division multiplexing optical transmission system, comprising the steps of: inputting one light of each signal light wavelength used in the wavelength division multiplexing optical transmission system in a non-pumped state; Then, a predetermined first parameter of the amplification medium at the signal light wavelength is obtained from the input light intensity dependency of the output light intensity, and then one light of the signal light wavelength is input in the excited state, and the output light intensity is determined. An optical fiber, wherein a predetermined second parameter of an amplification medium at a pumping light wavelength is obtained from input light intensity dependency, and a relationship between input light intensity and output light intensity is obtained based on the first and second parameters. How to evaluate amplifier characteristics. 2. A method for evaluating the characteristics of an optical fiber amplifier used in a wavelength division multiplexing optical transmission system, comprising the steps of: inputting one light of each signal light wavelength used in the wavelength division multiplexing optical transmission system in a non-pumped state; Then, the output light intensity under the three or more input light intensity conditions is extracted, and The predetermined parameters A _k , P _k ^IS and L _k of the amplifying medium at the signal light wavelength are obtained according to the following formula. Then, one wave of the signal light wavelength is input in the excited state, and the output under the two or more input light intensity conditions is obtained. Extract the light intensity, The values of the predetermined parameters A _p and P _p ^IS of the amplification medium at the excitation light wavelength are obtained according to the following equation. The input light intensity P _k of each signal light at the time of wavelength multiplexing based on
^{2. The} method for evaluating characteristics of an optical fiber amplifier according to claim 1, wherein a relationship between ⁱⁿ and the output light intensity P _k ^out is _obtained . 3. An optical fiber amplifier used in a wavelength division multiplexing optical transmission system, comprising: a detecting unit for detecting the presence or absence of an optical signal of each wavelength; a light intensity adjusting unit for adjusting the signal light intensity of each wavelength; An optical fiber amplifier for amplifying an optical signal output from the optical intensity adjusting unit, a desired output light intensity from the optical fiber amplifier, and a predetermined parameter of an amplification medium obtained by the method according to claim 1 or 2. A wavelength division multiplexing optical amplifying apparatus, comprising: a control unit that calculates a required value of the input light intensity to the optical fiber amplifier and controls the intensity of the signal light output from the light intensity adjusting unit. 4. An amplifying medium obtained by a method according to claim 1 or 2, further comprising a plurality of optical fiber amplifiers connected in cascade, wherein the control unit determines a desired output light intensity from the last-stage optical fiber amplifier and the method according to claim 1 or 2. 4. The wavelength division multiplexing optical amplifying device according to claim 3, wherein a required value of the input light intensity to said optical fiber amplifier is calculated based on said predetermined parameter. 5. An apparatus used for evaluating characteristics of an optical fiber amplifier used in a wavelength division multiplexing optical transmission system, wherein the light source unit is capable of outputting light having an arbitrary signal light wavelength used in the wavelength division multiplexing optical transmission system. And a light intensity measuring unit for measuring the light intensity output from the optical fiber amplifier,
A control unit for controlling the wavelength and intensity of output light from the light source unit and the presence or absence of excitation of the optical fiber amplifier, and the relationship between input light intensity and output light intensity of the optical fiber amplifier by the method according to claim 1 or 2. An apparatus for evaluating characteristics of an optical fiber amplifier, comprising a calculating unit for calculating. 6. A wavelength division multiplexing optical transmission device comprising the wavelength division multiplexing optical amplifying device according to claim 3. 7. The optical fiber amplifier according to claim 1, further comprising: a light source section for outputting optical signals having different wavelengths and variable intensities; and an optical fiber amplifier for amplifying the wavelength-multiplexed optical signal. A wavelength division multiplexing optical transmission device, wherein the intensity of output light from a light source unit is determined using a characteristic evaluation method. 8. An output light from the light source unit based on a method according to claim 1 or 2, comprising a plurality of optical fiber amplifiers connected in cascade, and a desired output light intensity from the last stage optical fiber amplifier. The wavelength multiplexing optical transmission device according to claim 7, wherein a required value of the intensity is calculated. 9. A plurality of light source units for outputting optical signals having different wavelengths and variable intensities, a wavelength multiplexing unit for wavelength multiplexing the optical signals output from the plurality of light source units, and a wavelength multiplexed light. An optical fiber amplifier that amplifies a signal, a branch unit that branches the optical signal output from the optical fiber amplifier, and a light intensity measurement unit that measures one of the optical signals output from the branch unit. 3. The method according to claim 1, wherein required output light intensities from said plurality of light source units are calculated and controlled based on a desired output light intensity from an optical fiber amplifier, and whether or not said optical fiber amplifier is excited is controlled. The wavelength division multiplexing optical transmission device according to claim 7, further comprising a control unit.