JP3257345B2 - Operation margin measuring apparatus and operation margin measuring method for optical repeater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication system using an optical repeater including an optical amplifier and an optical filter.
The present invention relates to an operation margin measuring device and an operation margin measuring method for measuring an operation margin of an optical repeater.

[0002]

2. Description of the Related Art The operating margin of an optical repeater is defined as the received light intensity (reception sensitivity) required for the receiver of the optical repeater to receive an optical signal at a specified error rate or less, and the minimum of the optical repeater. This is the difference from the received light intensity. As the optical repeater is used for a long period of time, various components are deteriorated or the adjustment is shifted, the amount of intersymbol interference increases, and the receiving sensitivity decreases. Therefore, a predetermined difference is previously given between the reception sensitivity and the minimum reception light intensity as an operation margin.

In an operation margin measuring apparatus, when light having a minimum received light intensity is incident on a receiver, intersymbol interference is artificially applied to the main signal light, and the degree of deterioration of error rate characteristics and the amount of intersymbol interference are determined. The operation margin of the optical repeater is evaluated by measuring.
FIG. 7 shows a configuration example of a conventional operation margin measuring device for an optical repeater. In the figure, an operation margin measuring device 10 is inserted between an optical repeater 1-1 and an optical repeater 1-2. The transmitter 110 of the optical repeater 1-1 outputs a main signal light intensity-modulated by the transmission signal given from the pulse pattern generator 11 of the operation margin measuring device 10. Operation margin measuring device 10
The intersymbol interference noise light generation circuit 12 generates the intersymbol interference noise light whose intensity is modulated at a different bit rate asynchronously with the main signal light. The main signal light and the intersymbol interference noise light are input to the variable attenuators 13 and 14, respectively, adjusted to predetermined light intensities, and multiplexed by the multiplexer / demultiplexer 15. The output light of the multiplexer / demultiplexer 15 is transmitted to the optical intensity detector 16 and the optical repeater 1-
2 receiver 120. The control circuit 17 controls the variable attenuators 13 and 14 according to the detection result of the light intensity detector 16.
Control the amount of attenuation. The received signal output from the receiver 120 is input to the error rate measuring device 18 of the operation margin measuring device 10. Here, the variable attenuator 1 is controlled by the control circuit 17.
3, 14 are adjusted to set the intersymbol interference amount corresponding to the average power ratio between the main signal light and the intersymbol interference noise light. The error rate measuring device 18 measures an error rate according to the intersymbol interference amount to determine an operation margin of the optical repeater.

[0004]

FIG. 8 shows the configuration of the receiver 120.
An example of the configuration will be described. The receiver shown in FIG.
23, an equalizing amplifier circuit 124, and an identification circuit 125. In this receiver, the intersymbol interference amount before the identification circuit 125 is defined by the average power ratio between the main signal light and the intersymbol interference noise light input to the receiver. Therefore,
The operation margin of the optical repeater can be measured according to the inter-symbol interference amount set by the operation margin measurement device 10.

[0005] The receiver shown in FIG.
1, an optical filter 122, a light receiving element 123, an equalizing amplifier circuit 124, and an identification circuit 125. In this receiver, when the wavelength of the intersymbol interference noise light is out of the band of the optical filter 122, the main signal light passes through the optical filter 122, but the intersymbol interference noise light is blocked by the optical filter 122. For example, when an LED having a signal band of about 100 nm is used as the intersymbol interference noise light generation circuit 12 and an optical filter 122 having a bandwidth of 1 nm is used, the intersymbol interference noise light can be reduced to 20 dB.
It is attenuated to some extent. Therefore, the amount of intersymbol interference defined by the average power ratio between the main signal light and the intersymbol interference noise light is smaller at the output point of the optical filter 122 (input point of the identification circuit 125) than at the input point of the receiver. Become. That is, the amount of intersymbol interference at the input point of the identification circuit 125 cannot be specified by the operation margin measuring apparatus 10.

Further, for an optical repeater having an optical amplifier, it is necessary to measure an operation margin including spontaneous emission optical noise generated in the optical amplifier. Was. The present invention provides an operation margin measurement apparatus and an operation margin measurement method for an optical repeater that can define an intersymbol interference amount for an optical repeater having an optical amplifier and an optical filter and measure a corresponding operation margin. The purpose is to do.

[0007]

SUMMARY OF THE INVENTION An operating margin measuring apparatus and an operating margin measuring method for an optical repeater according to the present invention measure a wavelength of a main signal light, and determine an intersymbol interference noise light based on the wavelength of the main signal light. Set the wavelength. At this time, the wavelength of the intersymbol interference noise light is set so that it is within the pass band of the optical filter included in the optical repeater and the wavelength difference from the main signal light is at least 6 times the bit rate of the main signal light. I do.

In addition, the main signal light and the intersymbol interference noise light are converted into orthogonal linear polarizations and polarization-multiplexed. Further, noise light which simulates spontaneous emission optical noise generated in the optical amplifier of the optical repeater is generated, and is transmitted while being superimposed on the main signal light and the intersymbol interference noise light.

[0009]

In the operation margin measuring apparatus and the operation margin measuring method of the present invention, the wavelength of the intersymbol interference noise light is set according to the wavelength of the main signal light. The operation margin of the optical repeater can be measured without being disturbed by the wavelength filter built in the optical repeater.

[0010] Further, by polarization-multiplexing the main signal light and the intersymbol interference noise light, it is possible to ease the restriction on the wavelength difference between the main signal light and the intersymbol interference noise light. Further, since the spontaneous emission optical noise generated in the optical amplifier of the optical repeater can be simulated, the operation margin of the optical repeater having the optical amplifier can be accurately measured.

[0011]

【Example】

(First Embodiment) FIG. 1 shows a configuration of a first embodiment of an operation margin measuring apparatus for an optical repeater according to the present invention. The configuration of this embodiment is
A wavelength discriminating circuit 21 for discriminating the wavelength of the main signal light and a wavelength control circuit 22 for controlling the wavelength of the intersymbol interference noise light according to the wavelength of the main signal light are added to the conventional configuration shown in FIG. is there. The main signal light is input to the wavelength discrimination circuit 21 via the multiplexer / demultiplexer 20 inserted between the variable attenuator 13 and the multiplexer / demultiplexer 15. Intersymbol interference noise light generation circuit 1
2 is wavelength-controlled by the wavelength control circuit 22.

FIG. 2 shows a configuration example of the wavelength discrimination circuit 21. The wavelength discriminating circuit shown in FIG. 2A includes a splitter 31 for splitting the main signal light into two, a wavelength-dependent loss element 32 whose loss has a known wavelength dependency, and light intensity detectors 34 and 35. One of the two branched main signal lights is a wavelength-dependent loss element 3.
2, and the other main signal light is input to the light intensity detector 35, and the light intensity is measured respectively. The difference between the light intensities corresponds to the amount of loss in the wavelength-dependent loss element 32, and corresponds to the wavelength of the main signal light.

In the wavelength control circuit 22, the light intensity detector 3
By comparing the light intensities detected in steps 4 and 35, the amount of loss in the wavelength-dependent loss element 32 is obtained, the wavelength corresponding to the amount of loss is determined with reference to a data table, and the wavelength of the main signal light is determined. The wavelength discriminating circuit shown in FIG. 2 (b) inputs the main signal light branched by the splitter 31 to the light intensity detectors 34 and 35 via the wavelength dependent loss elements 32 and 33, respectively, and measures the light intensity. It is a configuration to do. Wavelength dependent loss element 3
When an ordinary optical band-pass filter is used as 2, 33, and the center wavelength of the pass band is shifted, there is an advantage that the wavelength dependence of the loss becomes sharper than the configuration of (a) between the two center wavelengths. . This is because the wavelength dependence of the loss of the optical bandpass filter becomes slow at wavelengths near the center wavelength and at a distance of 10 dB or more from the center wavelength.

The wavelength discriminating circuit shown in FIG. 2C splits the main signal light into two by a WDM coupler 36 having a known wavelength dependency, and inputs the branched signal light to light intensity detectors 34 and 35 to measure the light intensity. Configuration. The difference between the light intensities corresponds to the branching ratio in the WDM coupler 36, and corresponds to the wavelength of the main signal light. Hereinafter, the measurement procedure in this example will be described.

(1) The amount of attenuation set in the variable attenuator 14 is increased (60 dB or more), and the intersymbol interference noise light is
To be typed in. (2) The wavelength of the main signal light is measured by the wavelength discrimination circuit 21 and the wavelength control circuit 22. (3) The control circuit 17 calibrates the attenuation of the variable attenuator 13 according to the light intensity of the main signal light detected by the light intensity detector 16.

(4) The attenuation set in the variable attenuator 13 is increased (60 dB or more) so that the main signal light is not input to the multiplexer / demultiplexer 15. (5) The wavelength control circuit 22 sets the wavelength of the intersymbol interference noise light based on the wavelength of the main signal light. The wavelength of the intersymbol interference noise light is set so that the amount of detuning from the main signal light is at least six times the bit rate of the main signal light and within the band of the optical filter built in the receiver 120. That is, as the intersymbol interference noise light, intensity-modulated light that is asynchronous with the main signal light and that is modulated at or above the low cutoff frequency of the receiver 120 is used. The reason why the bit rate of the main signal light is set to six times or more is to prevent excessive beat noise due to interference in an optical region corresponding to the detuning difference.

(6) The control circuit 17 calibrates the attenuation of the variable attenuator 14 according to the light intensity of the intersymbol interference noise light detected by the light intensity detector 16. (7) Increase the amount of attenuation set in the variable attenuator 14 (60 dB
As described above, the intersymbol interference noise light is prevented from being input to the multiplexer / demultiplexer 15. (8) The variable attenuator 13 is controlled to set the light intensity of the main signal light.

(9) The variable attenuator 14 is controlled based on the light intensity of the main signal light to set the intersymbol interference amount (S / X) to a specified value, and to output intersymbol interference noise light. (10) The error rate measuring device 18 measures the error rate of the received signal output from the receiver 120, and measures the operation margin of the optical repeater. (Second Embodiment) FIG. 3 shows the configuration of a second embodiment of the operation margin measuring apparatus for an optical repeater according to the present invention.

In this embodiment, in addition to the configuration of the first embodiment,
A noise light generating circuit for generating noise light corresponding to spontaneous emission light generated by an optical repeater including an optical amplifier; and a variable attenuator for adjusting the light intensity of the noise light. And superimposes the noise light on the main signal light via the main signal light.
FIG. 4 shows a configuration example of the noise light generation circuit 23.

The noise light generating circuit shown in FIG. 4A includes a laser 41 for generating pump light input to an erbium-doped fiber 43, an isolator 42, an erbium-doped fiber 43, an isolator 44, and a spontaneous emission generated by an optical repeater. The optical filter 45 is configured to limit the band of noise light according to the bandwidth of light. The spontaneous emission light generated in the erbium-doped fiber 43 excited by the excitation light is output after being band-limited by the optical filter 45 and output from the variable attenuator 2.
At 4, a predetermined light intensity is set. Thus, noise light corresponding to spontaneous emission light generated in the optical repeater can be superimposed on the main signal light.

The noise light generating circuit shown in FIG. 4 (b) has the configuration shown in FIG.
The light is input to the erbium-doped fiber 43 via the M coupler 47. The return light from the erbium-doped fiber 43 is terminated at the non-reflection termination 46 via the WDM coupler 47. Thus, the input-side isolator 42 becomes unnecessary. The same applies when an optical circulator is used instead of the WDM coupler 47.

In the noise light generating circuit shown in FIG. 4C, the pumping light output from the laser 41 is input from the output side of the erbium-doped fiber 43 in the configuration of FIG. Thereby, it is possible to prevent the excitation light from being output. FIG.
The noise light generation circuit shown in (d) uses a semiconductor optical amplifier 48 instead of the laser 41 and the erbium-doped fiber 43 that generate the pump light in the configurations of (a) to (c). The semiconductor optical amplifier 48 is driven by a stabilizing power supply 49, and the generated light is condensed by a lens 50 and output via an isolator 44 and an optical filter 45.

The noise light generating circuit shown in FIG. 4E uses an SLD (super luminescent diode) 51 or an LED instead of the semiconductor optical amplifier 48 in the configuration of FIG. In this case, the isolator 44 is unnecessary.
Further, by using the semiconductor optical amplifier 48 or the SLD 51, the size of the device can be reduced. Hereinafter, the measurement procedure in this example will be described.

(1) The amount of attenuation set in the variable attenuator 14 is increased (60 dB or more) so that the intersymbol interference noise light is
To be typed in. (2) Increase the amount of attenuation set in the variable attenuator 24 (60 dB
As described above, noise light is prevented from being input to the multiplexer / demultiplexer 20. (3) The wavelength of the main signal light is measured by the wavelength discrimination circuit 21 and the wavelength control circuit 22.

(4) The control circuit 17 calibrates the attenuation of the variable attenuator 13 according to the light intensity of the main signal light detected by the light intensity detector 16. (5) Increase the amount of attenuation set in the variable attenuator 13 (60 dB
As described above, the main signal light is prevented from being input to the multiplexer / demultiplexer 15. (6) The wavelength control circuit 22 sets the wavelength of the intersymbol interference noise light based on the wavelength of the main signal light. The wavelength of the intersymbol interference noise light is set so that the amount of detuning from the main signal light is at least six times the bit rate of the main signal light and within the band of the optical filter built in the receiver 120. That is, as the intersymbol interference noise light, intensity-modulated light that is asynchronous with the main signal light and that is modulated at or above the low cutoff frequency of the receiver 120 is used.

(7) The control circuit 17 calibrates the attenuation of the variable attenuator 14 according to the light intensity of the intersymbol interference noise light detected by the light intensity detector 16. (8) Increase the amount of attenuation set in the variable attenuator 14 (60 dB
As described above, the intersymbol interference noise light is prevented from being input to the multiplexer / demultiplexer 15. (9) The control circuit 17 calibrates the attenuation of the variable attenuator 24 according to the light intensity of the noise light detected by the light intensity detector 16.

(10) The attenuation set in the variable attenuator 24 is increased (60 dB or more) so that noise light is not input to the multiplexer / demultiplexer 20. (11) The variable attenuator 13 is controlled to set the light intensity of the main signal light. (12) The variable attenuator 14 is controlled based on the light intensity of the main signal light to set the intersymbol interference (S / X) to a specified value, and to output intersymbol interference noise light.

(13) The noise light intensity density is set to a specified value by controlling the variable attenuator 24 based on the light intensity of the main signal light, and the noise light is output. The bandwidth of the noise light spectrum is
The bandwidth is set equal to the bandwidth of the noise light spectrum generated by the optical repeater having the optical amplifier and the optical filter. (14) The error rate measuring device 18 measures the error rate of the received signal output from the receiver 120, and measures the operation margin of the optical repeater.

(Third Embodiment) FIG. 5 shows the configuration of a third embodiment of the operation margin measuring apparatus for an optical repeater according to the present invention. In this embodiment, the main signal light and the intersymbol interference noise light are changed to an arbitrary polarization state instead of the configuration in which the intersymbol interference noise light is superimposed on the main signal light by the multiplexer / demultiplexer 15 in the first embodiment. In this configuration, polarization controllers 26 and 27 are provided to set the linear signal into a linear polarization state, and the main signal light and the intersymbol interference noise light are polarization-multiplexed using the polarization combiner 28. The polarization controllers 26 and 27 and the polarization combiner 28 are coupled by a polarization maintaining optical fiber 29 or a spatial system.

In such a configuration, even if the detuning of the main signal light and the intersymbol interference noise light is set within six times the bit rate, the light is input to the receiver as polarized waves orthogonal to each other. Does not occur, and the intersymbol interference noise light can be superimposed while suppressing excessive beat noise. Hereinafter, the measurement procedure in this example will be described.

(1) The amount of attenuation set in the variable attenuator 14 is increased (60 dB or more) so that the intersymbol interference noise light is
To be typed in. (2) The wavelength of the main signal light is measured by the wavelength discrimination circuit 21. (3) The control circuit 17 controls the polarization controller 26 in accordance with the light intensity of the main signal light detected by the light intensity detector 16 to set the polarization state of the main signal light to linear polarization.

(4) The control circuit 17 calibrates the attenuation of the variable attenuator 13 according to the light intensity of the main signal light detected by the light intensity detector 16. (5) Increase the amount of attenuation set in the variable attenuator 13 (60 dB
As described above, the main signal light is prevented from being input to the multiplexer / demultiplexer 15. (6) The wavelength control circuit 22 sets the wavelength of the intersymbol interference noise light based on the wavelength of the main signal light. The wavelength of the intersymbol interference noise light is within the band of the optical filter built in the receiver 120, since the restriction on the amount of detuning with respect to the main signal light is relaxed. That is, as the intersymbol interference noise light, intensity-modulated light that is asynchronous with the main signal light and that is modulated at or above the low cutoff frequency of the receiver 120 is used.

(7) The control circuit 17 controls the polarization controller 27 according to the light intensity of the intersymbol interference noise light detected by the light intensity detector 16 to change the polarization state of the intersymbol interference noise light to a straight line. The polarization is adjusted so that the polarization plane of the intersymbol interference noise light and the polarization plane of the main signal light are orthogonally combined. (8) The control circuit 17 calibrates the attenuation of the variable attenuator 14 according to the light intensity of the intersymbol interference noise light detected by the light intensity detector 16.

(9) The attenuation set in the variable attenuator 14 is increased (60 dB or more) so that the intersymbol interference noise light is
To be typed in. (10) The variable attenuator 13 is controlled to set the light intensity of the main signal light. (11) Based on the light intensity of the main signal light, the variable attenuator 14 is controlled to set the intersymbol interference amount (S / X) to a specified value, and to output intersymbol interference noise light.

(12) The error rate measuring unit 18 measures the error rate of the received signal output from the receiver 120, and measures the operation margin of the optical repeater. (Fourth Embodiment) FIG. 6 shows the configuration of a fourth embodiment of the operation margin measuring apparatus for an optical repeater according to the present invention. The present embodiment is different from the second embodiment in that the inter-symbol interference noise light is superimposed on the main signal light by the multiplexer / demultiplexer 15, and the main signal light and the inter-symbol interference noise light are changed to an arbitrary polarization state. In this configuration, polarization controllers 26 and 27 are provided to set the linear signal into a linear polarization state, and the main signal light and the intersymbol interference noise light are polarization-multiplexed using the polarization combiner 28. The polarization controllers 26 and 27 and the polarization combiner 28 are coupled by a polarization maintaining optical fiber 29 or a spatial system. Further, the position where the noise light is superimposed on the main signal light is changed from the multiplexer / demultiplexer 20 to the multiplexer / demultiplexer 15.

In such a configuration, even if the detuning of the main signal light and the intersymbol interference noise light is set within 6 times the bit rate, the light is input to the receiver as polarized waves orthogonal to each other. Does not occur, and the intersymbol interference noise light can be superimposed while suppressing excessive beat noise. Hereinafter, the measurement procedure in this example will be described.

(1) The amount of attenuation set in the variable attenuator 14 is increased (60 dB or more) so that the intersymbol interference noise light is
To be typed in. (2) Increase the amount of attenuation set in the variable attenuator 24 (60 dB
As described above, noise light is prevented from being input to the multiplexer / demultiplexer 20. (3) The wavelength of the main signal light is measured by the wavelength discrimination circuit 21.

(4) The control circuit 17 controls the polarization controller 26 in accordance with the light intensity of the main signal light detected by the light intensity detector 16 to change the polarization state of the main signal light to linear polarization. . (5) The control circuit 17 calibrates the attenuation of the variable attenuator 13 according to the light intensity of the main signal light detected by the light intensity detector 16. (6) Increase the amount of attenuation set in the variable attenuator 13 (60 dB
As described above, the main signal light is prevented from being input to the multiplexer / demultiplexer 15.

(7) The wavelength control circuit 22 sets the wavelength of the intersymbol interference noise light based on the wavelength of the main signal light. The wavelength of the intersymbol interference noise light is within the band of the optical filter built in the receiver 120, since the restriction on the amount of detuning with respect to the main signal light is relaxed. That is, as the intersymbol interference noise light, intensity-modulated light that is asynchronous with the main signal light and that is modulated at or above the low cutoff frequency of the receiver 120 is used.

(8) The control circuit 17 controls the polarization controller 27 in accordance with the light intensity of the intersymbol interference noise light detected by the light intensity detector 16 to linearly change the polarization state of the intersymbol interference noise light. The polarization is adjusted so that the polarization plane of the intersymbol interference noise light and the polarization plane of the main signal light are orthogonally combined. (9) The control circuit 17 calibrates the attenuation of the variable attenuator 14 according to the light intensity of the intersymbol interference noise light detected by the light intensity detector 16.

(10) The attenuation set in the variable attenuator 14 is increased (60 dB or more) so that the intersymbol interference noise light is
To be typed in. (11) The control circuit 17 calibrates the attenuation of the variable attenuator 24 according to the light intensity of the noise light detected by the light intensity detector 16. (12) Increase the amount of attenuation set in the variable attenuator 24 (60 dB
As described above, noise light is prevented from being input to the multiplexer / demultiplexer 20.

(13) The variable attenuator 13 is controlled to set the light intensity of the main signal light. (14) Based on the light intensity of the main signal light, the variable attenuator 14 is controlled to set the intersymbol interference (S / X) to a specified value, and to output intersymbol interference noise light. (15) Based on the light intensity of the main signal light, the variable attenuator 24 is controlled to set the noise light intensity density to a specified value and to output noise light. The bandwidth of the noise light spectrum is set equal to the bandwidth of the noise light spectrum generated in the optical repeater having the optical amplifier and the optical filter.

(16) The error rate measuring unit 18 measures the error rate of the received signal output from the receiver 120, and measures the operation margin of the optical repeater.

[0044]

As described above, according to the operation margin measuring apparatus and the operation margin measuring method of the optical repeater of the present invention, the amount of intersymbol interference given to the test signal light to the optical repeater having the optical amplifier and the optical filter is reduced. It can be specified exactly. Therefore, the operation margin of the optical repeater with respect to the intersymbol interference amount can be accurately measured.

Further, since the wavelength difference between the main signal light and the intersymbol interference noise light can be reduced by polarization multiplexing the main signal light and the intersymbol interference noise light, the amount of intersymbol interference given to the test signal light can be further reduced. It can be specified exactly. Further, by using the test signal light including the noise light simulating the spontaneous emission optical noise generated in the optical amplifier of the optical repeater, the operation margin of the optical repeater having the optical amplifier can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of an operation margin measuring device for an optical repeater according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a wavelength discrimination circuit 21.

FIG. 3 is a block diagram showing a configuration of a second embodiment of the operation margin measuring device for an optical repeater according to the present invention.

FIG. 4 is a block diagram showing a configuration example of a noise light generation circuit 23.

FIG. 5 is a block diagram showing the configuration of a third embodiment of the operation margin measuring device for an optical repeater according to the present invention.

FIG. 6 is a block diagram showing the configuration of a fourth embodiment of the operation margin measuring device for an optical repeater according to the present invention.

FIG. 7 is a block diagram showing a configuration example of a conventional operation margin measuring device for an optical repeater.

FIG. 8 is a block diagram showing a configuration example of a receiver 120.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 operation margin measuring device 11 pulse pattern generator 12 intersymbol interference noise light generation circuit 13, 14, 24 variable attenuator 15, 20 multiplexer / demultiplexer 16, 34, 35 light intensity detector 17 control circuit 18 error rate measurement device Reference Signs List 21 wavelength discrimination circuit 22 wavelength control circuit 23 noise light generation circuit 26, 27 polarization controller 28 polarization combiner 29 polarization maintaining optical fiber 31 branch device 32, 33 wavelength dependent loss element 36, 47 WDM coupler 41 laser 42, 44 Isolator 43 Erbium-doped fiber 45 Optical filter 46 Non-reflection termination 48 Semiconductor optical amplifier 49 Stabilized power supply 50 Lens 51 SLD

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-120896 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14 / 00-14/08 G01M 11/00 JICST file (JOIS)

Claims (8)

(57) [Claims] 1. A main signal light intensity-modulated at a predetermined bit rate is input, an intersymbol interference noise light intensity-modulated at a different bit rate asynchronously with the main signal light is generated, and the main signal light and a code are generated. The optical interfering noise light is superimposed at a predetermined light intensity ratio and transmitted to the optical repeater, and the error rate of the received signal output from the receiver of the optical repeater is measured, and the optical repeater corresponding to the intersymbol interference amount is measured. In the operation margin measuring device of the optical repeater for measuring the operation margin of the optical device, the wavelength of the main signal light is measured, and based on the wavelength of the main signal light,
Within the pass band of the optical filter included in the optical repeater.
And a wavelength control means for setting a wavelength of the intersymbol interference noise light. 2. The wavelength control means according to claim 1, wherein the wavelength difference between the main signal light and the wavelength of the intersymbol interference noise light is set to at least six times the bit rate of the main signal light. 2. The operation margin measuring device for an optical repeater according to claim 1. 3. A main signal light intensity-modulated at a predetermined bit rate is input, and an intersymbol interference noise light intensity-modulated at a different bit rate asynchronously with the main signal light is generated. The optical interfering noise light is superimposed at a predetermined light intensity ratio and transmitted to the optical repeater, and the error rate of the received signal output from the receiver of the optical repeater is measured, and the optical repeater corresponding to the intersymbol interference amount is measured. In the operation margin measuring device of the optical repeater for measuring the operation margin of the optical device, the wavelength of the main signal light is measured, and based on the wavelength of the main signal light,
Within the pass band of the optical filter included in the optical repeater.
In the wavelength control means for setting the wavelength of the intersymbol interference noise light, converts a predetermined set to the light intensity ratio was the main signal light and the intersymbol interference noise light to linearly polarized waves orthogonal to each other, polarization An operation margin measuring device for an optical repeater, comprising: polarization multiplexing means for multiplexing and outputting. 4. A means for generating noise light which simulates spontaneous emission light generated in an optical repeater including an optical amplifier, and superimposing the noise light on the main signal light and the intersymbol interference noise light and outputting the same. 4. An apparatus for measuring an operation margin of an optical repeater according to claim 1, wherein: 5. The wavelength control means has a wavelength-dependent loss element whose loss changes depending on the wavelength, splits the main signal light into two, and passes at least one of the two through the wavelength-dependent loss element,
4. The operation margin measuring device for an optical repeater according to claim 1, wherein the optical intensity of each branch path is detected and the wavelength of the main signal light is discriminated from the optical intensity difference. 6. The wavelength control means has an optical branching element whose branching ratio changes depending on the wavelength, and branches the main signal light using the optical branching element to detect the light intensity of each branching path. 4. The operation margin measuring device for an optical repeater according to claim 1, wherein a wavelength of the main signal light is discriminated from the branch ratio. 7. A main signal light intensity-modulated at a predetermined bit rate is input, an intersymbol interference noise light intensity-modulated at a different bit rate asynchronously with the main signal light is generated, and the main signal light and a code are generated. The optical interfering noise light is superimposed at a predetermined light intensity ratio and transmitted to the optical repeater, and the error rate of the received signal output from the receiver of the optical repeater is measured, and the optical repeater corresponding to the intersymbol interference amount is measured. in operation margin measuring method for an optical repeater which measures the operational margin of the vessels, and procedures for measuring the wavelength of the main signal light, the wavelength of the intersymbol interference noise light, including the optical repeater
Setting a wavelength difference from the main signal light to at least 6 times the bit rate of the main signal light within the pass band of the optical filter to be operated. . 8. A main signal light intensity-modulated at a predetermined bit rate is input, an intersymbol interference noise light intensity-modulated at a different bit rate is generated asynchronously with the main signal light, and the main signal light and a code are generated. The optical interfering noise light is superimposed at a predetermined light intensity ratio and transmitted to the optical repeater, and the error rate of the received signal output from the receiver of the optical repeater is measured, and the optical repeater corresponding to the intersymbol interference amount is measured. in operation margin measuring method for an optical repeater which measures the operational margin of the vessels, and procedures for measuring the wavelength of the main signal light, the wavelength of the intersymbol interference noise light, including the optical repeater
Setting the wavelength difference between the main signal light and the main signal light to at least 6 times the bit rate of the main signal light within the pass band of the optical filter to be inserted; and setting the main signal light and the code set at a predetermined light intensity ratio. Means for converting the interfering noise light into linear polarizations orthogonal to each other, and polarization multiplexing and outputting the resultant signals.