JPH09224016A - Device and method for detecting light intensity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the intensity of respective optical signals for constituting wavelength multiplexed optical signals without using a wavelength selection element such as an optical filter or the like. SOLUTION: By using a timing control part 1, optical transmitters 2-1-2-N, optical attenuators 3-1-3-N and a photocoupler 4, in time sections determined so as not to overlap for respective light sources (optical transmitters), pilot signals for detecting the intensity of the optical signals are frequency multiplexed to electric signals for modulating the respective light sources. The optical signals are amplified in an optical amplifier 5 and inputted to a light intensity detection part 6. In the light intensity detection part 6, after optically/ electrically converting the plural wavelength multiplexed optical signals altogether, the levels of the pilot signals multiplexed in the respective time sections are detected and the intensity of the respective optical signals is obtained. In an optical attenuator control part 7, error signals are generated by comparing the level of the pilot signals with a reference level and the object optical attenuator is controlled so as to turn the error signals to zero. Thus, the intensity of the respective optical signals of optical amplifier output becomes equal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light intensity detecting apparatus and method for detecting the intensity of each optical signal constituting a wavelength-multiplexed optical signal, and particularly to a wavelength selecting element without using a wavelength selecting element such as an optical filter. The present invention relates to a light intensity detection device and method capable of detecting the intensity of each multiplexed optical signal.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting the intensity of each wavelength-multiplexed optical signal, after separating the wavelength-multiplexed optical signal using an optical filter that passes a specific wavelength band,
A method of measuring light intensity is known.

[0003]

However, the above-mentioned conventional techniques have the following problems to be solved. First of all, a plurality of optical filters are required corresponding to the wavelength of each optical signal, which complicates the configuration of the optical system and causes an obstacle to downsizing of the device and an increase in cost. Secondly, when using an optical filter that selects a specific wavelength band, if there is crosstalk (signal leakage) from adjacent optical signals of wavelengths, an error due to this occurs. Third,
If the insertion loss (also referred to as insertion loss) of the optical filter has wavelength dependence, it is necessary to correct the influence of this.

Furthermore, in a wavelength division multiplexing optical network, even if the optical output intensities of the optical transmitters are set equal, the dispersion of the insertion loss between the ports of the multiplexing optical coupler or the wavelength dependence of the gain of the optical amplifier is increased. As a result, an intensity difference may occur between the optical signals in the output of the optical amplifier.

In view of the problems to be solved by the prior art as described above, the first object of the present invention is to eliminate the use of a wavelength selection element such as an optical filter or the like for each optical signal forming a wavelength-multiplexed signal. An object of the present invention is to provide a light intensity detection device and a light intensity detection method capable of easily detecting the intensity.

A second object of the present invention is to provide a light intensity detecting device and a light intensity detecting method capable of equalizing the levels of the respective optical signals output from the optical amplifier, in addition to the above characteristics. .

[0007]

In order to achieve the first object, the light intensity detecting device of the present invention is a wavelength division multiplexing optical transmission system in which a plurality of light sources are set so as not to overlap each other in a time interval. A wavelength multiplexing means for frequency-multiplexing and transmitting identification information of each light source as a pilot signal for detecting the intensity of the optical signal with respect to an electric signal for modulating each light source, and output from the wavelength multiplexing means. Detecting the level of the pilot signal multiplexed in each of the time intervals defined for each light source, after collectively performing optical / electrical conversion of a plurality of optical signals that make up the wavelength-multiplexed optical signal According to the present invention, there is provided a detector for detecting the intensity of each of the wavelength-multiplexed optical signals.

In order to achieve the above second object, a light intensity detecting device of the present invention is provided in a wavelength division multiplexing optical transmission system.
In a time interval that is determined so that it does not overlap for each of multiple light sources, the identification information of each light source is frequency-multiplexed and transmitted as a pilot signal for detecting the intensity of the optical signal for the electrical signal that modulates each light source. Wavelength multiplexing means, a plurality of optical attenuating means for individually attenuating each optical signal output from each of the light sources in the wavelength multiplexing means, and wavelength multiplexed optical signals output from the wavelength multiplexing means And a plurality of optical signals that constitute the wavelength-multiplexed optical signal output from the optical amplifying means are collectively subjected to optical / electrical conversion, and then each of the light sources determined for each light source is converted. An error signal is generated by detecting the level of the pilot signal multiplexed in the time section and comparing the level of the pilot signal detected by the detecting unit with a reference level. Characterized by a control means for controlling the optical attenuation means of interest as said error signal becomes zero.

The apparatus of the present invention has, as one form thereof,
The light source may be an optical transmission device having a function of frequency-multiplexing, as the pilot signal, identification information unique to a time interval determined not to overlap.

In another form of the apparatus of the present invention, the wavelength multiplexing means has a pilot signal multiplexing timing control device for supplying a timing signal for controlling the timing of multiplexing the pilot signals to the light source. Can be characterized.

In a further form of the apparatus of the present invention, the detecting means has a function of detecting the level of the pilot signal frequency-multiplexed with the optical signal and the identification information. it can.

In order to achieve the above-mentioned first object, the light intensity detecting method of the present invention uses a plurality of light sources for each electric signal that modulates each of the light sources in a time interval determined so as not to overlap with each other. After frequency-multiplexing and transmitting identification information of the light source as a pilot signal for detecting the intensity of the optical signal, and collectively performing optical / electrical conversion of the plurality of optical signals forming the wavelength-multiplexed optical signal Detecting the intensity of each wavelength-multiplexed optical signal by detecting the level of the pilot signal multiplexed in each of the time intervals defined for each light source. .

The method of the present invention, as one form thereof,
In a time interval that is determined not to overlap for each of the multiple optical transmitters, the identification information of each optical transmitter is used as a pilot signal for the electrical signal for modulating the light source of each of the optical transmitters. Degree of modulation, using a common modulation method, time-division multiplexing so that the times to be multiplexed between the optical transmitters do not overlap in the same frequency band,
After optical / electrical conversion of the wavelength-multiplexed optical signals at once,
Extracting only the frequency band of the pilot signal, detecting the identification information of the optical transmitter included in the pilot signal, and detecting the level of the pilot signal, the level value of the detected pilot signal and the pilot Detecting the intensity of the optical signal from the optical transmitter that has multiplexed the pilot signal from the optical modulation degree of the signal.

In order to achieve the above-mentioned second object, the light intensity detecting method of the present invention uses a plurality of light sources for each electric signal that modulates each light source in a time interval determined so as not to overlap with each other. A step of frequency-multiplexing and transmitting identification information of the light source as a pilot signal for detecting the intensity of the optical signal, and in the step, each optical signal output from each of the light sources is individually attenuated by a plurality of optical attenuators. A step of amplifying the wavelength-multiplexed optical signal, and a plurality of optical signals constituting the wavelength-multiplexed and amplified optical signal being collectively optoelectrically converted, and each of the light sources being determined for each light source. The step of detecting the level of the pilot signal multiplexed in the time period, and the error signal by comparing the detected level of the pilot signal with a reference level Form, characterized by a step of controlling the optical attenuator of interest as said error signal becomes zero.

As another form of the method of the present invention, an electric signal for modulating each light source of each of the optical transmitters is applied to a plurality of optical transmitters in a time interval determined so as not to overlap with each other. As a pilot signal, the identification information of each optical transmitter is time-divided using the same optical modulation degree and common modulation method so that the times to be multiplexed between the optical transmitters do not overlap in the same frequency band. The step of multiplexing, the step of attenuating each optical signal output from the optical transmitter by an individual optical attenuator, the step of amplifying the wavelength-multiplexed optical signal, and the wavelength-multiplexed and amplified optical signal After collectively performing optical / electrical conversion, only the frequency band of the pilot signal is extracted, the identification information of the optical transmitter included in the pilot signal is detected, and the level of the pilot signal is determined. And a step of generating an error signal by comparing the level of the detected pilot signal with a reference level, and controlling the attenuation amount of the target optical attenuator so that the error signal becomes zero. It can be characterized by having.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment in which the present invention is applied to the optical level management of a wavelength division multiplexing optical network. First, the outline of the configuration of FIG. 1 will be described. The pilot signal multiplexing timing control unit 1, as will be described later with reference to FIG.
A plurality of N (N is an integer of 2 or more) optical transmitters 2-1 and 2-
2, ... In a time interval determined so as not to overlap for each 2-N, a pilot signal for detecting the intensity of the optical signal is frequency-multiplexed with an electric signal that modulates the light source of each optical transmitter. Timing control for. That is, in each light source of those optical transmitters, an identification signal of each light source is frequency-multiplexed and transmitted as an pilot signal with respect to an electric signal (main signal in FIG. 2) for modulating each light source. In this case, the time interval in which the pilot signals from the respective light sources are multiplexed is determined so that the pilot signals from the respective light sources do not overlap in the state where the plurality of optical signals are wavelength-multiplexed.

These optical transmitters 2-1, 2-2, ... 2-N
Each optical signal output from the optical signal passes through dedicated optical attenuators 3-1, 3-2, ... 3-N provided for each optical signal and is multiplexed into one optical signal by the multiplexing optical coupler 4. Be converted.
The wavelength-multiplexed optical signal is amplified to a constant level by the optical amplifier 5, a part of the output optical signal is guided to the optical intensity detector 6, and the rest passes through an optical transmission path such as an optical waveguide or an optical fiber. It is output to the outside.

As will be described later with reference to FIGS. 3 and 4, the light intensity detecting section 6 performs optical / electrical conversion on the wavelength-multiplexed optical signals all at once, and then identifies the pilot signals multiplexed in each time section. And the level of the pilot signal thereof are detected, and the identification information S1 and the level detection signal S2 obtained thereby are supplied to the optical attenuator controller 7. The identification information S1 is an identifier for identifying each optical signal forming the wavelength-multiplexed input optical signal, and the level detection signal S2 is detection data representing the intensity (light intensity) of each optical signal. From the value of the level detection signal S2 and the known optical modulation degree of the pilot signal, the intensity of the optical signal from the light source (optical transmitter) in which the pilot signal is multiplexed can be known.

As will be described later with reference to FIG. 5, the optical attenuator controller 7 is based on the identification information S1 and the level detection signal S2, and the N optical attenuators 3-1, 3-2, ... A control signal S5 for individually adjusting the respective attenuation amounts is generated. These optical attenuators are provided with a control signal S individually instructed for each optical attenuator.
By adjusting each attenuation individually according to 5,
Even if there are variations in the insertion loss between the ports of the multiplexing optical coupler 4 or the wavelength dependence of the gain of the optical amplifier 5, the optical signals of the wavelength-multiplexed optical signals output from the optical amplifier 5 are Levels can be equal.

FIG. 2 shows each of the optical transmitters 2-1 and 2-2 of FIG.
An example of multiplexing pilot signals in 2-N is shown. FIG.
11A shows an example of pilot signal multiplexing timing. In each optical transmitter, as shown in FIG. 2A, the identification information of each optical transmitter is used as a pilot signal in the same frequency band by using the same optical modulation degree and common modulation method. Time division multiplexing is performed so that the times to be multiplexed between transmitters do not overlap.

FIG. 2B shows each of the above optical transmitters 2.
-1, 2-2, ... 2-N shows the frequency spectrum of the modulation signal of each optical transmitter at the time when the pilot signals are multiplexed. The control of the pilot signal multiplexing timing is controlled by the pilot signal multiplexing timing control unit 1 of FIG.

FIG. 3 shows an example of the configuration of the light intensity detecting section 6 shown in FIG. In the light intensity detection unit 6, after the wavelength-multiplexed optical signals are collectively optoelectrically converted by the photoelectric converter (O / E) 61, only the frequency band of the pilot signal is used by the pilot signal bandpass filter 62. The identification information of the optical transmitter included in the pilot signal is detected by the identification information detection unit 63, and the level of the pilot signal is detected by the level detection unit 64.

FIG. 4 shows the identification information S1 of the optical transmitter and the pilot signal level (level detection signal S2) detected by the light intensity detector 6 when there is an intensity difference between the optical signals.
The output timing of is shown.

FIG. 5 shows an example of the configuration of the optical attenuator controller 7 of FIG. The optical attenuator control unit 7 generates the error signal S4 by comparing the level S2 of the pilot signal detected by the light intensity detection unit 6 with the reference level 72 by the level comparator 71, and the error signal S4 becomes zero. The target optical attenuator is controlled by the controlled optical attenuator switching unit 73 so that.
That is, the controlled optical attenuator switching unit 73 inputs the error signal S4 and the identification information S1 and generates a control signal S5 which makes the error signal zero, and the identification information S1 indicates the control signal S5. Supply to the optical attenuator.

In this example, since the pilot signals multiplexed in each optical transmitter have the same optical modulation degree, FIG.
1 so that the level difference between the received pilot signals becomes zero, the attenuation amounts of the optical attenuators 3-1, 3-2, ... 3-N in the preceding stage of the multiplexing optical coupler 4 in FIG. By controlling by the control unit 7, the intensity of each optical signal at the output of the optical amplifier 5 becomes equal.

(Other Embodiments) In the above description, the case where the pilot signals are specified to have the same optical modulation degree has been exemplified.
The present invention is not limited to this, and even if the light modulation degrees are not the same, the light intensity detecting section 6 can be similarly realized by having the calibration data.

[0028]

As described above, according to the present invention, in the time interval determined so that the light sources (optical transmitters) do not overlap with each other, the light signals of the optical signals are modulated with respect to the electric signals that modulate the respective light sources. The pilot signal for detecting the intensity is frequency-multiplexed, and a plurality of wavelength-multiplexed optical signals are collectively
After electrical conversion, the level of each pilot signal multiplexed in each time interval is detected to obtain the intensity of each optical signal.
The intensity of each optical signal forming the wavelength-multiplexed optical signal can be easily detected without performing wavelength separation by a wavelength selection element such as an optical filter.

Further, according to the present invention, an error signal is generated by comparing the level of the detected pilot signal with a reference level, and the target optical attenuator is controlled so that the error signal becomes zero. , The intensity of each optical signal at the output of the optical amplifier can be made equal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment when the present invention is applied to optical level management of a wavelength division multiplexing optical network.

FIG. 2 is a diagram showing an example of multiplexing pilot signals in each optical transmitter of FIG. 1, (a) is a time chart showing an example of pilot signal multiplexing timing, and (b) is each optical transmitter. FIG. 4 is a spectrum diagram showing a frequency spectrum of a modulation signal of each optical transmitter at a time when pilot signals are multiplexed.

FIG. 3 is a block diagram showing a configuration example of a light intensity detection unit in FIG.

FIG. 4 shows identification information S1 of an optical transmitter detected by a light intensity detection unit in FIG. 3 when there is a difference in intensity between optical signals.
3 is a time chart showing the output timing of the pilot signal level (level detection signal S2).

5 is a block diagram showing a configuration example of an optical attenuator control unit in FIG.

[Explanation of symbols]

 1 Pilot Signal Multiplexing Timing Control Unit 2-1, 2-2, ... 2-N Optical Transmitter 3-1, 3-2, ... 3-N Optical Attenuator 4 Multiplexing Optical Coupler 5 Optical Amplifier 6 Optical Intensity Detection unit 7 Optical attenuator control unit 61 Photoelectric converter 62 Pilot signal band pass filter 63 Identification information detection unit 64 Level detection unit 71 Level comparator 72 Reference level 73 Controlled optical attenuator switch S1 Identification information S2 Level detection signal S4 Error signal S5 Control signal

Claims (9)

[Claims] 1. In a wavelength-division-multiplexed optical transmission system, identification information of each light source is given to an electric signal that modulates each light source in a time interval determined so as not to overlap each of the plurality of light sources, Wavelength multiplexing means for frequency-multiplexing and transmitting as a pilot signal for detection, and a plurality of optical signals constituting the wavelength-multiplexed optical signal output from the wavelength multiplexing means are collectively optoelectrically converted. And a detecting unit for detecting the intensity of each of the wavelength-multiplexed optical signals by detecting the level of the pilot signal multiplexed in each of the time intervals determined for each light source. Light intensity detector. 2. In a wavelength division multiplexing optical transmission system, identification information of each light source is given to an electric signal which modulates each light source in a time interval determined so as not to be overlapped for each of the plurality of light sources, and the intensity of the optical signal. Wavelength multiplexing means for frequency-multiplexing and transmitting as a pilot signal for detection, a plurality of optical attenuating means for individually attenuating each optical signal output from each light source in the wavelength multiplexing means, and the wavelength multiplexing Optical amplification means for amplifying the wavelength-division-multiplexed optical signal output from the converting means, and a plurality of optical signals constituting the wavelength-division-multiplexed optical signal output from the optical amplification means are collectively converted into optical / electrical signals. After doing
Detection means for detecting the level of the pilot signal multiplexed in each of the time intervals defined for each light source, and an error signal by comparing the level of the pilot signal detected by the detection means with a reference level And a control means for controlling the target light attenuating means so that the error signal becomes zero. 3. The optical transmission device according to claim 1, wherein the light source is an optical transmission device having a function of frequency-division-multiplexing, as the pilot signal, identification information unique to a time interval determined not to overlap. Light intensity detector. 4. The pilot signal multiplexing timing control device for supplying a timing signal for controlling the timing of multiplexing the pilot signal to the light source, according to claim 1, wherein the wavelength multiplexing means has a pilot signal multiplexing timing control device. The light intensity detection device according to any one of claims. 5. The light intensity according to claim 1, wherein the detection means has a function of detecting the level of a pilot signal frequency-multiplexed with the optical signal and the identification information. Detection device. 6. The identification information of each light source is used as a pilot signal for detecting the intensity of the optical signal with respect to an electric signal that modulates each light source in a time section determined so as not to overlap for each of the plurality of light sources. A step of frequency-multiplexing and transmitting, and a plurality of optical signals constituting a wavelength-multiplexed optical signal are collectively optoelectrically converted, and then multiplexed in each of the time intervals defined for each light source. Detecting the intensity of each of the wavelength-multiplexed optical signals by detecting the level of the pilot signal. 7. Identification of each optical transmitter as a pilot signal with respect to an electric signal for modulating each light source of each of the plurality of optical transmitters in a time period determined so as not to overlap with each other. Using the same degree of optical modulation and a common modulation method, time-division-multiplexing the information so that the times to be multiplexed between the respective optical transmitters do not overlap in the same frequency band; After converting signals to light / electricity collectively,
Extracting only the frequency band of the pilot signal, detecting the identification information of the optical transmitter included in the pilot signal, and detecting the level of the pilot signal; the level value of the detected pilot signal and the pilot And detecting the intensity of the optical signal from the optical transmitter that has multiplexed the pilot signal from the optical modulation degree of the signal. 8. The identification information of each light source is used as a pilot signal for detecting the intensity of the light signal with respect to an electric signal that modulates each light source in a time interval determined so as not to overlap for each of the plurality of light sources. Frequency-multiplexing and transmitting, individually attenuating each optical signal output from each light source by a plurality of optical attenuators in the step, amplifying the wavelength-multiplexed optical signal, and wavelength-multiplexing Detecting the level of the pilot signal multiplexed in each of the time intervals defined for each light source after collectively performing optical / electrical conversion on a plurality of optical signals that form the amplified optical signal. An error signal is generated by comparing the level of the detected pilot signal with a reference level, and the target light is generated so that the error signal becomes zero. Light intensity detecting method characterized by a step of controlling the 衰器. 9. The optical transmitters are identified as pilot signals with respect to electric signals for modulating the respective light sources of the optical transmitters in a time period determined so as not to overlap for each of the optical transmitters. Using the same degree of optical modulation and a common modulation method, the information is time-division-multiplexed so that the times to be multiplexed between the respective optical transmitters in the same frequency band do not overlap, and from the optical transmitter After attenuating each output optical signal by an individual optical attenuator, amplifying the wavelength-multiplexed optical signal, and converting the wavelength-multiplexed and amplified optical signal into light / electricity at once, Extracting only the frequency band of the pilot signal,
An error signal is generated by detecting the identification information of the optical transmitter included in the pilot signal and detecting the level of the pilot signal, and comparing the detected pilot signal level with a reference level. Controlling the attenuation amount of the target optical attenuator so that the error signal becomes zero.