JP2003060291A - Wavelength control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength control apparatus which can be manufactured easily, is suitable for mass-production, and can meet the requirements concerning the widening of a band width of a wavelength in use. SOLUTION: A monitoring luminous signal M oscillated by a light source 1 is made incident on an optical wavelength filter 24, whose transmittance and reflectance depend upon a wavelength as a parallel light. The light intensities of the transmitted light and the reflected light are first and second photodiodes 25 and 27. After electrical signals P1 and P2, corresponding to the light intensities are electrically changed into electrical signals P1' and P2', a value of (P1'-P2')/(P1+P2) is calculated by a third operating device 38. A controller 6 controls the light source 1, so as to make the changed value of the calculated value approximately zero due to aging, so as to keep the oscillation wavelength of the light source 1 to be a wavelength in use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength management device for controlling the oscillation wavelength of a light source so as to keep it at a preset operating wavelength.

[0002]

2. Description of the Related Art In a wavelength division multiplexing system (hereinafter referred to as WDM system), signal lights of a plurality of wavelengths are used.
As the used wavelength spacing becomes higher, the adjacent wavelength spacing becomes smaller. A semiconductor laser (LD) is generally used as a light source in the WDM system, but the LD causes a change in center wavelength of emitted light due to a change with time or an environment, which causes crosstalk with adjacent wavelengths. Interference may occur. Therefore, in order to keep the oscillation wavelength of the LD constant, for example, a wavelength management device using a wavelength selection means such as an optical resonator having a transmission characteristic having wavelength dependence is used.

FIG. 5 is a schematic configuration diagram showing an example in which a wavelength management device is configured by using an optical resonator as a wavelength selection means. In this figure, reference numeral 1 is an LD light source, and 11 is a wavelength management module. The LD light source 1 is configured so that the oscillation wavelength can be controlled by controlling the temperature of the LD element or the LD introduction current, and in the former case, a thermoelectric element (not shown) is provided. Light emitted from the LD light source 1 is split into two by the optical coupler 2. With this optical coupler 2, for example, 95% of the emitted light is output as the main signal light,
The remaining 5% enters the wavelength management module 11 as monitor signal light. In the wavelength management module 11, first, the collimator 12 causes the monitor signal light to enter the half mirror 13 as parallel light. The transmitted light of the half mirror 13 is incident on the optical resonator 14, and the transmitted light intensity of the optical resonator 14 is measured by the first photodiode 15. On the other hand, the reflected light of the half mirror 13 is guided to the second photodiode 17 via the reflecting mirror 16 and the light intensity thereof is measured.
Generally, the collimator 12, the half mirror 13, the optical resonator 14, the first photo diode 15, the reflection mirror 16, and the second photo diode 1 that constitute the wavelength management module 11 are included.
7 and the like are fixed to a board or a housing that collectively accommodates them.

The optical resonator 14 has two substrates whose inner surfaces have a predetermined reflectance, and sandwiches a medium such as an air layer between them.
They are arranged so as to face each other at a predetermined interval (gap length), and the light transmittance has wavelength dependency. The optical resonator 14 is
For example, it has a wavelength-transmittance characteristic close to a sine wave as shown in FIG. 6, and if the wavelength of the monitor signal light incident on the optical resonator 14 is constant (for example, λ11), the first light The transmitted light intensity measured by the diode 15 is constant. On the other hand, when the wavelength of the monitor signal light changes, the transmittance of the optical resonator 14 changes, and therefore the transmitted light intensity measured by the first photodiode 15 changes.

The intensity of the light emitted from the LD light source 1 may change with time. In this case, the intensity of the transmitted light measured by the first photodiode 15 is constant even if the wavelength of the emitted light is constant. Will change. This is measured by the first photodiode 15, because the value of the reflected light intensity of the half mirror 13 measured by the second photodiode 17 changes according to the change of the emitted light intensity of the LD light source 1. By using the value of the light intensity and the value of the light intensity measured by the second photodiode 17 to perform a calculation process so that the change amount of the transmitted light intensity due to the change of the emitted light intensity is offset, It is possible to obtain the amount of change in the transmitted light intensity due to the change in the wavelength of the emitted light. Then, the change over time of the transmitted light intensity after this arithmetic processing is monitored, and if there is a change, the wavelength of the emitted light should be restored to the original, that is, the transmitted light after the arithmetic processing. L so that the amount of change in intensity is zero
The temperature of the thermoelectric element of the D light source 1 or the LD introduction current is controlled. In the figure, reference numeral 5 indicates a computing device, and 6 indicates a control device. Reference numeral 18 in the figure is a temperature sensor, which is provided as necessary. The temperature sensor 18 detects a temperature change in the optical resonator 14 and is provided with a circuit (not shown) for performing temperature compensation based on the detection result.

[0006]

However, since the optical resonator 14 is required to have a high processing accuracy for its fabrication, it has a problem that it is difficult to mass-produce and the cost becomes high. In addition, since a plurality of wavelengths are used in the WDM system, it is required to perform wavelength management so as to eliminate wavelength fluctuation (drift) for each used wavelength.
Since the optical resonator 14 has a wavelength-transmittance characteristic close to a sine wave as shown in FIG. 6, for example, a wavelength management device using this theoretically has a plurality of wavelength bands over a wide band without changing the configuration. Wavelength used (eg λ11, λ12, λ13, λ14)
It is possible to apply to the wavelength management of. However, since the transmission characteristics of the optical resonator 14 are likely to change due to a slight difference in the structure of the optical resonator 14 or a minute deviation of the incident angle, the applicable usable wavelength band is actually limited. .

The present invention has been made in view of the above circumstances, and provides a wavelength management device which is easy to manufacture and can be mass-produced, and further, a wavelength management device which can easily cope with a wide band of used wavelengths. The purpose is to provide.

[0008]

In order to solve the above-mentioned problems, a wavelength management device of the present invention is a wavelength management device for controlling the oscillation wavelength of a light source so as to keep it at a preset use wavelength, and the transmittance And an optical wavelength filter whose reflectance has wavelength dependence, an incidence unit that causes the optical wavelength filter oscillated from the light source to enter into the optical wavelength filter as parallel light, and receives the transmitted light of the optical wavelength filter. Measuring means for outputting a first electric signal P1 corresponding to the light intensity, and a second electric signal P2 corresponding to the light intensity for receiving the reflected light of the optical wavelength filter. Second measuring means for controlling, first output adjusting means for electrically increasing or decreasing the first electric signal P1 while maintaining sensitivity to light intensity, and the second electric signal P2. The sensitivity to light intensity Second output adjusting means capable of increasing or decreasing electrically while maintaining, a first electric signal P1 ′ output from the first output adjusting means, and output from the second output adjusting means. Second electrical signal P
2'is input, (P1'-P2 ') / (P1 + P2)
And a calculation means for calculating the value of.

In the wavelength control device having such a configuration, the optical wavelength filter used as the wavelength selecting means is easier to manufacture and can be mass-produced as compared with the optical resonator, so that the wavelength control device is easy to manufacture and the manufacturing cost is high. Will also be cheaper. Also, a first measuring means for measuring the transmitted light intensity of the optical wavelength filter,
Second measuring means for measuring the reflected light intensity of the optical wavelength filter, and the first electrical signal P1 and the second electrical signal P2 output from these measuring means are
It is possible to electrically increase or decrease the sensitivity to the light intensity while maintaining the sensitivity to the light intensity by the first output adjusting means and the second output adjusting means, respectively, so that the transmitted light intensity of the optical wavelength filter may be changed depending on different wavelengths used. And even if the reflected light intensity changes, (P1′-P
2 ′) / (P1 + P2) can be adjusted to have the same value. As a result, for a plurality of used wavelengths, it is possible to perform wavelength management by simply operating the output adjusting means for each wavelength and using the wavelength management device having the same configuration, without changing the set values for control and the like. In the present specification, electrically increasing or decreasing while maintaining the sensitivity to the light intensity means P1 ′ = a · P
1, P2 ′ = b · P2, such as electrical signal (P
1, P2) is multiplied by a predetermined coefficient to perform conversion in a proportional function.

In the present invention, the electrical signals P1 and P2 output as a result of measuring the light intensity of the transmitted light and the reflected light of the optical wavelength filter are (P1) after the output is adjusted if necessary. Since the calculation processing of “−P2”) / (P1 + P2) is performed, it is possible to detect the wavelength change of the incident light to the optical wavelength filter by monitoring the change with time of the calculation result. By using the result of such arithmetic processing, the light with respect to the wavelength change of the incident light to the optical wavelength filter is compared with the case where the wavelength management is performed based on the measurement result of either the transmitted light intensity or the reflected light intensity. The sensitivity of intensity change can be improved. When the intensity of the light emitted from the light source drifts over time, the first electrical signal P1 and the second electrical signal P2 are generated.
Both of them change according to the change amount of the emitted light intensity of the LD light source 1. Therefore, by performing the arithmetic processing of (P1′−P2 ′) / (P1 + P2), the emitted light intensity of the LD light source 1 drifts. The change in light intensity is offset. Therefore, a value representing the change in the transmitted light intensity and the reflected light intensity of the optical wavelength filter due to the change in the wavelength of the emitted light of the LD light source 1 (also referred to as the light intensity change value in this specification) is accurately detected, and the wavelength management is performed. The accuracy of is improved. In the present invention, the arithmetic processing method by the arithmetic means can detect a change in the light intensity due to a change in the wavelength of the incident light to the optical wavelength filter, and cancel out the amount of change in the light intensity due to the drift of the intensity of the emitted light. Method, but especially (P1 '
A method of obtaining −P2 ′) / (P1 + P2) is preferable.

In the present invention, the first output adjusting means and the second output adjusting means may be arranged such that when the wavelength of the monitor optical signal incident on the optical wavelength filter is the working wavelength. The first output from the output adjusting means
It is preferable that the electric signal P1 'and the second electric signal P2' output from the second output adjusting means are set to be equal to each other.

According to this structure, P1 '= P2' holds whenever the wavelength of the light incident on the optical wavelength filter is the used wavelength, even if the used wavelengths are different. Therefore, (P1'-P2 ') / (P1 + P2) The value of the result of) becomes zero. Therefore, if the oscillation wavelength of the light source is controlled so that the calculation result in the calculation means becomes zero, the oscillation wavelength can be maintained at the used wavelength, and the setting for wavelength control is simple.

Further, in the wavelength control device of the present invention, it is preferable to provide a correction means capable of converting the sign of the time-dependent change value of the calculation result of (P1'-P2 ') / (P1 + P2) into an opposite sign.

In the wavelength control device of the present invention, the wavelength used is on the long wavelength side of the peak wavelength at which the transmittance (or reflectance) of the optical wavelength filter reaches a peak, and on the short wavelength side. The sign of the change value over time of the calculation result of (P1′−P2 ′) / (P1 + P2) is opposite to the change over time of the light source light wavelength. Therefore, if the above correction means is provided, for example, the used wavelength is on the short wavelength side (or the long wavelength side).
If the wavelength used is on the long wavelength side (or the short wavelength side), the same device configuration and the same setting can be obtained by simply converting the sign of the change value with time of the calculation result to the opposite sign by the correction means. It becomes possible to manage wavelengths.

Further, the wavelength control device of the present invention may be provided with an amplifying means capable of amplifying a time-dependent change value of the calculation result of (P1'-P2 ') / (P1 + P2). According to this configuration, the full width at half maximum (FWHM) in the mountain distribution showing the transmission characteristics of the optical wavelength filter is wide,
Even if the change in the transmitted light intensity with respect to the wavelength change is relatively small and the sensitivity is low, it is possible to compensate for this and obtain good sensitivity in wavelength management. This makes it possible to perform highly sensitive wavelength management using an optical wavelength filter having a wide full width at half maximum (FWHM). The wider the full width at half maximum of the optical wavelength filter that constitutes the wavelength management device, the more the wavelengths can be managed by the wavelength management device having the same configuration for a plurality of used wavelengths over a wider band. Further, the dielectric multilayer filter having a wide full width at half maximum has a smaller number of laminated dielectric films than the conventional general bandpass filter, and can be manufactured at low cost.

In the wavelength control device of the present invention, when the transmission characteristics of the optical wavelength filter are represented by a graph in which the horizontal axis represents wavelength and the vertical axis represents transmittance or reflectance, a peak distribution with a full width at half maximum of 2 nm or more is obtained. It is preferable to use the optical wavelength filter shown. Thus, by configuring the wavelength management device of the present invention using the optical wavelength filter having a relatively wide full width at half maximum, for a plurality of used wavelengths over a wide band,
Wavelength management can be performed by wavelength management devices having the same configuration.

Further, the wavelength management device of the present invention is suitable for constructing a wavelength management system for controlling the oscillation wavelengths of a plurality of light sources so as to maintain the respective used wavelengths. The wavelength management system of the present invention comprises the wavelength management device of the present invention, a plurality of light sources having different oscillation wavelengths, and a plurality of monitoring optical signals respectively oscillated from the plurality of light sources, one by one for the incident means. Switching means for making the light incident on
A unit for changing the adjustment amount of the electrical signal in the first output adjusting unit and the second output adjusting unit in synchronization with the switching of the monitoring optical signal incident on the incident unit; (P1'-P2 ') /
The control means for outputting an electric signal for controlling the light source so that the value of (P1 + P2) becomes a preset value, and the monitoring optical signal incident on the incidence means are switched in synchronization with the switching. It is characterized by comprising means for switching the light source to which the electric signal from the control means is inputted.

According to the wavelength management system having such a configuration,
A single wavelength management device of the present invention can perform wavelength management of a plurality of used wavelengths. Since this wavelength management device is easy to manufacture and can be mass-produced, a wavelength management system for a plurality of used wavelengths can be constructed at low cost.

Alternatively, in the wavelength control device of the present invention, an optical wavelength filter whose transmittance and reflectance have wavelength dependence, and a monitoring optical signal oscillated from the light source are incident on the optical wavelength filter as parallel light. Incident means for making, the measuring means for receiving either one of the transmitted light or the reflected light of the optical wavelength filter and outputting an electric signal according to the light intensity, and an electric signal outputted from the measuring means It is also possible to adopt a configuration provided with an amplifying means for amplifying the time-dependent change value of.

With such a configuration, the measuring means may be provided so as to receive either the transmitted light or the reflected light, and neither the output adjusting means nor the calculating means is required, so that the wavelength can be adjusted with a simple device configuration. It is possible to manage. In addition, the transmitted light (or reflected light) with respect to the wavelength change by the amplification means
It is possible to amplify the sensitivity of the intensity change of. Therefore, even if the graph showing the transmission characteristics of the optical wavelength filter shows a relatively broad mountain-shaped distribution and the change in the transmitted light intensity with respect to the wavelength change is relatively small and the sensitivity is low, this is compensated for and good wavelength management is achieved. Sensitivity can be obtained.

Further, in the wavelength control device of the present invention, it is preferable to provide a correction means capable of converting the sign of the temporal change value of the electric signal output from the measuring means into an opposite sign.

In the wavelength control device of the present invention, the wavelength used is on the long wavelength side of the peak wavelength at which the transmittance (or reflectance) of the optical wavelength filter reaches a peak, and on the short wavelength side. The sign of the temporal change value of the electric signal output from the measuring means is opposite to the temporal change of the light source light wavelength. Therefore, if the correction means is provided, for example, when the used wavelength is on the short wavelength side (or the long wavelength side), the correction means converts the sign of the time-dependent change value of the electrical signal to the opposite sign, It is possible to perform wavelength management with the same device configuration and the same settings as when the wavelength is on the long wavelength side (or the short wavelength side).

In the wavelength control device of the present invention, when the transmission characteristics of the optical wavelength filter are represented by a graph in which the horizontal axis represents wavelength and the vertical axis represents transmittance or reflectance, the full width at half maximum is 2 nm or more in a mountain distribution. Is preferably used. As described above, by configuring the wavelength management device of the present invention using the optical wavelength filter having a relatively wide full width at half maximum, wavelength management can be performed by a wavelength management device having the same configuration for a plurality of used wavelengths over a wide band. .

Further, the wavelength management device of the present invention is suitable for constructing a wavelength management system using this to control the oscillation wavelengths of a plurality of light sources so as to maintain their respective used wavelengths. The wavelength management system of the present invention comprises the wavelength management device of the present invention, a plurality of light sources having different oscillation wavelengths, and a plurality of monitoring optical signals respectively oscillated from the plurality of light sources, one by one for the incident means. Switching means for making the light incident on
Control means for outputting an electric signal for controlling the light source so that the value of the electric signal output from the measuring means becomes a preset value; and the monitor optical signal incident on the incident means. In synchronism with the switching, a means for switching the light source to which the electric signal from the control means is input is provided. According to the wavelength management system having such a configuration, one wavelength management device having a simpler device configuration can perform wavelength management of a plurality of used wavelengths.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
FIG. 1 shows a first embodiment of a wavelength management device of the present invention. In FIG. 1, the same components as those in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted. In this embodiment, the light emitted from the LD light source 1 is reflected by the optical coupler 2.
Branched into two. With this optical coupler 2, for example, 95% of the emitted light is output as the signal light S, and the remaining 5% is used as the monitoring optical signal M for wavelength management. The monitor optical signal M is collimated by the collimator (incident means) 22 and then incident on the optical wavelength filter 24. Then, the transmitted light intensity of the optical wavelength filter 24 is measured by the first photodiode (first measuring means) 25, and the optical wavelength filter 2
The reflected light intensity of No. 4 is measured by the second photodiode (second measuring means) 27. In the present embodiment, the collimator 22, the optical wavelength filter 24, the first photodiode 2
5, and the second photodiode 27 are collectively housed in a housing (not shown). In addition, a temperature sensor may be provided in the housing as needed.

The light wavelength filter 24 has a characteristic of transmitting a part or all of incident light and reflecting the rest, and the transmittance and the reflectance have wavelength dependence. The transmission characteristics of the optical wavelength filter 24, when represented by a graph in which the horizontal axis represents wavelength and the vertical axis represents transmittance, show a relatively broad mountain-shaped distribution as shown in FIG. The peak wavelength λp and the full width at half maximum (FWHM) in this chevron distribution is preferably set such that a plurality of wavelengths to be wavelength-controlled are included in this chevron distribution. However, the peak wavelength λp and the used wavelength should not match. Here, the full width at half maximum (FWHM) refers to the width (wavelength interval) between points at which the transmittance is 1/2 (Tp / 2) of the peak value Tp in the mountain distribution.

The full width at half maximum (FWHM) in the mountain distribution showing the transmission characteristics of the light wavelength filter 24 is preferably 2 nm or more, more preferably 5 nm or more.
The wider the full width at half maximum of the optical wavelength filter 24, the more the wavelength management devices of the same configuration can perform wavelength management for a plurality of used wavelengths over a wider band. A dielectric multilayer filter is preferably used as the optical wavelength filter 24 having such characteristics. In the case of the dielectric multilayer filter, the peak wavelength λp and the full width at half maximum (FWHM) can be changed by changing the material of the dielectric film, the number of laminated layers, the film thickness, and the like.
Can be controlled.

The first photodiode 25 receives the transmitted light of the optical wavelength filter 24 and outputs the first electrical signal P1 corresponding to the light intensity thereof, and the second photodiode 27 is the optical wavelength filter. The reflected light of 24 is received and the electrical signal P2 according to the light intensity is output. Further, in the subsequent stage of the first photodiode 25 and the subsequent stage of the second photodiode 27,
A first output adjusting means 31 and a second output adjusting means 32 are provided respectively, so that the first electric signal P1 and the second electric signal P2 can be electrically increased or decreased respectively. ing.

First and second output adjusting means 31, 32
Has a function of electrically increasing or decreasing an electrical signal. In the present embodiment, each of the operational amplifiers (operation
amplifiers 31a, 32a and variable resistors 31b, 32b connected in parallel with the amplifiers 31a, 32a. The first output adjusting means 31 is connected to the output terminal of the first photodiode 25, and the second output adjusting means 32 is connected to the output terminal of the second photodiode 27, respectively.
Variable resistance 3 of the first and second output adjusting means 31, 32
Variable resistors whose resistance values can be controlled are used as 1b and 32b. By adjusting the resistance values of the variable resistors 31b and 32b, the first electrical signal P1 output from the first photodiode 25 is obtained. And the second photodiode 2
The electrical signal P2 output from 7 can be electrically increased or decreased. In the present specification, the first and second electric signals P1 and P2 are respectively signals output from the first and second output adjusting means 31 and 32, respectively.
Described as 1 ', P2'.

Adjustment amounts (P1 and P1 ') of the output adjustment in the first output adjusting means 31 and the second output adjusting means 32.
And the difference between P2 and P2 ') is the monitor optical signal M
P1 '= P when the wavelength of
Initially set to 2 '. When performing wavelength management for a certain used wavelength, P1 and / or P2 are always increased / decreased by the initially set adjustment amount. It is preferable that the resistance values of the variable resistors 31b and 32b in the output adjusting means 31 and 32 can be adjusted with an accuracy of about 0.01 kΩ in the range of 1 kΩ to 100 kΩ.

The outputs P1 'and P2' from the first output adjusting means 31 and the second output adjusting means 32, respectively, are input to the first arithmetic unit 35, where (P1'-P
The value of 2 ') is calculated. Further, the second arithmetic unit 37 receives the first electric signal P1 and the second electric signal P2 output from the first photodiode 25 and the second photodiode 27, respectively, where ( P1 + P
The value of 2) is calculated. Then, the calculation result in the first calculation device 35 and the calculation result in the second calculation device 37 are input to the third calculation device 38, where (P1′−
The value of (P2 ') / (P1 + P2) is calculated. This third
The time-dependent change value of the calculation result in the calculation device 38 corresponds to the light intensity change value corresponding to the wavelength shift of the monitoring optical signal M.

For example, in the present embodiment, when the transmission characteristic of the optical wavelength filter 24 is represented by the graph shown in FIG. 2, the electrical signal P1 output from the first photodiode 25 and the second photodiode 27 are output. The relationship with the electrical signal P2 output from the device is shown in FIG.
The sum of 2 is always the magnitude of the electrical signal corresponding to the transmitted light intensity at the peak wavelength λp. In this example, the wavelength of the monitoring optical signal M incident on the optical wavelength filter 24 is λ3.
, P1 = 50 μA and P2 = 50 μA, and when the wavelength of the monitoring optical signal M is λ4, P1 = 40 μA,
P2 = 60 μA. Therefore, the adjustment amount of the output adjustment in the first output adjusting means 31 and the second output adjusting means 32 (the difference between P1 and P1 ′, the difference between P2 and P2 ′).
P1 '= P2' = (P1 + P2) / 2 = 50 when the wavelength of the monitoring optical signal M matches the wavelength used.
It is preferable to perform the initial setting so that it becomes μA. In this example, assuming that the wavelength used is λ4, P1 is always (50 μA / 40 μ) in the first output adjusting means 31.
A) Electrical adjustment is performed to increase the value by a factor of 2, and P2 is always (50 μA / 60 μ) in the second output adjusting means 32.
A) Initialization is performed to make an electrical adjustment that reduces by a factor of two. The relationship between the outputs P1 'and P2' from the first output adjusting means 31 and the second output adjusting means 32 in the state thus initialized is shown in FIG. 3 (b). Then, it is output from the third arithmetic unit 38 (P
The value of 1′−P2 ′) / (P1 + P2) has a wavelength dependency as shown in FIG. 3C with respect to the wavelength of the monitoring optical signal M. This (P1'-P2 ') / (P1 +
The wavelength dependence of P2) has higher sensitivity than the wavelength dependence of P1 ′ and P2 ′, and the light intensity change value when the wavelength changes is apparently large.

Therefore, in this example, if the wavelength of the monitoring optical signal M incident on the optical wavelength filter 24 is equal to the used wavelength λ4, as shown in FIG. Output from the arithmetic unit 38 (P1'-P
The value of 2 ′) / (P1 + P2) becomes zero, and when the wavelength of the monitor optical signal M deviates from the used wavelength (λ4) to the long wavelength side with time, (P1′−P2 ′) / (P1 + P2)
Value changes from zero to the minus (-) direction and deviates from the used wavelength (λ4) to the short wavelength side (P1'-P
The value of 2 ′) / (P1 + P2) changes from zero to the plus (+) direction with time. Therefore, (P1'-P2 ') /
The oscillation wavelength of the LD light source 1 is controlled by controlling the temperature of the thermoelectric element of the LD light source 1 or the LD introduction current by the control device 6 so that the change value of the calculation result of (P1 + P2) with time becomes zero. can be held at λ4).

In the present embodiment, the above (P
There is provided an amplifying means for amplifying the time-dependent change value of the calculation result of 1'-P2 ') / (P1 + P2). Specifically, the operational amplifier 3 that performs the arithmetic processing of (P1'-P2 ')
A variable resistor 35b is provided in parallel with 5a. By adjusting the resistance value of the variable resistor 31b, the value of (P1'-P2 ') can be amplified, whereby (P1'-P2') / (P1 +).
The time-dependent change value of the calculation result of P2) is amplified. Therefore, the light intensity change value when the wavelength changes, that is, the change value of the above calculation result over time, apparently becomes larger, and therefore the sensitivity in wavelength management is further improved.
Response characteristics are further improved. In the present embodiment, (P
The amplification amount for amplifying the value of 1'-P2 ') can be adjusted by the resistance value of the variable resistor 35b, and is initially set so that the gain has a desired response speed. Then, when wavelength management is performed for a certain used wavelength, amplification of (P1′−P2 ′) is always performed with the initially set size. The resistance value of the variable resistor 35b used here is
It is preferable that it can be adjusted with an accuracy of about 0.01 kΩ in the range of 1 kΩ to 100 kΩ.

According to the present embodiment, the wavelength management device can be constructed by using the optical wavelength filter 24 having transmittance and reflectance wavelength dependency in a relatively wide wavelength band as the wavelength selection means. Then, for example, as shown in FIG. 2, within the wavelength range forming the mountain distribution in the graph showing the transmission characteristics of the optical wavelength filter 24, the wavelength λ3 at which the transmitted light intensity P1 and the reflected light intensity P2 are equal is used wavelength. Or the transmitted light intensity P1 and the reflected light intensity P2 are not equal to each other, for example, λ1, λ2,
Even when λ4 or the like is set as the used wavelength, wavelength management can be performed without changing the configuration of the wavelength management device. Further, since the optical wavelength filter 24 is used as the wavelength selecting means, the device can be manufactured easily and the manufacturing cost can be reduced as compared with the case where the optical resonator is used. In addition, since there is no limitation on the wavelength interval for which wavelengths can be managed, it is easy to support a wide band and has high versatility.
Further, as the optical wavelength filter 24 in the present embodiment, a dielectric multi-layer film filter having a wider full width at half maximum than that of the conventional band pass filter can be preferably used, and therefore, the dielectric film filter of the conventional band pass filter can be used. The number of layers is small and the cost is low.

When the intensity of emitted light from the light source drifts with time, both the first electrical signal P1 and the second electrical signal P2 become changes in the intensity of emitted light from the LD light source 1. Since (P1'-P2 ') / (P1
By performing the calculation process of + P2), the change in the light intensity due to the drift of the emitted light intensity of the LD light source 1 is offset. Therefore, the light intensity change value due to the wavelength change of the emitted light of the LD light source 1 is accurately detected, and the accuracy of wavelength management is improved.

Further, since the value of (P1'-P2 ') is amplified, the graph showing the transmission characteristics of the optical wavelength filter 24 is relatively broad, as shown in FIG. Even when the distribution is shown, that is, even when the change of the transmitted light intensity with respect to the wavelength change is relatively small and the sensitivity is low, it is possible to compensate for this and obtain good sensitivity in wavelength management.

FIG. 4 is a schematic configuration diagram showing a second embodiment of the wavelength management device of the present invention. The wavelength management device of this embodiment is different from that of the first embodiment in that the correction means 3
6 is provided. 4, the same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.
In the present embodiment, when the used wavelength is on the shorter wavelength side than the peak wavelength of the optical wavelength filter 24 (for example, λ0 in FIG. 2), the correction unit 36 (P1′−P2 ′) in the third arithmetic unit 38. The sign of the temporal change value of the calculation result of / (P1 + P2) is electrically inverted and corrected and output to the control device 6. The time-dependent change value of the calculation result is, for example, (P1′−P2 ′) at time t1.
It is obtained by taking the difference between the value of the operation result of / (P1 + P2) and the value of the operation result of (P1'-P2 ') / (P1 + P2) at time t2. The correction means 36
May be included in the third arithmetic device 38 or the control device 6, or may be provided as a device separate from these.

According to this embodiment, the same effect as that of the first embodiment can be obtained, and in the mountain distribution showing the transmission characteristics of the optical wavelength filter 24, the used wavelength is on the short wavelength side of the peak wavelength (λp). And the third computing means 38
The wavelength management can be performed with the same device configuration and the same settings as when the used wavelength is on the long wavelength side of the peak wavelength (λp), only by inverting and correcting the sign of the change value with time of the calculation result in the above. Therefore, it is possible to obtain a wavelength management device suitable for supporting multiple wavelengths in a wider band.

For example, in the conventional wavelength management device using a bandpass filter having a full width at half maximum (FWHM) of about 1 nm, the wavelength management device of the same configuration can handle only one wavelength in use. In the wavelength management device of the present embodiment including the correction means 36, the optical wavelength filter 2
If a dielectric multilayer filter having a full width at half maximum (FWHM) of 10 nm is used as 4, the wavelength controllable band is 20 to 3
0-7, wavelength interval 0.4-0.8 nm 20-7
With respect to the used wavelength of 0 wavelength, it becomes possible to perform wavelength management with the wavelength management device having the same configuration. If the full width at half maximum of the optical wavelength filter 24 is 2 nm or more, wavelength management can be performed by the wavelength management device having the same configuration for at least four wavelengths having a wavelength interval of 0.4 nm. Further, for example, the dielectric multilayer filter having a full width at half maximum of 10 nm has a smaller number of laminated dielectric films, which is 2/3, than the bandpass filter including the conventional dielectric multilayer filter having a full width at half maximum of about 1 nm. There is also an advantage that it can be manufactured at low cost.

When the oscillation wavelength of the LD light source 1 deviates from the used wavelength, the correction means 36 determines the direction of the deviation (deviation toward the long wavelength side or deviation toward the short wavelength side) and the third arithmetic unit. As long as the relationship between the calculation result of (P1′-P2 ′) / (P1 + P2) in 38 and the sign of the change value over time can be made the same on the long wavelength side and the short wavelength side of the peak wavelength (λp). Good. Therefore, in the present embodiment, for example, only when the used wavelength is on the shorter wavelength side than the peak wavelength of the optical wavelength filter 24, the sign of the change value over time of the calculation result of the third calculation device 38 is inverted and corrected. However, even if the wavelength used is on the longer wavelength side than the peak wavelength of the optical wavelength filter 24, the sign of the change value with time of the calculation result of the third calculation device 38 may be inverted and corrected. Good.

Next, a third embodiment of the present invention will be described. In each of the above-described embodiments, the light intensity of both the transmitted light and the reflected light of the optical wavelength filter 24 is measured, and (P1 ′)
Although the deviation of the oscillation wavelength of the light source 1 is detected by the change of the calculation processing result of −P2 ′) / (P1 + P2), only the light intensity of either the transmitted light or the reflected light of the optical wavelength filter 24 is detected. It is also possible to have a configuration for measuring In the present embodiment, the first photodiode 25 serves as a detection unit that detects the light intensity change value of the transmitted light of the light wavelength filter 24.
In addition to the above, on the line for inputting the output from the first photo diode 25 to the control means 6, an amplifying means for electrically amplifying the temporal change value of the measurement result of the first photo diode 25 is provided. The second photodiode 27 that receives the reflected light of the optical wavelength filter 24 is not provided. Alternatively,
A second photodiode 27 is provided as a detecting means for detecting the light intensity change value of the reflected light of the optical wavelength filter 24, and the second photodiode 27 is provided on the line for inputting the output from the second photodiode 27 to the control means 6. A configuration may be adopted in which an amplifying means for electrically amplifying the time-dependent change value of the measurement result of the photodiode 27 is provided, and the first photodiode 25 for receiving the transmitted light of the optical wavelength filter 24 is not provided.

According to such a configuration, the accuracy is inferior to the configuration in which the light intensity of both the transmitted light and the reflected light of the optical wavelength filter 24 is measured and the difference is obtained, but wavelength management is possible with a simple device configuration. It is possible to do. Further, since the amplification means is provided, the sensitivity of the intensity change of the transmitted light (or the reflected light) to the wavelength change can be amplified.
Therefore, the graph showing the transmission characteristic of the optical wavelength filter 24 shows a relatively broad mountain-shaped distribution, and even if the change in the transmitted light intensity with respect to the wavelength change is relatively small and the sensitivity is low, this is compensated for and good wavelength management is achieved. It is possible to obtain high sensitivity.

Also in this embodiment, a correction means can be provided as in the second embodiment. By providing the correction means, wavelength management can be performed by the wavelength management device having the same configuration on both the long wavelength side and the short wavelength side of the peak wavelength (λp) in the mountain distribution showing the transmission characteristics of the optical wavelength filter 24. Therefore, it is possible to obtain a wavelength management device suitable for supporting multiple wavelengths in a wider band.

FIG. 7 is a schematic configuration diagram of a wavelength management system showing an example in which the wavelength management device of the first embodiment is applied to wavelength management of a plurality of used wavelengths. In this example,
The emitted light from the first to fourth LD light sources 1a to 1d is the first to fourth
The optical couplers 2a to 2d split the light into two. By the first to fourth optical couplers 2a to 2d, for example, 95% of the light emitted from the first to fourth LD light sources 1a to 1d are output as the first to fourth signal lights S1 to S4, respectively.
The remaining 5% is the first to fourth monitor optical signals M1 respectively.
Used for wavelength management as M4. Reference numeral 41 in the figure represents an optical multiplexer. First to fourth monitor optical signals M1
~ M4 is an optical switch (switching means) via an optical fiber
42, from which the first to fourth monitoring optical signals M1 to M4 are sequentially emitted to collimator (incident means) 2
2 is incident. Although not shown, initial setting values in the first and second output adjusting means 31 and 32 are adjusted in accordance with the timing at which the first to fourth monitoring optical signals M1 to M4 emitted from the optical switch 42 are switched, And a means for switching the initial setting value of the variable resistor 35b of the amplifying means to an appropriate value according to the used wavelength of each of the LD light sources 1a to 1d, and a control signal (electrical signal from the control circuit 6 ) Is switched to any of the first to fourth LD light sources 1a to 1d, and a means for appropriately feeding back the light source is provided.

According to the wavelength management system having such a configuration,
A single wavelength management device of the first embodiment can perform wavelength management of a plurality of used wavelengths. Since this wavelength management device is easy to manufacture and can be mass-produced, a wavelength management system for a plurality of used wavelengths can be constructed at low cost.
Further, in synchronization with the switching of the monitor optical signals M1 to M4, the initial setting values of the first and second output adjusting means 31 and 32, the initial setting value of the variable resistor 35b of the amplifying means,
The output destination of the control signal from the control circuit 6 may be switched, and wavelength management of a plurality of used wavelengths can be performed without changing other settings. Therefore, it is possible to easily respond to changes in the wavelength used,
It is easy to deal with further increase in wavelength and wider band.

[0047]

As described above, according to the present invention,
By using an optical wavelength filter that is relatively inexpensive and can be mass-produced, it is possible to obtain a wavelength management device that can support multiple wavelengths and can easily support a wide band of used wavelengths. Therefore, it is possible to easily manufacture an accurate wavelength management device capable of handling multiple wavelengths, and the manufacturing cost is also low.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a wavelength management device of the present invention.

FIG. 2 is a graph showing an example of transmission characteristics of an optical wavelength filter according to the present invention.

FIG. 3 shows the wavelength dependence of an electrical signal corresponding to the transmitted light intensity and the reflected light intensity of the optical wavelength filter according to the present invention, (a) is a graph showing the wavelength dependence of P1 and P2 respectively. Yes, (b) is a graph showing wavelength dependence of each of P1 ′ and P2 ′, and (c) is (P
It is a graph which shows the wavelength dependence of the value of the calculation result of 1'-P2 ') / (P1 + P2).

FIG. 4 is a schematic configuration diagram showing a second embodiment of the wavelength management device of the present invention.

FIG. 5 is a schematic configuration diagram showing an example of a conventional wavelength management device.

FIG. 6 is a graph showing transmission characteristics of an optical resonator according to a conventional example.

FIG. 7 is a schematic configuration diagram showing an embodiment of a wavelength management system of the present invention.

[Explanation of symbols]

1, 1a, 1b, 1c, 1d ... Light source, 6 ... Control device, 2
2 ... Collimator (incident means), 24 ... Optical wavelength filter,
25 ... 1st photo diode (1st measurement means), 27 ...
2nd photo diode (2nd measurement means), 31 ... 1st output adjustment means, 32 ... 2nd output adjustment means, 35 ... 1st
Arithmetic unit, 35a ... operational amplifier, 35b ... variable resistor,
36 ... Correction means, 37 ... Second arithmetic device, 38 ... Third arithmetic device, 42 ... Optical switch (switching means).

Claims (10)

[Claims] 1. A wavelength management device for controlling an oscillation wavelength of a light source so as to keep it at a preset use wavelength, the optical wavelength filter having transmittance and reflectance having wavelength dependence, and the optical wavelength filter. An incident means for injecting the monitor optical signal oscillated from the light source as parallel light; and a first electric signal P1 for receiving the transmitted light of the optical wavelength filter and outputting a first electric signal P1 corresponding to the light intensity. The second measuring means for receiving the reflected light of the optical wavelength filter and outputting the second electric signal P2 corresponding to the light intensity thereof, and the first electric signal P1 for A first output adjusting means capable of electrically increasing or decreasing while maintaining sensitivity to intensity; and a first output adjusting means capable of electrically increasing or decreasing the second electrical signal P2 while maintaining sensitivity to light intensity. 2 output adjusting means The first first electrical signal P1 output from the output adjustment means ', and the second electrical signal P2 outputted from the second output adjustment means' is input, (P1'-P
2 ′) / (P1 + P2) value calculating means for calculating the value. 2. The first output adjusting means and the second output adjusting means output the first output when the wavelength of the monitor optical signal incident on the optical wavelength filter is the use wavelength. The first electrical signal P1 'output from the adjusting means and the second electrical signal P2' output from the second output adjusting means are set to be equal to each other. 1. The wavelength management device according to 1. 3. The (P1′-P2 ′) / (P1
3. The wavelength management device according to claim 1, further comprising a correction unit capable of converting the sign of the temporal change value of the calculation result of + P2) into an opposite sign. 4. The (P1′-P2 ′) / (P1 + P2)
4. The wavelength control device according to claim 1, further comprising an amplifying unit capable of amplifying the temporal change value of the calculation result of <1>. 5. A transmission characteristic of the optical wavelength filter,
The wavelength management device according to any one of claims 1 to 4, wherein the wavelength management device has a mountain-shaped distribution having a full width at half maximum of 2 nm or more when represented by a graph in which the horizontal axis represents wavelength and the vertical axis represents transmittance or reflectance. 6. A wavelength management system for controlling the oscillation wavelengths of a plurality of light sources so as to maintain the respective use wavelengths by using the wavelength management device according to claim 1, wherein the oscillation wavelengths are different. A plurality of light sources, a switching means for sequentially inputting a plurality of monitoring optical signals respectively oscillated from the plurality of light sources to the incidence means, and switching of the monitoring optical signals incident on the incidence means In synchronization with the means for changing the adjustment amount of the electric signal in the first output adjusting means and the second output adjusting means, and (P1'-P2 ') / (P1 + P in the calculating means.
The control means for outputting an electric signal for controlling the light source so that the value of 2) becomes a preset value, and the control in synchronization with the switching of the monitor optical signal incident on the incident means. A wavelength management system comprising means for switching a light source to which an electric signal from the means is input. 7. A wavelength management device for controlling the oscillation wavelength of a light source so as to keep it at a preset operating wavelength, wherein the optical wavelength filter has transmittance and reflectance having wavelength dependence, and the optical wavelength filter includes: An incident means for injecting the monitor optical signal oscillated from the light source as parallel light, and one of the transmitted light and the reflected light of the optical wavelength filter is received to generate an electrical signal corresponding to the light intensity. A wavelength management device comprising: a measuring unit for outputting and an amplifying unit for amplifying a temporal change value of an electric signal output from the measuring unit. 8. The wavelength management apparatus according to claim 7, further comprising a correction unit capable of converting the sign of the temporal change value of the electric signal output from the measuring unit into an opposite sign. 9. A transmission characteristic of the optical wavelength filter,
The wavelength management device according to claim 7 or 8, wherein the wavelength management device has a mountain-shaped distribution having a full width at half maximum of 2 nm or more when represented by a graph in which the horizontal axis represents wavelength and the vertical axis represents transmittance or reflectance. 10. A wavelength management system for controlling the oscillation wavelengths of a plurality of light sources so as to maintain respective operating wavelengths by using the wavelength management device according to claim 7, wherein the oscillation wavelengths are different. A plurality of light sources, a switching unit for sequentially inputting a plurality of monitoring optical signals respectively oscillated from the plurality of light sources to the incidence unit, and a value of an electrical signal output from the measurement unit are set in advance. A control unit that outputs an electric signal that controls the light source so as to have a set value, and an electric signal from the control unit in synchronization with switching of the monitoring optical signal that is incident on the incident unit. A wavelength management system, comprising means for switching a light source to which is input.