JPH10313146A - Wavelength variable light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wavelength variable light source device which is capable of outputting a laser beam that is kept constant in laser ray intensity over a wide range of wavelength. SOLUTION: A wavelength variable light source 1 capable of outputting laser rays is provided, a branch plate 3 which branches incident light into output light and reference light at a prescribed branching ratio corresponding to the polarization angle of the incident light, and a polarizing plate 2a which transmits only the certain polarized light component of laser rays that is obtained in the prescribed branching ratio through the branch plate 3 is provided onto an optical path between the wavelength variable light source 1 and the branch plate 3. A photodetector 4 detects reference light sent from the branch plate 3 and outputs detection signals corresponding to the intensity of the branched light. A control circuit 5 controls laser rays, outputted from the wavelength variable light source 1 in intensity, corresponding to a change in detection signals outputted from the photodetector 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable wavelength light source device capable of changing the wavelength of laser light, and more particularly to a laser light source for stably outputting the laser light at a constant level over a wide wavelength range. The present invention relates to a variable wavelength light source device.

[0002]

2. Description of the Related Art A variable wavelength light source generally used as a light source of a variable wavelength light source device is configured so that one of a number of modes in which a semiconductor laser element can oscillate is selected by a wavelength selector and output. . As this kind of variable wavelength light source, there are an external resonance type in which the semiconductor laser element and the wavelength selection section are separately formed, and a type in which the semiconductor laser element and the wavelength selection section are integrally formed. is there.

FIG. 9 shows a configuration of an external resonance type variable wavelength light source. This tunable wavelength light source returns to the semiconductor laser element 21 only a predetermined wavelength of the laser light output from the semiconductor laser element 21 which receives the power supply and generates laser light, and the laser light output from the non-reflection coat on one end of the semiconductor laser element 21. It comprises a wavelength selector 22. When the wavelength selection unit 22 is configured by a diffraction grating, the wavelength of the oscillating laser light can be varied by rotating the diffraction grating.

The intensity of output light with respect to the wavelength of a variable wavelength light source of this type changes with the change of the wavelength, and the intensity of the output light also changes due to a change in ambient temperature or the like.

In order to solve the above problem, the present applicant has already filed an application for a variable wavelength light source device disclosed in Japanese Patent Application Laid-Open No. Hei 8-172233 in which the wavelength of laser light can be varied.

FIG. 10 shows an example of the configuration of this variable wavelength light source device.
The variable wavelength light source device performs setting of the wavelength λ for the variable wavelength light source 31 and output of the setting value S for the control circuit 32 by the wavelength / intensity setting device 33,
The intensity of the laser light output from the variable wavelength light source 31 is varied by an intensity varying means 34 such as an optical attenuator or an optical amplifier, and a part of the varied laser light is branched by a branching means 35, and the branched laser light is branched. Light is received by the light receiver 36. Then, the control circuit 32 controls the intensity of the laser beam to be constant based on a change in the light receiving signal of the light receiver 36. Before controlling the intensity of the laser light, the received signal level at which the intensity of the laser light becomes constant at each wavelength is stored in advance in the wavelength intensity characteristic storage 3.
7, and the intensity of the laser light is controlled so that the level of the received signal at that wavelength is obtained when the laser light is output.

[0007]

By the way, in the branching means 35 of the variable wavelength light source device, the branching ratio is set in advance according to the polarization state of the light of the wavelength to be used. Therefore, if the polarization state changes before the light is input to the branching unit 35, the branching ratio between the output light branched by the branching unit 35 and the branched light changes.

However, in the above variable wavelength light source device, when the intensity varying means 34 is connected between the variable wavelength light source 31 and the branching means 35 via an optical fiber, the polarization state is determined at the connection point of the optical fiber. When the attenuation or the degree of amplification of the intensity varying means 34 is varied, the polarization extinction ratio of the laser light changes or polarization fluctuation occurs. As a result, the laser light output from the variable wavelength light source 31 is
The polarization state changes before being input to the branching unit 35. Therefore, light is output from the branching unit 35 in a state different from the original branching ratio. Then, the control circuit 32 controls the intensity varying means 34 according to the level change of the branch light received by the light receiver 36 at that time to vary the intensity of the laser light. Could not.

As described above, in the above-described conventional variable wavelength light source device, the polarization extinction ratio of the laser light changes before the laser light output from the variable wavelength light source 31 is input to the branching means 35. When the polarization fluctuation occurs, laser light cannot be output at a constant level over a wide wavelength range.

Therefore, the present invention has been made in view of the above-mentioned problems, and there is no change in the polarization extinction ratio of a laser beam or change in a branching ratio due to polarization fluctuation, and a constant level over a wide wavelength range. It is an object of the present invention to provide a variable wavelength light source device capable of outputting laser light.

[0011]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a variable wavelength light source 1 for outputting light controlled to a predetermined wavelength, and a variable wavelength light source 1 according to the polarization angle. A branching unit 3 that branches at a predetermined branching ratio and outputs one as output light and the other as reference light, and is disposed on an optical path between the variable wavelength light source and the branching unit, A polarizing means 2 for receiving light, transmitting only one polarization component of a polarization angle at which the branching ratio is obtained from the received light to the branching means, and receiving a reference light branched by the branching means; Intensity detection means 4 for outputting a detection signal corresponding to the intensity of the reference light, and a detection signal output from the intensity detection means, and a light output from the tunable wavelength light source output in response to a change in the detection signal. The reference light by controlling the intensity It is characterized in that a control unit 5 to make the intensity of the output light becomes a desired value.

According to a second aspect of the present invention, there is provided a variable wavelength light source 1 for outputting light controlled to a predetermined wavelength, an intensity variable for receiving light from the variable wavelength light source, and varying the intensity of the received light to output the light. A splitting means for splitting incident light at a predetermined splitting ratio according to its polarization angle, outputting one as output light and the other as reference light, and the intensity varying means and the splitting means. A polarizing means 2 disposed on an optical path between which receives light from the intensity varying means and transmits only one polarization component of a polarization angle at which the branching ratio is obtained from the received light to the branching means; An intensity detection unit for receiving the reference light branched by the branching unit and outputting a detection signal corresponding to the intensity of the received reference light; and a detection signal for receiving the detection signal output from the intensity detection unit. Output from the intensity varying means in response to a change in Intensity of the reference light or output light characterized by comprising a control unit 5 to make a desired value by controlling the intensity of light.

According to a third aspect of the present invention, in the variable wavelength light source device according to the first or second aspect, the polarizing means 2 comprises a polarizer 2
a or an optical isolator 2b provided with a polarizer and a Faraday element.

According to a fourth aspect of the present invention, in the variable wavelength light source device according to the first or second aspect, the predetermined wavelength is set for the variable wavelength light source 1 and the desired value is set for the control means 5. The wavelength / intensity setting means 6 is provided.

According to the variable wavelength light source device of the present invention, even if the polarization state of the light output from the variable wavelength light source 1 changes,
By the polarizing means 2 provided in front of the splitting means 3, light having only one polarization component of a polarization angle at which the spectral ratio of the splitting means 3 is obtained is incident on the splitting means 3. Therefore, there is no change in the polarization extinction ratio of light or change in the branching ratio of the branching means 3 due to polarization fluctuation, and the light intensity can be controlled to be constant over a wide wavelength range.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of a variable wavelength light source device according to the present invention, and FIG. 2 is a diagram showing one configuration example of a variable wavelength light source used in the device.

As shown in FIG. 1, the variable wavelength light source device according to the first embodiment includes a variable wavelength light source 1, a polarizing means 2, a branch plate 3, a light receiver 4, a control circuit 5, a wavelength / intensity setting device 6,
It has a schematic configuration including a wavelength intensity characteristic storage device 7.

As shown in FIG. 2, the variable wavelength light source 1 is of an external resonance type, and has a semiconductor laser element 8 driven by a constant active layer current and a wavelength provided at one end of the semiconductor laser element 8. A selection unit 9 and a lens 10 for converting laser light output from the other end of the semiconductor laser element 8 into parallel light and outputting the parallel light to the outside. The optical conditions of the wavelength selection unit 9 can be changed by external control. Thus, the configuration is such that the wavelength of the laser light oscillated and output by the semiconductor laser element 8 changes.

The wavelength selecting section 9 includes a lens 9a for converting the laser light output from the non-reflection coating on one end side of the semiconductor laser element 8 into parallel light, and receiving the parallel light and setting only a desired wavelength to the semiconductor laser element 8. And a diffraction grating 9b returning to the side. The wavelength selector 9 selects a wavelength by rotating the diffraction grating 9b by a rotating device (not shown). The angle of the diffraction grating 9b is determined by the wavelength / intensity setting unit 6
The angle is set in accordance with the wavelength information λ from.

The laser light output from the variable wavelength light source 1 is input to the polarizing means 2. A polarizer 2a serving as the polarization means 2 is disposed on an optical path (optical axis) between the variable wavelength light source 1 and the branch plate 3, and converts light having only one polarization component of the input laser light to the branch plate 3 side. Through. Polarizer 2a
Is set such that the transmitted light is in a polarization state in which the branching ratio set in the spectral plate 3 is obtained.

The branching plate 3 as a branching means is formed of a member having a very small change in the light transmittance T (reflectance 1−T), such as a type in which a dielectric multilayer film is deposited on glass, and the like. the laser beam intensity P ₁ output from the child 2a, branches and output light intensity T · P _1, the reference light intensity _{(1-T) · P 1} . The branching ratio of the intensity at the branch plate 3 is set to a desired value in advance according to the polarization state of the incident light.

The reference light split by the splitting plate 3 is received by a light receiver 4 as intensity detecting means. Receiver 4
Outputs a detection signal Ps having a magnitude proportional to the intensity (1-T) · P ₁ of the input reference light, that is, a magnitude proportional to the intensity Po (= T · P ₁ ) of the output light.

The wavelength / intensity setting device 6 as setting means includes:
The wavelength information λ set from an operation unit (not shown) or an external device is transmitted to the variable wavelength light source 1. Then, the variable wavelength light source 1 outputs a laser beam having a wavelength corresponding to the wavelength information of the wavelength / intensity setting device 6 according to a control signal from the control circuit 5. In the wavelength / intensity setting device 6, a set value S for setting the intensity Po of the output light of the variable wavelength light source device is set from an operation unit (not shown), an external device, or the like. The wavelength intensity characteristic storage unit 7 as a storage unit stores in advance the intensity characteristics of the variable wavelength light source 1 with respect to the wavelength.

The set value S set by the wavelength / intensity setting device 6 is input to the control circuit 5 together with the detection signal Ps detected by the light receiver 4. The control circuit 5 as a control means is constituted by, for example, a differential amplifier having a very large gain, and detects a difference between the set value S and the detection signal Ps.
The variable wavelength light source 1 uses the amplified output of the difference component as a control signal.
And the intensity Po of the output light of the variable wavelength light source 1 is controlled to be equal to the set value S.

The wavelength / intensity setting unit 6 determines and corrects the wavelength information λ input from an operation unit or the like (not shown) and the intensity setting value S of the output light by a microcomputer before operating the D / A converter. It may be configured to output to the tunable light source 1 or the control circuit 5 via the control unit.

When the set value S and the wavelength λ are set by an operation unit (not shown) or the like,
The intensity information corresponding to the set wavelength λ is read from the wavelength intensity characteristic storage unit 7, and the upper limit value of a set value of a range in which the laser light of this wavelength can be controlled to a constant intensity is calculated. The set value S may be compared with the set value S, and when a set value S larger than the upper limit value is set, an alarm may be displayed on a display device or a warning may be given by sound.

Further, the wavelength / intensity setting device 6 reads out a wavelength range that can be output with an intensity equal to the set value S from the wavelength intensity characteristic storage device 7 and checks whether the wavelength set from outside is within this wavelength range. It may be determined whether the wavelength information is not in the wavelength range or not, and an alarm may be displayed on a display device or a warning may be given by sound.

As described above, in the variable wavelength light source device according to the first embodiment, the polarizer 2 a that allows only one polarization component to pass is disposed on the optical path between the variable wavelength light source 1 and the branch plate 3. Then, the light transmitted through the polarizer 2a is split by the splitter 3 into output light and reference light, and the reference light split by the splitter 3 is received by the light receiver 4 and a detection signal corresponding to the intensity of the reference light is received. And outputs a detection signal output from the photodetector 4 to the control circuit 5, and varies a control signal for the variable wavelength light source 1 in accordance with a change in the detection signal. Control so that the intensity is constant.

Therefore, the light input to the branch plate 3 is
Since the polarizer 2a always provides a constant polarization at which the spectral ratio of the spectroscopic plate 3 can be obtained, there is no change in the polarization extinction ratio of the laser beam or the change in the branching ratio of the branch plate 3 due to polarization fluctuation, and a wide wavelength range. , The laser beam intensity can be controlled to be constant. Further, even if the intensity of the output light of the tunable wavelength light source 1 changes due to a tunable operation of the wavelength or a change in environment, the intensity of the laser light output from the tunable light source device is kept constant by the above-described control.

The intensity control is performed by the variable wavelength light source 1.
This is performed on the laser light output from the tunable wavelength light source 1 without changing the active layer current of the semiconductor laser element 8 inside the semiconductor laser device 8, so that mode hopping and wavelength fluctuation due to intensity control do not occur at all, and the intensity and Laser light having both stable wavelengths can be output. For this reason, even when measuring the response of various optical components and optical devices to the wavelength, sufficiently accurate measurement can be performed using the laser light output from the variable wavelength light source device.

Next, FIG. 3 is a view showing a second embodiment of the variable wavelength light source device according to the present invention. Note that, in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the variable wavelength light source device according to the second embodiment, an optical attenuator 11a as intensity varying means 11 is disposed on an optical path (optical axis) between the variable wavelength light source 1 and the polarizer 2a. The other configuration is the same as that of the first embodiment.

The optical attenuator 11a includes, for example, a Faraday element for rotating a plane of polarization of incident light by an angle corresponding to the strength of an applied magnetic field, a coil for applying a magnetic field to the Faraday element, and a plane of polarization fixed. And a polarizer that outputs only a component that matches the plane of polarization of the light component that has passed through the Faraday element.

More specifically, the polarization plane of the polarizer is shifted by a predetermined angle with respect to the polarization plane of the laser light output from the variable wavelength light source, and the Faraday element is in a state where no magnetic field is applied (current is supplied to the coil). Is not done),
The incident light is directly output to the polarizer without changing the polarization plane.
Therefore, if the magnetic field applied to the Faraday element is controlled by the control signal from the control circuit 5, the attenuation of the laser light from the variable wavelength light source 1 can be varied, and the intensity of the output light can be kept constant.

FIG. 4 is a view showing a third embodiment of the variable wavelength light source device according to the present invention. In the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the tunable wavelength light source device of the third embodiment, an optical amplifier 11b as intensity varying means 11 is provided on the optical path between the tunable wavelength light source 1 and the polarizer 2; This is the same as the first embodiment.

The optical amplifier 11b uses, for example, a semiconductor laser element as an amplifying element, and amplifies and outputs input light by a current injected into the semiconductor laser element.
It is composed of a fiber amplifier and the like. And the optical amplifier 11
If the amplification degree of b is controlled by the control signal from the control circuit 5, the intensity of the output light can be made constant.

Incidentally, the semiconductor laser amplifier is connected to the optical amplifier 11.
When used as b, the injection current into the semiconductor laser element is varied to variably control the amplification degree. Since this semiconductor laser amplifier has a high-speed response and can attenuate the input light in a range where the injection current is small,
The intensity of the output light can be varied over a wide range.

When a fiber amplifier is used as the optical amplifier 11b, the degree of amplification is controlled by varying the injection current of the semiconductor laser element for excitation.

In these optical amplifiers 11b, the wavelength band that can be amplified is limited, and the amplification degree often changes depending on the wavelength. However, the wavelength band that can be amplified by the optical amplifier 11b is limited to the wavelength band of the variable wavelength light source 1. As long as the light is in the variable band, the control circuit 5 can always output a laser beam having a constant intensity without being affected by a change in the amplification factor due to the wavelength of the optical amplifier 11b itself.

The laser light passing through the intensity varying means 11 according to the second and third embodiments is
It is input to a polarizer 2 as a polarizing means. The polarizer 2
Light of only one polarization component of the input laser light is transmitted to the branch plate 3 side.

As described above, in the variable wavelength light source devices of the second and third embodiments, the polarizer 2 that passes only one polarization component is provided with the intensity varying means (the optical attenuator 11a or the optical amplifier 11b) 11. It is arranged on the optical path between the branch plate 3.
The light transmitted through the polarizer 2 is split by the splitter 3 into output light and reference light, and the reference light split by the splitter 3 is received by the light receiver 4 and a detection signal corresponding to the intensity of the reference light is received. And a detection signal output from the light receiver 4 is input to the control circuit 5, and a control signal for the intensity varying means 11 is varied according to a change in the detection signal to change the control signal for the laser light output from the intensity varying means 11. Control so that the intensity is constant.

Thus, the light input to the branch plate 3 is
As in the first embodiment, the polarizer 2 always controls the spectral plate 3.
Since the polarization is constant, the splitting ratio of the splitting plate 3 does not change due to the polarization extinction ratio of the laser light or the polarization fluctuation, and the laser light intensity is controlled to be constant over a wide wavelength range. Can be.

The laser beam having passed through the intensity varying means 11 is transmitted through the polarizer 2 and then branched by the branch plate 3 into output light and reference light.
Since the amount of attenuation and the degree of amplification of 1 are controlled, there is no influence of the characteristic variation of the intensity varying means 11 itself (the variation of the amount of attenuation depending on the wavelength of the input light or the change of the environment) or the nonlinearity of the amount of attenuation. .

Next, FIG. 5 is a diagram showing a fourth embodiment of the variable wavelength light source device according to the present invention. In the fourth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the tunable wavelength light source device of the fourth embodiment, an optical isolator 2b is disposed as a polarizing means 2 on the optical path (optical axis) between the tunable wavelength light source 1 and the branch plate 3, and other components are provided. The configuration is the same as that of the first embodiment.

The optical isolator 2b as a polarizing means is
It comprises a Faraday element and a polarizer. In the optical isolator 2b, when the direction and strength of the magnetic field applied to the Faraday element are variably controlled, the polarization plane of the incident light in the Faraday element rotates by an angle corresponding to the strength of the applied magnetic field. Then, after the laser light from the variable wavelength light source 1 is polarized by the Faraday element and passes through, only one polarization component of the light component passes through the polarizer and is incident on the branch plate 3. Note that the polarization angle of the polarizer constituting the optical isolator 2b is set so that the transmitted light is in a polarization state in which the branching ratio set in the spectral plate 3 is obtained.

As described above, in the variable wavelength light source device according to the fourth embodiment, since the optical isolator 2b is used as the polarization means 2, the configuration is the same as when the polarizer 2a is used.
The output light of the optical isolator 2b has a constant polarization at which the spectral ratio of the spectral plate 3 can be obtained, and the same effects as those of the above-described first and second embodiments can be obtained. Moreover, since the influence of the return light to the variable wavelength light source 1 is removed, a laser light output with more stable intensity can be obtained.

Next, FIG. 6 is a view showing a fifth embodiment of the variable wavelength light source device according to the present invention. Note that, in the fifth embodiment, the same components as those in the second embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The tunable wavelength light source device according to the fifth embodiment includes a polarizing means 2 on the optical path between the intensity varying means 11 and the branch plate 3.
An optical isolator 2b is provided as the second embodiment, and the other configuration is the same as that of the second embodiment.

In the variable wavelength light source device according to the fifth embodiment, the optical isolator 2b is used as the polarization means 2 as in the fourth embodiment. The output light of the isolator 2b has a constant polarization at which the spectral ratio of the spectral plate 3 can be obtained.
The same effects as in the embodiment and the second embodiment can be obtained. Moreover, since the influence of the return light to the variable wavelength light source 1 is removed, a laser light output with more stable intensity can be obtained.

Next, FIG. 7 is a view showing a sixth embodiment of the variable wavelength light source device according to the present invention. Note that, in the sixth embodiment, the same components as those of the fifth embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the variable wavelength light source device of the sixth embodiment, the intensity varying means 11 is composed of an optical amplifier 11c and an optical attenuator 11d, and the other configuration is the same as that of the fifth embodiment.

The optical amplifier 11c is provided on an optical path (optical axis) between the variable wavelength light source 1 and the optical isolator 2b.
The amplification degree of the optical amplifier 11 c is continuously variably controlled by a control signal output from the control circuit 5 in response to a change in the detection signal output from the light receiver 4, and the laser light from the variable wavelength light source 1 is variably controlled. The signal is amplified by the controlled amplification degree and output to the optical attenuator 11d.

The optical attenuator 11d is roughly variably controlled by the control circuit 5 to attenuate the light from the optical amplifier 11c by the variably controlled attenuation and outputs the light to the optical isolator 2b.

Next, FIG. 8 is a view showing a seventh embodiment of the variable wavelength light source device according to the present invention. Note that, in the seventh embodiment, the same components as those in the sixth embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The variable wavelength light source device according to the seventh embodiment uses an optical attenuator 11e instead of the optical amplifier 11c according to the sixth embodiment.

The optical attenuator 11e is provided on an optical path (optical axis) between the variable wavelength light source 1 and the optical isolator 2b.
The optical attenuator 11e continually variably controls the amount of attenuation by a control signal output from the control circuit 5 in response to a change in the detection signal output from the light receiver 4, and outputs the laser light from the tunable wavelength light source 1. The light is attenuated by the variably controlled attenuation and output to the optical attenuator 11d.

The optical attenuator 11d is composed of, for example, an ND (Neutral Density) filter capable of setting different amounts of attenuation. The control circuit 5 roughly controls the amount of attenuation, and variably controls the light from the optical amplifier 11e. The signal is attenuated by the amount of attenuation and output to the optical isolator 2b.

In the structure shown in FIG. 7 or 8, a polarizer 2a may be provided instead of the optical isolator 2b.

As described above, the same effects as in the fourth embodiment can also be obtained by the variable wavelength light source devices shown in the sixth and seventh embodiments. In other words, the output light of the optical isolator 2b has a constant polarization at which the spectral ratio of the beam splitter 3 can be obtained. The laser light intensity can be controlled to be constant over the wavelength range. Moreover, since the influence of the return light to the variable wavelength light source 1 is removed, a laser light output with more stable intensity can be obtained.

Incidentally, as the intensity varying means 11,
JP-A-8-17223, besides an optical attenuator by rotation of an optical surface
Lithium niobate (LiN
bO _Three) Light using electro-optic and acousto-optic effects
Attenuation type, semiconductor laser amplifier and fiber amplifier
The used optical amplification type or the like can be used.

In the above embodiment, an example using the external resonance type variable wavelength light source 1 has been described. However, an integrated variable wavelength light source element as disclosed in Japanese Patent Application Laid-Open No. 8-172233 is disclosed. A black reflection type variable wavelength light source element or a distributed feedback type (DFB) variable wavelength light source element may be used.

[0064]

As described above, according to the present invention,
Since the light input to the branching unit is polarized at a constant polarization by the polarizing unit, there is no change in the polarization extinction ratio of the laser beam or change in the branching ratio due to polarization fluctuation, and the laser beam intensity is kept constant over a wide wavelength range. Can be controlled. Also, if an optical isolator is used as the polarization means, the output light of the optical isolator will have a constant polarization, and the influence of the return light to the variable wavelength light source and the intensity variable means will be removed, so that more stable laser light intensity will be obtained. can get.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a variable wavelength light source device according to the present invention.

FIG. 2 is a diagram illustrating a configuration example of a variable wavelength light source of the variable wavelength light source device according to the present invention.

FIG. 3 is a block diagram showing a second embodiment of the variable wavelength light source device according to the present invention.

FIG. 4 is a block diagram showing a third embodiment of the variable wavelength light source device according to the present invention.

FIG. 5 is a block diagram illustrating a variable wavelength light source device according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing a fifth embodiment of the variable wavelength light source device according to the present invention.

FIG. 7 is a block diagram showing a variable wavelength light source device according to a sixth embodiment of the present invention.

FIG. 8 is a block diagram showing a seventh embodiment of the variable wavelength light source device according to the present invention.

FIG. 9 is a diagram illustrating a configuration example of a variable wavelength light source.

FIG. 10 is a block diagram showing a configuration of a conventional variable wavelength light source device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Variable wavelength light source, 2 ... Polarizing means, 2a ... Polarizer, 2b
... optical isolator, 3 ... branch plate (branching means), 4 ... light receiver (intensity detecting means), 5 ... control circuit (control means), 11
… Intensity variable means.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuaki Nagashima 5-10-27 Minamiazabu, Minato-ku, Tokyo Anritsu Corporation

Claims (4)

[Claims] 1. A variable wavelength light source (1) for outputting light controlled to a predetermined wavelength, an incident light being branched at a predetermined branching ratio according to its polarization angle, one being output light, and the other being referred to. A branching unit (3) that outputs light, and is disposed on an optical path between the variable wavelength light source and the branching unit, receives light from the variable wavelength light source, and the branching ratio of the received light is A polarizing unit (2) for transmitting only one polarization component of the obtained polarization angle to the branching unit; receiving the reference light branched by the branching unit; and outputting a detection signal corresponding to the intensity of the received reference light. Receiving the detection signal output from the intensity detection means, and controlling the intensity of the light output from the variable wavelength light source in accordance with a change in the detection signal. So that the output light intensity is the desired value That the control unit (5) and the variable wavelength light source apparatus comprising the. 2. A variable wavelength light source (1) for outputting light controlled to a predetermined wavelength, and an intensity varying means (11) for receiving light from the variable wavelength light source, varying the intensity of the received light, and outputting the light. A branching means (3) for branching incident light at a predetermined branching ratio in accordance with the polarization angle thereof and outputting one as output light and outputting the other as reference light; Polarization means (2) for receiving light from the intensity varying means and transmitting only one polarization component of a polarization angle at which the branching ratio is obtained from the received light to the branching means. ), An intensity detecting means (4) for receiving the reference light branched by the splitting means, and outputting a detection signal corresponding to the intensity of the received reference light, and a detection signal output from the intensity detecting means. Receiving means for changing the intensity of the detection signal. Variable wavelength light source device, characterized in that the intensity of the reference light or output light and a control means to ensure a desired value (5) by controlling the intensity of light et output. 3. The tunable wavelength light source device according to claim 1, wherein said polarizing means comprises a polarizer or an optical isolator having a polarizer and a Faraday element. 4. A wavelength / intensity setting means (6) for setting the predetermined wavelength for the variable wavelength light source (1) and for setting the desired value for the control means (5). Item 3. The variable wavelength light source device according to item 1 or 2.