JP2000223761A - Wavelength monitor and laser light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength monitor accurately monitoring the wavelength of a light source and a laser light source using the wavelength monitor. SOLUTION: An incident light from a light source is branched with a beam sampler 11, and two branch lights whose angles are slightly different are obtained. By making the branch lights enter an etalon 13, characteristics wherein phases of wavelength-transmittance characteristics are different from each other are obtained. Wavelength-transmittance characteristics are normalized, and the wavelength changing amount from a reference wavelength is calculated by using wavelength-transmittance curves excellent in mutual linearities. Transmission lights of the beam sampler 11 are branched with a beam sampler 12, and other two branch lights are obtained. The branch lights are directly received via a slope filter 18, and a reference wavelength of an incident light is obtained from wavelength-transmittance of the slope filter 18. The reference wavelength and the wavelength changing amount are added, and an accurate wavelength of the incident light is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength monitor for monitoring the wavelength of a laser light source and a laser light source device using the same.

[0002]

2. Description of the Related Art Conventionally, as a laser light source device capable of controlling an emission wavelength, a laser light source which uses a distributed feedback laser diode to control its current, temperature, etc., and changes the wavelength within a range of several nm, for example. Devices are known.
Also, a laser light source device that can control a wider emission wavelength by changing a resonance wavelength by using an external resonator, and a laser light source device using a monolithic semiconductor laser having a wavelength control region are known. I have.

As a wavelength monitor for monitoring the wavelength of a laser beam, a slope filter whose transmission wavelength continuously changes is used, and a wavelength monitor which measures the wavelength based on a level transmitted through the filter is also used. Have been.

[0004]

However, the wavelength control in such a conventional laser light source device is based on the relationship between the amount of control such as current and ambient temperature and the emission wavelength in a light source using a distributed feedback semiconductor laser. Recognize in advance,
An open-loop control method in which a control amount is changed according to a desired emission wavelength is used. In addition, even in the external cavity type laser light source device, the relationship between the control amount of the resonance wavelength and the emission wavelength is recognized in advance, and the open-loop control in which the control amount is changed according to the desired emission wavelength is performed. A method is used.

[0005] In recent years, in the field of optical communication, a wavelength multiplexing communication system for simultaneously transmitting laser beams of many wavelengths to one optical fiber is being used. According to such a wavelength division multiplexing communication system, in order to increase the number of channels within a limited wavelength band, the wavelength of each channel is accurately defined, and the wavelength interval between channels is made as narrow as possible. You need to do multiplexing. Therefore, high wavelength setting accuracy is required for a laser light source for wavelength multiplex communication. However, in the conventional wavelength-variable laser light source, the accuracy of the set wavelength is determined by the resolution and reproducibility of the open-loop control system. However, if the open-loop control system has high resolution and high accuracy, the device becomes large and expensive. In addition, the open loop control system has a drawback that sufficient accuracy and resolution cannot be obtained. Therefore, in order to control the wavelength of the laser light source with high accuracy, a wavelength monitor device capable of checking the emission wavelength in a wide band with high accuracy is required.

In general, an optical wavelength meter using a Michelson interferometer is known for measuring a wavelength over a wide band and with high accuracy. However, the Michelson interferometer has disadvantages in that the apparatus itself is large, expensive and the measurement speed is slow. It is conceivable to configure a wavelength monitor using an etalon in a narrow wavelength range. The wavelength monitor using the etalon is small, has no moving parts, and can have a relatively simple configuration. However, since the transmission characteristics of the etalon periodically change with wavelength, the measurement range is the period of the etalon, that is, FSR.
Is limited to the range. Also, there is a problem that the resolution is reduced in the peaks and valleys at both ends of the transmission characteristics even within the range of the FSR.

Further, in a wavelength monitor which uses a slope filter in which the amount of transmitted light continuously changes in response to a change in emission wavelength, and detects the wavelength of incident light from the amount of transmitted light,
There is a drawback that it is difficult to achieve both high bandwidth and high accuracy.

The present invention has been made in view of such conventional problems, and the inventions of claims 1 to 4 use an etalon having a high resolution in a narrow wavelength range to accurately control a wavelength in a wide band. It is an object of the present invention to provide a wavelength monitor capable of measuring. The invention of claims 5 to 11 of the present application provides a laser light source device capable of setting an arbitrary wavelength within a wide predetermined band with high accuracy by using such a wavelength monitor and emitting laser light. The purpose is to do.

[0009]

According to the invention of claim 1 of the present application, a part of incident light is branched to obtain first to n-th (n ≧ 3) branched lights different from the parallel state by a predetermined angle. A first optical branching unit, a second optical branching unit that branches a part of the incident light to obtain the (n + 1) th and (n + 2) th branched lights, and has a periodic wavelength-transmittance characteristic; An etalon that outputs wavelength-transmittance characteristics of the first to n-th branched lights emitted from the optical branching unit with phases shifted from each other, and a first etalon transmitted through the etalon.
A first to an n-th photoelectric conversion unit for photoelectrically converting the n-th branched light, and a slope filter having a characteristic that a transmittance characteristic with respect to an incident wavelength changes continuously, and the n + 2-th branched light is incident. And an nth photoelectric conversion unit for photoelectrically converting the (n + 1) th branched light and the (n + 2) th branched light transmitted through the slope filter.
+1 and n + 2 photoelectric conversion units; first to n-th division units for normalizing by dividing the first to n-th branch lights by the (n + 1) -th branch light, respectively; A switching unit for selecting one of the output values in a predetermined range from among the outputs of the n-th division unit; and an (n + 1) -th division unit for normalizing by dividing the (n + 2) -th division light by the (n + 1) -th division light. A dividing unit, a wavelength change calculating unit that calculates a wavelength change of incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristic of the etalon, and an output of the (n + 1) th dividing unit. The wavelength of the incident light is calculated by adding the outputs of the wavelength calculator and the wavelength calculator for calculating any one of the reference wavelengths of the periodic wavelength-transmittance characteristics of the etalon based on the wavelength. And an adder that performs the operation.

According to a second aspect of the present invention, there is provided a first light branching unit for branching a part of incident light to obtain first and second branched lights having different angles by a predetermined angle from a parallel state. Branch off,
A second optical splitter for obtaining third and fourth split lights, and a first and second split light having periodic wavelength-transmittance characteristics and emitted from the first optical splitter. An etalon that outputs a wavelength-transmittance characteristic out of phase, a first and a second photoelectric conversion unit that photoelectrically converts the first and second branched lights transmitted through the etalon, respectively, The transmittance characteristic has a characteristic of continuously changing, and the slope filter into which the fourth branched light is incident, and the third branched light and the fourth branched light transmitted through the slope filter are photoelectrically converted. A third and a fourth photoelectric conversion unit; a first and a second division unit for normalizing the first and the second branch light by dividing the first and the second branch light by the third branch light, respectively; A switching unit for alternately selecting an output value within a predetermined range among the outputs of the first and second division units; A third dividing unit for normalizing by dividing by three branched lights, and a wavelength for calculating a wavelength change of incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristic of the etalon. A change calculator, and a wavelength calculator that calculates any reference wavelength of the periodic wavelength-transmittance characteristic of the etalon based on the output of the third divider,
An adder for calculating the wavelength of the incident light by adding the outputs of the wavelength calculator and the wavelength change calculator.

As the slope filter, a filter whose transmittance characteristic with respect to the wavelength of the incident light monotonously changes and whose resolution is higher than the periodic change in the transmittance of the etalon is used. First to n-th division units, switching units,
The wavelength change calculator, the wavelength calculator, and the adder may be configured by hardware, or may be realized by software processing using a microcomputer.

According to a third aspect of the present invention, in the wavelength monitor according to the first aspect, the etalon has a phase difference of wavelength-transmittance characteristics with respect to the first and second branched lights within a range of 90 ° ± 10 °. Is characterized in that:

The invention of claim 4 of the present application is the invention of claim 1 or 2
In the above wavelength monitor, the etalon is an etalon having a reflection film having a surface reflectance of 10 to 20%.

According to a fifth aspect of the present invention, in the wavelength monitor of the first aspect, a constant-temperature layer holding at least the first to n-th optical branching units, the etalon and the slope filter, and a constant-temperature layer are provided. A temperature adjusting unit for maintaining the temperature in the range.

According to a sixth aspect of the present invention, in the wavelength monitor of the second aspect, a constant-temperature layer holding at least the first and second optical branching units, the etalon and the slope filter, and a constant-temperature layer are provided. A temperature adjusting unit for maintaining the temperature in the range.

According to a seventh aspect of the present invention, there is provided a wavelength tunable light source for changing a wavelength of light emitted by an external control signal, and a part of light emitted from the wavelength tunable light source is branched to be different from a parallel state by a predetermined angle. A first optical branching unit that obtains the first to n-th branched lights, and a part of the incident light, and branches the n + 1,
A second optical branching section for obtaining the (n + 2) th branched light; and a first to n-th branched light having periodic wavelength-transmittance characteristics and emitted from the first optical branching section. An etalon that outputs wavelength-transmittance characteristics out of phase, and first to n-th photoelectric conversions of the first to n-th branched lights transmitted through the etalon.
And a slope filter into which the transmittance characteristic with respect to the incident wavelength continuously changes, and the light passes through the slope filter into which the (n + 2) -th branched light is incident, and passes through the (n + 1) -th branched light and the slope filter. The (n + 1) th and (n + 2) th photoelectric conversion units for photoelectrically converting the (n + 2) th branched light;
A first to an n-th division unit for normalizing by dividing the n-th divided light by the (n + 1) -th divided light, and a predetermined range among outputs of the first to the n-th division units And a switching unit for selecting one of the output values of (n) and (n) for normalizing by dividing the (n + 2) -th branched light by the (n + 1) -th branched light.
A division unit for calculating a wavelength change amount of incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristic of the etalon, and a (n + 1) th division unit. The wavelength of the incident light is obtained by adding the output of the wavelength calculator and the wavelength calculator for calculating any one of the reference wavelengths of the periodic wavelength-transmittance characteristics of the etalon based on the output. And a light source drive unit that controls the emission wavelength of the variable wavelength light source to be a set value based on an output from the addition unit.

The invention according to claim 8 of the present application is a wavelength tunable light source for changing the wavelength of light emitted by an external control signal, and a part of light emitted from the wavelength tunable light source is branched so as to be different from a parallel state by a predetermined angle. A first optical branching section for obtaining the first and second branched lights, and a third and fourth
A second optical branching unit that obtains the first and second branched light beams having a periodic wavelength-transmittance characteristic. An etalon that outputs an out-of-phase transmittance characteristic, a first and a second photoelectric conversion unit that photoelectrically converts the first and second branched lights transmitted through the etalon, and a transmittance characteristic for an incident wavelength is continuous. And a third filter and a fourth filter that photoelectrically convert the third branched light and the fourth branched light that has passed through the slope filter.
A first and a second divider for normalizing the first and second branched lights by dividing the first and second branched lights by the third branched light, respectively; A switching unit that alternately selects an output value in a predetermined range among the outputs of the division unit, a third division unit that normalizes the fourth branch light by dividing the fourth branch light by a third branch light, A wavelength change calculator that calculates a wavelength change of incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristic of the etalon, and a wavelength change calculator that calculates the wavelength of the etalon based on an output of the third divider. A wavelength calculator that calculates any reference wavelength of the periodic wavelength-transmittance characteristic, and an adder that calculates the wavelength of the incident light by adding the outputs of the wavelength calculator and the wavelength change calculator. The emission wavelength of the tunable light source is controlled to a set value by an output from the adding unit. A light source driving section, and is characterized in that it has a.

According to a ninth aspect of the present invention, there is provided a tunable light source for changing a wavelength of light emitted by an external control signal, and a part of light emitted from the tunable light source is branched to be different from a parallel state by a predetermined angle. A first optical splitter for obtaining the first to n-th split lights, a second optical splitter for splitting a part of the incident light to obtain the (n + 1) th split light, and a periodic wavelength-transmittance. It has characteristics, and the first to first emitted from the first optical branching unit
An etalon that outputs a wavelength-transmittance characteristic out of phase with respect to the n-th branched light, and first to n-th photoelectric conversions that photoelectrically convert the first to n-th branched lights transmitted through the etalon. Unit, an (n + 1) th photoelectric conversion unit that photoelectrically converts the (n + 1) -th branched light, and the (n + 1) -th branched light
Are normalized by dividing by the split light of
An n-th division unit, a switching unit for alternately selecting an output value in a predetermined range among the outputs of the first to n-th division units, and a predetermined unit for each cycle of the wavelength-transmittance characteristic of the etalon. A wavelength change calculator that calculates the wavelength change of the incident light from the reference wavelength, and an adder that calculates the wavelength of the incident light by adding the discrete emission wavelength data and the output of the wavelength change calculator. And, while controlling the emission wavelength of the variable wavelength light source to be a set value by the output from the addition unit,
A light source control unit that outputs any reference wavelength data of the wavelength-transmittance characteristics of the etalon to the addition unit.

According to a tenth aspect of the present invention, there is provided a wavelength tunable light source for changing a wavelength of light emitted by an external control signal, and a part of light emitted from the wavelength tunable light source is branched to be different from a parallel state by a predetermined angle. A first optical splitter for obtaining first and second split lights, a second optical splitter for splitting a part of incident light and obtaining a third split light, and a periodic wavelength-transmittance. A first and a second light exiting from the first optical branching section
An etalon that outputs a wavelength-transmittance characteristic out of phase with respect to each of the branched light beams;
A first and second photoelectric converter that photoelectrically converts the second branched light, a third photoelectric converter that photoelectrically converts the third branched light, and the first and second branched light Switching for alternately selecting output values within a predetermined range among the outputs of the first and second division units, each of which is normalized by dividing by the three split lights, and output of the first and second division units. Part and the wavelength of the etalon-
By adding a wavelength change calculator for calculating the wavelength change of the incident light from a predetermined reference wavelength for each cycle of the transmittance characteristic, discrete emission wavelength data and the output of the wavelength change calculator. An adder for calculating the wavelength of the incident light, and controlling the emission wavelength of the variable wavelength light source to be a set value by an output from the adder, and any reference wavelength of the wavelength-transmittance characteristic of the etalon. And a light source control unit that outputs data to the addition unit.

According to an eleventh aspect of the present invention, in the laser light source device of the seventh or ninth aspect, a part of incident light is branched,
An (n + 1) th optical splitter that obtains an (n + 3) th split light; a photoelectric converter that receives the split light from the (n + 3) th optical splitter; and the wavelength tunable light source based on an output of the (n + 3) th photoelectric converter. And an output control unit for keeping the output level of the control signal constant.

According to a twelfth aspect of the present invention, in the laser light source device according to the eighth or tenth aspect, a third optical branching unit that branches a part of the incident light to obtain a fifth branched light; Further comprising: a photoelectric conversion unit that receives the branched light from the optical branching unit; and an output control unit that keeps the output level of the variable wavelength light source constant based on the output of the fifth photoelectric conversion unit. It is assumed that.

The invention of claim 13 of the present application is directed to claims 7-1
3. The laser light source device according to claim 2, wherein the variable wavelength light source is an external resonance type variable wavelength light source having an external resonator.

According to a fourteenth aspect of the present invention, in the laser light source device of the eighth or tenth aspect, the etalon has a phase difference of 90 ° ± 10 ° in wavelength-transmittance characteristics with respect to the first and second branched lights. Is within the range.

According to a fifteenth aspect of the present invention, in the laser light source device of the seventh or ninth aspect, there is provided a thermostatic layer for holding at least the first to n-th optical branch portions and the etalon,
A temperature adjusting unit for maintaining the temperature of the thermostatic layer within a predetermined range.

According to a sixteenth aspect of the present invention, in the laser light source device of the eighth or tenth aspect, at least the first and second laser light sources are provided.
It is characterized by further comprising a second optical branching section, a constant temperature layer for holding the etalon, and a temperature adjusting section for keeping the temperature of the constant temperature layer within a predetermined range.

The invention of claim 17 of the present application is directed to claims 7-1
7. The laser light source device according to claim 6, wherein the etalon is an etalon having a reflective film having a surface reflectance of 10 to 20%.

[0027]

(First Embodiment) Next, a wavelength monitor according to a first embodiment of the present invention will be described. The wavelength monitor according to this embodiment measures the wavelength of laser light from a light source and outputs wavelength data. Here, the wavelength range that can be measured is 1500 to 1600.
It is assumed that the laser light is in the range of nm. First, the first
, For example, a beam sampler 11 is provided.
The beam sampler 11 is made of a substantially parallel glass plate,
The exit surface is slightly inclined, for example, from the incident surface by 0.2 ° so that the entrance / exit surface has a predetermined reflectance. Here, the reflectance of the incident surface and the exit surface is set to, for example, 1%, and the beam sampler 11 is arranged at an angle of 45 ° with respect to the incident light from the left end in the drawing. In this way, the first split light reflected on the incident surface of the beam sampler 11 and the second split light transmitted through the beam sampler 11 and reflected on the inner surface are obtained. For this reason, the first and second branched lights have slightly different angles from the parallel state. The transmitted light of the beam sampler 11 is incident on a second light branching unit, for example, the beam sampler 12. The beam sampler 12 is formed of a parallel glass plate, and the reflectance on the incident surface and the exit surface is set to 1% as in the beam sampler 11. In this case, third and fourth branched lights can be obtained from the incident surface and the reflecting surface, respectively. The first and second branched lights from the beam sampler 11 enter the etalon 13. The etalon 13 is arranged at a position where one of the first and second split lights, which are incident lights, is perpendicular to the surface thereof and the other split light is incident at a slightly different angle than this. The etalon 13 is, for example, a solid etalon in which two layers of reflective films of about ８λ of incident light are provided on both surfaces of a glass plate having a thickness of 1 mm, and is a reflective film having a low reflectance of, for example, about 15%.

A first light receiving element, for example, a photodiode 14 is disposed at a position for receiving the first branched light transmitted through the etalon 13, and a second light receiving element is disposed at a position for receiving the second branched light transmitted through the etalon 13. , For example, a photodiode 15 is disposed. The beam sampler 1 described above
A photodiode 16 as a third light receiving element is arranged at a position where the third branch light reflected by the surface of the second light receiving element is received. A photodiode 17 as a fourth light receiving element is arranged at a position where the fourth branched light reflected by the inner surface is received. Further, a slope filter 18 is disposed between the beam sampler 12 and the photodiode 17. The slope filter 18 is a filter whose transmittance changes monotonously in the wavelength range of the incident light and whose wavelength-transmittance characteristics are known. Slope filter 18
Is used to roughly determine the wavelength of the incident light.
These optical elements have a constant temperature layer 19 to maintain the temperature at a predetermined value.
It shall be stored inside.

The outputs of the photodiodes 14 to 17 are supplied to light receiving amplifiers 21 to 24 in the signal processing section 20A, respectively. The light receiving amplifiers 21 to 24 convert an optical signal into an electric signal and amplify the electric signal.
Together with the components 17 to 17, they constitute the first to fourth photoelectric conversion units.
The output of the light receiving amplifier 21 is supplied to a divider 25,
Is supplied to a divider 26, and the output of the light receiving amplifier 23 is supplied to dividers 25 and 26. The divider 25 normalizes the output by dividing the first split light reflected from the first beam sampler 11 by the third split light serving as a reference reflected from the second beam sampler 12. Things.
The divider 26 normalizes the output by dividing the second branched light reflected from the first beam sampler 11 by the third branched light serving as a reference reflected from the second beam sampler 12. Things. These dividers 25 and 26
Is supplied to the switching unit 27. The switching unit 27 alternately uses regions having good linearity of the etalon 13 by switching both outputs except for the peak portion from the two calculation powers. The output of the switching unit 27 is input to the A / D converter 28. An A / D converter 28 converts an input into a digital signal, and a read-only memory (hereinafter referred to as a ROM) 29 uses this digital value as an address signal to output a wavelength change within a predetermined period as described later. Is what you do. Here, the A / D converter 28 and the read-only memory 29 constitute a wavelength change calculator for calculating a change from the wavelength of the incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristics of the etalon. are doing.

On the other hand, the outputs of the light receiving amplifiers 23 and 24 are supplied to a divider 30, respectively. The divider 30 divides the fourth branched light by the level of the third branched light to normalize the divided light.
The split calculation power is given to the A / D converter 31. A / D
The output of the converter 31 is a digital value obtained by normalizing the characteristics of the slope filter 18. The ROM 32 previously holds the normalized transmittance-wavelength characteristics of the slope filter 18, and the output of the A / D converter 31 is stored in the ROM 32.
As an address signal. The A / D converter 31 and the ROM 32 constitute a wavelength calculating unit that calculates any reference wavelength of the wavelength-transmittance characteristics of the etalon based on the output of the third dividing unit. The wavelength data read by the ROM 32 is given to the adder 33. The adder 33 calculates the wavelength of the incident light by adding the outputs of the ROMs 29 and 31, and outputs the calculated light.
Each optical element in the thermostatic layer 19 is maintained at a predetermined temperature by the temperature control unit 34.

Next, the operation of the wavelength monitor according to the present embodiment will be described. When a laser beam to be measured enters the beam sampler 11 via an optical fiber or a space, part of the light is reflected on the surface and the rest is transmitted.
Then, part of the transmitted light is reflected on the emission surface,
Transmit through the surface. These first and second branched lights are both incident on the etalon 13 and received by the photodiodes 14 and 15 via the etalon 13. The light transmitted through the beam sampler 11 is incident on the second beam sampler 12, and a part of the light is reflected by the surface to become a third branched light,
The rest is transparent. A part of the transmitted light is reflected on the exit surface and transmits through the surface to become fourth branched light. The third branch light is received by the photodiode 16, and the fourth branch light is received by the photodiode 17 via the slope filter 18.

The levels of the first to fourth branched lights are defined as I1 to I
4. Outputs obtained from the light receiving amplifiers 21 to 24 by photoelectrically converting the output are referred to as S1 to S4. As described above, since the etalon 13 is provided with a reflective film having a low reflectance of about 15%, the characteristic of the surface reflected light with respect to the wavelength fluctuates periodically, and the period is the etalon free spectrum range (FSR). Is determined by This FSR is 100GHz
Then, the fluctuation cycle is about 0.8 nm. In this case, if the characteristics of the etalon with respect to the reflection level I1 are normalized by the reflection level I3, the light reception levels I1 and I2
Fluctuates periodically. The transmittance T of the etalon 13 is calculated by the following equation (1), where R is the reflectance of the boundary surface.

(Equation 1) However, A is represented by the reflectance R as shown in the following equation (2).

(Equation 2) δ is represented by the following equation (3), where n is the refractive index of the etalon 13, L is its thickness, θ is the angle of incidence on the etalon 13, and λ is the wavelength of light incident on the etalon.

(Equation 3)

As described above, if the reflectance R of the etalon 13 is, for example, 0.15, the transmittance characteristic represented by the equation (1) becomes close to a sine curve. Therefore, the normalized output obtained from the divider 25 is as shown in FIG. Similarly, the normalized output obtained from the divider 26 is shown in FIG.
The result is as shown in FIG. These transmittance characteristics have a phase shift of about 90 °. This phase shift corresponds to the angle difference between the first and second branched lights that are incident lights on the etalon 13. The phase difference of this transmittance characteristic is 90 °
In this case, the front surface and the back surface of the beam sampler 11 are inclined at an angle of 0.2 ° from parallel.

The switching section 27 alternately switches between the outputs of the dividers 25 and 26 with a portion having a high resolution as shown in FIG. That is, at certain wavelengths λ1, λ5, λ9,..., The transmittance of the reflected light I1 transmitted through the etalon 13 peaks, and the normalized value A is 1.0, ie, 0.4 from this position.
It is assumed that the transmittance is the lowest at wavelengths λ3, λ7, λ11,. λ1, λ5, λ
The interval between 5 and λ9 is 0.8 nm as described above. The switch 27 selects the output of the divider 25 if the transmittance is in the range of 0.956 to 0.744, and selects the output of the divider 26 if the transmittance is any other value. In that case, the divider 26 is in the range of transmittance 0.956 to 0.744. This makes it possible to alternately switch between thick and high-resolution split calculation powers depending on the wavelength of the incident light.

On the other hand, it is assumed that the slope filter 18 has a slope-like wavelength-transmittance characteristic that changes monotonously in a wavelength range from 1500 to 1600 nm in which light can be incident. The photodiodes 16 and 17 receive the third and fourth branched lights, and the light receiving amplifiers 23 and 24 output S3 and S3.
Convert to 4. Then, by dividing the level S4 of the fourth split light by the level S3 of the third split light by the divider 30, the characteristics of the slope filter 18 can be normalized. FIG. 3A shows the overall characteristics of the normalized slope filter 18, and FIG. 3B shows an enlarged view of a part of the normalized slope filter 18. The wavelength of the incident light is roughly determined based on the normalized characteristics. Can be calculated. The A / D converter 31 converts this into a digital value, and reads out discrete wavelength data λ1, λ2, λ3... Corresponding to the digital value from the ROM 32, thereby obtaining the data shown in FIG. Either the maximum value or the minimum value of the transmission characteristic of the etalon shown in FIG. At this time, the wavelength to be read is changed depending on whether any one of the outputs of the dividers 25 and 26 is selected. For example, when the divider 25 is selected, λ1, λ3, λ5
The data of the shortest wavelength closest to
Read as r. For example, when it is within the range of λ5 to λ7, the reference wavelength λr is set to λ5. Then, a change Δλ in wavelength from λ5 is calculated from the output of the divider 25. When the divider 26 is selected, λ2, λ4, λ6
Read data of the shortest wavelength closest to. For example, when it is within the range from λ2 to λ4, the reference wavelength λr is set to λ2. Then, a change Δλ in wavelength from λ2 is calculated from the output of the divider 26. Thus, the divider 25 or 2
6, a wavelength Δλ different from the reference wavelength λr, for example, λ5 or λ2, can be read out. By adding the reference wavelengths λr and Δλ in the adder 33, the wavelength of the incident light can be accurately calculated and output.

The wavelength read from the ROM 32 is shown in FIG.
.., Or λ4, λ8... Only the peak value of each wavelength-transmittance characteristic of (a) and (b), and Δλ is determined by either the rising or falling slope of the transmittance characteristic. May be added or subtracted to obtain an accurate wavelength value. Also, the slope filter 18 can accurately calculate λn
May be held as it is. Alternatively, the transmittance characteristics for many wavelengths having higher resolution may be held, and the peak values of the two wavelength-transmittance characteristics shown in FIG. 2 may be calculated by linear interpolation or the like. Good. Further, the variable wavelength range is wide, and FIG.
If the period of the wavelength-transmittance characteristic of the etalon shown in (b) is not a constant value and the period changes according to the wavelength, the period is changed by the approximate value of the wavelength obtained from the slope filter 18. Alternatively, two wavelength-transmittance characteristics may be switched to calculate Δλ.

In this embodiment, a solid etalon having a coating with a reflectance of 15% is used as the etalon 13. If the reflectivity of the etalon 13 is increased, the fluctuation range of the transmittance increases, but the deviation from the sinusoidal waveform increases, and the error in calculating the wavelength deviation Δλ by combining the two characteristics increases. If the reflectance is reduced, the transmission characteristic becomes closer to a sine wave, but the resolution decreases because the amplitude value decreases. Therefore, this reflectance is preferably in the range of, for example, 10 to 20%. Here, the reflectance of the etalon is set to 15%. Further, by setting the thickness of the etalon to, for example, 1 mm, the FSR becomes 100 GH.
z. If the thickness is further increased, the period of the transmission characteristic is shortened, but if the resolution of the slope filter 18 is poor, an erroneous position may be used as a reference wavelength. Also, if the thickness of the etalon is reduced, the cycle of the wavelength-transmittance characteristic of the etalon becomes longer, and the resolution of wavelength detection decreases. Therefore, for example, the period of the transmission characteristic is 0.75 to 0.5.
It is preferable to set the range to 85 nm. Further, the etalon is not limited to a solid etalon, but may be a void etalon composed of a pair of parallel flat plates. Further, the phase difference of the wavelength-transmittance characteristic obtained from the etalon 13 is preferably set to a phase difference within a range of 90 ° ± 10 ° in order to use portions having good linearity alternately. Is most preferred.

(Second Embodiment) Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram showing a configuration of a wavelength monitor according to the second embodiment. In this embodiment, the wavelength is calculated using a microprocessor (CPU) in the signal processing unit 20B. In this figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description is omitted. In this embodiment, the first
Similarly to the embodiment, the outputs of the photodiodes 14 to 17 are supplied to light receiving amplifiers 21 to 24, and the outputs of the respective light receiving amplifiers are input to A / D converters 41 to 44 and converted into digital values. Then, the data is input to the microprocessor 46 via the interface 45. The microprocessor 46 performs a division process, an output switching process, and a wavelength addition process described later. Microprocessor 46
The RAM 47 holds a processing program, and holds the wavelength-transmittance characteristics of the etalon 13 described above.
A ROM 48 for holding data of transmittance characteristics of the slope filter 18 is connected. Microprocessor 46
Calculates wavelength data based on these programs and data, and outputs the calculated data to the outside via the output interface 49.

FIGS. 5 and 6 show this microprocessor 46.
6 is a flowchart showing the operation of the first embodiment. When the microprocessor 46 starts processing, first, in step 51, the outputs of the A / D converters 41 to 44 are fetched. Outputs of the light receiving amplifiers 21 to 24 are denoted by S1 to S4. Then, the process proceeds to step 52, where the A / D converted values S1, S2, S
4 are normalized by S3 to A, B, and C, respectively. As shown in FIG. 2, these normalized values A and B are
Gives a sinusoidal wavelength-transmittance characteristic, but the phase is shifted by 90 °. Then step 53
, The scale is adjusted by multiplying the level of A by a predetermined count α, and A ′ is obtained by adding an offset component β. Similarly, the scale is adjusted by multiplying the level of B by a predetermined count α, and an offset component β is added to obtain B ′.
In this way, conversion is performed so that A 'and B' change within the range of ± 1.

Next, in step 54, the normalized value C is applied to the wavelength-transmittance characteristic of the slope filter 18 to calculate the approximate wavelength of the incident light. Here, a numerical value I obtained by enlarging the change in the wavelength oscillated by the laser light source is used.
The minimum wavelength can oscillate lambda _min, the maximum wavelength is lambda _max,
Assuming that the oscillation wavelength is λ, the numerical value I is expressed by the following equation (4). I = (λ−λ _min ) × 100 (4) In this case, the numerical value I = 0 at the minimum wavelength λ _min . And λ
_{If min} is 1500 nm and λ _max is 1600 nm,
The numerical value at the time of λ _max is I = 10000. And as described above, the normalized values C, obtaining the numerical I _A corresponding to the schematic wavelengths with reference to FIG.

Next, at step 55, it is determined whether or not the converted value A 'is within the range of the lower limit value k1 to the upper limit value k2. Here, the lower limit value k1 is an intermediate switching level between λ2 and λ3, and the upper limit value k2 is an intermediate switching level between λ1 and λ2, which are approximately -0.7 and 0.7, respectively, as shown in FIG.
If within this range, it calculates the oscillation wavelength λ using the values A 'and I _A converted in step 56 below. Hereinafter, this procedure will be described in detail.

First, it is assumed that the transmittance change of the equation (1) can be approximated by a sine wave as shown in FIG. 2 with respect to the numerical value I, and its angle L is calculated as described later, with the period of the sine wave being π. I do. However, within a relatively wide wavelength range, the period H (nm) of the transmittance characteristic also changes due to the change in the oscillation wavelength λ. FIG. 8A is a graph showing an example of a transmittance characteristic in a range of several nm. Here, the period H of the transmittance characteristic with respect to the numerical value I is linear as shown in FIG. 8B and equation (5), where H _{0 is} the initial period when I = 0, and D ₀ is the change. It changes to something that changes. H = D ₀ I + H ₀ (5) For example, when the emission wavelength changes from 1500 nm to 1600 nm, the period changes in a range of about 0.75 nm to 0.85 nm. Therefore if it is assumed to represent the transmittance with respect to the angle L of the oscillation smallest possible wavelength lambda _{mi n} in Figure 7, the angle L and the numerical I, the following equation (6) holds between the period H.

(Equation 4) Therefore, if the angle at I = 0 is L ₀ , the angle change from the minimum oscillatable wavelength λ _min to the oscillation wavelength λ is integrated, and the relationship between L and I is expressed by the following equation (7). Holds.

(Equation 5)

The angle L _X at the oscillating wavelength is I
= 0 to the angle L from the positive or negative peak value of the transmittance characteristic
2 and the small angle ΔL. Obtaining an angle L _A schematic numerical I _A schematic obtained in step 54 are substituted into equation (7). Since each has one positive and negative peak per cycle (= [pi), by integer the angular L _A at that time by the following equation (8), peak number N is determined.

(Equation 6) The angle L2 is expressed by the following equation using the number of peaks N. L2 = N · (π / 2) + L ₀ (9)

Next, at step 57, the angle L1 from the positive peak value to the oscillating wavelength is calculated using the selected A '. In this case, the oscillation wavelength angle L _X
Is calculated by the following equation (10) or (11) using L1 and L2. When N is an odd number, as shown in FIG. 8C, L _X = L 2 + ΔL = L 2 + L 1 (10) When N is an even number L _X = L 2 + ΔL = L 2 + (π / 2) −L 1 (11) ). That is, when the transmittance characteristic is positive or negative, the angles L _X up to the respective wavelengths are expressed by Expressions (10) and (11).
In step 58 to calculate the L _X. Seeking again precise figures Ic from this angle L _X in step 59, it is possible to obtain an accurate oscillation wavelength λ from conversion equation wavelength and numerical I (4) using the same. In this case, the wavelength corresponding to the angle L2 becomes the reference wavelength λr, and the wavelength corresponding to ΔL is added to calculate the oscillation wavelength.

In step 55, A 'is k1 to k2.
If it is not within the range, B 'is selected, and the routine proceeds to step 61, where the angle L2 is calculated in the same manner as in step 56.
In step 2, the angle L1 is calculated from B '. And similarly in step 59 calculates an angle L _X of the oscillation wavelength.

The wavelength of the laser beam thus incident is calculated, and output to the outside via the output interface 49 in step 60. This makes it possible to monitor the wavelength of the incident light with high accuracy over a wide wavelength range.

(Third Embodiment) Next, a wavelength monitor according to a third embodiment of the present invention will be described. FIGS. 9 and 10 are block diagrams showing the configuration of the wavelength monitoring device. The same parts as those in the first and second embodiments described above are denoted by the same reference numerals, and detailed description thereof will be omitted. In this embodiment, a beam sampler 51 is provided in the constant temperature layer 19 on the output side of the beam sampler 11, and the first to third branch lights are formed so that incident lights have different angles. The emitted light is incident on the beam sampler 12, and fourth and fifth branched lights are obtained from the incident surface and the output surface. The first to third branched lights are received by the photoelectric converters 14, 15, and 52, respectively, and the fourth and fifth branched lights are received by the photoelectric converters 16 and 17, respectively. As shown in FIG. 10, the output of the photoelectric converter 52 is also amplified by the light receiving amplifier 53, A / D converted by the A / D converter 54, and applied to the microprocessor 46 via the interface circuit 45. In this case, as shown in FIGS. 11A to 11C, the incidence angle to the etalon 13 is set so that the normalized outputs have different phase differences, for example, 60 °, respectively. . In this way, one output in the area with the highest linearity near the center is selected from the three normalized photoelectric conversion outputs. This makes it possible to more accurately detect the wavelength of the incident light.

In this embodiment, the first to third incident lights are made to enter the etalon, but the first to n-th (n ≧ 3) incident lights having different angles from each other are made to enter the etalon. A similar process may be performed. In this case, n + 1,
The n + 2 branched light is used for detecting the characteristics of the slope filter.

(Fourth Embodiment) Next, a laser light source device according to a fourth embodiment will be described. FIG. 12 is a block diagram showing the overall configuration of the laser light source device. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and detailed description is omitted. In FIG. 1, a variable wavelength light source 101 is a laser light source that can continuously change an oscillation wavelength by an external control signal. Here, the wavelength variable light source 101 is, for example, a distributed feedback type laser diode, and the wavelength is changed within a wavelength range of several nm by controlling the current, temperature, and the like. The emitted laser light is guided to the optical bandpass filter 102. The optical band-pass filter 102 is a filter of a laser light source that transmits laser light having a wavelength within a range that can be emitted. Light having a wavelength that has passed through the filter 102 is held in the constant temperature layer 19 of the above-described wavelength monitor. Irradiation is performed on the beam sampler 11. The optical elements in the constant temperature layer 19 are the same as the wavelength monitor described above. That is, beam sampler 1
Reference numeral 1 denotes a substantially parallel glass flat plate whose exit surface is slightly inclined, for example, by 0.2 ° from the entrance surface so that the entrance / exit surface has a predetermined reflectance. Here, the reflectivity of the incident surface and the exit surface is set to, for example, 1%, and the beam sampler 11 is formed at an angle of 45 ° with respect to the incident light from the left end in the drawing.
Place. In this way, the first split light reflected on the incident surface of the beam sampler 11 and the second split light transmitted through the beam sampler 11 and reflected on the inner surface are obtained. For this reason, the first and second branched lights have slightly different angles from the parallel state. The transmitted light of the beam sampler 11 is incident on a second light branching unit, for example, the beam sampler 12. The beam sampler 12 is formed of a parallel glass plate, and the reflectance of the incident surface and the exit surface is measured by the beam sampler 11.
1% as in. In this case, third and fourth branched lights can be obtained from the incident surface and the reflecting surface, respectively. The first and second branched lights from the beam sampler 11 enter the etalon 13. The etalon 13 is arranged at a position where one of the first and second split lights, which are incident lights, is perpendicular to the surface thereof and the other split light is incident at a slightly different angle than this. The etalon 13 is, for example, a solid etalon in which two layers of reflective films of about ８λ of incident light are provided on both surfaces of a glass plate having a thickness of 1 mm, and is a reflective film having a low reflectance of, for example, about 15%.

Then, a first light receiving element, for example, a photodiode 14 is disposed at a position for receiving the first branch light transmitted through the etalon 13, and a second light receiving element is disposed at a position for receiving the second branch light transmitted through the etalon 13. , For example, a photodiode 15 is disposed. The beam sampler 1 described above
A photodiode 16 as a third light receiving element is arranged at a position where the third branch light reflected by the surface of the second light receiving element is received. A photodiode 17 as a fourth light receiving element is arranged at a position where the fourth branched light reflected by the inner surface is received. Further, a slope filter 18 is disposed between the beam sampler 12 and the photodiode 17. The slope filter 18 is a filter whose transmittance changes monotonously in the wavelength range of the incident light and whose wavelength-transmittance characteristics are known. Slope filter 18
Is used to roughly determine the wavelength of the incident light.
These optical elements have a constant temperature layer 19 to maintain the temperature at a predetermined value.
It shall be stored inside. These elements are controlled at a constant temperature by a temperature control unit 34.

FIG. 13 is a block diagram showing the control device 103. The control device 103 is provided with light receiving amplifiers 21 to 24 for amplifying the outputs of the photodiodes 14 to 17, similarly to the above-described second embodiment, and A / D converters 41 to 41 for A / D converting the outputs. 44, interface 4
5 and a microprocessor 46 and the like. As in the second embodiment, the microprocessor 46 normalizes the level of the incident light and detects the wavelength based on the wavelength transmittance characteristics of the slope filter 18 and the etalon 13. The output of the beam sampler 12 of the wavelength monitor is emitted to the outside via the optical attenuator 104. Further, a wavelength setting unit 105 is connected to the control device 103, and a photodiode 104a of the optical attenuator 104 is connected via an amplifier and an A / D converter 107. The output interface 49 has a laser diode (LD).
And an attenuator (ATT) drive unit 109 are connected. The wavelength setting unit 105 sets an emission wavelength and its output level. The control device 103 controls the wavelength of the tunable light source 101 so that the wavelength becomes the set wavelength, and sets the output level to a predetermined value. The optical attenuator 104 is a photodiode 1 for detecting the level of the output laser light.
04a and an output level adjustment unit, which feeds back the output level to the control device 103 and attenuates the output level to a predetermined value based on a control signal from the attenuator drive unit 109 of the control device 103. is there.

Next, the operation of this embodiment will be described. The wavelength tunable light source 1 is set in advance by the wavelength setting unit 105.
It is assumed that an arbitrary wavelength capable of emitting light at 01 and its output level are set. In this way, the wavelength emitted from the variable wavelength light source 101 is incident on the beam samplers 11 and 12 in the constant temperature layer via the band pass filter 102, and the emission wavelength is calculated as described above. Then, the control device calculates the emission wavelength in the same manner as in the flowcharts of FIGS. 5 and 6 described above. Then, an error between the emission wavelength and the set wavelength is calculated, and the emission wavelength of the variable wavelength light source is controlled so that the error becomes zero. Also, the attenuation ratio of the optical attenuator 104 is controlled so as to be at the set level. In this case, the emission wavelength of the laser light source can be accurately controlled using the above-described wavelength monitor.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described with reference to the block diagram of FIG. In this embodiment, the wavelength-variable light source 1 is
The fourth embodiment is the same as the fourth embodiment except that the optical bandpass filter 01 and the optical bandpass filter 102 are housed at the same time.
In this case, the emission wavelength of the variable wavelength light source 101 is controlled by controlling the drive current. In this case, it is not necessary to control the temperature of the light source again, and the main part of the laser light source device can be housed in the constant temperature layer, so that the size and weight can be extremely reduced.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described with reference to the block diagram of FIG. In this embodiment, an external resonance type light source having an external resonator is used as the wavelength variable light source 110. In the figure, the left end face of the laser diode 111 is provided with an anti-reflection coating (AR coating). A lens 112 and a diffraction grating 113 and a mirror 114 disposed at a position inclined by a predetermined angle with respect to the lens 112 and the diffraction grating 113 are provided on the left side of the emission surface, and these constitute an external resonator. The diffraction grating 113 has a rotating table 115 as shown.
The emission wavelength can be changed, for example, in the range of 100 nm by changing the incident position and the incident angle of the laser light. A lens 116 and an isolator 117 are provided on the emission end side of the laser diode 111. The isolator 117 suppresses return light. On the emission end side of the isolator 117, an optical band-pass filter 118 for changing a transmission wavelength by external control and an optical unit of a wavelength monitor are arranged. The optical band-pass filter 118 is a 7-7 Japanese Patent Publication.
As shown in No. 2530, this is an interference light filter in which a multilayer film is deposited on a substrate such as glass or silicon, and the optical thickness of each layer is λ / 4, and the optical thickness is continuous in the longitudinal direction. Thus, the transmission wavelength λ is continuously changed according to the incident position. Then, the incident position is changed by the band-pass filter driving unit so as to coincide with the emission wavelength. The other optical parts of the wavelength monitor are the same as those in the third embodiment described above, and include the beam samplers 11 and 12, the etalon 13, the four photodiodes 14 to
17, a slope filter 18 is provided, and outputs of the photodiodes 14 to 17 are input to a control device 120 including a microprocessor. Further, an optical attenuator 121 and a lens 122 are arranged at a position where the light passes through the beam sampler 12. The lens 122 irradiates a laser beam to the optical fiber 124 via the optical fiber connector 123. The optical fiber 124 is provided with a branch portion 126 fused with the fiber 125, and the laser light passing through the branch portion 126 is emitted to the outside. At one end of the optical fiber 125, a photodiode 127 is provided. The photodiode 127 converts the branched laser light into an electric signal, and its output is given to the control device 120.

FIG. 16 is a block diagram showing the configuration of the control unit 120. The same parts as those in the above-described second embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. In this embodiment, the output from the photodiode 127 is
6 and the interface 4 via the A / D converter 107
5 is input. The output from the microprocessor 46 is the rotation table driving unit 131 and the attenuator driving unit 1.
32. The rotary table driving unit 131 controls the emission wavelength by changing the rotation angle of the rotary table of the variable wavelength light source 111 and the distance from the laser diode. The attenuator driving unit 132 controls the output level from the optical attenuator 121. The band-pass filter driving unit 133 controls the optical band-pass filter 1 so that the emission wavelength at that time becomes the transmission wavelength.
The incident position of the incident light incident on the reference numeral 18 is changed in the X-axis direction. The microprocessor 46 has a RAM 13
4, ROM 135 is connected. The control device 120 detects the emission wavelength of the laser light source and controls the wavelength to be a predetermined wavelength set by the wavelength setting unit 105, as in the fourth embodiment. And the photodiode 127
Is controlled so that the output level obtained from the optical attenuator 121 becomes constant, and the current value supplied to the laser diode 111 is controlled so that the emission wavelength matches the transmission wavelength of the optical bandpass filter 118. It controls the position.

In this embodiment, as in the fourth embodiment, the wavelength to be emitted by the laser light source is set by the wavelength setting unit 105. Then, the actual emission wavelength is detected, and the wavelength is controlled by controlling the emission wavelength within a range of, for example, about 100 nm based on the rotation angle of the turntable 115 and the distance between the laser diode 111. In this embodiment, the laser diode 111 and the lens 10 are also used.
2, 106, the isolator 117, the optical band-pass filter 118, and the optical part of the wavelength monitor
It is preferable to control the temperature so that the temperature is kept constant. This way, regardless of temperature changes,
It is possible to output a laser beam having a wavelength that is accurately set.

(Seventh Embodiment) Next, a seventh embodiment of the present invention will be described. FIG. 17 is a block diagram showing the overall configuration of the laser light source device according to this embodiment. The same parts as those in the above-described sixth embodiment are denoted by the same reference numerals, and description thereof is omitted. This embodiment is configured by removing the slope filter 18 and the photodiode 17 and the light receiving amplifier 24 as the fourth light receiving elements from the sixth embodiment. Since the approximate value of the emission wavelength of the light source is known from the rotation angle of the turntable 115, the control device 140 can calculate an accurate emission wavelength using this data and control the emission wavelength to be a desired emission wavelength. .

FIGS. 18 and 19 are flow charts showing the operation of this embodiment. When the control device 140 starts the operation, first, in step 141, the control device 140 takes in the A / D conversion value. Then, in step 142, normalized values A and B are calculated from the A / D converted values in the same manner as in the second embodiment. This value has a substantially sinusoidal waveform as described above. Then, as shown in step 143, A,
The scale is adjusted by multiplying the level of B by a predetermined coefficient α, and an offset component β is added to calculate A ′ and B ′. Then the routine proceeds to step 144 to calculate the numerical value I _A schematic corresponding the rotation angle of the wavelength that varies in response to the rotational angle as shown in Figure 20 of the rotary table 115 at this time. For example, if the motor that controls the rotary table is a pulse motor, the rotation angle can be calculated from the number of pulses output to the pulse motor. Thus obtained in response to the rotation angle can be calculated numerically I _A corresponding to the approximate value of the emission wavelength. In steps 145 to 150, if the correction value A 'is within the range of the predetermined lower limit value k1 to the upper limit value k2, A',
To calculate the λ than I _A. The 'If is not within the range of K1～K2, the routine proceeds to step 151 and 152 similarly B and step 61 of FIG. 6' A, calculates the λ from I _A.

Next, at step 153, the set wavelength λ
The difference λ _ERR from _S is calculated, and in step 154, the difference λ _ERR
The turntable driving unit 131 outputs a wavelength control signal so that _ERR becomes 0. At this time, the attenuation rate of the optical attenuator 121 is changed so that the output level is set at the same time. Instead of the optical attenuator 121, the output level of the laser diode 111 may be controlled. Here, the controller 140 controls the emission wavelength of the variable wavelength light source to be a set value in steps 144, 153, and 154, and reads out any reference wavelength data of the wavelength-transmittance characteristics of the etalon. It has the function of a light source control unit that outputs to the addition unit.

As described above, a discrete wavelength value is calculated from the rotation angle, and the wavelength at that time can be calculated by adding the wavelength value to the wavelength value obtained via the etalon. In this case, there is no need to provide a slope filter, a fourth light receiving element that transmits through the slope filter, and a light receiving amplifier, so that the configuration can be simplified.

[0061]

As described above in detail, according to the first to sixth aspects of the present invention, the high-resolution portions are alternately switched and used, so that a high-precision and wide-band wavelength monitor is constructed. The effect that it can be obtained is obtained. Further, since an etalon having a low reflectance is used as the etalon, the etalon can be easily manufactured and can be manufactured at low cost. Furthermore, the size of the optical system can be extremely reduced, and the reliability can be improved because there are no movable parts. According to the fifth and sixth aspects of the present invention, the main components of the optical system are held in a constant temperature bath and maintained at a constant temperature, so that a wavelength monitor that is not affected by a temperature change can be provided. Further, according to the laser light source device of claims 7 to 16 of the present application, it is possible to accurately control the wavelength so as to have a constant wavelength by using the above-described wavelength monitor. According to the ninth and tenth aspects of the present invention, since the slope filter is not used, the configuration can be simplified. Further, according to the present invention, the output level can be kept constant. Furthermore, in the thirteenth aspect, since an external resonance type laser light source device having an external resonator is used, it is possible to obtain an effect that the wavelength can be accurately controlled in a wide range. Furthermore, according to the fifteenth and sixteenth aspects of the present invention, the main components of the optical system are held in a constant temperature bath and maintained at a constant temperature, so that a laser light source which is not affected by a temperature change can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a wavelength monitoring device according to a first embodiment of the present invention.

FIG. 2 is a graph showing normalized wavelength-transmittance characteristics of the etalon according to the present embodiment.

FIG. 3 is a graph showing a wavelength-transmittance characteristic of a normalized slope filter of the present invention.

FIG. 4 is a block diagram showing an overall configuration of a wavelength monitor according to a second embodiment of the present invention.

FIG. 5 is a flowchart (part 1) illustrating an operation of the wavelength monitor device according to the present embodiment.

FIG. 6 is a flowchart (part 2) illustrating the operation of the wavelength monitor device according to the present embodiment.

FIG. 7 is a graph showing a change in normalized transmittance with respect to an angle L according to the present embodiment.

FIG. 8 is a graph showing a change in wavelength and transmittance and a cycle thereof according to the present embodiment.

FIG. 9 is a block diagram illustrating a configuration of an optical unit of a wavelength monitor according to a third embodiment of the present invention.

FIG. 10 is a block diagram illustrating a configuration of a signal processing unit of a wavelength monitoring device according to a third embodiment of the present invention.

FIG. 11 is a graph showing normalized wavelength-transmittance characteristics of the etalon according to the present embodiment.

FIG. 12 is a block diagram showing an overall configuration of a laser light source device according to a fourth embodiment of the present invention.

FIG. 13 is a block diagram illustrating a configuration of a control device of a laser light source device according to a fourth embodiment of the present invention.

FIG. 14 is a block diagram illustrating an overall configuration of a laser light source device according to a fifth embodiment of the present invention.

FIG. 15 is a block diagram showing an overall configuration of a laser light source device according to a sixth embodiment of the present invention.

FIG. 16 is a block diagram illustrating a configuration of a control device of a laser light source device according to a sixth embodiment of the present invention.

FIG. 17 is a block diagram illustrating an overall configuration of a laser light source device according to a seventh embodiment of the present invention.

FIG. 18 is a flowchart (part 1) illustrating a wavelength calculation process of the laser light source device according to the present embodiment.

FIG. 19 is a flowchart (part 2) illustrating a wavelength calculation process of the laser light source device according to the present embodiment.

FIG. 20 is a graph showing the relationship between the rotation angle and the wavelength of the motor according to the present embodiment.

[Explanation of symbols]

 11, 12 beam sampler 13 etalon 14 to 17, 104a, 127 photodiode 18 slope filter 19, 128 thermostat 20A, 20B signal processing unit 21 to 24, 106 light receiving amplifier 25, 26, 30 divider 27 switching unit 28, 31, 41-44, 107 A / D converters 29, 32, 48 ROM 33 Adder 34 Temperature controller 46 Microprocessor 47 RAM 101, 110 Variable wavelength light source 102, 118 Optical bandpass filter 103, 120, 140 Control device 104, 121 Optical attenuator 105 Wavelength setting unit 111 Laser diode 112, 116, 122 Lens 113 Diffraction grating 114 Mirror 115 Rotary table 117 Isolator 124, 125 Optical fiber 126 Fusion unit 131 Rotary table drive unit 132 Attenuator driver 133 Optical bandpass filter driver

Claims (17)

[Claims] A first light branching unit that branches a part of the incident light to obtain first to n-th (n ≧ 3) branched lights different in angle by a predetermined angle from a parallel state; A second optical branching unit that obtains the (n + 1) th and (n + 2) th branched light beams, and a first to n-th light beams having a periodic wavelength-transmittance characteristic and emitted from the first optical branching unit; Each wavelength-
An etalon that outputs an out-of-phase transmittance characteristic; a first to an n-th photoelectric conversion unit that photoelectrically converts the first to n-th branched lights transmitted through the etalon; A slope filter that has a characteristic that changes in a horizontal direction and into which the (n + 2) -th branched light is incident;
2, a first to n-th division unit for normalizing by dividing the first to n-th branch light by the (n + 1) -th branch light, respectively, and a first to n-th division unit. A switching unit for selecting one of the output values in a predetermined range from among the outputs of the division unit; and an (n + 1) th division unit for normalizing the division by dividing the (n + 2) th divided light by the (n + 1) th divided light. A wavelength change calculator that calculates a wavelength change of the incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristic of the etalon, and based on an output of the (n + 1) th division unit. A wavelength calculator for calculating any reference wavelength of the periodic wavelength-transmittance characteristics of the etalon, and an adder for calculating the wavelength of the incident light by adding the outputs of the wavelength calculator and the wavelength change calculator. And a wavelength monitor comprising: 2. A first light branching unit for branching a part of the incident light to obtain first and second branched lights different in angle by a predetermined angle from a parallel state, and a third light branching unit for branching a part of the incident light to obtain a third light. , To obtain the fourth branched light
An optical branching portion having a periodic wavelength-transmittance characteristic, and each of the first and second branched lights emitted from the first optical branching portion has a wavelength
An etalon that outputs an out-of-phase transmittance characteristic, a first and a second photoelectric conversion unit that photoelectrically converts the first and second branched lights transmitted through the etalon, and a transmittance characteristic with respect to an incident wavelength is continuous. A slope filter having a characteristic that changes in a vertical direction, and the third branch light and the fourth branch light photoelectrically converting the third branch light and the fourth branch light transmitted through the slope filter, into which the fourth branch light is incident. And a first and second division unit for normalizing by dividing the first and second branch lights by the third branch light, respectively, and the first and second division units. A switching unit that alternately selects an output value within a predetermined range among the outputs of the division unit; a third division unit that normalizes the fourth branch light by dividing the fourth branch light by a third branch light; Wavelength change of incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristic of the etalon A wavelength change calculating section for calculating the wavelength, a wavelength calculating section for calculating any reference wavelength of the periodic wavelength-transmittance characteristic of the etalon based on the output of the third dividing section, A wavelength monitor, comprising: an adder that calculates the wavelength of incident light by adding outputs of a calculator and a wavelength change calculator. 3. The wavelength monitor according to claim 2, wherein the etalon has a phase difference of wavelength-transmittance characteristics with respect to the first and second branched lights within a range of 90 ° ± 10 °. 4. The etalon has a surface reflectance of 10 to 10.
3. The wavelength monitor according to claim 1, wherein the wavelength monitor is an etalon having a reflection film of 20%. 5. At least the first to n-th optical branching units,
The wavelength monitor according to claim 1, further comprising: a constant temperature layer that holds the etalon and the slope filter; and a temperature adjustment unit that keeps the temperature of the constant temperature layer within a predetermined range. 6. At least the first and second optical branching units,
The wavelength monitor according to claim 2, further comprising: a constant temperature layer that holds the etalon and the slope filter; and a temperature adjustment unit that keeps the temperature of the constant temperature layer in a predetermined range. 7. A wavelength-variable light source for changing a wavelength of light emitted by an external control signal, a part of light emitted from the wavelength-variable light source being branched, and first to n-th light beams different from the parallel state by a predetermined angle. The first to obtain the split light
An optical branching unit, a second optical branching unit for branching a part of the incident light to obtain the (n + 1) th and (n + 2) th branched lights, and having a periodic wavelength-transmittance characteristic, wherein the first light For each of the first to n-th branched lights emitted from the branch part,
An etalon that outputs an out-of-phase transmittance characteristic; a first to an n-th photoelectric conversion unit that photoelectrically converts the first to n-th branched lights transmitted through the etalon; A slope filter that has a characteristic that changes in a horizontal direction and into which the (n + 2) -th branched light is incident;
2, a first to n-th division unit for normalizing by dividing the first to n-th branch light by the (n + 1) -th branch light, respectively, and a first to n-th division unit. A switching unit for selecting one of the output values in a predetermined range from among the outputs of the dividing unit; and an (n + 1) th dividing unit for normalizing by dividing the (n + 2) th branched light by the (n + 1) th branched light. A calculating unit, a wavelength change calculating unit that calculates a wavelength change of incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristic of the etalon, based on an output of the (n + 1) th dividing unit. A wavelength calculator that calculates any reference wavelength of the periodic wavelength-transmittance characteristics of the etalon, and calculates the wavelength of the incident light by adding the outputs of the wavelength calculator and the wavelength change calculator. An adder, and an output of the wavelength tunable light source based on an output from the adder. A light source driving unit that controls a light wavelength to be a set value. 8. A wavelength-variable light source for changing a wavelength of light emitted by an external control signal, and a first and a second light sources that branch a part of light emitted from the wavelength-variable light source and that differ from the parallel state by a predetermined angle. The first to obtain the split light
And a second branch for splitting a part of the incident light to obtain third and fourth split lights.
An optical branching portion having a periodic wavelength-transmittance characteristic, and each of the first and second branched lights emitted from the first optical branching portion has a wavelength
An etalon that outputs an out-of-phase transmittance characteristic, a first and a second photoelectric conversion unit that photoelectrically converts the first and second branched lights transmitted through the etalon, and a transmittance characteristic with respect to an incident wavelength is continuous. A slope filter having a characteristic that changes in a vertical direction, and the third branch light and the fourth branch light photoelectrically converting the third branch light and the fourth branch light transmitted through the slope filter, into which the fourth branch light is incident. And a first and second division unit for normalizing by dividing the first and second branch lights by the third branch light, respectively, and the first and second division units. A switching unit that alternately selects an output value within a predetermined range among the outputs of the division unit; a third division unit that normalizes the fourth branch light by dividing the fourth branch light by a third branch light; Wavelength change of incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristic of the etalon A wavelength change calculating section for calculating the wavelength, a wavelength calculating section for calculating any reference wavelength of the periodic wavelength-transmittance characteristic of the etalon based on the output of the third dividing section, An addition unit that calculates the wavelength of the incident light by adding the outputs of the calculation unit and the wavelength change calculation unit; and a light source that controls the emission wavelength of the variable wavelength light source to be a set value by the output from the addition unit. And a driving unit. 9. A wavelength-variable light source for changing a wavelength of light emitted by an external control signal, a part of light emitted from the wavelength-variable light source being branched, and a first to n-th light sources different from the parallel state by a predetermined angle. The first to obtain the split light
An optical branching unit, a second optical branching unit that branches a part of the incident light to obtain an (n + 1) th branched light, and has a periodic wavelength-transmittance characteristic. For each of the emitted first to n-th branched lights, the wavelength-
An etalon that outputs an out-of-phase transmittance characteristic; a first to an n-th photoelectric conversion unit that photoelectrically converts the first to n-th branched light transmitted through the etalon; An (n + 1) th photoelectric conversion unit to be converted; a first to an nth division unit for normalizing by dividing the first to nth branched light by the (n + 1) th branched light, respectively; A switching unit for alternately selecting an output value within a predetermined range from among the outputs of the nth division unit; and a wavelength change amount of incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristic of the etalon. A wavelength change calculator that calculates the wavelength of the incident light by adding the discrete emission wavelength data and the output of the wavelength change calculator, and the wavelength based on the output from the adder. When the emission wavelength of the variable light source is controlled to the set value, A laser light source device, comprising: a light source control unit that outputs any reference wavelength data of the wavelength-transmittance characteristics of the etalon to the addition unit. 10. A wavelength-variable light source that changes a wavelength of light emitted by an external control signal, and a first and a second light sources that branch a part of light emitted from the wavelength-variable light source and that differ from the parallel state by a predetermined angle. The first to obtain the split light
An optical branching unit, a second optical branching unit that branches a part of the incident light to obtain a third branched light, and has a periodic wavelength-transmittance characteristic. The wavelengths of the emitted first and second branched lights are respectively-
An etalon that outputs an out-of-phase transmittance characteristic; a first and a second photoelectric converter that photoelectrically converts the first and second branch lights that have passed through the etalon; A third photoelectric conversion unit for converting; a first and second division unit for normalizing by dividing the first and second branch lights by the third branch light, respectively; A switching unit for alternately selecting a predetermined range of output values from the outputs of the second division unit; and a wavelength change of incident light from a predetermined reference wavelength for each cycle of the wavelength-transmittance characteristic of the etalon. A wavelength change calculator that calculates the wavelength of the incident light by adding the discrete emission wavelength data and the output of the wavelength change calculator, and the wavelength based on the output from the adder. The emission wavelength of the variable light source is controlled to a set value, and A laser light source device comprising: a light source control unit that outputs any reference wavelength data of the wavelength-transmittance characteristic of the Talon to the addition unit. 11. An (n + 1) th optical splitter for splitting a part of incident light to obtain an (n + 3) th split light; a photoelectric conversion unit for receiving split light from the (n + 3) th optical splitter; The laser light source device according to claim 7, further comprising: an output control unit that keeps an output level of the variable wavelength light source constant based on an output of the n + 3 photoelectric conversion unit. 12. A third light branching unit that branches a part of the incident light to obtain a fifth branched light, a photoelectric conversion unit that receives the branched light from the fifth light branching unit, The laser light source device according to claim 8, further comprising: an output control unit that keeps the output level of the variable wavelength light source constant based on the output of the photoelectric conversion unit. 13. The laser light source device according to claim 7, wherein the variable wavelength light source is an external resonance type variable wavelength light source having an external resonator. 14. The laser according to claim 8, wherein the etalon has a phase difference of wavelength-transmittance characteristics with respect to the first and second branch lights within a range of 90 ° ± 10 °. Light source device. 15. The apparatus further comprises: a thermostatic layer for holding at least the first to n-th optical branching units and the etalon; and a temperature adjusting unit for keeping the temperature of the thermostatic layer within a predetermined range. The laser light source device according to claim 7 or 9, wherein 16. The apparatus according to claim 1, further comprising: a constant temperature layer for holding at least the first and second optical branching units and the etalon; and a temperature adjusting unit for keeping the temperature of the constant temperature layer within a predetermined range. The laser light source device according to claim 8 or 10, wherein 17. The etalon has a surface reflectance of 10
The laser light source device according to any one of claims 7 to 16, wherein the etalon has a reflection film of about 20%.