JP2000337963A - Optical wavelength-measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the feedback control of wavelength by dividing light to be measured according to the wavelength so that the light become parallel, then being branched into two, received at each branch point, and subjected to correction so that the change for the wavelength of reception intensity becomes linear. SOLUTION: The optical wavelength-measuring device is composed of an input fiber 1-a, diffraction gratings 2-a and 2-b, a rectangular prism 5, photo diodes 6-a and 6-b, and a signal-processing part 13. Light to be measured is emitted from the input fiber 1-a as n-branched light, is converted to parallel light via an optical system, is incident on the first diffraction grating 2-a, and is divided according to wavelength to be incident on the second diffraction grating 2-b. Since the diffraction gratins 2-a and 2-b have an equal groove interval and are arranged parallel opposingly, the radiation position of the emission light of the second diffraction grating 2-b at the rectangular prism 6 is moved parallel continuously along an X axis according to the wavelength, and the rectangular prism 5 divides the radiation light by a surface that is vertical to the X axis. Therefore, light intensity ratio that the photo diodes 6-a and 6-b receive changes continuously depending on the wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength measuring device used in the optical communication field, for example.

[0002]

2. Description of the Related Art Wavelength division multiplexing (Wavelength)
In a Division Multiplex (WDM) system, in order to use a plurality of light sources at equal optical frequency intervals, a Distri that oscillates in a single mode is used.
butted FeedbackLaser Diode
Light source and Distributed Bragg Refl
A large number of external laser type variable wavelength light sources or the like configured to be able to vary a single-mode oscillation wavelength by using an external laser diode light source or a diffraction grating disposed outside are used. Furthermore, in response to the rapid increase in communication capacity in recent years, WDM systems have become more densely packed with De.
nse WDM (hereinafter referred to as DWDM). However, when the wavelength interval is narrowed like DWDM,
The influence on communication wavelengths such as wavelength fluctuations and long-term wavelength drift due to temperature changes cannot be ignored, and precise wavelength measurement and wavelength control are required to maintain accurate communication. I have. As a wavelength measuring means, an optical spectrum analyzer (hereinafter referred to as an optical spectrum analyzer), a wavelength meter, or the like is used.

First, an optical spectrumr will be described with reference to FIG. FIG. 17 is a block diagram illustrating a configuration example of the optical spectrumr. The optical spectrumr includes an input fiber 1-b, concave mirrors 9-a and 9-b, a diffraction grating 2, a rotation mechanism 10, a rotation drive circuit 11, a slit 12,
It comprises a photodiode (light receiver) 6, a signal processing unit 13, and the like.

The light to be measured having entered from the input fiber 1-b is converted into parallel light by the concave mirror 9-a and enters the diffraction grating 2. The light to be measured having the wavelength λ incident on the diffraction grating 2 is given by the following equation 1.
Is reflected in the direction according to the relationship. λ = d (sin θ + sin β) / m (Equation 1) Here, d is the groove interval of the diffraction grating 2, m is the diffraction order of the diffraction grating 2, θ is the incident angle of the light to be measured incident on the diffraction grating 2, β is the angle of the measured light reflected from the diffraction grating 2. The rotation mechanism 10 is rotated by the rotation drive circuit 11,
By controlling the angle of the diffraction grating 2, the incident angle θ in (Equation 1) changes, and the angle β can be controlled. The light to be measured reflected by the diffraction grating 2 at an angle β is condensed by the concave mirror 9-b, passes through the slit 12 disposed at the focal position of the concave mirror 9-b, and enters the photodiode 6. Signal processing unit 1
Numeral 3 calculates an optical spectrum from the wavelength calculated from the angle of the diffraction grating 2 output from the rotation drive circuit 11 and the received light intensity of the photodiode 6 at that time. Some optical spectrumrs can measure a wide wavelength range of 1000 nm or more.

As described above, an optical spectrum analyzer can measure a spectrum in a wide wavelength range. However, since there is a movable mechanism, a mechanical error factor cannot be ignored, and a precise wavelength required for a wavelength monitoring device of a DWDM system. Not very suitable for measurement.

On the other hand, examples of precise optical wavelength measurement include an interferometer such as a Michelson interferometer and a Fabry-Perot interferometer. Here, the wavelength measurement using a Fabry-Perot etalon (hereinafter referred to as an etalon) will be described. The etalon includes an input unit, two reflectors (etalons) placed parallel to each other, a light receiver, a signal processing unit, and the like.

This wavelength measuring device specifies the wavelength of the light to be measured by using the interference fringes generated from the relationship between the wavelength and the intensity of the etalon transmitted light by utilizing the multiple interference of light.
In addition, a free spectral region (hereinafter, referred to as FSR) is a guideline for a measurement wavelength range of the etalon. Where F
SR is an interval between the peaks of the interference curve, and is obtained from the following equation 2. FSR = λ ² / (2nd) (Expression 2) Here, λ represents the wavelength of the incident light, n represents the refractive index of the etalon, and d represents the thickness of the etalon.

In a general etalon, since the FSR is about several nm, a high wavelength resolution can be expected, and since the etalon is fixedly used, at least a mechanical error factor such as an optical spectrumr can be avoided. However, there is a problem that the measurement wavelength range cannot sufficiently cope with a wavelength bandwidth required by DWDM.

On the other hand, as a wavelength measuring device capable of measuring a wavelength range more precisely than an optical spectrum analyzer and a wider wavelength range than an interferometer spectrometer such as an etalon, for example, Japanese Patent Application No.
No. -17346, "Wavelength Measuring Apparatus" proposes a wavelength measuring apparatus for a control feedback system. FIG. 12 is a block diagram of the wavelength measuring device. This wavelength measuring device includes an input fiber 1-b, an optical system (not shown), a diffraction grating 2-
a, 2-b (spectral means), right-angle prism 5 (first branching means), photodiodes 6-a, 6-b (light receiver), signal processing unit 13, and the like.

The light to be measured emitted from the input fiber 1-b enters the optical system and is converted into parallel light, and is incident on two diffraction gratings 2-a and 2-b arranged in parallel and opposed to each other and having the same groove interval, and diffracted. Then, the light is irradiated to the right-angle prism 5. The right-angle prism 5 splits the diffracted light to be measured into two. The light to be measured branched into two by the right-angle prism 5 enters the photodiodes 6-a and 6-b, respectively, and the signal processing unit 13 calculates the wavelength from the received light intensity of the two photodiodes 6-a and 6-b. .

Since the irradiation position of the light to be measured on the right-angle prism 5 continuously depends on the wavelength, the light receiving intensity ratio of the light to be measured branched into two is also a function of the wavelength. Therefore, the signal processing unit 13 can determine the wavelength of the measured light from the relationship between the received light intensity ratio and the reference wavelength.

In this wavelength measuring apparatus, since there is no movable part, mechanical error factors can be avoided. Further, since the spectroscopic means is the diffraction gratings 2-a and 2-b, about several tens nm required from DWDM. Has a feature that can be measured sufficiently.

[0013] The change of the received light intensity with respect to the wavelength will be specifically described with reference to FIGS. 13 and 14. First, the light beam has a Gaussian function (hereinafter referred to as Gaussian) beam profile, which is represented by a one-dimensional Gaussian beam profile for simplicity. Since the exact beam profile is not discussed, there is no problem with this replacement either in terms of explanation or principle. If the loss and the like are neglected, the sum of the received light intensities received by the two light receivers is the total measured light intensity applied to the right-angle prism 5, so only the received light intensity at the first photodiode 6-a will be described. However, the same applies to the second photodiode 6-b.

FIG. 14 is a diagram showing a change in received light intensity with respect to wavelength. The positional relationship between the Gaussian beam profile and the right-angle prism 5 at the wavelengths λ1 to λ3 is shown in FIGS. The amount of change in the light intensity branched by the right-angle prism 5, that is, the slope of the graph of FIG. 14, becomes maximum when the light is branched at the center of the Gaussian beam profile shown in FIG. Decreasing.

However, when this measuring device is used, the spatial distribution of the light to be measured received by the right-angle prism 5 is a Gaussian distribution, so that the relationship between the incident wavelength and the received light intensity greatly deviates from the linear relationship. As a result, the measurement wavelength resolution varies depending on the wavelength, and the wavelength stability appears in the wavelength stability by the feedback control.

[0016]

As described above, when a conventional wavelength measuring device as disclosed in Japanese Patent Application Laid-Open No. H10-17346 is used, for example, the spatial distribution of the light to be measured branched into two by a right-angle prism is reduced. Because of the Gaussian distribution, the relationship between the incident wavelength and the received light intensity of the branched light to be measured greatly deviates from the linear relationship. As a result, since the measurement wavelength resolution differs depending on the wavelength, there is a problem that wavelength stability appears in the wavelength stability due to feedback control.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical wavelength measuring apparatus in which the relationship between the measured wavelength and the received light intensity is linear.

[0018]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a collimated light to be measured is incident, and the collimated light is transmitted in a predetermined first direction. The position of the measured light to be transmitted is determined according to the wavelength of the measured light,
A spectroscopic unit that translates in the second direction including the vertical component in the first direction, and light to be measured that is transmitted from the spectroscopic unit,
A first branching unit that divides and divides into two at a predetermined branch line including each vertical component in the first direction and the second direction, and a light receiving unit that receives the branched light branched by the first branching unit A wavelength specifying device for specifying the wavelength of the incident light based on the amount of the split light received by the light receiving unit, wherein the wavelength measuring device operates on the light to be measured until the light reaches the light receiving unit. Correction means for making the relationship between the wavelength of the measured light and the received light amount close to linear.

Here, the first branching means can be composed of, for example, a right-angle prism, and the light receiving section can be composed of, for example, a photodiode. The wavelength specifying means is, for example, a CPU (Central Processing Unit).
nit), ROM (Re
ad Only Memory), RAM (Rando)
m Access Memory) and an external input device such as a keyboard. However, it is preferable that the wavelength specifying unit or the correction unit be configured without using software, but the processing may be performed via software as described above.

As described above, according to the first aspect of the present invention, the light wavelength measuring device converts the light to be measured into parallel light divided according to the wavelength by the spectroscopic means and then uses the branching means. The light is branched and light is received for each of the branched lights, and the wavelength specifying means detects the received light intensity and compares it with data relating to the reference wavelength in the storage device, so that the measured wavelength can be calculated by, for example, a processing program. In addition, since the change in the received light intensity with respect to the wavelength is corrected so as to be linear, the feedback control of the wavelength is easy.

According to a second aspect of the present invention, there is provided the optical wavelength measuring apparatus according to the first aspect, wherein the correcting means converts the measured light into n.
By branching and synthesizing each branch light in parallel with the center of the wave packet being shifted, the relationship of the light amount with respect to each point on the X axis is defined as the X-axis corresponding to the second direction at this synthesis point. , An n-branching unit that approaches a trapezoidal function with the X-axis as the base, and wherein the n-branching unit is provided on the optical path of the light to be measured on the incident side of the first branching unit.

Here, the X-axis corresponding to the above-mentioned second direction means that, when the ray is moved along the X-axis at the combining point, the ray moves in the second direction immediately before the first branching means. This is the axis corresponding as described above. For example, if the combining point is immediately before the first branching unit, the axis is in the same direction as the second direction. If a system is installed, the axis is in a direction corresponding to the optical system. The n-branching means is a means for branching and combining light into a plurality of lights, and the number of branches may be any number as long as it is two or more.

As described above, according to the optical wavelength measuring apparatus of the second aspect of the present invention, the light to be measured is branched into n beams and the center of the wave packet is shifted so as to be substantially parallel to each other, thereby being emitted from the spectral means. The light amount distribution of the parallel light can be approximated to a trapezoidal function. Then, the light beam having the trapezoidal function distribution is divided into two by the first branching unit, and when the light beam is translated in the second direction, the amount of the parallel movement and the amount of light received by the light receiving unit are determined by the n-branching unit. It approaches a linear relationship compared to none. This makes it possible to reduce the wavelength-dependent characteristics of the received light intensity of the measured light.

According to a third aspect of the present invention, in the optical wavelength measuring apparatus according to the second aspect, an optical coupler 7 is provided as the n-branching means, and the optical coupler 7 is arranged on an incident side of the spectral means. , Is characterized.

According to the third aspect of the present invention, the light to be measured can be easily and reliably divided into n parts by providing the optical coupler on the incident side of the light separating means. Further, by selecting or exchanging the optical coupler, the light to be measured can be easily converted into an arbitrary number of branches.

According to a fourth aspect of the present invention, there is provided the optical wavelength measuring apparatus according to the second aspect, wherein the n-branching means includes a birefringent element 8 for branching an optical path by polarized light. On the incident side of the spectral unit, in the middle of the spectral unit,
Alternatively, it is arranged between the spectroscopy unit and the first branching unit.

According to the fourth aspect of the invention, by inserting the birefringent element into the optical path, it is possible to easily and surely branch and combine the measured light. Further, the birefringent element can continuously shift the input portion and the output portion of the light, and since the input light and the output light also change in the same manner, the incident side than the spectral unit, the middle of the spectral unit, or A variety of installation locations can be provided, such as between the spectral unit and the first branching unit. In addition, the number of birefringent elements can be increased or decreased as necessary, and the number of branches by the measured light can be easily adjusted.

According to a fifth aspect of the present invention, there is provided the optical wavelength measuring device according to the second aspect, wherein the n-branching means is covered by each reflected light of the first surface 31 and the second surface 33 opposed thereto. A rhombic prism 3 for branching the measuring light, wherein the rhombic prism 3 is arranged on the incident side of the spectral unit, in the middle of the spectral unit, or between the spectral unit and the first branching unit. And

As described above, according to the fifth aspect of the present invention, the rhombic prism is easily inserted into the optical path of the light to be measured so that the light enters and exits from the light path appropriately. The light can be branched, and the incident side of the light splitting means, in the middle of the light splitting means, or
A variety of installation locations can be provided, such as between the spectral unit and the first branching unit. In addition, by increasing or decreasing the number of rhombic prisms as necessary, the number of branches and the emission direction of the measured light can be easily adjusted.

According to a sixth aspect of the present invention, there is provided the optical wavelength measuring apparatus according to the fifth aspect, wherein the n-branching means reflects the light transmitted through the rhombic prism 3 to form one branch light. The feature is that it is provided.

As described above, according to the sixth aspect of the present invention, in the light to be measured that has entered the rhombic prism, light that has not been reflected by the rhombic prism can be converted into one parallel branched light again by the mirror. Therefore, the incident light to be measured can be efficiently converted into one split light.

According to a seventh aspect of the present invention, in the optical wavelength measuring apparatus according to the first aspect, the correction means increases or decreases the light amount of the measured light in accordance with the wavelength and adjusts the wavelength of the measured light. Filter means for making the relationship with the received light amount close to linear,
The filter means is provided on an optical path between an incident part of the light to be measured and the light receiving part.

As described above, according to the seventh aspect of the present invention, the filter means is provided between the incident part and the light receiving part. The relationship with the amount of received light in the section can be made closer to linear.

More specifically, in the optical wavelength measuring apparatus according to the seventh aspect, fiber grading is used as the filter means, and the fiber grading is provided at an incident portion of the light to be measured. As a result, the relationship between the wavelength and the received light intensity in the photodetector can be made a linear relationship, and the fiber grating has good characteristics in matching with the input fiber transmission line. It is possible to provide.

According to a ninth aspect of the present invention, in the optical wavelength measuring apparatus according to any one of the first to eighth aspects, the spectroscopic means includes a first diffraction grating 2 that receives the measured light and disperses the wavelength.
-A, and a second diffraction grating 2-b that receives the dispersed light from the first diffraction grating 2-a and disperses the wavelength again.

As described above, according to the ninth aspect of the present invention, since the diffraction grating is used as means for dividing the light to be measured in accordance with the wavelength, it is relatively easy to use the conventional optical component manufacturing technology. The performance required by the system can be realized.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical wavelength measuring device according to the present invention will be described below with reference to FIGS. <First Embodiment> First, FIG. 1 is a block diagram showing a configuration of an optical wavelength measuring device as a first embodiment to which the present invention is applied. In FIG. 1, 1-a is an input fiber, 2-a and 2-b are diffraction gratings (spectral means), 5 is a right-angle prism (first branching means), and 6-a and 6-b are photodiodes (light-receiving devices). ) And 13 are signal processing units.

The optical wavelength measuring apparatus includes an input fiber 1-a for branching out the measured light into n beams and emitting the light, an optical system (not shown) for converting the measured light into parallel light and emitting the same, and an incident light from the optical system. A diffraction grating 2-a that diffracts light, and a diffraction grating 2-b that further disperses and diffracts the incident light from the diffraction grating 2-a and has the same groove interval as the diffraction grating 2-a and is installed in parallel with each other. Right-angle prism 5 for splitting outgoing light from diffraction grating 2-b into two
Photodiodes 6-a and 6-b for receiving the branched light from the right-angle prism 5;
And a signal processing unit 13 for calculating the wavelength of the measured light from the received light intensity at -b.

FIG. 4 is a diagram showing a process of diffracting light in diffraction gratings arranged in parallel and opposed to each other. In FIG.
Reference numerals 14, 15-a, 16-a, 15-b, and 16-b denote optical axes, and the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted here. As shown in FIG. 4, the measured light is
The light is emitted as n-branch light from the input fiber 1-a, is subsequently converted into parallel light by passing through an optical system, and is incident on the first diffraction grating 2-a at an angle θ0 at the incident optical axis 14. At this time, the incident light is split according to the wavelength. Among them, the lights of the wavelengths λ1 and λ2 are the optical axes 15-a and 16-, respectively.
reflected at angles β1 and β2 in the direction of
-B. Since the two diffraction gratings 2-a and 2-b are arranged so as to face each other in parallel with the same groove spacing, the first
Angle of Diffraction Grating 2-a and Second Diffraction Grating 2-b
The incident angles to are equal. For this reason, according to the above equation 1, the diffraction angle by the second diffraction grating 2-b becomes the first diffraction grating 2
−a, the light having the wavelengths λ1 and λ2 enters the second diffraction grating 2-b at angles β1 and β2 from the directions of the optical axes 15-a and 16-a, respectively. Then, they are both emitted at the diffraction angle θ0 in the directions of the optical axes 15-b and 16-b. The outgoing light has its irradiation position on the right-angle prism 5 continuously translated along the X-axis according to the wavelength, and the right-angle prism 5 divides the irradiation light on a plane perpendicular to the X-axis. The light intensity ratios received at 6-a and 6-b change continuously depending on the wavelength.

As described above, the irradiation position and irradiation intensity of the light to be measured to the right-angle prism 5 change continuously, so that the ratio of the received light intensity of the light to be measured branched into two is also a function of the wavelength. Therefore, if this relationship is linear, the wavelength wavelength control device has high wavelength feedback controllability.

FIG. 2 shows the relationship between the light beam profile to be measured at wavelengths λ1 to λ3 and the right-angle prism 5 when the light to be measured is branched into two as an example of an embodiment of the optical wavelength measuring apparatus according to the present invention. FIG. FIG. 3 is a diagram showing the relationship between the received light intensity and the wavelength when the light to be measured is branched into two at the incident part, as an example of the embodiment of the optical wavelength measuring device according to the present invention. Because the measured light was split into two,
The beam profile is made up of a steep Gaussian, and the slope of the graph in FIG. 3 is close to a constant value. in this way,
In the present embodiment, by dividing the n-branched light to be measured in accordance with the wavelength, the rate of change of the received light intensity with respect to the wavelength can be made close to a constant value, so that the feedback control of the wavelength can be accurately performed over a wide wavelength range. Can be performed.

Here, an optical coupler 7 may be provided at the input section as a means for branching the measured light into n branches. For example, the light emitted from the optical coupler 7 is converted into parallel light by a lens (optical system), and is transmitted to the spectroscopic means. The division and reception of the light to be measured from here are described with reference to FIG. 2 described in the first embodiment.
The description is omitted.

When this configuration is adopted as the optical input unit to be measured, since the input unit of the wavelength measuring device is usually a fiber input, the use of the optical coupler 7 whose input / output unit is a fiber makes it possible to match the joint. Is good. Further, by optimally designing the interval between the two output fibers in the optical coupler 7,
The relationship between the received light intensity and the wavelength in the photodiodes 6-a and 6-b can be easily linearly approximated.

Further, a birefringent element 8 may be provided as a means for n-branching the measured light between the measured light input section and the branching means. FIG. 5 is a diagram showing that one input light is converted into a parallel two-branched light according to the polarization by the birefringent element 8.

The birefringent element 8 (birefringent crystal) is an optical element having a property that the direction of the optical axis in the element varies depending on the polarization state of the incident light. is there. As the birefringent element 8, calcite (C
aCO3) and the like. The characteristics of the received light intensity with respect to the wavelength when the birefringent element 8 is used are the same as those in FIGS. 2 and 3 described in the first embodiment.
The description is omitted.

Further, by using the optical coupler 7 and the birefringent element 8 at the same time as the branching means, the light to be measured can be changed to an arbitrary n-branch light.

In the case of employing this configuration, the birefringent element 8 can easily split the light beam into two, so that it is only necessary to set the birefringent element 8 on the optical axis incident on the first diffraction grating. Also, by using the optical coupler 7 together with the optical coupler 7, it is possible to easily expand the optical coupler 7 into multiple branches. Further, by optimally designing the element length, it is possible to easily make the relationship between the received light intensity and the optimum wavelength close to a linear one.

<Second Embodiment> FIG. 6 shows, as a second embodiment of the present invention, a rhombic prism 3 provided between a first diffraction grating 2-a and a second diffraction grating 2-b. FIG. 2 is a block diagram showing an optical wavelength measurement device installed in the apparatus. In FIG. 6, 1-b is an input fiber, 2-a and 2-b are diffraction gratings (spectral means), 3 is a rhombic prism (n-branching means), 4 is a mirror (n-branching means), and 5 is a right-angle prism ( First branch means), 6-a and 6-b are photodiodes (light-receiving devices),
13 is a signal processing unit (not shown), 18, 19-a, 19
-B, 19-c, 20-a, 20-b, 20-c, 21
-A, 21-b, 21-c are optical axes, 31, 32, 33,
Reference numeral 34 denotes a surface of the rhombic prism 3.

The optical wavelength measuring apparatus according to the present invention comprises an input fiber 1-b for emitting light to be measured, an optical system (not shown) for converting incident light into parallel light, and an incident light from the optical system. First diffraction grating 2-a for diffracting light, and first diffraction grating 2
A rhombic prism 3 for splitting incident light from -a, a mirror 4 for reflecting transmitted light from the rhombic prism 3, and a second diffraction grating 2-b for diffracting incident light from the rhombic prism 3 and the mirror 4; A right-angle prism 5 for splitting the incident light from the second diffraction grating 2-b into two, photodiodes 6-a and 6-b for receiving the split light from the right-angle prism 5, and the light to be measured based on the received light intensity. A signal processing unit 13 (not shown) for calculating a wavelength.

The rhombic prism 3 is installed so that the incident light can be sent out as two parallel optical axes 20-a and 20-b depending on the wavelength. The mirror 4 moves the optical axis 19-c transmitted through the surface 33 of the rhombic prism 3 to the optical axis 2.
It is installed so as to be transmitted along an optical axis 20-c parallel to 0-a and 20-b.

The light to be measured is emitted from the input fiber 1-b, is subsequently converted into parallel light by passing through an optical system, and is incident on the first diffraction grating 2-a at the incident optical axis 18. At this time, the incident light is split according to the wavelength. inside that,
The light of wavelength λ is reflected at an angle β in the direction of the optical axis 19-a,
Irradiate the surface 31 of the rhombic prism 3. Subsequently, a part of the optical axis 19-a is reflected on the surface 31 and the optical axis 20-a is reflected.
Proceed with a. Optical axis 19 not reflected on surface 31
b is incident on the rhombic prism 3 and subsequently reflects part of it on the surface 33, further impinges on the surface 32 and partly exits the rhombic prism 3 and travels along the optical axis 20-b, where the surface 32 In this case, the amount of light reflected in the rhombic prism 3 is small and is ignored. On the other hand, the light 19-c transmitted through the rhombic prism 3 on the surface 33 is reflected by the reflection mirror 4.
And travels along an optical axis 20-c parallel to the optical axes 20-a and 20-b.

The optical axes 20-a, 20-b, 20-
Light traveling at c enters the second diffraction grating 2-b. Second
The diffraction grating 2-b of the optical axis 20-a, 20-b, 20-
c are converted into parallel optical axes 21-a, 21-b, and 21-c, respectively. The optical axes 21-a, 21-b and 21-c irradiate the right-angle prism 5 to be branched into two, and
-A, 6-b.

FIG. 7 shows the relationship between the wavelength detected at this time and the received light intensity. FIG. 15 is a block diagram showing an example of a conventional optical wavelength measuring device, and FIG. 16 shows the relationship between the wavelength detected at that time and the received light intensity. In contrast, FIG. 7 shows that the optical wavelength measuring apparatus according to the present invention has a structure in which the spatial light received by the right-angle prism 5 is close to a rectangular wave determined by the superposition of three Gaussian distributions.

Thus, the light to be measured is transmitted to the rhombic prism 3
By combining the light and the mirror 4, the light to be measured is split and received, so that the received light intensity with respect to the wavelength can be made linear. <Third Embodiment> FIG. 8 is a block diagram showing an optical wavelength measuring apparatus according to a third embodiment of the present invention. 8, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The input fiber 1-b has a filter (not shown) for changing the light intensity according to a specific wavelength. FIG. 10 is a diagram showing a change in received light intensity with respect to wavelength. 9 to show the positional relationship between the measured light beam profile and the right-angle prism 5 at the wavelengths λ1 to λ4. FIGS. 11A and 11B illustrate the relationship between the transmitted light intensity and the received light intensity of the optical filter in detail, taking as an example a case where the measured light input unit includes an optical filter.

Conventionally, as shown by the dashed line in FIG. 10, the relationship between the received light intensity and the wavelength greatly deviates from the linear relationship. However, by using a filter that reduces the intensity of the measured light in the wavelength range where the received light intensity increases significantly, the relationship can be made closer to a more linear relationship as shown by the solid line in FIG. became.
Since the measured light intensity decreases around wavelengths λ2 to λ3, the slope of the graph in FIG. 10 is close to a constant value. FIG. 11A shows a change in the measured light intensity by the optical filter, and FIG. 11B shows a change in the received light intensity with respect to the wavelength. Since the intensity of the light to be measured is reduced by the optical filter from the point where the slope of the graph of the received light intensity with respect to the wavelength becomes steep in the related art, the change in the slope can be made constant. For this reason, the wavelength range with a fixed inclination of the graph of the received light intensity with respect to the wavelength can be expanded.

As described above, in the case of this configuration in which the optical means whose light intensity changes according to the wavelength of the light to be measured is arranged, the specifications of the optical filter and the like for the wavelength to be measured are optimized, so that the light receiving device can be easily obtained. Can be improved to a linear relationship between the wavelength and the received light intensity.

<Fourth Embodiment> FIG. 8 can be a block diagram showing an optical wavelength measuring apparatus as a fourth embodiment to which the present invention is applied. The description of the same reference numerals is omitted. The fourth embodiment is characterized in that an FBG is provided as a measured wavelength input section.

The FBG is an element which forms a kind of diffraction grating by giving a periodic change in the refractive index inside the optical fiber, and reflects back light of a specific wavelength (λc) determined by the following equation. . The specific wavelength (λc) is obtained by the following equation (3).

Λc = 2ncoΛ Equation 3 where λc is the wavelength reflected by the FBG, nc
o represents the effective refractive index of the fiber propagation mode, and Λ represents the period of change in the refractive index.

The light to be measured enters through the FBG. Here, the relationship between the wavelength after emission from the measured wavelength input unit and the received light intensity is described with reference to FIG. 10 described in the third embodiment.
The description is omitted here.

When this configuration is adopted, the FBG is used as the input section of the wavelength meter, which is usually a fiber input, so that the matching is good. Furthermore, the FB of the optimally designed optical filter characteristics
By using G, the relationship between the received light intensity and the optimum wavelength can be easily linearized.

The number of optical elements, the installation position, and the like are also arbitrary.
In addition, although the first and second diffraction gratings are used as the spectral means, two prisms can be used. In addition, it goes without saying that the detailed structure and the like specifically shown in this embodiment can be appropriately changed without departing from the gist of the invention.

[0064]

As described above, according to the optical wavelength measuring device according to the first aspect of the present invention, this optical wavelength measuring device converts the light to be measured into parallel light according to the wavelength by the spectral means. After that, by using the branching means, the light is split into two and received for each of the branched lights.
The received light intensity is detected and compared with the data on the reference wavelength on the storage device, and the measured wavelength can be calculated by, for example, a processing program. Moreover, since the change in the received light intensity with respect to the wavelength is corrected so as to be linear, the feedback controllability of the wavelength is high.

According to the optical wavelength measuring apparatus of the second aspect of the present invention, the light to be measured is branched into n light beams and the center of the wave packet is shifted so as to be substantially parallel to each other, so that the amount of parallel movement and the light reception at the light receiving portion are obtained. The relationship with the quantity approaches a linear relationship as compared with the case without the n-branch means. This makes it possible to reduce the wavelength-dependent characteristics of the received light intensity of the measured light.

According to the optical wavelength measuring apparatus according to the third aspect of the present invention, the light to be measured can be easily and reliably divided into n by using the optical coupler as the n-branching means. The measurement light can be converted into an arbitrary number of branches.

According to the optical wavelength measuring apparatus of the present invention, the light to be measured is branched and combined by inserting the birefringent element into the optical path. The number of branches by light can be easily and reliably adjusted.

According to the optical wavelength measuring apparatus of the fifth aspect, since the rhombic prism is used as the n-branching means, it is possible to provide a variety of installation locations and, if necessary, the rhombic prism. By increasing or decreasing the number of prisms, the number of branches and the emission direction of the measured light can be easily adjusted.

According to the optical wavelength measuring apparatus of the present invention, in the light to be measured incident on the rhombic prism,
Since the light not reflected by the rhombic prism can be converted into one split light again by the mirror, the incident light to be measured can be efficiently converted into one parallel split light.

According to the optical wavelength measuring apparatus of the present invention, the relationship between the wavelength of the light to be measured and the amount of light received by the light receiving section can be made linear by providing the filter means.

According to the optical wavelength measuring apparatus of the present invention, in the optical wavelength measuring apparatus of the present invention, by using fiber grading as the filter means, the wavelength and the received light intensity of the light receiver can be determined. Since the relationship can be a linear relationship, and the fiber grating has a good characteristic of matching with the input fiber transmission line, it can be easily provided in the input section.

According to the optical wavelength measuring apparatus of the ninth aspect, since a diffraction grating is used as the spectral means, the conventional optical component manufacturing method can be compared with other optical devices such as a fiber type or a waveguide type. By utilizing the technology, the performance required by the system can be realized relatively easily.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an optical wavelength measuring device as a first embodiment to which the present invention is applied.

FIG. 2 shows an optical wavelength measurement device according to a first embodiment.
It shows the light intensity as viewed from the spatial distribution along the X-axis direction in front of the first branch (right-angle prism), and is a graph according to each wavelength.

FIG. 3 is a graph showing the relationship between the light intensity at a light receiving unit (photodiode) and the wavelength of the light to be measured in the optical wavelength measuring device.

FIG. 4 is a diagram showing a process of diffracting light in diffraction gratings arranged in parallel and opposed to each other.

FIG. 5 is a diagram illustrating an example of branching of an optical axis by a birefringent element.

FIG. 6 is a block diagram showing an example of an optical wavelength measurement device as a second embodiment to which the present invention is applied.

FIG. 7 is a graph showing the relationship between wavelength and received light intensity in an optical wavelength measuring device as a second embodiment to which the present invention is applied.

FIG. 8 is a block diagram showing an optical wavelength measuring device as a third and a fourth embodiment to which the present invention is applied.

FIG. 9 illustrates an optical wavelength measurement device according to a third embodiment.
It shows the light intensity as viewed from the spatial distribution along the X-axis direction in front of the first branch (right-angle prism), and is a graph according to each wavelength.

FIG. 10 is a diagram showing a relationship between wavelength and received light intensity in the optical wavelength measurement device.

FIG. 11 is a diagram showing a relationship (a) between the wavelength of the optical filter and the transmitted light intensity and a relationship (b) between the wavelength and the received light intensity in the optical wavelength measurement device.

FIG. 12 is a block diagram showing a first example of a conventional optical wavelength measuring device.

FIG. 13 shows the light intensity as viewed from the spatial distribution along the X-axis direction in front of the first branching portion (right-angle prism) in the conventional optical wavelength measuring apparatus. It is.

FIG. 14 is a diagram showing the relationship between the wavelength and the received light intensity of the optical wavelength measuring device.

FIG. 15 is a block diagram showing a second example of a conventional optical wavelength measuring device.

FIG. 16 is a diagram showing a relationship between wavelength and received light intensity in the optical wavelength measurement device.

FIG. 17 is a block diagram showing an optical spectrum analyzer as a conventional optical wavelength measuring device.

[Explanation of symbols]

 1-a Input fiber (with n-branch means) 1-b Input fiber (without n-branch means) 2,2-a, 2-b Diffraction grating (spectral means) 3 Rhombic prism (n-branch means) 4 Reflection Mirror (n-branching means) 5 Right-angle prism (first branching means) 6,6-a, 6-b Photodiode (receiver) 7 Optical coupler (n-branching means) 8 Birefringent element (n-branching means) 9-a , 9-b concave mirror 10 rotation mechanism 11 rotation drive circuit 12 slit 13 signal processing unit 14 optical axis 15-a, 15-b optical axis 16-a, 16-b optical axis 18 parallel light 19-a, 19-b, 19-c Optical axis 20-a, 20-b, 20-c Optical axis 21-a, 21-b, 21-c Optical axis 31, 32, 33, 34 Surface of prism

Claims (9)

[Claims] 1. A light beam to be measured which has been made parallel is incident, the light beam to be measured is transmitted in a predetermined first direction, and the position of the light beam to be measured is determined according to the wavelength of the light beam to be measured. A spectroscopic unit that translates in the second direction including the vertical component in the first direction; and a predetermined branch line that converts the light to be measured transmitted from the spectroscopic unit to include the vertical components in the first direction and the second direction. First splitting means for splitting into two at the boundary, a light receiving unit for receiving the split light split by the first splitting means, and the incident light based on the amount of the split light received by the light receiving unit. An optical wavelength measuring device provided with wavelength specifying means for specifying the wavelength of the light, wherein the relation between the wavelength of the light to be measured and the amount of received light is made close to linear by acting on the light to be measured until the light reaches the light receiving section. An optical wavelength measurement device, comprising: . 2. The correction means according to claim 1, wherein the light to be measured is branched into n light beams, and each of the branched light beams is shifted in parallel with the center of the wave packet. An n-branching unit that makes the relationship of the light amount to each point on the X-axis closer to a trapezoidal function with the X-axis as a base, and The optical wavelength measurement device according to claim 1, wherein the optical wavelength measurement device is provided on an optical path of the measurement light. 3. An optical wavelength measuring apparatus according to claim 2, wherein an optical coupler is provided as said n-branching means, and said optical coupler is arranged on an incident side of said spectral means. 4. A birefringent element for splitting an optical path by polarized light as said n-branching means, wherein said birefringent element is placed on the incident side of said spectral means, in the middle of said spectral means, or said spectral means and said first 3. The optical wavelength measuring device according to claim 2, wherein the optical wavelength measuring device is disposed between the optical wavelength measuring device and the branching device. 5. The apparatus according to claim 5, wherein the n-branching means includes a rhombic prism for branching the light to be measured by each reflected light of the first surface and the second surface opposing the first surface. The optical wavelength measuring apparatus according to claim 2, wherein the light wavelength measuring device is disposed between the spectral unit and the first branching unit in the middle of the spectral unit. 6. The optical wavelength measuring apparatus according to claim 5, wherein the n-branching means includes a mirror that reflects light transmitted through the rhombic prism to form one branch light. 7. The filter means for increasing or decreasing the light quantity of the light to be measured in accordance with the wavelength so as to make the relationship between the wavelength of the light to be measured and the amount of received light close to linear. 2. The optical wavelength measuring apparatus according to claim 1, wherein the optical wavelength measuring apparatus is provided on an optical path between an incident portion of the light to be measured and the light receiving portion. 8. The optical wavelength measuring apparatus according to claim 7, wherein fiber grading is used as said filter means, and said fiber grading is provided at an incident portion of the light to be measured. 9. The spectroscopic means comprises: a first diffraction grating that receives the light to be measured and wavelength-disperses the light; and a second diffraction grating that receives light dispersed from the first diffraction grating and wavelength-disperses the light again. The optical wavelength measurement device according to claim 1, wherein: