JPH02194333A - Optical spectrum analyzer - Google Patents

Abstract

PURPOSE:To always accurately measure the wavelength of light to be measured by guiding polarized light components of the light to be measured which are different from each other through separate light guides and respectively diffracting and deflecting the light with separate surface acoustic waves. CONSTITUTION:A light beam L emitted from a light source 23 is separated to two polarized light components whose deflecting directions are orthogonal with each other by a polarizing beam splitter 22 through an optical fiber 24, a coupler 25, an optical fiber 26 and a collimator lens 21. Then, the light beam L which passes the beam splitter 22 and the light beam L which is reflected by the beam splitter 22 and reflected by a mirror 28 irradiate the part of LGCs (linear diffraction gratings) 13 and 13' for inputting light beams of the light guides 12 and 12'. Thus, the light beam L is diffracted by the LGCs 13 and 13', efficiently incorporated in the light guides 12 and 12' and guided through the light guides 12 and 12' in a TE mode and a TM mode. The guided light L1 and L'1 becomes diffracted light L2 and L'2 to be outputted as the light beams L3 and L'3, detected 31 and 31' and added 34.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an optical spectrum analyzer that performs optical spectrum analysis, and particularly relates to an optical spectrum analyzer that analyzes optical spectrum using the acousto-optic effect. .

(Prior Art) Various types of optical spectrum analyzers for analyzing optical spectra are known.

As one of the optical spectrum analyzers that have been widely used in practical use, for example, there is known a so-called Zzerny-Turner type optical spectrum analyzer. After this, the spectrum analyzer rotates the diffraction grating that diffracts the irradiated light to be measured, thereby moving the diffracted light on the slit, and detecting the diffracted light through the slit based on the rotation angle of the diffraction grating. It analyzes the light spectrum.

Such optical spectrum analyzers are capable of analyzing optical spectra with high resolution.

However, such optical spectrum analyzers are large and heavy, making them difficult to handle, making them unsuitable for portable use, for example. Various optical spectrum analyzers that can be made small and lightweight have been considered, but many of these have the problem of low resolution.

Therefore, the applicant first proposed an optical spectrum analyzer that can be made small and lightweight and has high resolution (
(Patent Application No. 1982-1.80779). This spectrum analyzer has an optical waveguide made of a material that allows surface acoustic waves to propagate, and a surface acoustic wave that travels in a direction that intersects the optical path of guided light as measured light that enters the optical waveguide and travels within the optical waveguide. do,
surface acoustic wave generating means for generating a surface acoustic wave whose frequency changes continuously to diffract and deflect the guided light in the optical waveguide; and the measured light that is deflected by the surface acoustic wave and emitted out of the optical waveguide. The present invention is characterized in that it is comprised of a light detection means for detecting the light to be measured, and a frequency detection means for detecting the frequency of the surface acoustic wave when the light detection means detects the light to be measured.

When the guided light guided in the optical waveguide intersects with the surface acoustic wave propagated in this optical waveguide, it enters an acousto-optic phase r7. It is diffracted and deflected by the action. This deflection angle δ is δ−20, where θ is the incident angle of the guided light with respect to the traveling direction of the surface acoustic wave. Let the wavelength of the guided light be λ, the effective refractive index of the optical waveguide be Nc, and the wavelength, frequency, and velocity of the surface acoustic wave be A, , f, respectively.

■If it is, then it is Su. Since Nc and V are constant, if the incident angle θ and the surface acoustic wave frequency f at which the guided light is diffracted most efficiently satisfying the Bragg condition expressed by this formula are known, the guided light, that is, the measured light The wavelength λ of is known.

Further, when the guided light (light to be measured) includes a plurality of spectral components whose wavelengths are very close to each other, each spectral component can be separated by the diffraction effect of the surface acoustic wave. Therefore, for example, if a pinhole plate or the like is placed in front of the photodetector so that the light of each spectral component can be detected individually, even if the wavelengths are close to each other as described above, each Spectral components can be accurately determined by δ-'.

(Problem to be Solved by the Invention) By the way, when performing optical spectrum analysis using the optical spectrum analyzer as described above, unless special attention is paid to the polarization direction of the light to be measured, the light to be measured in the optical waveguide will be TE, TM, etc. Both waveguide modes will be guided in a state where they are excited together. Since the effective refractive index Ne of an optical waveguide is often different for each mode of guided light, if the TE mode guided light and the TM mode guided light have the same incident angle to the surface acoustic wave, then Surface acoustic waves of different frequencies are most efficiently diffracted. Therefore, in actual optical spectrum analysis, two types of VIG light are detected with a time lag, and it becomes difficult to determine which detected light should be used to determine the optical wavelength. Further, when the light to be measured is composed of a plurality of spectral components having wavelengths close to each other, the two types of peak light may overlap each other, making spectrum analysis completely impossible.

In order to prevent the above-mentioned problems from occurring, a polarizing plate or the like may be placed in the optical system that guides the light to be measured into the optical waveguide so that only the TE mode or only the TM mode is excited in the optical waveguide. However, in such a case, if the polarization direction of the light to be measured cannot be controlled appropriately, the light to be measured will not be guided within the optical waveguide, and therefore optical spectrum analysis may become impossible at all. In addition, in order to confirm the reliability of optical spectrum analysis, there is a demand for confirming the absolute intensity of the diffracted light to be measured using the light detection means.
Since the amount of light to be measured that enters the optical waveguide changes depending on its polarization direction, it becomes impossible to measure the absolute intensity of the light to be measured.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to always correctly obtain the optical spectrum of the light to be measured, regardless of the polarization direction of the light, and also to obtain the absolute intensity thereof. The purpose is to provide an optical spectrum analyzer that enables

(Means for Solving the Problems) A first optical spectrum analyzer according to the present invention includes an optical waveguide as described above, a surface acoustic wave generating means, a light detecting means, and a frequency detecting means. In a wave-type optical spectrum analyzer, two optical waveguides, a first and a second optical waveguide, are provided, and a polarizing beam splitter, etc. that separates the measured light into two polarization components whose polarization directions are orthogonal to each other is used. and an input optical system for inputting each separated measured light into the first and second optical waveguides so as to be guided in TE mode and TM mode, respectively, and surface acoustic wave generation. Two means are provided to diffract and polarize the guided light in each optical waveguide, and the light detection means optically or electrically detects the deflected measured light emitted from the first and second optical waveguides. It is characterized in that it is formed so that it can be detected at both times.

The second optical spectrum analyzer according to the present invention includes first and second light detection means that separately detect Mj constant light that is deflected and emitted from the first and second optical waveguides, respectively, as the light detection means. The frequency detecting means is formed to detect the frequency of the surface acoustic wave when at least one of these light detecting means detects the light to be measured, and the other structure is the same as that of the first optical spectrum analyzer. It is something.

The third optical spectrum analyzer according to the present invention replaces the input optical system in the first optical spectrum analyzer and guides each separated measured light into the first and second optical waveguides in the same mode. This optical spectrum analyzer is characterized in that it is provided with an input optical system for inputting data to the optical spectrum analyzer, and is otherwise configured in the same manner as the first optical spectrum analyzer.

Furthermore, in the fourth optical spectrum analyzer according to the present invention, instead of the input optical system (same as the first optical spectrum analyzer) in the second optical spectrum analyzer, the input optical system is the same as the input optical system of the third optical spectrum analyzer. This optical spectrum analyzer is characterized in that it is provided with an input optical system and is otherwise configured in the same manner as the second optical spectrum analyzer.

(Function) In the first and second optical spectrum analyzers described above, various factors (such as the incident angle of the guided light to the surface acoustic wave and the incident angle of the guided light to the surface acoustic wave, For example, in the first optical spectrum analyzer, it is possible to simultaneously diffract TE mode guided light and 1M mode guided light with maximum efficiency; The second optical spectrum analyzer can independently obtain the optical wavelength analysis value based on the TE mode guided light and the optical wavelength analysis value based on the 1M mode guided light (they are the same value). Therefore, it is possible to avoid overlapping of two types of peak light as described above.

In addition, in the third and fourth optical spectrum analyzers, the light to be measured is guided in the same mode in the two optical waveguides, so the problem caused by the difference in the waveguide modes mentioned above is essentially solved. can be prevented.

In addition, in all of the first to fourth optical spectrum analyzers, no matter what direction the light to be measured is polarized and enters the separation means, the entire amount of the light to be measured is in the optical waveguide (both optical waveguides , or in one of the optical waveguides), there is no possibility that the light to be measured cannot be detected at all. In particular, in the first and third optical spectrum analyzers, since the measured light emitted from the first and second optical waveguides is summed and detected, the absolute light intensity of the measured light can also be easily detected. It is possible.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 shows a plan view of an optical spectrum analyzer according to a first embodiment of the present invention, and FIG. 2 shows a side view of a peripheral portion of one optical waveguide 12 of this optical spectrum analyzer. This optical spectrum analyzer includes a first optical waveguide 12 formed on a first substrate 11, and a linear diffraction grating (L1near G) for light beam input formed on the surface of this optical waveguide j2.
ra, tjng coupler.

(hereinafter referred to as LGC) 13 and LGC for light beam output
14, and a first chirped inter-comb electrode pair that generates a first surface acoustic wave 15 that travels in a direction intersecting the optical path of the guided light L1 that travels between these L G C1B and 14. D Igi
a high frequency amplifier 19 that applies a high frequency alternating voltage to the first chirp IDT 17 in order to generate the surface acoustic wave 15; a sweeper 20 that changes (sweeps), a collimator lens 21, a polarizing beam splitter 22, and a mirror 28.
It has

Further, at the position where the light beam L3 emitted from the light beam output LGC 14 is irradiated, there is a first pinhole plate 30 and a first photodetector such as a photodiode for measuring the intensity of the light beam L3. A container 31 is arranged. The light amount signal S1 output from this photodetector 31 is sent to the A/D converter 3.
2, the digital light amount data S2 obtained by the A/D conversion is input to the arithmetic processing section 33.

Also, as shown in FIG. 1, among the elements described above, the high frequency amplifier 19, the sweeper 20, the collimator lens 21, the polarizing beam splitter 22, and the mirror 28
For items other than , equivalent items are placed side by side. These elements, signals, etc. are shown in the figure by adding a dash (') to the numbering of those already explained.
Important explanations about them will be omitted unless necessary (the same applies hereafter). In the following, each element will be explained in detail by taking the first optical waveguide 12 side as an example, but unless otherwise specified, the explanation will be about the second optical waveguide 12' side. The same holds true.

In this embodiment, as an example, the substrate 11 has LiNbO
The optical waveguide 12 is formed by using three wafers and providing a Ti diffusion film on the surface of the wafer. Note that substrate 1
Alternatively, a crystalline substrate made of phosphor, Si, or the like may be used. Moreover, the optical waveguide 12 is also
The material is not limited to i-diffusion, but may also be formed by sputtering or vapor depositing other materials on the substrate 11. However, this optical waveguide 12 must be formed of a material such as the above-mentioned Ti diffusion film that can propagate surface acoustic waves, which will be described later. Further, the optical waveguide may have a laminated structure of two or more layers.

The Charb IDT 17 is manufactured by, for example, applying a positive electron beam resist to the surface of the optical waveguide 12, further depositing an Au conductive thin film thereon, drawing an electrode pattern with an electron beam, peeling off the Au thin film, and then developing it. It can be formed by performing lift-off in an organic solvent after depositing a Cr thin film or an A1 thin film. Note that if the substrate 11 and the optical waveguide 12 are made of a piezoelectric material, the Charb IDT 17 can generate the surface acoustic wave 15 even if it is installed directly inside the optical waveguide 12 or on the substrate 11. If not, a piezoelectric thin film made of, for example, ZnO may be formed on a part of the substrate 11 or the optical waveguide 12 by vapor deposition, sputtering, etc., and the IDT 1.7 may be installed there.

For example, a light beam L emitted from a light source 23 such as a semiconductor laser and subjected to spectrum analysis is emitted as diverging light from the end face of an optical fiber 26 via an optical fiber 24 connected to the light source 23 and a coupler 25. This light beam L is made into parallel light by the collimator lens 21,
Next, the polarizing beam splitter 22 separates the light into two polarized components whose polarization directions are orthogonal to each other. In this example,
The polarization direction of the light beam L that has passed through the polarizing beam splitter 22 is parallel to the plane of the paper in FIG. This light beam L passes through the obliquely cut end surface 11a of the substrate 11 (see FIG. 2) and passes through the first optical waveguide 12.
The portion of LGCl, 3 is irradiated. Thereby, this light beam L is diffracted by LGCl3, efficiently taken into the first optical waveguide 12, and guided within the optical waveguide 12 in the TE mode. If the Bragg condition shown in (1) above is satisfied, this guided light L1 is diffracted (Bragg diffraction) due to acousto-optic interaction with the first surface acoustic wave 15 emitted from the Chirb IDT 17. The diffracted waveguide light L2 is diffracted toward the substrate 11 side in LGCl4,
The light is emitted to the outside of the optical waveguide element from the obliquely cut substrate end face 1.1b (see FIG. 2). This emitted light beam L
3 is focused into a small spot by a focusing lens 27.

Hereinafter, the diffraction and deflection of the guided light within the optical waveguide 12 will be explained in detail with reference to FIGS. 3 and 4.

FIG. 3 shows an enlarged detailed view of the Chirb IDT 17, and FIG. 4 shows wave number vectors of the guided light L1 and the first surface acoustic wave 15. As shown in FIG. 3, the guided light L1 is incident at a constant angle θ with respect to the traveling direction of the surface acoustic wave 15. Further, if the wave number vectors of the guided light L1 before entering the surface acoustic wave 15 and the guided light L2 after passing through the surface acoustic wave 15 are respectively lk, , lk, and the wave number vector of the surface acoustic wave 15 is IKl, then (1) When the Bragg condition shown in the formula is satisfied, as shown in FIG. -2
θ. If this angle of incidence θ is constant as mentioned above,
The deflection angle δ when the above ('2J formula holds) is also constant. Therefore, the light beam L3 that completely satisfies the Bragg condition and is emitted out of the optical waveguide 12 is emitted in a fixed direction. The front pinhole plate 30 is arranged so that the light beam L3 emitted in the above fixed direction passes through the pinhole 30a.
Instead, a slit plate may be used.

The wavelength of the guided light LX (measured light) is λ, and the surface acoustic wave 1
If the wavelength of 5 is 8, it is 1kll-2π/λ, and the wavelength of the guided light L2 is also λ, so lkl
1=llk21-2π/λ. Therefore, llK+= which satisfies the above equation (2)
Since the incident angle θ is fixed, the value of 2π/A is one 1
There is only one γj for lk11. So this (2
) when the formula holds true (that is, when the light beam L3 passes through the pinhole 30a and is detected by the photodetector 31), I
The wavelength λ can be determined from the value of IKII, that is, from the value of the wavelength of the surface acoustic wave 15.

This wavelength λ can of course be determined from the above equation (1), but it is also possible to determine the wavelength λ using the incident angle θ and the optical waveguide 1 for the guided light L1.
Even if the refractive index Ne of 2 is unknown, it can be determined.

That is, it is assumed that a reference guided light having a known frequency (assumed to be λrer) is made to enter the optical waveguide 12, and at that time, this reference guided light is diffracted by a reference surface acoustic wave having a wavelength Δref. In Figure 4, the wave number vector of the reference waveguide light is OP
1 wavelength A re! 'The wave number vector of the reference surface acoustic wave is PQ, and the diffracted reference waveguide light ΔOPQ is ΔSPR, so OP PQ OP-2yr/λref, PQ-2π/Arer
Therefore, λ-λrcf (A/Arcf) Here, the velocity and frequency of the surface acoustic wave 15 are respectively v1f
1 The velocity and frequency of the reference surface acoustic wave are respectively Vrel'
, frer, then v −f A, vrer−f ref IIArer
, v−vref, so from the above equation, λ−λref' (f rel' / f ) −
-G. In other words, if the wavelength λrer of the reference guided light and the frequency f ref' of the reference surface acoustic wave are checked in advance, the wavelength λ of the measured light can be determined from equation (3).

The frequency of the high-frequency alternating voltage applied to the chirp IDT 17 when performing optical spectrum analysis is determined by the sweeper 20.
is swept from fml,n to fl1ax. Note that the timing of this frequency sweep is controlled based on the clock signal C output by the overall control section 95. When the frequency of the alternating voltage, that is, the frequency of the surface acoustic wave 15 is swept in this way,
If the value of is set appropriately, a certain surface acoustic wave frequency f (fmin≦f≦ff1la
x), the guided light L1 is diffracted most efficiently. At this time, the light beam L3 emitted from the optical waveguide 12 is
The light passes through the pinhole 30a and is detected by the photodetector 31.

The light amount signal S1 outputted by the photodetector 31 is passed through an A/D converter 32 and digitized. The sampling period at this time is controlled based on the clock signal C output by the overall control section 95, and corresponds to the frequency sweep period of the surface acoustic wave 15. Therefore, the A/D converter 32
Of the digital light quantity data S2 outputted from the digital light amount data S2, it is automatically known at what Hz the frequency of the surface acoustic wave 15 is.

In other words, if this light amount data S2 is shown continuously, it can show the relationship between the surface acoustic wave frequency f (horizontal axis) and the detected light amount, as shown in FIG. Note that, as is clear from the explanation of the two layers, in this example, the overall control section 95 controls the light beam L.
This constitutes a frequency detection means for detecting the surface acoustic wave frequency f when 3 is detected.

On the other hand, the light beam L reflected by the polarizing beam splitter 22 is reflected by the mirror 28, diffracted by L G C13', and guided within the second optical waveguide 12° in TK.1 mode.

In addition, the second Chirb IDT17' is a high frequency amplifier]
9 and the sweeper 20, the first chirb IDT1
．． 7 and is driven in parallel. Therefore, "1. Guided light L
1° intersects with the surface acoustic wave 15' generated by the second chirable rDT 17', and is diffracted and deflected. This diffracted waveguide light L2' is emitted to the outside of the optical waveguide 12' in the same way as the waveguide light L2', and is directed to the second pinhole plate 30'.
through which the light is detected by the second photodetector 31'.

In this example, the first surface acoustic wave 15 and the second surface acoustic wave 15' are frequency swept so as to always have the same frequency. The optical systems are adjusted separately on the first optical waveguide j2 side and the second optical waveguide 12' side, so that the TE mode guided light L1 and the TM mode guided light L1' have a common frequency. surface acoustic wave 1
It is most efficiently diffracted by 5.15°, and then the leading beams L3 and L3'' are each detected by a photodetector 31.31°.

After the frequency sweep of the surface acoustic wave 15 is completed, the arithmetic processing unit 33 shows the relationship between the surface acoustic wave frequency and the amount of detected light.
C, the light amount data S2 is expressed as the wavelength λre of the input reference guided light and the frequency f of the reference surface acoustic wave.
ers and the above equation (3), it is converted into data indicating the relationship between the guided light wavelength and the detected light amount. Similarly, the arithmetic processing unit 33' converts the light amount data S2' indicating the relationship between the surface acoustic wave frequency and the detected light amount into the wavelength λre of the reference guided light and the frequency fr of the reference surface acoustic wave, which have been input in advance.
ef' and the above equation (3), it is converted into data indicating the relationship between the guided light wavelength and the monthly detected light amount.

The converted light amount data S3, S3' is sent to the adder 3.
4, the data are added for each data corresponding to the same wavelength of the light to be measured. The added light amount data S obtained in this way
4 indicates the total light amount of the light beams L3 and L3'' in association with their wavelengths. This added light amount data S4 is input to a display device 35, such as a CRT.

In this display device 35, as an example, the light beam L3
, L3, the relationship between the total light amount and the wavelength is displayed in a graph.

Therefore, from this display, when the light beams L3 and L3 are detected, that is, when the Bragg condition is satisfied, the wavelength λ
If you find it, it becomes the desired wavelength of the light to be measured.

Note that the addition data S4 includes the light beams L3 and L3+ as described above.
Therefore, it is also possible to indicate the absolute light amount of the diffracted light to be measured on the display device 3G based on this data S4. If this absolute light amount is known, it is possible to check whether the guided lights L1 and L1' are indeed efficiently diffracted, and the reliability of optical spectrum analysis can be improved.

Note that the display device 35 may be replaced with a suitable recording device or the like. Also, in the two-layer embodiment, the photodetector 31.
31° not only when it detects the light beams L3, L3', but also all the time while frequency-sweeping the surface acoustic wave 15, and also calculates the frequency f of the light beams L3, L3'.
The light amount signal S1.81'' is continuously sent to the A/D converter 32.32'' regardless of whether or not the light beam L3 is detected, and the relationship between the light amount and the wavelength is displayed in a graph. ,L3
The wavelength λ at which the wavelength λ is detected may be automatically detected, and only the value of the wavelength λ may be displayed on a display device or recorded. However, the above embodiment is more preferable because the display device 35 clearly shows the wavelength range in which the light beams L3 and L3 are not detected at all (that is, the range in which no spectral components exist). In this case, since noise components are generally included in the light intensity signal S1.81' etc., the detected light intensity display may not be 0 (zero) even in the wavelength range where the thickened light beams L3 and L3 are not detected. many. Even if this happens, there is no problem as long as it is known in advance that up to a certain level of the light amount display is a noise component. In order to avoid such a situation, a predetermined level slightly higher than the two-layer noise component may be displayed as the light ff1o (zero) level. Further, by setting this predetermined level higher than the above, it is possible to display only wavelengths near the center wavelength of the spectrum (one or more longitudinal modes may be used).

Here, the spectrum analyzer of the present invention is capable of measuring each spectral component with high resolution even when the light to be measured is composed of a plurality of spectral components whose wavelengths are very close to each other. This point will be explained in detail below.

For example, illumination constant light has wavelengths λl and λ2 that are close to each other.
, λ3 (λ1 × λ2 × λ3).

As shown in FIG. 5, it is assumed that the Bragg condition is satisfied between the guided light having the intermediate wavelength λ2 and the surface acoustic wave 15, and the diffracted light is emitted in the direction of the vector lk2. At this time, the guided lights of wavelengths λI and λ3 also almost satisfy the Bragg condition for the surface acoustic wave 15, although not completely. Therefore, the guided lights of these wavelengths λ1 and λ3 are also diffracted by the surface acoustic wave 15 and exit from the optical waveguide 12.

However, the diffraction angles of these lights are different from the diffraction angles of light with wavelength λ2, and as shown in FIG.
, in the direction of vector Ik5 (in Fig. 5, G
ISc3 are the starting points of the wave number vector of the guided light with wavelengths λ11 and λ3, respectively). Therefore, the light beam emitted from the optical waveguide 12 is separated into each spectral component. In this way, each spectrum is formed on the pinhole plate 30.
)) are completely separated, when the frequency of the alternating voltage is swept, three beam spots move on the pinhole plate 30, and the light of each wavelength is sequentially and individually passed through the pinhole 80.
Pass through a.

Therefore, the relationship between the amount of light detected by the photodetector 31 and the alternating voltage frequency, that is, the surface acoustic wave frequency is as shown in FIG. In other words, wavelength λ, λ2, λ
The three spectral components are individually detected when the surface acoustic wave frequencies are fl, f2, and f3, respectively. Once these surface acoustic wave frequencies fl, f2, and f3 are detected, wavelengths λ1, λ2, and λ3 can be determined in the same manner as described above.

Of course, the above also applies to the second optical waveguide 12' side.

Next, a second embodiment of the present invention will be described with reference to FIG. In Fig. 7, the same elements as those already explained are given the same reference numerals, and the explanation thereof will be omitted unless it is particularly necessary (the same applies hereinafter).
.

In the apparatus shown in FIG. 7, the optical systems are adjusted separately for the first optical waveguide 12 and the second optical waveguide 12°, and the guided light L1 in TE mode and the guided light L1 in TM mode are adjusted separately.
l' is most efficiently diffracted by the surface acoustic wave 15.15'' of a common frequency, and then the light beams L3 and L
3° are detected by photodetectors ai and at', respectively.

In this device, the first photodetector 31 and the second
Analog light amount signal S1 outputted by the photodetector 31',
Sl" is added by an adder 40.

The sum signal S5 obtained in this way is the light beam L3 and L31.
The total amount of light is inputted to the arithmetic processing circuit 42. On the other hand, the frequency measuring circuit 41 receives the high frequency signal Sf sent from the sweeper 20 to the high frequency amplifier 9 and determines the constantly changing alternating voltage frequency, that is, the surface acoustic wave frequency f. This signal S6 indicating the continuously changing frequency f is input to the two-layer arithmetic processing circuit 42. This arithmetic processing circuit 42 has the wavelength λ of the reference waveguide light mentioned above.
re' and the frequency f ref of the reference surface acoustic wave are stored in advance, and the arithmetic processing circuit 42 uses these wavelengths λ
From the surface acoustic wave frequency f indicated by the signal S6, the frequency f rer, and the surface acoustic wave frequency f indicated by the signal S6, the wavelength λ of the guided light beams L1 and L1' is calculated based on the above-mentioned equation (3).
Based on the light amount signal S5 synchronized with 6, the relationship between the detected light amount and the wavelength λ is determined.

The signal S7 indicating the relationship between the guided light Ll, L,', that is, the wavelength λ of the light to be measured and the amount of detected light, obtained in this way is input to a display device 43 such as a liquid crystal display device or a phototube display device, and this signal S7 Based on the above light amount vs. wavelength λ
The relationship is displayed in a graph as an example. Therefore, from this display, light beam L3. If the wavelength λ at which L3' is detected, that is, the Bragg condition is satisfied, is found, it becomes the wavelength of the desired M1 constant light.

In this case as well, by using the addition signal S5, the absolute light amount of the diffracted light to be measured can be displayed or recorded.

Next, a third embodiment of the present invention will be described with reference to FIG. This device differs from the device shown in FIG. 7 in that it detects the amounts of light to be measured separated into two systems by optically summing them up instead of electrically summing them up. That is, the light beam L3 emitted from the first optical waveguide 12 is transmitted through the polarizing beam splitter 50, and the light beam L3' emitted from the second optical waveguide I2 is reflected by the mirror 51. The beam enters the bipedal polarizing beam splitter 50, is reflected there, and is sent to the photodetector 3 together with the light beam L3.
1. In this case as well, the photodetector 8
1 can be used to indicate the absolute light amount of the diffracted light to be measured.

Note that a half mirror may be provided in place of the polarizing beam splitter 50 described above, but in that case, the amount of light received by the photodetector 31 will be approximately half that of the above case.

Next, a fourth embodiment of the present invention will be described with reference to FIG. This device is different from the device shown in FIG. 1 in that the means for inputting the light to be measured into the optical waveguide and the means for outputting it from the optical waveguide are different, and the adder 34 is omitted.

That is, the light beam L transmitted through the polarizing beam splitter 22 and the light beam L reflected by the polarizing beam splitter 22
are narrowed flat by cylindrical lenses 130° and 60°, respectively, and on the end faces of the optical waveguides 12 and 12',
The light is irradiated in such a way that the focused direction coincides with the thickness direction of the optical waveguide, so that the light is efficiently incident into the optical waveguide 12, I2°. - Light beam L3 emitted from the sword optical waveguide 12.12' in a state of being diffused in the thickness direction
, L3' are cylindrical lenses 61.6, respectively.
After the light is collimated by the focusing lens 27.
27'.

In addition, the light amount data S2 and S2' are each input to a separate arithmetic processing unit 33.33°, and the wavelength λ of the light to be measured is
The relationship between and the amount of detected light is determined based on each of the TE mode guided light L1 and the TM mode guided light L1'.

The relationships thus obtained are both equal.

Data S4, S4 indicating the relationship between this wavelength λ and the amount of detected light
' is sent to a display device 35.35° for displaying this relationship or for recording the relationship in a recording means.

In this case as well, the light intensity of each of the light beams L3 and I31 can be determined based on the light intensity data S2 and S2', and by adding them together through separate calculations, the absolute light intensity of the diffracted light to be measured can be determined. is possible.

Next, an embodiment will be described in which the light to be measured is guided in the same waveguide mode in the first and second optical waveguides 12.12°.

Compared to the device shown in FIG. 1, the optical spectrum analyzer of the fifth embodiment shown in FIG. The difference is that they are arranged. The light to be measured passing through this λ/2 plate 70 has its polarization direction rotated by 90'. Therefore, the second optical waveguide 12゛
The guided light LI' is guided in the TE mode similarly to the guided light L1 in the first optical waveguide 12. If this is done, the Bragg condition will be satisfied in exactly the same way on the first optical waveguide 12 side and the second optical waveguide 12' side, and both optical systems will be formed exactly the same. can do.

Next, a sixth embodiment of the present invention will be described with reference to FIG. Compared to the device shown in FIG. 8, this optical spectrum analyzer has a polarizing beam splitter 22 and a mirror 2.
8, a λ/2 plate 70 is placed in the optical path of the light to be measured.
Furthermore, a λ/2 plate 71 is disposed in the optical path of the light beam L3' between the mirror 51 and the polarizing beam sifter 50, and cylindrical lenses 80 and 60' are disposed in place of the LGCs 13 and 13'. The difference is that there are

By arranging the above-mentioned λ/2 plate 70, the guided light L1 in the second optical waveguide 12' is guided in the TE mode in the same manner as the guided light L1 in the first optical waveguide 12 in this case as well. Therefore, in this case as well, the same effects as in the apparatus shown in FIG. 10 can be obtained. Further, in this device, by disposing the λ/2 plate 71, the polarization direction of the light beam L3' incident on the polarizing beam splitter 50 is shifted by 90 degrees from that of the light beam L3, so that both the light beams L3, L31 can be efficiently combined using the polarizing beam splitter 50.

Next, a seventh embodiment of the present invention will be described with reference to FIG. This optical spectrum analyzer is constructed in the same manner as the apparatus shown in FIG. 9, except that a λ/2 plate 70 is disposed in the optical path of the light to be measured between the polarizing beam splitter 22 and the mirror 28.

By arranging the above-mentioned λ/2 plate 70, the guided light L1 in the second optical waveguide 12' is guided in the TE mode in the same manner as the guided light L1 in the first optical waveguide 12 in this case as well. However, in this case as well, the same effects as in the apparatus shown in FIG. 10 can be obtained.

Furthermore, the light beam L3 emitted from the first optical waveguide 12 and the light beam L3 emitted from the second optical waveguide +2'
By separately detecting `` and '', the same effect as in the apparatus shown in FIG. 9 can be obtained.

Note that in each of the embodiments described above,
The frequencies of the surface acoustic waves 15.15' are always equal, but the frequencies of the first and second surface acoustic waves 15.15' may take different values. .

Further, the guided light, which is the light to be measured, may be diffracted twice or more by two or more surface acoustic waves in each of the first optical waveguide 12 and the second optical waveguide 12'. The resolution of optical spectrum analysis improves as the deflection angle δ of the guided light increases, so if diffraction is performed multiple times in this way, the resolution of spectrum analysis can be increased without significantly increasing the frequency of the surface acoustic waves. It is preferable. The reason why the resolution of optical spectrum analysis is increased by doing this is explained in the above-mentioned patent application No. 82-1807.
A detailed description is given in the specification of No. 79.

(Effects of the Invention) As described in detail above, the optical spectrum analyzer of the present invention enables optical spectrum analysis with high resolution. Furthermore, the optical spectrum analyzer of the present invention has a structure in which the light to be measured enters the optical waveguide and is diffracted by surface acoustic waves, so it is small and lightweight, and has two mechanical operating parts. Since it is not equipped with, durability and reliability are also high.

In the optical spectrum analyzer of the present invention, the different polarization components of the light to be measured are guided in separate optical waveguides, and are diffracted and deflected by separate surface acoustic waves. Solve the various problems caused by diffracting and deflecting the guided light of the mode into one surface acoustic wave in the same way.
The wavelength of the light to be measured can always be measured correctly. In addition, since it is configured like a double series, no matter what the polarization direction of the light to be measured is, it is always possible to guide the light to be measured in at least one optical waveguide side, which allows optical spectrum analysis. is never completely impossible.

Furthermore, in the two-layer configuration, it is also possible to detect the absolute light intensity of the diffracted light to be measured, so it is possible to check whether the results of optical spectrum analysis are reliable based on this absolute light intensity. You can also do that.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a device according to a first embodiment of the present invention, FIG. 2 is a side view showing a part of the device of the first embodiment, and FIG. 3 is a side view showing a part of the device of the first embodiment. FIG. 4 is an explanatory diagram illustrating optical beam deflection in the device of the first embodiment; FIG. 5 is an explanatory diagram illustrating separation of optical spectrum in the device of the present invention; FIG. Graphs 7.8.9.10.11 and 12 showing the relationship between the amount of detected light and the surface acoustic wave frequency in the inventive device are the devices in Embodiments 2.3.4.5.6 and 7 of the present invention, respectively. FIG. 11...Substrate 12...First optical waveguide 12'...Second optical waveguide 13.13°...LGC for light beam input 14,14°
...LGC 15 for light beam output...First surface acoustic wave 15'...Second surface acoustic wave 17...First Chirb IDT 17'...Second Chirb IDT 19... High frequency amplifier 20...Sweeper 21
...Collimator lens 22.50...Polarizing beam splitter 23...Light
Source 27.27゛ ...Focusing lens 28.5
1... Mirror 30... First pinhole plate 30
゛ ...Second vinyl pole board

Claims (4)

[Claims] (1) The first part is made of a material that allows surface acoustic waves to propagate.
and a second optical waveguide; a separating means for separating the light to be measured into two polarization components whose polarization directions are orthogonal to each other; and sending each separated light to be measured to the first and second optical waveguides; An input optical system that inputs waveguides in the TE mode and TM mode, respectively, and an input optical system that propagates in a direction intersecting the optical path of the guided light guided in each optical waveguide and continuously diffracts and deflects the guided light. first and second surface acoustic wave generation means for generating surface acoustic waves whose frequencies change in each optical waveguide; and totaling the measured light beams deflected by the surface acoustic waves and emitted to the outside of the respective optical waveguides. An optical spectrum analyzer comprising: a light detection means for detecting; and a frequency detection means for detecting the frequency of the surface acoustic wave when the light detection means detects the light to be measured. (2) The first part is made of a material that allows surface acoustic waves to propagate.
and a second optical waveguide; a separating means for separating the light to be measured into two polarization components whose polarization directions are orthogonal to each other; and sending each separated light to be measured to the first and second optical waveguides; An input optical system that inputs waveguides in the TE mode and TM mode, respectively, and an input optical system that propagates in a direction intersecting the optical path of the guided light guided in each optical waveguide and continuously diffracts and deflects the guided light. first and second surface acoustic wave generation means for generating surface acoustic waves whose frequencies change in each optical waveguide; and separately detecting the measured light beams deflected by the surface acoustic waves and emitted to the outside of the respective optical waveguides. an optical spectrum analyzer comprising: first and second light detection means; and a frequency detection means for detecting the frequency of the surface acoustic wave when at least one of these light detection means detects the light to be measured. (3) The first part is made of a material that allows surface acoustic waves to propagate.
and a second optical waveguide; a separating means for separating the light to be measured into two polarization components whose polarization directions are orthogonal to each other; and sending each separated light to be measured to the first and second optical waveguides; An input optical system that inputs waveguides in the same waveguide mode, and a continuous frequency waveguide that propagates in a direction intersecting the optical path of the guided light guided in each optical waveguide and diffracts and deflects the guided light. first and second surface acoustic wave generating means for generating surface acoustic waves whose values change in each optical waveguide; and detecting the sum of the measured light beams deflected by the surface acoustic waves and emitted to the outside of the respective optical waveguides. An optical spectrum analyzer comprising: a light detection means for detecting the light to be measured; and a frequency detection means for detecting the frequency of the surface acoustic wave when the light detection means detects the light to be measured. (4) The first part is made of a material that allows surface acoustic waves to propagate.
and a second optical waveguide; a separating means for separating the light to be measured into two polarization components whose polarization directions are orthogonal to each other; and sending each separated light to be measured to the first and second optical waveguides; An input optical system that inputs waveguides in the same waveguide mode, and a continuous frequency waveguide that propagates in a direction intersecting the optical path of the guided light guided in each optical waveguide and diffracts and deflects the guided light. first and second surface acoustic wave generation means for generating surface acoustic waves whose values change in each optical waveguide; and separately detecting the measured light beams deflected by the surface acoustic waves and emitted to the outside of the respective optical waveguides. An optical spectrum analyzer comprising first and second light detection means, and a frequency detection means for detecting the frequency of the surface acoustic wave when at least one of these light detection means detects the light to be measured.