JPH0587674A - Optical-transmission-characteristic measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to omit the mechanical angle-position adjusting work by providing a turning mechanism which turns a wavelength selecting diffraction grating and a spectroscopic diffraction grating at the same time, and providing a driving motor which changes a turning angle and a resonance distance at the same time. CONSTITUTION:When a voltage is applied on a piezoelectric element 47, a resonance distance L between a laser semiconductor 32 and a diffraction grating 34 is changed. Laser light 31 passes through a body to be measured 26 and enters into a spectrum analyzing part 28 in a cabinet 21 as light to be measured 38. In the analyzing part 28, the light to be measured 38 is converted into the parallel light through a collimator 40 and thereafter cast into a spectroscopic diffraction grating 35 at an incident angle of theta2. The diffracted light is condensed on a photodetector 45 through a condenser device 42, and the optical intensity signal corresponding to the intensity of the incident light is outputted. When a driving motor 37 is driven, the diffraction gratings 34 and 35 are also turned. The wavelength lambda2 is changed in response to the change in output wavelength of the laser light 31. In this constitution, the wavelength- selecting and spectroscopic-diffraction gratings 34 and 35 are changed in synchronization. Therefor, the adjusting work can be omitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a spectrum analyzing section having a variable wavelength light source composed of an external resonance type semiconductor laser device having a semiconductor laser incorporated therein and a spectroscope to measure the light of an object to be measured such as various optical parts. The present invention relates to an optical transmission characteristic measuring device that measures transmission characteristics.

[0002]

2. Description of the Related Art Generally, lenses, filters, prisms,
It is required to measure the optical transmission characteristics of optical components such as polarizers and optical fibers in a wide band with high sensitivity. An optical spectrum analyzer is a typical measuring device for quantitatively measuring optical transmission characteristics.

This is because white light output from a white light source is incident on one end of the object to be measured, light output from the other end is taken into an optical spectrum analyzer, and wavelength is analyzed by, for example, a spectroscope. To obtain the optical transmission characteristics of the device under test.

However, the light intensity of the generally used white light for each wavelength is a very low value of about -40 dBm. Therefore, the S / N ratio of the light of each wavelength after spectral separation was poor, and it was not possible to secure sufficiently high measurement accuracy.

In order to eliminate such inconvenience, FIG.
, Instead of a white light source, it has a single wavelength λ ₁ ,
An optical transmission characteristic measuring apparatus using a variable wavelength light source 2 that outputs a laser beam 1 that can arbitrarily change the wavelength λ ₁ has been proposed. That is, the laser light 1 output from the variable wavelength light source 2 is input to the spectrum analysis unit 4 as the measured light 12 via the measured body 3. In this case, if the sweep is synchronized with the measurement wavelength lambda ₂ at a wavelength lambda ₁ and the spectrum analyzing portion 4 of the laser beam 1 that is output from the variable wavelength light source 2 has a high dynamic range and S / N, high accuracy Transmission characteristics can be measured.

The variable wavelength light source 2 is composed of, for example, an external resonance type laser device shown in FIG. When a bias voltage is applied from the outside, the same wavelength λ is applied in both the front and rear directions.
_A collimator lens 6 and a diffraction grating 7 are arranged along the optical axis behind the semiconductor laser 5 that outputs laser beams 1a and 1b having ₁ . The collimator lens 6 is a lens for converting the laser light 1b output from the semiconductor laser 5 into parallel light and returning the light reflected by the diffraction grating and returned to the semiconductor laser 5 again. The diffraction grating 7 is fixed to a rotary shaft 9 via a circular support plate 8. The rotating shaft 9 is movably supported by a guide groove 11 formed in the frame 10 along the optical axis direction.

Therefore, when the rotary shaft 8 is rotated by a motor (not shown), the incident angle θ _{1 of} the laser beam 1b with respect to the diffraction grating 7 changes. Further, when the rotating shaft 9 is moved along the guide groove 11, the resonance distance L between the semiconductor laser 5 and the incident position of the diffraction grating 7 changes.

As is well known, by controlling the incident angle θ ₁ and the resonance distance L so as to satisfy the equations (1) and (2), the laser beam 1 output from the front surface of the semiconductor laser 5 can be obtained.
It is possible to arbitrarily change the wavelength λ ₁ of (1a) within a certain range. Here, n and m are natural numbers, and d is the grating interval of the diffraction grating 7.

Mλ ₁ = 2d sin θ ₁ (1) nλ ₁ = L (2) Further, FIG. 9 is a schematic diagram showing a spectroscope portion in a spectrum analysis unit 4 using a spectroscope having a diffraction grating incorporated therein. is there.

The light 12 to be measured which has passed through the device 3 to be measured is incident on the inside of the apparatus through the entrance slit 13 and the collimator 1
After being converted into parallel light at 4, the incident angle θ ₂ is incident on the diffraction grating 15.
Is incident at. The diffraction grating 15 is rotated by a drive motor (not shown). Therefore, the incident angle θ ₂ changes.
The diffracted light output from the diffraction grating 15 is incident on the light receiver 20 arranged behind the exit slit 17 by the condenser 16. The light receiver 20 outputs a light intensity signal corresponding to the light intensity of the incident light.

In such an optical transmission characteristic measuring apparatus, the light under test output from the diffraction grating 15 of the spectrum analysis unit 4 has a measurement wavelength λ ₂ which is uniquely determined by the incident angle θ ₂ at the diffraction grating 15. Becomes Therefore, for example, the wavelengths λ ₁ of the laser light 1 output from the variable wavelength light source 2 and the light receiver 20 of the spectrum analysis unit 4 are made incident by appropriately changing the incident angles θ ₁ and θ ₂ in conjunction with each other. The wavelength λ can be swept while the wavelength λ _{2 of the} diffracted light matches.

By using the variable wavelength light source 2 having such a structure, the light intensity of each wavelength can be increased to -10 dBm or more as compared with the light intensity of the white light described above. As a result, in the spectrum analysis unit 4, it is possible to perform measurement with a sensitivity that is 1000 times or more higher than in the case where the white light source described above is used as the light source.

[0013]

However, as described above, the rotation angle (incident angle) θ ₁ of the diffraction grating 7 of the variable wavelength light source 2 and the rotation angle (incidence angle) of the diffraction grating 15 of the spectrum analysis unit 4 are set. It is necessary to drive θ _{2 so} that the wavelength λ ₁ and the wavelength λ ₂ are always equal. Moreover, it is necessary to control each of the turning angles θ ₁ and θ ₂ with extremely high accuracy. If the synchronization is lost even a little, there is a problem that the spectrum analysis unit 4 cannot obtain the optical transmission characteristics at all.

Since each of the diffraction gratings 7 and 15 has a mechanical drive, it is affected by backlash and the like. Therefore, before the measurement is started, the mechanical angular positions of both must be accurately adjusted before the actual measurement. It is necessary to start the measurement. Therefore, a great deal of labor and time are required for the adjustment preparation work.
In addition, the S of the measured optical transmission characteristic is adjusted according to the adjustment accuracy.
There is also a problem that / N changes.

The present invention has been made in view of such circumstances, and it is provided between the diffraction grating for wavelength selection of the variable wavelength light source and the diffraction grating for spectroscopy of the spectrum analysis unit at the start of measurement and during measurement. An object of the present invention is to provide an optical transmission characteristic measuring device which can omit mechanical angular position adjustment work and can always obtain a constant and high measurement accuracy.

[0016]

In order to solve the above-mentioned problems, the present invention is to reflect the laser light outputted from one of the semiconductor lasers whose one end face is AR-coated by a diffraction grating for wavelength selection, and to select the wavelength. A variable wavelength light source for variably controlling the wavelength of laser light output from the other of the semiconductor lasers by changing the resonance distance from the diffraction grating for semiconductor laser to the semiconductor laser and the incident angle of laser light to the diffraction grating for wavelength selection. Optical transmission characteristics of the object to be measured by capturing the laser light output from the variable wavelength light source as the light to be measured through the object to be measured and analyzing the wavelength of the acquired light to be measured using a diffraction grating for spectroscopy. In the optical transmission characteristic measuring device including a spectrum analysis unit for measuring the wavelength, a rotation mechanism for rotating the wavelength selection diffraction grating and the spectroscopy diffraction grating about the same rotation axis is provided. Eteiru.

According to another aspect of the invention, the rotating mechanism includes a rotating arm to which a wavelength selecting diffraction grating and a spectral diffraction grating are mounted separately from each other, and a spectral diffraction grating in the rotating arm. The rotation axis provided at the incident point of and the rotation angle and the resonance distance of the diffraction grating and the wavelength selection diffraction grating are changed at the same time by rotating the rotation arm around the rotation axis. It is equipped with a drive motor for driving.

[0018]

With the optical transmission characteristic measuring device having such a configuration, the variable wavelength light source for outputting the laser beam incident on the object to be measured and the spectrum analyzing section on which the object to be measured via the object to be measured are incident For example, they are stored in the same case,
The diffraction grating for wavelength selection of the variable wavelength light source and the diffraction grating for spectroscopy of the spectrum analysis unit are rotated about the same rotation axis.

The rotational angular positional relationship between the diffraction gratings is adjusted in advance at the time of manufacturing this device. Therefore, for example, when the rotation shaft is rotated by the drive motor, each of these diffraction gratings is interlocked and rotated while maintaining a constant rotation angle positional relationship. Therefore, the positional relationship between the diffraction gratings is completely unaffected by backlash and the like. As a result, it is not necessary to perform adjustment work at the time of starting measurement. Further, the wavelength of the laser light output from the variable wavelength light source and the wavelength of the diffracted light output from the diffraction grating in the spectrum analysis unit, that is, the measurement wavelength always match exactly.

Further, in another invention, for example, a diffraction grating for spectroscopy in the spectrum analysis unit is attached to the rotation axis position set on the rotation arm. Therefore,
When the rotation arm is rotated around the rotation axis by the drive motor, the spectroscopic diffraction grating is rotated.

Further, a diffraction grating for wavelength selection in the variable wavelength light source is attached at a position apart from the rotation axis position of the rotation arm. Therefore, the incident position of the laser light from the semiconductor laser of the diffraction grating for wavelength selection does not coincide with the rotational axis position of the rotational arm. Therefore, when the rotating arm is rotated around the rotating shaft by the drive motor, the incident angle of the laser beam with respect to the wavelength selecting diffraction grating is changed and the resonance distance from the wavelength selecting diffraction grating to the semiconductor laser is changed. Also changes. That is, since the incident angle and the resonance distance change in conjunction with each other, when the rotation arm is rotated, the wavelength of the laser light output from the variable wavelength light source and the measurement wavelength of the spectrum analysis unit change in conjunction with each other.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is an external view showing the entire optical transmission characteristic measuring apparatus of the embodiment. An operation panel 22, on the front surface of the housing 21,
A display unit 23, a laser light output terminal 24a, a measured light input terminal 24b, and the like are provided. The laser light output from the output terminal 24a enters the device under test 26 through the optical fiber 25a. The laser light that has passed through the object to be measured 26 is measured as light to be measured through the optical fiber 25b and the input terminal
It is incident on 4b. That is, the variable wavelength light source and the spectrum analysis unit are incorporated in one housing 21.

FIG. 1 is a schematic diagram showing a variable wavelength light source incorporated in a housing 21 and a flow of light in a spectrum analysis unit. A spectrum analysis unit 28 is installed on a substrate 27, and the spectrum analysis unit 28 is installed. A variable wavelength light source 29 is installed on the upper surface of a ceiling plate (not shown).

In the tunable wavelength light source 29, laser light 31, 31a having the same wavelength λ _{1 in} both the front and rear directions.
A collimator lens 33 and a wavelength selection diffraction grating 34 are disposed behind the semiconductor laser 32 that outputs the light. The laser semiconductor 32 is attached to a piezoelectric element 47 fixed to the substrate 27 via a supporting member 46 as shown in FIG. This piezoelectric element 47 expands and contracts in the direction of the arrow in the figure when a voltage is applied from the outside. As a result, the resonance distance L between the laser semiconductor 32 and the diffraction grating 34 changes.
Specifically, the resonance distance L is described above in accordance with the wavelength change.
The voltage value applied to the piezoelectric element 47 is adjusted so as to satisfy the expression (2).

Nλ ₁ = L (2) The diffraction grating 34 shares the rotating shaft 36 with the diffraction grating 35 for spectroscopy of the spectrum analysis unit 28 located below the diffraction grating 34. The rotation shaft 36 penetrates the substrate 27 downward, and the drive motor 3 mounted on the lower surface of the substrate 27.
It is fixed to the rotating shaft of 7. Therefore, when the drive motor 37 is rotationally driven, the diffraction grating 34 of the laser light 31a
Since the incident angle θ ₁ with respect to
The wavelength λ _{1 of the} laser beam 31 outputted from the front changes. The laser light 31 having the wavelength λ ₁ output from the semiconductor laser 32 is incident on the DUT 26 via the output terminal 24a and the optical fiber 25a of FIG.

The laser light 31 which has passed through the object to be measured 26 is attenuated based on the optical transmission characteristics of the object to be measured 26, and as the light to be measured 38, is transmitted through the optical fiber 25b and the input terminal 24b to the inside of the housing 21. Spectrum analysis unit 28
Incident on.

In the spectrum analyzer 28, the measured light 38 incident from the outside passes through the entrance slit 39 and is converted into parallel light by the collimator 40.
The light is incident on the diffraction grating 35 fixed to 6 at an incident angle θ ₂ . The diffraction grating 35 is rotated by the drive motor 37, and the incident angle θ ₂ changes. The diffracted light output from the diffraction grating 35 is condensed by the condenser 42 into the light receiver 45 via the lens 44 disposed behind the emission slit 43. Light receiver 45
Outputs a light intensity signal corresponding to the light intensity of the incident light.

The light intensity signal output from the light receiver 45 is processed by a signal processing circuit (not shown), and then displayed in dB on the display 23 with the wavelength on the horizontal axis.

Therefore, when the drive motor 37 is rotationally driven, the diffraction gratings 34 and 35 rotate in conjunction with each other, and the laser light 31a and the measured light 3 incident on the diffraction gratings 34 and 35, respectively.
8 incident angle θ ₁ . θ ₂ changes in conjunction. Therefore, the output wavelength λ of the laser light 31 output from the variable wavelength light source 29
The measurement wavelength λ ₂ of the spectrum analysis unit 28 changes in response to the change of ₁ .

Next, the actual incident angles θ ₁ and θ ₂ and the respective waves λ
The relationship between ₁ and λ ₂ will be explained using equations.

Output laser light 3 from variable wavelength light source 29
The relationship between the wavelength λ _{1 of 1} and the incident angle θ ₁ with respect to the diffraction grating 34 is expressed by the above-mentioned expression (1).

[0033] _{mλ 1 = 2d sinθ 1 ... (} 1) Therefore, the wavelength of when the incident angle θ ₁ is Δθ ₁ change λ ₁
The variation Δλ _{1 of} is given by the following relational expression (3).

[0034] _{mΔλ 1 = (2d sinθ 1)} '= 2d cosθ 1 · Δθ 1 ... (3) Similarly, the measurement wavelength lambda ₂ of the variation Δλ of when the incident angle theta ₂ in the spectrum analyzing portion 28 is [Delta] [theta] ₂ was varied ₂ will be described.

Now, suppose that the incident angle of the measured light 38 with respect to the diffraction grating 35 is α and the outgoing angle is β, as shown in FIG. Now, incident light (incident angle α) and diffracted light (exit angle β)
With the bisector of the angle formed by and as a reference line, the angle between this reference line and the normal to the diffraction grating 35 is the above-mentioned angle θ, and the angle between the reference line and the incident light and the emitted light is α ₀ . To do.
Then, the relationship between the measurement wavelength λ ₂ and the angle θ of the diffraction grating 35 is given by equation (4).

Mλ ₂ = 2d cosα ₀ · sin θ (4) In this equation (4), since (2d cosα ₀ ) is a constant, if 2d cosα ₀ = A, then equation (4) becomes (5) ) It becomes an expression.

Mλ ₂ = A sin θ (5) Therefore, by the same method as in the case of the variable wavelength light source 29, the variation Δλ ₂ of the measurement wavelength λ ₂ , the angle θ and the variation Δ.
The relationship with θ is given by Eq. (6).

MΔλ ₂ = A cos θ · Δθ (6) From the above relational expression, the condition for synchronizing the output wavelength λ ₁ of the laser light 31 of the variable wavelength light source 29 and the measurement wavelength λ ₂ of the spectrum analysis unit 28 Ask. Now, at the wavelength λ ₁ of the laser light 31 output from the variable wavelength light source 28
Let θ _a , d _a , and m _{a in the} equation (1) be θ _a , d _a , and m _a , respectively.
Measurement wavelength lambda ₂ in (5) of theta of Supesutoramu analysis unit 28, d, respectively m θ _b, d _b, When _{m b, m a λ 1 =} 2d a sinθ a ... (7) m b λ 2 _{= A sinθ b ... (8)} m a Δλ 1 = 2d a cosθ a · Δθ ... (9) m b Δλ 2 = A cosθ b · Δθ ... (10) A = 2d b cosα 0 ... (11) here, In order to synchronize the wavelength λ ₁ of the variable long wavelength light source 29 and the measurement wavelength λ ₂ of the spectrum analysis unit 28,
In equations (7) and (8), λ ₁ = λ _2, and in (9) and (10),
It suffices if Δλ ₁ / Δθ = Δλ ₂ / Δθ holds. Therefore, the following equations (12) and (13) are obtained.

2d _a sin θ _a / m _a = A sin θ _b / m _b (12) 2d _a cos θ _a / m _a = A cos θ _b / m _b (13) Therefore, the expressions (12) and (13) are satisfied. As shown in FIG. 1, each diffraction grating 34.35 is fixed to the same rotary shaft 36 so that the rotary shaft 36 can be rotated by the drive motor 37. Thus, the output wavelength λ ₁ of the variable wavelength light source 29 and the measurement wavelength λ ₂ of the spectrum analysis unit 28 can be perfectly synchronized.

According to the optical transmission characteristic measuring device having such a configuration, the diffraction grating 3 for wavelength selection of the variable wavelength light source 29 is used.
4 and the spectral diffraction grating 35 of the spectrum analysis unit 28 are fixed to one rotary shaft 36, the incident angles θ of the laser light 31 and the measured light 38 with respect to each diffraction grating 34.35. ₁ and θ ₂ always change in a completely synchronized state while maintaining a constant relationship. As a result, there is no need to adjust the mechanical angular position of both. Therefore, the work efficiency of the adjustment preparation work can be significantly improved.

Further, once the angular position is adjusted accurately in the manufacturing process, the relative angular position between the two does not change thereafter, so that a consistently high measurement accuracy can be maintained.

FIG. 5 is a schematic view showing an essential part of an optical transmission characteristic measuring apparatus according to another embodiment of the present invention.

In the optical transmission measuring device of this embodiment,
Diffraction grating 34a for wavelength selection in the variable wavelength light source 29
As shown in the figure, the diffraction grating 35a for spectroscopy in the spectrum analysis unit 28 includes one rotation arm 48.
Installed on. Then, a rotating shaft 49 is attached to the incident position of the measured light 38 on the diffraction grating 35a for spectroscopy on the rotating arm 48. Therefore, the rotating shaft 4
9 is away from the incident position of the laser beam 31a output from the semiconductor laser 32 on the diffraction grating 34a for wavelength selection by a distance La. The rotary shaft 49 penetrates the substrate 27 downward and is fixed to a rotary shaft of a drive motor 59 attached to the lower side of the substrate 27. Therefore, when the drive motor 50 is rotated, the rotating arm 48 is rotated in the arrow direction.

When the rotating arm 48 rotates, the incident angle θ ₂ of the measured light 38 with respect to the diffraction grating 35a mounted at the center of rotation and the diffraction grating mounted at a position separated by a distance La from the center of rotation. Laser light 31a for 34a
The incident angle θ ₁ of changes. Further, when the rotating arm 48 rotates, the semiconductor laser 32 moves to the diffraction grating 34.
The resonance distance L up to a changes.

Therefore, when the drive motor 50 is rotated, not only the incident angles θ ₁ and θ ₂ of the respective incident lights with respect to the diffraction gratings 34a and 35a but also the resonance distance L are changed at the same time. Therefore, when the wavelength λ ₁ of the laser light 31 is changed as in the previous embodiment, the resonance distance L is independently changed as shown in FIG. 3 in response to the change of the wavelength λ ₁ . There is no need to provide a mechanism. Therefore, the configuration of the control system is further simplified. Also, the manufacturing cost of the entire device can be reduced.

Next, the distance La, the resonance distance L, and the diffraction grating 3
The relationship between the incident angle θ ₁ of the laser beam 31a with respect to 4a will be described with reference to FIGS.

As shown in FIG. 6A, the semiconductor laser 3
The laser light 31a output from the rear of the diffraction grating 34
Is incident at an incident angle theta ₁ with respect to the resonance distance in this case is at L, the relationship between the semiconductor laser 32 to the wavelength lambda ₁ of the laser beam 31 to be output to the forward previously described (1) (2) It becomes an expression.

Mλ ₁ = 2d sin θ ₁ (1) nλ ₁ = L (2) If m = 1, then equation (1) becomes equation (14).

Λ ₁ = 2d sin θ ₁ (14) Here, the resonance distance L and the incident angle θ ₁ (rotation angle) required when changing the output wavelength λ ₁ of the laser light 31 by a minute amount Δλ. Substituting the changes ΔL and Δθ into the above equations, the equations (15) and (16) are obtained.

ΔL = nΔλ (15) Δθ = Δλ / (2d cos θ ₁ ) (16) Next, as shown in FIG. 6B, on the extension line of the incident surface of the laser beam 31 a in the diffraction grating 34. By setting the rotation center (rotation axis 49), the diffraction grating 34 is rotated about the rotation axis 49 by Δ.
Change amount ΔL of the resonance distance L when rotated by θ
Can be approximated as ΔL = LaΔθ (17) when the change amount Δλ of the wavelength λ ₁ is small. Therefore, the turning radius La can be La = ΔL / Δθ = 2d (L / λ ₁ ) cos θ (18) When the incident angle (rotation angle) θ ₁ is changed by Δθ in order to change the wavelength λ ₁ by Δλ, the resonance distance L is also changed by the distance ΔL corresponding to the wavelength change amount Δλ.

Therefore, if the change range of the output wavelength λ ₁ is within the fixed wavelength range, the laser beam 1 output from the semiconductor laser 2 is simply changed by changing the turning angle of the turning arm 48.
The wavelength λ ₁ of a can be changed.

[0052]

As described above, according to the optical transmission characteristic measuring apparatus of the present invention, the diffraction grating for changing the wavelength of the laser light output from the variable wavelength light source and the measured light in the spectrum analyzing section. A rotating mechanism is provided for rotating the diffraction grating for separating the light around the same rotation axis.
Therefore, the wavelength of the laser light output from the variable wavelength light source and the measurement wavelength in the spectrum analysis unit can always be synchronized and maintained at the same wavelength. As a result, complicated adjustment work before and during the measurement can be omitted, and the measurement work efficiency can be significantly improved. Furthermore, it is possible to maintain a constantly high measurement accuracy. Further, since the driving mechanism of each diffraction grating is common, the structure of the entire device is simplified and the manufacturing cost can be reduced.

Further, by using the rotating arm, the incident angle and the resonance distance of the incident light on each diffraction grating can be simultaneously changed by one rotating mechanism. Therefore, the effects described above can be further improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an optical transmission characteristic measuring apparatus according to an embodiment of the present invention,

FIG. 2 is a perspective view showing the entire apparatus of the embodiment,

FIG. 3 is a schematic view showing a main part of a variable wavelength light source in the apparatus of the embodiment,

FIG. 4 is a diagram for explaining the operation principle of the apparatus of the embodiment.

FIG. 5 is a schematic view showing an essential part of an optical transmission characteristic measuring apparatus according to another embodiment of the present invention,

FIG. 6 is a view for explaining the operation principle of the apparatus of the embodiment,

FIG. 7 is a perspective view showing a conventional optical transmission characteristic measuring device,

FIG. 8 is a schematic configuration diagram of a variable wavelength light source in the conventional device,

FIG. 9 is a schematic configuration diagram of a spectrum analysis unit in the conventional apparatus,

[Explanation of symbols]

26 ... Object to be measured, 27 ... Substrate, 28 ... Spectrum analysis section, 29 ... Variable wavelength light source, 31 ... Laser light, 32 ... Semiconductor laser, 34, 34a ... Wavelength selection diffraction grating, 3
5.35a ... Diffraction grating for spectroscopy, 36, 49 ... Rotation axis,
37, 50 ... Drive motor, 38 ... Measured light, 40 ... Collimator, 42 ... Concentrator, 45 ... Photoreceiver, 47 ... Piezoelectric element, 48 ... Rotating arm.

Claims (2)

[Claims] 1. A laser beam (31a) output from one of the semiconductor lasers (32) is reflected by a diffraction grating (34) for wavelength selection, and a resonance distance from the diffraction grating for wavelength selection to the semiconductor laser. (L) and the incident angle (θ ₁ ) of the laser light with respect to the wavelength selection diffraction grating is changed to variably control the wavelength (λ ₁ ) of the laser light (31) output from the other of the semiconductor lasers. The external resonator type variable wavelength light source (29) and the laser light output from this variable wavelength light source are taken in as measured light (38) through the measured object (26), and the taken measured light is collected. In a light transmission characteristic measuring device comprising a spectrum analysis unit (28) for measuring the light transmission characteristic of the DUT by wavelength analysis using a diffraction grating for spectroscopy (35), the diffraction grating for wavelength selection and Rotate the spectroscopic diffraction grating about the same rotation axis. Optical transmission characteristic measuring apparatus comprising the rotating mechanism (36,37,48,49,50) that. 2. The rotating mechanism includes a rotating arm (48) to which the wavelength selecting diffraction grating and the spectral diffraction grating are attached separately from each other, and the spectral diffraction grating in the rotating arm. A rotating shaft (49) provided at a position to be the center of the rotating shaft, and the diffraction grating and the wavelength selecting diffraction grating by rotating the rotating arm with the rotating shaft as an axis. 2. The optical transmission characteristic measuring device according to claim 1, further comprising a drive motor (50) for simultaneously changing each rotation angle and the resonance distance.