JP2004157082A - Optical spectrum analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable high-speed measurement having a wide wavelength range. <P>SOLUTION: A reflector 30 for reflecting diffracted light G1 from a diffraction grating 25 is constituted of fixed substrates 31, 32, shaft parts 33, 34 torsionally deformable along the length direction, elongated with a prescribed width and a prescribed length from the edges thereof, a reflection plate 35 formed by being connected to the tips of the shaft parts 34, 34 at the edge parts thereof and having a reflecting surface formed on one face side. A force is applied to the reflection plate 35 by an electric signal having a frequency corresponding to the characteristic frequency of a part comprising the shaft parts 33, 34 and the reflection plate 35 of the reflector 30, and thereby the reflection plate 35 is reciprocatively rotated with the characteristic frequency or the frequency similar thereto. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for enabling a high-speed measurement of a wide wavelength band in an optical spectrum analyzer for measuring intensity characteristics with respect to light wavelength.
[0002]
[Prior art]
Conventionally, an optical spectrum analyzer 10 having the configuration shown in FIG. 11 has been used as a system for measuring the intensity characteristics with respect to the wavelength of light.
[0003]
In the optical spectrum analyzer 10, the measured light S input through an optical fiber or the like (not shown) is converted into a measured light (parallel light) S ′ having a substantially constant beam width by a collimating lens 11, and the diffraction grating 12 To the diffraction surface 12a.
[0004]
The diffraction grating 12 diffracts the measured light S ′ and emits each wavelength component included in the measured light S ′ at an angle corresponding to the wavelength.
[0005]
Diffracted light G1 emitted from the diffraction grating 12 with respect to the measured light S 'is reflected by the reflection surface 13a of the reflector 13, and the reflected light R is incident on the diffraction surface 12a of the diffraction grating 12.
[0006]
The diffracted light G2 of the diffraction grating 12 with respect to the reflected light R is emitted to the light receiving element 14 side.
[0007]
The drive unit 15 changes the angle of the reflection surface 13a of the reflector 13 to vary the wavelength of the light received by the light receiving element 14.
[0008]
In the optical spectrum analyzer 10 configured as described above, the wavelength of the light received by the light receiving element 14 is swept within a predetermined range by rotating the reflector 13 by the driving unit 15, and each light included in the light to be measured is included. The intensity of the light having the wavelength can be detected.
[0009]
In the optical spectrum analyzer 10 having such a configuration, the reflector 13 and the driving unit 15 may be configured such that a plane mirror is rotationally driven by a motor or a U-shaped tuning fork having a plane mirror fixed to a free end. A type in which the angle of a plane mirror is changed (Patent Document 1) or a type in which a plane mirror is fixed to one end of a bending displacement type actuator made of piezoelectric ceramics, and the actuator is vibrated with reference to the other end. (Patent Document 2).
[0010]
[Patent Document 1]
Japanese Patent Publication No. 5-28331 [Patent Document 2]
JP-A-6-341901
[Problems to be solved by the invention]
However, in the case where the plane mirror is rotationally driven by the motor as described above, a large rotation angle can be obtained, but high-speed wavelength sweep cannot be performed.
[0012]
On the other hand, in the case of using the vibration of the U-shaped tuning fork or the piezoelectric element described above, high-speed wavelength sweeping is possible, but since the center of the vibration is far away from the plane mirror, the angle of the plane mirror itself changes greatly. This makes it difficult to perform measurement over a wide wavelength range.
[0013]
SUMMARY OF THE INVENTION It is an object of the present invention to solve this problem and to provide an optical spectrum analyzer capable of measuring a high-speed and wide wavelength range.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, an optical spectrum analyzer according to claim 1 of the present invention comprises:
Incident portions (22, 24) for receiving the light to be measured;
A diffraction grating (25) for receiving the light to be measured incident from the incident portion;
A reflector (30) that receives, on a reflecting surface, diffracted light emitted from the diffraction grating with respect to the incident light to be measured, and reflects the diffracted light to the diffraction grating;
A light receiving element (45) for receiving diffracted light emitted from the diffraction grating with respect to reflected light emitted from the reflector;
Reflector driving means (41, 41 ', 42, 42', 50) for varying the wavelength of light received by the light receiving element by changing the angle of the reflection surface of the reflector with respect to the diffraction grating; In an optical spectrum analyzer,
The reflector is
Fixed substrates (31, 32),
A shaft portion (33, 34) extending from the edge portion of the fixed substrate at a predetermined width and a predetermined length and capable of being twisted and deformed along the length direction;
A reflection plate (35) formed by being connected to the tip of the shaft portion at its own edge, and having on one surface thereof the reflection surface for reflecting the diffracted light from the diffraction grating; ,
The reflector driving means,
A force is applied to the reflector by an electric signal having a frequency corresponding to the natural frequency of the portion composed of the shaft portion and the reflector of the reflector, and the reflector is reciprocated at the natural frequency or a frequency close to the natural frequency. It is characterized in that it is configured to cause
[0015]
An optical spectrum analyzer according to a second aspect of the present invention is the optical spectrum analyzer according to the first aspect,
The reflector driving means,
The apparatus is characterized in that an electrostatic force based on the electric signal is periodically applied to an end of the reflector, and the reflector is reciprocated at the natural frequency or a frequency close to the natural frequency.
[0016]
An optical spectrum analyzer according to a third aspect of the present invention is the optical spectrum analyzer according to the first aspect,
The reflector driving means,
An electromagnetic force based on the electric signal is periodically applied to an end of the reflector, and the reflector is reciprocally rotated at the natural frequency or a frequency close to the natural frequency.
[0017]
According to a fourth aspect of the present invention, in the optical spectrum analyzer of the first aspect,
The reflector driving means is configured to transmit the vibration of the vibrating body vibrating by the electric signal to the reflector, and reciprocate the reflector at the natural frequency or a frequency close to the natural frequency. It is characterized by.
[0018]
An optical spectrum analyzer according to a fifth aspect of the present invention is the optical spectrum analyzer according to any one of the first to fourth aspects,
A condenser lens (46) is provided between the diffraction grating and the light receiving element.
[0019]
An optical spectrum analyzer according to claim 6 of the present invention is the optical spectrum analyzer according to any one of claims 1 to 5,
A slit (47) is provided between the diffraction grating and the light receiving element.
[0020]
An optical spectrum analyzer according to a seventh aspect of the present invention is the optical spectrum analyzer according to any one of the first to sixth aspects,
A plurality of the light receiving elements are provided at different positions.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show the configuration of an optical spectrum analyzer 20 to which the present invention is applied.
[0022]
As shown in these figures, the optical spectrum analyzer 20 is configured on a base 21.
[0023]
A high step portion 21 a and a low step portion 21 b are formed on the upper surface side of the base 21, and a fiber support portion 23 supporting one end of the optical fiber 22 is provided on the high step portion 21 a, A collimating lens 24 that converts the measurement light S emitted from the tip of the optical fiber 22 into a light to be measured (parallel light) S ′ having a substantially constant beam width and emits the light upward of the low step portion 21b is fixed. .
[0024]
Here, the optical fiber 22 and the collimating lens 24 constitute an incident portion for receiving the light S to be measured, and a lens is integrally formed at the tip of the optical fiber 22. When the measured light S 'having a substantially constant beam width is emitted, the collimator lens 24 can be omitted.
[0025]
The measured light S ′ emitted from the collimator lens 24 (or the optical fiber 22) is diffracted by a diffraction surface 25a (diffraction groove) of a diffraction grating 25 fixed upright on the low step portion 21b of the base 21. Is formed on the surface on which is formed).
[0026]
The diffraction grating 25 emits light components of each wavelength included in the incident light to be measured S ′ at a diffraction angle corresponding to the wavelength.
[0027]
The diffracted light G1 emitted from the diffraction grating 25 with respect to the measured light S ′ enters a reflector 30 disposed on the low step portion 21b of the base 21.
[0028]
As shown in FIG. 3, the reflector 30 includes a pair of fixed substrates 31 and 32 arranged in parallel with each other in a horizontally long rectangle, and fixed substrates 31 and 32 from the center of the long side edges of both fixed substrates 31 and 32. A pair of shaft portions 33, 34 extending in a direction orthogonal to 31, 32 with a predetermined width and a predetermined length and capable of being twisted and deformed along the length direction, and one long side edge portion of a horizontally long rectangle. It has a reflector 35 connected at the center to the tip of the shaft 33 and connected to the tip of the shaft 33 at the center of the other long side edge.
[0029]
Since the central portion of the reflecting plate 35 is supported by the torsionally deformable shaft portions 33 and 34, the reflecting plate 35 can rotate with respect to the fixed substrates 31 and 32 around a line connecting the shaft portions 33 and 34 as a center axis. it can. The natural frequency f0 of the portion composed of the shaft portions 33 and 34 and the reflection plate 35 is determined by the shape and mass of the reflection plate 35 itself and the spring constant of the shaft portions 33 and 34.
[0030]
A reflection surface 36 for reflecting light is formed on one surface 35 a of the reflection plate 35. The reflecting surface 36 may be formed by mirror-finishing the reflecting plate 35 itself, or may be formed by depositing or bonding a film having a high reflectance (not shown). The reflector 30 is cut out of a highly conductive substrate and has conductivity.
[0031]
The reflector 30 is supported on one surface side of a support substrate 40 that is fixed upright on the low step portion 21 b of the base 21.
[0032]
The support substrate 40 is made of a material having an insulating property, and support tables 40a and 40b protruding forward are formed on the upper and lower portions on one surface side. The fixed substrates 31 and 32 of the reflector 30 are Are fixed in contact with the support bases 40a and 40b.
[0033]
Electrode plates 41 and 42 are formed at opposite ends of the central portion of the support substrate 40 on one surface side, respectively, to face both ends of the reflector 35 of the reflector 30 in a pattern.
[0034]
The electrode plates 41 and 42 constitute a reflector driving unit of this embodiment together with a drive signal generator 50 to be described later, and apply an electrostatic force alternately and periodically to both ends of the reflector 35. Then, the reflection plate 35 is reciprocally rotated.
[0035]
The reflector 30 configured as described above receives the diffracted light G1 from the diffraction grating 25 on the reflection surface 36 of the reflection plate 35, makes the reflected light R incident on the diffraction grating 25, and diffracts the light.
[0036]
The light receiving element 45 is fixed to the high step portion 21a of the base 21, and receives the diffracted light G2 emitted from the diffraction grating 25 with respect to the reflected light R.
[0037]
The wavelength of the diffracted light G2 received by the light receiving element 45 changes according to the angle of the reflector 35 of the reflector 30.
[0038]
Further, as shown in FIGS. 4A and 4B, the drive signal generator 50 corresponds to the natural frequency f0 with respect to the electrode plates 41 and 42 based on the potential of the reflector 30. Applied to the electrode plate 41 and one end of the reflection plate 35 and between the electrode plate 42 and the An electrostatic force (attraction) is alternately and periodically applied between the reflection plate 35 and the electrode plate 38, and the reflection plate 35 is reciprocated within a predetermined angle range at a natural frequency f0 or a frequency near the natural frequency f0. Although FIG. 4 shows a case where the two signals E1 and E2 are rectangular waves with a duty ratio of 50%, the duty ratio of both signals may be 50% or less, and the waveforms are also rectangular waves. The present invention is not limited to this, and may be a sine wave, a triangular wave, or the like.
[0039]
The output signal of the light receiving element 45 is sampled for each wavelength corresponding to the angle of the reflection plate 35 in a signal processing unit (not shown) and stored in a memory as spectrum data indicating the intensity of light for each wavelength. Is displayed on a display device or the like.
[0040]
In the optical spectrum analyzer 20 configured as described above, the reflector 30 is extended from the pair of fixed substrates 31 and 32 and the edges thereof by a predetermined width and a predetermined length, and can be twisted and deformed along the length direction. The shafts 33, 34, and their own edges are connected to the ends of the shafts 33, 34, are formed in a symmetrical shape with respect to the shafts 33, 34, and the reflection surface 36 is formed on one surface 35a. The reflection plate 35 is configured by the reflection plate 35, and a force is applied to the reflection plate by an electric signal having a frequency corresponding to the natural frequency f0 of a portion formed by the shaft portions 33 and 34 of the reflector 30 and the reflection plate 35. Is rotated back and forth at the natural frequency f0 or a frequency near the natural frequency f0.
[0041]
Therefore, the reflection plate 35 can be reciprocated at high speed with a small amount of electric energy, and the rotation center is located inside the reflection plate 35 (in this case, the center portion). The amount of change in the angle of reflection of the incident light on the reflection surface 36 of the reflection plate 35 is the largest, and the wavelength sweep range can be significantly widened.
[0042]
The spring constant of the shaft portions 33, 34 is determined by the length, width, thickness, and material of the shaft portions 33, 34. The natural frequency f0 depends on the spring constant and the shape, thickness, material, and the like of the reflection plate 35. The natural frequency f0 can be set within a range of several hundreds Hz to several tens KHz by being determined and selecting these parameters.
[0043]
In the optical spectrum analyzer 20 of this embodiment, the reflector 30 is made of a material having high conductivity. However, when the reflector 30 is made of a material having low conductivity, as shown in FIG. The electrode plates 51 and 52 facing the electrode plates 41 and 42 are provided on both sides (or the entire surface) on the opposite surface side of the reflection plate 35, and the electrode plates 53 and 54 are also provided on the back side of the fixed substrates 31 and 32. The electrode plates 51 to 54 are connected by a connection line 55. Electrode plates 56 and 57 that contact the electrode plates 53 and 54 are patterned on the surfaces of the support bases 40a and 40b of the support substrate 40, and at least one of the electrode plates 56 and 57 is used as a reference potential line as described above. What is necessary is just to connect to the signal generator 50.
[0044]
In the reflector 30 of the optical spectrum analyzer 20, the reflecting plate 35 is supported from above and below by the shaft portions 33 and 34 extending from the pair of fixed substrates 31 and 32 separated vertically. The reflector 35 may be supported only by the shaft 34 extending from the shaft 32. However, in this case, when an attractive force in the direction of the support substrate 40 is applied to one end of the reflector 35, the shaft 34 may be inclined toward the support substrate 40. This inclination is corrected by applying a force in a direction away from the camera.
[0045]
Alternatively, the fixed substrates may be formed in a U-shaped frame or a rectangular frame shape by connecting between one ends or both ends of the fixed substrates 31 and 32.
[0046]
Further, the shape of the reflection plate 35 is also arbitrary, and in addition to the above-described horizontally long rectangle, a circle, an ellipse, an ellipse, a rhombus, a square, a polygon, or the like may be used. May be formed asymmetrically.
[0047]
In addition, a large hole or a large number of small holes may be provided inside the reflection plate 35 in order to reduce air resistance during high-speed reciprocating rotation.
[0048]
In the optical spectrum analyzer 20 described above, two electrode plates 41 and 42 facing each other are provided at both ends of the reflector 35 of the reflector 30. However, as shown in FIG. 6, one electrode plate ( For example, the electrostatic force may be applied only by the electrode plate 41).
[0049]
Further, in the optical spectrum analyzer 20 described above, the electrostatic force is applied to the reflection plate 35 by the electrode plates 41 and 42 having a flat plate structure. However, as shown in FIG. 7, both ends of the reflection plate 35 are comb-shaped. On the supporting substrate 40 side, there are provided comb-tooth electrode plates 41 'and 42' for receiving both ends of the comb-tooth shape of the reflection plate 35 with a gap therebetween, and the comb-tooth electrode plates 41 'and 42' are provided. An electrostatic force may be applied to both ends of the reflection plate 35. When such a comb structure is used, both end portions of the reflection plate 35 can be rotated to a position where they enter the gap between the comb electrode plates 41 'and 42'.
[0050]
When the both ends of the reflector 35 are formed in a comb shape as described above and the comb electrode plates 41 'and 42' are used, the reflector 35 and the comb electrode plates 41 'and 42' are Need not overlap, as shown in FIG. 7, a large hole 44 having substantially the same width as the reflector 35 can be provided in the center of the support substrate 40, and air generated when the reflector 35 reciprocally rotates. The resistance can be reduced, and a faster wavelength sweep can be performed.
[0051]
Even in the case of the above-described comb-tooth structure, it is also possible to apply an electrostatic force to only one of the comb-tooth electrode plates (for example, the comb-tooth electrode plate 41 ') as in the case shown in FIG. Good.
[0052]
In each of the above-described reflectors 30, the reflection plate 35 is reciprocally rotated by electrostatic force, but the reflection plate 35 may be reciprocated by electromagnetic force.
[0053]
In this case, for example, a coil is used instead of the above-mentioned electrode plates 41, 41 ', 42, 42', and a magnetic material or a coil is provided at both ends of the reflection plate 35, and between the coils or between the coil and the magnetic material. The reflection plate 35 is reciprocated by the attraction and repulsion generated by the generated magnetic field.
[0054]
Further, as described above, in addition to the method of directly applying the electrostatic force or the electromagnetic force to the reflecting plate 35, the above-described natural frequency f0 by an ultrasonic vibrator or the like or a vibration near the natural frequency f0 is applied to the entire reflecting body 30, and the It is also possible to transmit the vibration to the reflection plate 35 and rotate it back and forth. In this case, the vibration can be transmitted to the reflection plate 35 by providing the vibrator on the back side of the support substrate 40 or on the support bases 40a and 40b.
[0055]
Further, in the above-described optical spectrum analyzer 20, the diffracted light G2 emitted from the diffraction grating 25 with respect to the reflected light R from the reflector 30 is directly incident on the light receiving element 45, but as shown in FIG. A condensing lens 46 is provided between the diffraction grating 25 and the light receiving element 45, and a structure in which the diffracted light G2 from the diffraction grating 25 is condensed by the condensing lens 46 and made incident on the light receiving element 45, as shown in FIG. Thus, the optical spectrum analyzer 20 having a structure in which the slit 47 is provided between the diffraction grating 25 and the light receiving element 45 and the component passing through the slit 47 from the diffracted light G2 from the diffraction grating 25 is incident on the light receiving element 45. The invention can be similarly applied, and the driving method of the reflector 30 having each structure described above can be used. Although not shown, a light component that has passed through the slit 47 from light condensed by the condenser lens 46 may be incident on the light receiving element 45.
[0056]
As shown in FIG. 10, a plurality of (three in this example) light receiving elements 45A, 45B, and 45C are arranged at predetermined intervals, and diffracted lights G2a to G2c of different wavelength bands are provided for each light receiving element. The present invention can be similarly applied to the optical spectrum analyzer 20 configured to receive light, and the reflector 30 having each structure described above and the driving method thereof can be used.
[0057]
Although not shown, the present invention can also be applied to a device in which the above-described condenser lens 46 and slit 47 are provided before each of the light receiving elements 45A to 45C of the optical spectrum analyzer 20 in FIG.
[0058]
【The invention's effect】
As described above, in the optical spectrum analyzer of the present invention, the reflector for reflecting the diffracted light from the diffraction grating is provided with a fixed substrate and a predetermined width extending from the edge thereof at a predetermined width. A shaft portion that can be twisted and deformed along a direction, and a reflection plate formed by connecting its edge to the tip of the shaft portion and having a reflection surface formed on one surface side, and a shaft portion of a reflector. A force is applied to the reflector by an electric signal having a frequency corresponding to the natural frequency of the portion composed of the reflector and the reflector, and the reflector is reciprocated at the natural frequency or a frequency close to the natural frequency.
[0059]
Therefore, the reflecting plate can be reciprocated at high speed, and since the center of rotation is in the reflecting plate, the amount of change in the angle of reflection of the incident light on the reflecting surface of the reflecting plate with respect to the change in the angle can be reduced. The wavelength sweep range can be significantly widened.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration of an embodiment of the present invention. FIG. 2 is a plan view of an embodiment of the present invention. FIG. 3 is an exploded perspective view of a main part of the embodiment of the present invention. FIG. 5 is a diagram illustrating an example of a drive signal according to the embodiment. FIG. 5 is a diagram illustrating a modification of the main part of the embodiment. FIG. 6 is a diagram illustrating a modification of the main part of the embodiment. FIG. 8 shows a modification. FIG. 8 is a plan view of another embodiment of the present invention. FIG. 9 is a plan view of another embodiment of the present invention. FIG. 10 is a plan view of another embodiment of the present invention. ] Plan view of conventional device [Explanation of reference numerals]
20 optical spectrum analyzer 21 base 22 optical fiber 23 fiber support 24 collimating lens 25 diffraction grating 25 a diffractive surface 30 reflector 31, 32 ... fixed substrate, 33, 34 ... shaft portion, 35 ... reflective plate, 36 ... reflective surface, 51 to 54, 56, 57 ... electrode plate, 40 ... support substrate, 41, 42 ... ... Support stand, 44 ... Hole, 45, 45A-45C ... Light receiving element, 46 ... Condenser lens, 47 ... Slit, 50 ... Drive signal generator

Claims (7)

Incident portions (22, 24) for receiving the light to be measured;
A diffraction grating (25) for receiving the light to be measured incident from the incident portion;
A reflector (30) that receives, on a reflecting surface, diffracted light emitted from the diffraction grating with respect to the incident light to be measured, and reflects the diffracted light to the diffraction grating;
A light receiving element (45) for receiving diffracted light emitted from the diffraction grating with respect to reflected light emitted from the reflector;
Reflector driving means (41, 41 ', 42, 42', 50) for varying the wavelength of light received by the light receiving element by changing the angle of the reflection surface of the reflector with respect to the diffraction grating; In an optical spectrum analyzer,
The reflector is
Fixed substrates (31, 32),
A shaft portion (33, 34) extending from the edge portion of the fixed substrate at a predetermined width and a predetermined length and capable of being twisted and deformed along the length direction;
A reflection plate (35) formed by being connected to the tip of the shaft portion at its own edge, and having on one surface thereof the reflection surface for reflecting the diffracted light from the diffraction grating; ,
The reflector driving means,
A force is applied to the reflector by an electric signal having a frequency corresponding to the natural frequency of the portion composed of the shaft portion and the reflector of the reflector, and the reflector is reciprocated at the natural frequency or a frequency close to the natural frequency. An optical spectrum analyzer characterized in that the optical spectrum analyzer is configured to perform the following. The reflector driving means,
The apparatus according to claim 1, wherein an electrostatic force based on the electric signal is periodically applied to an end of the reflection plate, and the reflection plate is reciprocated at the natural frequency or a frequency close thereto. 2. The optical spectrum analyzer according to 1. The reflector driving means,
The electromagnetic force by the electric signal is periodically applied to an end of the reflector, and the reflector is reciprocated at the natural frequency or a frequency close to the natural frequency. 2. The optical spectrum analyzer according to 1. The reflector driving means is configured to transmit the vibration of the vibrating body vibrating by the electric signal to the reflector, and reciprocate the reflector at the natural frequency or a frequency close to the natural frequency. The optical spectrum analyzer according to claim 1, wherein: The optical spectrum analyzer according to any one of claims 1 to 4, wherein a condenser lens (46) is provided between the diffraction grating and the light receiving element. The optical spectrum analyzer according to claim 1, wherein a slit (47) is provided between the diffraction grating and the light receiving element. 7. The optical spectrum analyzer according to claim 1, wherein a plurality of said light receiving elements are provided at different positions.

Images