JP2000304619A - Group velocity decentralized control equipment and group velocity decentralized measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a group velocity decentralized measurement and the control of various objects to be controlled, without trying alignment again. SOLUTION: A light 20 to be controlled enters a diffraction grating 12, and each wavelength is separated and diffracted in the direction corresponding to the wavelength, and enters a corner-cube reflector 10. The reflector is a prism which outputs a reflected light parallel with an incident light, and reflects a light diffracted by the diffraction grating again toward the diffraction grating. The reflector is capable of rectilinear movement while maintaining the incidence direction of the light to be controlled to the reflector to be constant. By moving the reflector, the distance between the reflector and the diffraction grating is changed, and the optical path difference between wavelength components is changed. When the intensity of the light to be controlled is measured with an APD 30 while moving the reflector, peaks corresponding to the compression factor of pulses are detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a group velocity dispersion control device and a group velocity dispersion measurement device used in an optical domain time multiplex system.

[0002]

2. Description of the Related Art With the research and development of an optical domain time multiplex system using ultrashort pulse light, the necessity of controlling and measuring the group velocity dispersion of the ultrashort pulse light is increasing. This is because pulse spread of pulse light occurs due to group velocity dispersion occurring in the transmission path.

In order to utilize the 1.3 μm band zero-dispersion fiber, which has already been laid in large quantities as an optical transmission line, in the 1.55 μm band, it is necessary to make the dispersion of the entire transmission line zero. Thus, there is a need to compensate for group velocity dispersion using a group velocity dispersion controller.

Conventionally, as a group velocity dispersion control device, for example, a document “Ultra High Speed Optical Technology”, published by Maruzen Co., Ltd., pp.228-2
32 "is used.

[0005]

However, in the case of the above-mentioned diffraction grating pair, there is a problem that the components of the diffraction grating pair must be realigned according to the controlled object. Therefore, every time the controlled object is changed, the setting is troublesome.

Accordingly, there has been a demand for a group velocity dispersion control apparatus that can easily control the group velocity dispersion for various controlled objects.

[0007]

According to the present invention, there is provided a group velocity dispersion control apparatus comprising a diffraction grating, a first reflector and a second reflector, wherein the diffraction grating includes a controlled light beam incident from outside. The first reflector reflects the controlled light incident through the diffraction grating in a direction parallel to the incident direction of the controlled light. In order to change the distance between the first reflector and the diffraction grating, the first reflector is configured to be linearly movable, and the second reflector is formed by the first reflector and the diffraction grating. It is characterized in that the controlled light incident through the grating is reflected in a direction parallel to the incident direction of the controlled light and returned to the diffraction grating.

Therefore, first, the controlled light propagated from the outside enters the diffraction grating, and each wavelength component of the controlled light is diffracted in a direction corresponding to the wavelength. Each wavelength component of the controlled light enters the first reflector disposed at a predetermined position, and is reflected in a direction parallel to the respective incident directions, and is therefore reflected toward the diffraction grating.

Subsequently, the controlled light is diffracted by the diffraction grating toward the second reflector. In the second reflector, each wavelength component of the controlled light is reflected in a direction parallel to the incident direction, and is reflected toward the diffraction grating. Therefore, the controlled light follows the same optical path as the outward path, and the diffraction grating, the first reflector,
After propagating in the order of the diffraction grating, it returns to the incident position.

[0010] With this configuration, an optical path difference is generated between the wavelength components in accordance with the distance between the diffraction grating and the first reflector. That is, the component of the long wavelength is propagated in the optical path of a longer distance than the component of the short wavelength. For example, in a pulse that has received a positive group velocity dispersion (a pulse that has received a positive chirp), there is a blue-shifted component near the rear end of the pulse, and the front end of the pulse is a red-shifted component. Thus, as the pulse passes through the device of the present invention, the leading edge approaches the trailing edge during the passage, compressing the pulse. That is, the group velocity dispersion is compensated.

The controlled light returned to the incident position is separated from the incident optical path by using, for example, a beam splitter or the like, and is incident on the light receiver. Then, the light intensity is detected by the light receiver. When the above optical path difference is changed by moving the first reflector, the light intensity detected by the light receiver becomes
It is maximum when the pulse is compressed most. By previously inputting light having a known group velocity dispersion and making the peak position of the light intensity correspond to the position of the first reflector, the magnitude of the target group velocity dispersion of the controlled light can be measured. Can be.

As described above, according to the group velocity dispersion control device of the present invention, it is possible to measure various types of controlled light simply by moving the position of the first reflector linearly. This eliminates the need for re-alignment each time the control target is changed.

In the group velocity dispersion control device according to the present invention,
Preferably, a corner cube reflector is used as the first reflector.

Here, the corner cube reflector is also called a retro-reflector, which causes reflected light to exit from the surface of the corner cube in parallel with the incident light, even if the light beam is incident on the effective incidence surface at any angle. It is a kind of prism that can be.

Further, in the group velocity dispersion control device according to the present invention, preferably, as the second reflector, a first mirror for reflecting incident control light in a predetermined direction, and a controlled mirror reflected by the first mirror. It is preferable to use a polarizing means including a Faraday rotator for rotating the polarization plane of the light by 90 ° and a second mirror for reflecting the controlled light incident through the Faraday rotator toward the diffraction grating.

It is preferable that a Faraday rotator for rotating the polarization plane of the light by 45 ° is provided between the second reflector and the diffraction grating.

By providing the Faraday rotator as described above, the polarization plane of the measured light can be changed by 90 ° between the forward path and the return path. As a result, the loss according to the polarization generated in each element is compensated, so that a polarization independent device can be configured.

In the group velocity dispersion control device according to the present invention, preferably, a right-angle prism having two reflection surfaces perpendicular to each other is used as the first and second reflectors, respectively. It is preferable that the surface perpendicular to each reflection surface of the right-angle prism and the surface perpendicular to each reflection surface of the right-angle prism used as the second reflector are arranged orthogonal to each other.

With such a configuration, the incident light path and the output light path of the controlled light can be separated from each other. Therefore, there is no need to use a beam splitter or the like.

Further, in the group velocity dispersion control device according to the present invention, preferably, a controlled light having a predetermined length, into which the controlled light propagated in the order of the second reflector, the diffraction grating, the first reflector and the diffraction grating is incident. An optical fiber for dispersion compensation may be provided.

The above-described diffraction grating, first reflector, and second
The group velocity dispersion control device including the reflector can control the red chirp, that is, can suppress the advance of the red component. However, blue chirp control (suppression of the advance of the blue component) cannot be performed.
That is, this device has a negative group velocity dispersion (abnormal dispersion). Therefore, as described above, the blue chirp is controlled by passing the controlled light through an appropriate optical fiber exhibiting a positive group velocity dispersion.

For example, a dispersion compensating fiber may be used as the optical fiber.

Usually, this dispersion compensating fiber (DCF: Di
Spersion Compensating Fiber) is used to utilize the optical transmission system for the 1.3 μm band in the 1.55 μm band. A single mode fiber (SMF: Single Mode Fiber) used in the 1.3 μm band has a wavelength of 1.3 μm.
Since m shows zero dispersion, the dispersion is relatively large in the 1.55 μm band. Since the dispersion compensating fiber has the dispersion of the opposite sign, if this dispersion compensating fiber is inserted into the transmission line, the dispersion becomes zero as a whole transmission line and 1.3 μm.
An optical transmission system for the m band can be used in the 1.55 μm band. Such a dispersion compensating fiber has 1.3 μm.
To show a positive group velocity dispersion (normal dispersion) in the m band,
Blue chirp in this band can be controlled.

According to the group velocity dispersion measuring apparatus of the present invention, the apparatus further comprises a diffraction grating, a first reflector and a second reflector,
The diffraction grating diffracts each wavelength component of the controlled light incident from the outside in a direction corresponding to the wavelength,
The first reflector reflects the controlled light incident through the diffraction grating in a direction parallel to the incident direction of the controlled light and returns the light to the diffraction grating. The first reflector is configured to be movable linearly in order to make the distance of the variable light variable, and the second reflector shifts the controlled light incident through the first reflector and the diffraction grating in the incident direction of the controlled light. An avalanche photodiode for detecting the light intensity of the controlled light transmitted in the order of the second reflector, the diffraction grating, the first reflector, and the diffraction grating; It is characterized by having.

Avalanche photodiode (Avalanch)
e Photodiode; hereinafter abbreviated as APD. ) Uses a nonlinear effect, so that the conversion speed from an optical signal to an electric signal is relatively high. Therefore, the pulse width of the controlled light is several hundred fs.
Even in this case, since the light intensity of the controlled light can be measured, the magnitude of the group velocity dispersion can be accurately obtained.

In the group velocity dispersion measuring apparatus of the present invention, preferably, a material having no sensitivity to one-photon absorption and having relatively high sensitivity to two-photon absorption is used as a material for the avalanche photodiode. Good to be.

For example, the material of the avalanche photodiode is preferably Si.

A photodetector using Si (silicon) is
No detection sensitivity for wavelengths of 1.1 μm or more. However, if a light source having a high peak intensity is used so that two-photon absorption occurs, the detection sensitivity to short pulse light having a wavelength of 1.55 μm is increased. The shorter the time width, the higher the peak power and the higher the sensitivity. Since the sensitivity becomes maximum when dispersion compensation is performed, the magnitude of the group velocity dispersion can be accurately measured.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the drawings only schematically show the configuration, arrangement, and size to the extent that the invention can be understood. Further, the conditions and materials such as numerical values described below are merely examples. Therefore, the present invention
There is no limitation to this embodiment.

FIG. 1 is a plan view showing the configuration of the group velocity dispersion control device according to the embodiment. The group velocity dispersion control device of this embodiment includes a corner cube reflector (hereinafter, simply referred to as a reflector) 10 as a first reflector, a diffraction grating (grating) 12, and a mirror 14 as a second reflector. I have. In FIG. 1, the light propagation path is indicated by a solid line b and a broken line r.

Here, the diffraction grating 12 diffracts each wavelength component of the controlled light 20 incident from the outside in a direction corresponding to the wavelength. The reflector 10 converts the controlled light 20 incident through the diffraction grating 12 into the controlled light 20.
Is reflected in a direction parallel to the incident direction of the laser beam and returned to the diffraction grating 12. In addition, in order to make the distance between the reflector 10 and the diffraction grating 12 variable, the reflector 10 is configured to be linearly movable. Further, the mirror 14 controls the controlled light 2 incident through the reflector 10 and the diffraction grating 12.
0 is reflected in a direction parallel to the incident direction of the controlled light 20 and returned to the diffraction grating 12.

FIG. 2 is a diagram showing the configuration of the reflector 10. 2A is a front view, FIG. 2B is a view from above, and FIG. 2C is a view from below.

The reflector 10 is a triangular pyramid-shaped prism and has three right-angled triangular surfaces 11 orthogonal to each other.
a, 11b and 11c and one equilateral triangular surface 11d
And The light incident on the equilateral triangular surface 11d is
The light is reflected by each of the other three surfaces 11a to 11c and exits from the equilateral triangular surface 11d in a direction parallel to the incident beam. Therefore, the light incident on the reflector 10 is reflected in a direction parallel to the incident direction.

The controlled light 20 propagates through the optical fiber 16 and is introduced into the apparatus from the outside. A lens 18 is connected to the tip of the optical fiber 16, and the controlled light 20 is converted into a parallel beam by the lens 18. Then, the controlled light 20 is incident on the main surface 12a (the surface on which the grating is formed) of the diffraction grating 12. Thus, the diffraction grating 12 is arranged at the position where the controlled light 20 is incident.
Note that FIG. 1 shows the positional relationship between the constituent components.
Are shown in such a manner that the incident direction coincides with the horizontal direction in the figure.

The controlled light 2 incident on the diffraction grating 12
0 is separated for each wavelength component and diffracted in a direction corresponding to the wavelength. In FIG. 1, the optical path of the component having a longer wavelength (red) is indicated by a broken line r, and the optical path of the component having a shorter wavelength (blue) is indicated by a solid line b. Since the long wavelength component has a larger diffraction angle than the short wavelength component,
The solid line r and the solid line b do not match.

The reflector 10 is arranged at a position where the controlled light 20 diffracted by the diffraction grating 12 is incident. As shown in FIG. 2, the position 22 at which the controlled light 20 is incident on the diffraction grating 12 passes through the vertex α common to the three right-angled triangles 11 a to 11 c constituting the reflector 10 and passes through the surface 11 d of the regular triangle. Should be located on a straight line β perpendicular to. The pitch of the diffraction grating 12, the diffraction grating 12 and the reflector 10
Is designed in consideration of the wavelength of the controlled light 20 and the like.

The reflector 10 can move linearly while keeping the incident direction of the controlled light 20 on the reflector 10 constant. That is, the reflector 10
Can move in the direction a shown in FIG. 1, that is, the direction along the straight line β shown in FIG. In FIG. 1, the state of the reflector after the movement is indicated by a broken line 10a. When the reflector 10 is moved, the distance between the reflector 10 and the diffraction grating 12 changes, so that the optical path difference between the wavelength components changes.

The controlled light 20 diffracted by the diffraction grating 12
Are incident on the reflector 10 and reflected, and then enter the diffraction grating 12 again. The incident position of the controlled light 20 is different from the incident position 22 described above, and is different depending on the wavelength component. Each wavelength component of the controlled light 20 is diffracted by the diffraction grating 12 in the same direction as the incident direction (horizontal direction in the figure),
Be parallel to each other. Then, each wavelength component enters the mirror 14. Since each wavelength component is reflected in the direction perpendicular to the mirror 14, it is reflected in a direction parallel to the incident direction (horizontal direction in the figure). Therefore, each wavelength component returns to the diffraction grating 12 again. Subsequently, each wavelength component follows the same optical path as the outward path, that is, propagates in the order of the reflector 10 and the diffraction grating 12, and returns to the incident optical path.

A beam splitter 24 is provided on the incident optical path, that is, on the optical path between the lens 18 and the diffraction grating 12. The beam splitter 24 reflects the controlled light 20 propagated in the order of the mirror 14, the diffraction grating 12, the reflector 10, and the diffraction grating 12, and separates the controlled light 20 from the incident optical path. Thereafter, the controlled light 20 passes through the lens 26 and the optical fiber 28 and enters an avalanche photodiode (hereinafter, abbreviated as APD) 30 as a light receiver. The light intensity of the controlled light 20 is detected by the APD 30.

It is preferable to use a material having no sensitivity to one-photon absorption and relatively high sensitivity to two-photon absorption as a crystal material constituting the APD 30. For example, S
It is preferable to use an APD using i as a crystal material.

In this example, the APD is used as the light receiver. However, the present invention is not limited to this, and another device may be used as long as the detection sensitivity changes in proportion to the square of the light intensity.

With the configuration described above, in a system including the reflector 10, the diffraction grating 12, and the mirror 14, the long wavelength component r propagates along an optical path of a longer distance than the short wavelength component b. Therefore, at the time when the light enters the APD 30, an optical path difference occurs between the wavelength components of the controlled light 20 according to the distance between the diffraction grating 12 and the reflector 10.

For example, the controlled light 20 is transmitted from the optical fiber 16
Is assumed to have received a positive group velocity dispersion (positive chirp) at the time of transmission. In such a pulse, there is a blue-shifted component near the rear end of the pulse, and the front end of the pulse is composed of a red-shifted component. Therefore, when this pulse passes through the reflector 10, the diffraction grating 12, and the mirror 14, the front end approaches the rear end during the passage, and the pulse is compressed. That is, the group velocity dispersion is compensated.

The above-mentioned optical path difference changes due to the movement of the reflector 10. As the reflector 10 is moved, the light intensity detected by the APD 30 becomes maximum when the pulse is compressed most. By previously inputting light having a known group velocity dispersion and making the peak position of the light intensity correspond to the position of the reflector 10, the magnitude of the target group velocity dispersion of the controlled light can be measured. .

However, the system composed of the reflector 10, the diffraction grating 12 and the mirror 14 can suppress the advance of the red component, but cannot suppress the advance of the blue component. In such a case, the above-described optical fiber 28 designed to have a predetermined length is used for dispersion compensation.

For example, the wavelength of the controlled light 20 is 1.3 μm
And this light is assumed to have undergone negative group velocity dispersion.
In this case, it is preferable to use a dispersion compensating fiber as the optical fiber 28. 1.3 μm dispersion compensating fiber
To show a positive group velocity dispersion (normal dispersion) in the m band,
Blue chirp control can be performed on light in this band.

With the apparatus configuration described above, the light intensity of the controlled light 20 is measured by the APD 30 while moving the reflector 10. When the reflector 10 is moved along the straight line β, the delay time (delay) between the wavelength components b and r decreases at a certain position. At this time, the pulse width of the light to be measured becomes narrow, and therefore, the power of the light incident on the APD 30 increases, so that two-photon absorption occurs.

FIG. 3 is a graph showing a measurement example (calculation result) by the group velocity dispersion control device of this embodiment. On the horizontal axis, the delay from the peak position at the time of zero dispersion is taken in ps, and the range from -0.1 ps to 0.1 ps is set to 0.0.
The scale is shown every 2ps. The ordinate indicates the APD power in arbitrary units. The scale on the horizontal axis has been calibrated in advance, and the position of 0 (ps) represents the peak position of light without dispersion. The plus (+) direction on the horizontal axis corresponds to the direction of "+" in FIG. 1, and the minus (-) direction corresponds to the direction of "-" in FIG. When the peak position appears in the plus region, it means that the rising portion of the pulse (the front end of the pulse) is red-shifted. That is, a longer wavelength component is advanced as compared with the center wavelength.

As shown in FIG. 3, when the peak position appears in the minus region, it means that the rising portion of the pulse (the front end of the pulse) is shifted blue. That is,
This indicates that the short wavelength component is advanced compared to the center wavelength.

The peaks in the graph are detected when two-photon absorption occurs. The magnitude of this peak corresponds to the magnitude of the group velocity dispersion generated in the controlled object. Further, the deviation of the peak position from 0 (ps) corresponds to the magnitude of the second-order chromatic dispersion.

Therefore, according to the group velocity dispersion control device of this embodiment, the magnitude of the group velocity dispersion generated in an optical fiber or the like can be measured. Therefore, the configuration shown in FIG. 1 is used as a group velocity dispersion measuring device. On the other hand, by inserting this device into the optical path and adjusting the position of the reflector 10, it is possible to control (compensate) the group velocity dispersion generated in the optical fiber or the like.

Also, such a group velocity dispersion control device is
It is suitable for use when introducing laser light into a human body for medical purposes. For such a purpose, pulsed light having a width of about 100 fs is used. However, if the pulse light is introduced as it is through an optical fiber, the pulse spread occurs due to the self-phase modulation effect. So, for example, T
With an iAl ₂ O ₃ laser, 1
A pulse light having a pulse width of about 00 fs is output. This pulse light is input to the above-described group velocity dispersion controller, and a short wavelength component is advanced to broaden the pulse width to about 4 ps. Subsequently, this pulse light is passed through a dispersion compensating fiber to
The pulse width is reduced to about s. This dispersion compensating fiber is introduced into the body. At the tip of the dispersion compensating fiber,
A crystal such as ZnSe or CaSe having an absorption edge in a wavelength band of about 600 nm to 800 nm is provided. When the pulse light passes through this crystal, the pulse width becomes 100 fs.
Shrink to the extent. In this manner, short pulse light can be introduced into the body without causing pulse spread.

[First Modification] Next, a first modification of the group velocity dispersion control device will be described. FIG. 4 is a plan view showing a first modification. FIG. 4A is an enlarged view of a portion corresponding to the vicinity of the mirror 14 shown in FIG. FIG. 4B is a cross-sectional view taken along line II of FIG. 4A.

In this example, instead of the mirror 14, the first
Mirror 32, Faraday rotator 3
Polarizing means 38 constituted by fourth and second mirrors 36
Is provided. The first mirror 32 reflects light diffracted from the diffraction grating 12 in a predetermined direction. First mirror 32
Is reflected by the Faraday rotator 34, enters the second mirror 36, and is reflected toward the diffraction grating 12.
It is preferable to arrange the beam incident on the first mirror 32 and the beam emitted from the second mirror 36 in parallel.

The light reflected by the first mirror 32 has its polarization plane rotated by 90 ° by the Faraday rotator 34.
Therefore, the polarization state of the controlled light 20 is inverted before and after the light enters the polarization unit 38. With such a configuration, it is possible to compensate for a loss corresponding to polarization generated in each element, for example, the diffraction grating 12, and to configure a polarization independent device.

[Second Modification] Next, a second modification of the group velocity dispersion control device will be described. FIG. 5 is a plan view showing a second modification. FIG. 5 is an enlarged view of a portion corresponding to the vicinity of the mirror 14 shown in FIG.

In this example, a Faraday rotator 40 is provided between the mirror 14 and the diffraction grating 12. Diffraction grating 1
The controlled light 20 diffracted from 2 toward the mirror 14 is
The polarization plane is rotated by 45 ° by the Faraday rotator 40. The controlled light 20 reflected by the mirror 14 and returned to the diffraction grating 12 has a polarization plane of 45 by the Faraday rotator 40.
° rotated. Accordingly, the polarization plane of the controlled light reflected by the mirror 14 and returned to the diffraction grating 12 is rotated by 90 ° in the forward and backward directions and inverted. With such a configuration, it is possible to compensate for a loss corresponding to polarization generated in each element, for example, the diffraction grating 12, and to configure a polarization independent device.

[Third Modification] Next, a third modification of the group velocity dispersion control device will be described. FIG. 6 is a block diagram showing a third modification.

In this example, a right-angle prism 4 having two reflection surfaces perpendicular to each other is used as the first and second reflectors.
1 and 42 are used, respectively. Then, a surface perpendicular to each reflecting surface of the right-angle prism 41 used as the first reflector and a right-angle prism 42 used as the second reflector
Are perpendicular to each other. With this configuration, the controlled light 20 diffracted by the diffraction grating 12 enters the right-angle prism 41, is reflected twice in the right-angle prism 41 in the plane of FIG. Return. Then, the controlled light 20 further diffracted enters the right-angle prism 42, and is first reflected in the right-angle prism 42 in a direction perpendicular to the paper surface of FIG.
Subsequently, the light is reflected in a direction parallel to the plane of FIG.

The controlled light 20 passes through the optical fiber 16 and the lens 18 and is introduced into the apparatus from the outside. Then, the controlled light 20 is reflected by the mirror 44 and enters the main surface 12 a of the diffraction grating 12. Diffraction grating 1
The controlled light 20 incident on 2 is separated for each wavelength component and diffracted in a direction corresponding to the wavelength. In FIG. 6, the optical path of the long wavelength component is indicated by a broken line r, and the optical path of the short wavelength component is indicated by a solid line b.

Next, the controlled light 20 is transmitted to the right-angle prism 41
Incident on. The right-angle prism 41 can linearly move in the direction a in FIG. 6 while keeping the incident direction of the controlled light 20 on the right-angle prism 41 constant.
When the right-angle prism 41 is moved, the distance between the right-angle prism 41 and the diffraction grating 12 changes, and the optical path difference between each wavelength component changes.

The controlled light 20 reflected by the right-angle prism 41 enters the diffraction grating 12 again. Diffraction grating 1
Due to 2, each wavelength component of the controlled light 20 is diffracted in the same direction as the incident direction (horizontal direction in the figure) and becomes parallel to each other. Then, each wavelength component enters the right-angle prism 42. Each wavelength component is reflected by the right-angle prism 42 in a direction parallel to the incident direction, and is returned to the diffraction grating 12 again. The optical path from the right-angle prism 42 to the diffraction grating 12 is
It is included in a plane different from the plane of FIG. 6 including the outgoing optical path.

Then, each wavelength component of the controlled light 20 is propagated in the order of the right-angle prism 41 and the diffraction grating 12 through an optical path overlapping the outward path on the paper. Next, after being reflected by the mirror 46, the lens 26 and the optical fiber 28
And is emitted.

The configuration described above is functionally equivalent to the configuration of FIG. However, since the input optical path and the output optical path are separated, there is no need to use a duplexer such as a beam splitter. 1 is the same as that of FIG. 1 except that the diffraction grating 12 is rotated in the p-direction on the paper according to the wavelength of the controlled light 20.

[0065]

According to the group velocity dispersion control device of the present invention, the controlled light is separated into the wavelength components by the diffraction grating, and the wavelength component is controlled between the wavelength components according to the distance between the diffraction grating and the first reflector. Caused an optical path difference. When the optical path difference is changed by moving the first reflector, the light intensity detected by the light receiver becomes maximum when the pulse of the controlled light is compressed most. Therefore, the magnitude of the group velocity dispersion can be measured by this apparatus. Also, the group velocity dispersion can be compensated by using this device. Therefore, various types of controlled light can be measured simply by moving the position of the first reflector linearly, so that it is not necessary to perform alignment again each time the controlled object changes as in the related art.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a group velocity dispersion control device according to an embodiment.

FIG. 2 is a diagram showing a configuration of a corner cube reflector.

FIG. 3 is a diagram illustrating a measurement example by the group velocity dispersion control device according to the embodiment;

FIG. 4 is a diagram showing a first modified example of the group velocity dispersion control device.

FIG. 5 is a diagram showing a second modified example of the group velocity dispersion control device.

FIG. 6 is a diagram showing a third modified example of the group velocity dispersion control device.

[Explanation of symbols]

 10: Corner cube reflectors 11a to 11c: Right triangle surface 11d: Regular triangle surface 12: Diffraction grating 12a: Main surface 14, 44, 46: Mirror 16, 28: Optical fiber 18, 26: Lens 20: Controlled light 22: incidence position 24: beam splitter 30: APD 32: first mirror 34, 40: Faraday rotator 36: second mirror 38: polarizing means 41, 42: right angle prism

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazuo Kikuchi 1139-1 Shinyoshida-cho, Kohoku-ku, Yokohama-shi, Kanagawa 1304 Form Tsunashima Cres Towers 1304 F term (reference) 2G065 AB02 AB14 BA09 BB02 BB10 BB11 BB14 BB28 BB31 DA13 2H049 AA06 AA50 AA59 AA62 BA08 BB61 5K002 AA05 BA02 BA04 CA01 DA02 DA05 EA05 GA08

Claims (10)

[Claims] 1. A device comprising a diffraction grating, a first reflector and a second reflector, wherein the diffraction grating diffracts each wavelength component of the controlled light incident from the outside in a direction corresponding to the wavelength. The first reflector reflects the controlled light incident through the diffraction grating in a direction parallel to the incident direction of the controlled light and returns the light to the diffraction grating; In order to make the distance between the first reflector and the diffraction grating variable, the first reflector is configured to be linearly movable, and the second reflector receives the controlled light incident through the first reflector and the diffraction grating. A group velocity dispersion control device that reflects the controlled light in a direction parallel to the incident direction and returns the reflected light to the diffraction grating. 2. The group velocity dispersion control device according to claim 1, wherein a corner cube reflector is used as the first reflector. 3. The group velocity dispersion control device according to claim 1, wherein the second reflector is a first mirror that reflects the incident controlled light in a predetermined direction, and is reflected by the first mirror. A polarization means including a Faraday rotator for rotating the polarization plane of the controlled light by 90 ° and a second mirror for reflecting the controlled light incident through the Faraday rotator toward the diffraction grating is used. Group velocity dispersion controller. 4. The group velocity dispersion control device according to claim 1, wherein a Faraday rotator for rotating a polarization plane of light by 45 ° is provided between the second reflector and the diffraction grating. Characteristic group velocity dispersion control device. 5. The group velocity dispersion controller according to claim 1, wherein each of the first and second reflectors is a right-angle prism having two reflection surfaces perpendicular to each other, and the first reflector is provided. A plane perpendicular to each reflection surface of the right-angle prism used as the first prism and a surface perpendicular to each reflection surface of the right-angle prism used as the second reflector are arranged so as to be orthogonal to each other. Speed dispersion controller. 6. The group velocity dispersion control device according to claim 1, wherein the controlled light propagated in the order of the second reflector, the diffraction grating, the first reflector, and the diffraction grating is incident thereon. A group velocity dispersion control device comprising an optical fiber for dispersion compensation. 7. The group velocity dispersion controller according to claim 6, wherein a dispersion compensating fiber is used as the optical fiber. 8. A diffraction grating, comprising: a first reflector and a second reflector, wherein the diffraction grating diffracts each wavelength component of the controlled light incident from the outside in a direction corresponding to the wavelength. The first reflector reflects the controlled light incident through the diffraction grating in a direction parallel to the incident direction of the controlled light and returns the light to the diffraction grating; In order to make the distance between the first reflector and the diffraction grating variable, the first reflector is configured to be linearly movable, and the second reflector receives the controlled light incident through the first reflector and the diffraction grating. And the reflected light is returned to the diffraction grating in a direction parallel to the incident direction of the controlled light. The controlled light propagated in the order of the second reflector, the diffraction grating, the first reflector, and the diffraction grating To detect light intensity,
A group velocity dispersion measuring device comprising an avalanche photodiode. 9. The group velocity dispersion measuring apparatus according to claim 8, wherein a material having no sensitivity to one-photon absorption and having relatively high sensitivity to two-photon absorption is used as a material of the avalanche photodiode. A group velocity dispersion measuring device. 10. The group velocity dispersion measuring apparatus according to claim 9, wherein the material of the avalanche photodiode is Si.