JP2004233341A - Optical device and reverse dispersion type double spectrometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical device and a reverse dispersion type double spectrometer which can monitor light, without losing light intensity on a light path. <P>SOLUTION: The device comprises an input means 11 which emits an input light, consisting of plural wavelength regions into a free space; a collimating means 12 which collimates the input light and emits a parallel light L1; a wavelength dispersion means 13 which generates a first diffracted light L7 for use in an output, by giving at least once wavelength dispersion action to the parallel light; output means 18, 19 which output the first diffracted light and which are located at an extension of an output light path, starting from the parallel light L1 to the generation of the first diffracted light L7; monitoring means 20, 21 which monitor a spectral information on a second diffracted light L8, generated in the directions deviating from the output light path, among the diffracted lights generated by each wavelength dispersion action. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an optical device using a wavelength dispersion element such as a grating, a prism, or a grism (a combination of a grating and a prism) and an inverse dispersion double spectrometer, and more particularly, to a wavelength division multiplexing (WDM) system. The present invention relates to an optical device suitable for use in the field of optical communication and an inverse dispersion double spectrometer.

A technique for tapping a part of light using an optical coupler and monitoring this part of light is known (see, for example, Non-Patent Document 1). Also, in an optical device using a wavelength dispersion element (for example, an inverse dispersion double spectroscope), an optical coupler is disposed on the optical path of light input to this device or the light output from the device (that is, this optical path). Thus, a part of the light tapped by the optical coupler is monitored.
Yoshitaka Namihira “DWDM Optical Measurement Technology” published by Optronics, Inc. March 10, 2001 P95

However, when the above technique (optical tap) is used, a part of the light on the optical path is used as monitor light.
An object of the present invention is to provide an optical device and an inverse dispersion double spectroscope that can monitor light without losing the amount of light on the optical path.

  The optical device according to claim 1 is an input unit that emits input light having a plurality of wavelength ranges into free space, a collimator unit that collimates the input light and emits parallel light, and the parallel light. Wavelength dispersion means for generating first diffracted light for output by giving at least one chromatic dispersion action, and disposed on an extension of the output optical path from the parallel light until the first diffracted light is generated An output means for outputting the first diffracted light, and a monitor for monitoring spectral information of the second diffracted light generated in a direction deviating from the output optical path among the diffracted light generated for each wavelength dispersion action. Means.

According to a second aspect of the present invention, in the optical device according to the first aspect, among the diffracted lights generated for each of the wavelength dispersion actions, a predetermined value is provided for at least one of the diffracted lights generated along the output optical path. And a control means for controlling the light operating means based on the spectrum information monitored by the monitoring means.
According to a third aspect of the present invention, there is provided an inverse dispersion double spectroscope according to the first aspect of the present invention, an input unit that emits input light having a plurality of wavelength ranges into free space, and a first chromatic dispersion function for the input light. And a light operating means for performing a predetermined operation on the first diffracted light having a diffraction order different from the 0th-order diffracted light among the diffracted light generated from the first wavelength dispersive means, Generated from the second wavelength dispersion means, the second wavelength dispersion means for giving a second wavelength dispersion action opposite to the first wavelength dispersion action for the light after the operation by the light operation means, Of the diffracted light, all the wavelength elements included in the plurality of wavelength regions are combined to generate second diffracted light that can form the same image, and generated from the first wavelength dispersion means Diffracted light that is different from the 0th-order diffracted light and the first diffracted light At least of the third diffracted light spectrum information and the fourth diffracted light spectrum information of the fourth diffracted light different from the second diffracted light among the diffracted light generated from the second wavelength dispersion means. And a monitoring means for monitoring one of them.

According to a fourth aspect of the present invention, in the inverse dispersion double spectroscope according to the third aspect of the present invention, the inverse dispersive double spectroscope further includes a control unit that controls the optical operation unit based on a monitoring result by the monitoring unit. .
According to a fifth aspect of the present invention, in the inverse dispersion double spectroscope according to the third or fourth aspect, the input means includes an input port formed of a single-wire optical fiber or a multi-wire optical fiber bundle. And the output means includes an output port formed of a single-wire optical fiber or a multi-wire optical fiber bundle.

According to a sixth aspect of the present invention, in the inverse dispersion double spectroscope according to any one of the third to fifth aspects, the light operating means is an attenuation operation with respect to the first diffracted light. It is an attenuator that applies
A seventh aspect of the present invention is the inverse dispersion double spectroscope according to the sixth aspect, wherein the light operating means condenses the first diffracted light to collect a plurality of spectral images having different wavelength ranges. And the attenuation operation is performed for each of the plurality of spectral images.

The invention according to claim 8 is the inverse dispersion double spectroscope according to claim 7, wherein the optical operation means includes an array unit in which a plurality of micromirrors are arranged one-dimensionally, The attenuation operation is performed on each of the plurality of spectral images by each of the micromirrors.
According to a ninth aspect of the present invention, in the inverse dispersion double spectroscope according to the third or fifth aspect, the light operating means performs a beam steering operation on the first diffracted light. is there.

A tenth aspect of the present invention is the inverse dispersion double spectroscope according to the ninth aspect, wherein the light operating means collects the first diffracted light to collect a plurality of spectral images having different wavelength ranges. And the beam steering operation is performed for each of the plurality of spectral images.
The invention according to claim 11 is the inverse dispersion double spectroscope according to claim 10, wherein the optical operation means includes an array unit in which a plurality of micromirrors are arranged one-dimensionally, The beam steering operation is performed on each of the plurality of spectral images by each of the micromirrors.

A twelfth aspect of the present invention is the inverse dispersion double spectroscope according to any one of the third to fifth aspects, wherein the light operating means performs an attenuation operation on the first diffracted light. And beam steering operation.
In a thirteenth aspect of the present invention, in the inverse dispersion double spectroscope according to the twelfth aspect of the invention, the light operating means collects the first diffracted light to collect a plurality of spectral images having different wavelength ranges. And the attenuation operation and the beam steering operation are performed for each of the plurality of spectral images.

According to a fourteenth aspect of the present invention, in the inverse dispersion double spectroscope according to the thirteenth aspect, the optical operation means includes an array unit in which a plurality of micromirrors are arranged one-dimensionally, Each of the plurality of spectral images is subjected to the attenuation operation and the beam steering operation by each of the micromirrors.
The invention according to claim 15 is the inverse dispersion double spectrometer according to any one of claims 10, 11, 13, and 14, wherein the output means includes a plurality of optical fibers. The light operating means makes light having a different wavelength range incident on any one of the optical fibers in the output port.

  The invention according to claim 16 is the inverse dispersion double spectrometer according to any one of claims 10, 11, 13, and 14, wherein the output means includes at least one optical. The optical control unit includes an output port made of a fiber, and makes the light having a different wavelength range enter or not enter any optical fiber of the output ports.

The invention according to claim 17 is the inverse dispersion double spectroscope according to any one of claims 3 to 16, wherein an end of the input means, the first wavelength dispersion means, The optical manipulation means, the second wavelength dispersion means, the monitoring means, and the output means end are packaged in one casing.
According to an eighteenth aspect of the present invention, in the optical device according to the second aspect, an end of the input means, the wavelength dispersion means, the optical operation means, the monitoring means, and an end of the output means. Is packaged in one housing.

  According to the present invention, it is possible to monitor light without losing the amount of light on the optical path.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
Here, an inverse dispersion type double spectroscope will be described as an example. An inverse dispersion type double spectrometer is known as a spectrometer excellent in stray light reduction, and is sometimes called an inverse dispersion type double monochromator or a zero dispersion spectrometer. In this inverse dispersion type double spectroscope, two chromatic dispersion actions (in opposite directions) are sequentially given to the input light, and after receiving the first chromatic dispersion action, the second chromatic dispersion action is applied. Some operation (for example, an attenuation operation in the first embodiment) is performed on the previous diffracted light. Note that the light after the operation is output outside the inverse dispersion type double spectroscope after being subjected to the second wavelength dispersion action. The spectrum of the output light can change depending on the contents of the operation described above.

As shown in FIG. 1, an inverse dispersion double spectrometer 10 according to the first embodiment includes an optical fiber 11 of an input port, a collimator 12, a grating 13, an attenuator (14-17), and a condensing optical system. 18, an output port optical fiber 19, a spectrum monitor (20, 21), a processor 22, and a driver 23.
The inverse dispersion type dual spectrometer 10 is incorporated in, for example, an erbium-doped fiber amplifier (EDFA) in FIG. 2 in a wavelength division multiplexing (WDM) optical communication system, that is, a device for flattening the gain, that is, It operates as a dynamic gain equalizer (DGE). In addition to the inverse dispersion double spectroscope 10, the EDFA is provided with erbium-doped fibers (EDF) 31, 32, an optical multiplexer 33, an optical demultiplexer 34, optical isolators 35, 36, and excitation light sources 37, 38. ing.

  The inverse dispersion type double spectrometer 10 has an input end face (not shown) of the optical fiber 11 at the input port connected to the EDF 31, and an exit end face (not shown) of the optical fiber 19 at the output port connected to the EDF 32. Yes. In this inverse dispersion type double spectrometer 10, multiple types of light having different wavelength ranges are input from the EDF 31 to the optical fiber 11 in a multiplexed state (wavelength multiplexed light), and wavelength multiplexing after attenuation operation described later is performed. Light is output from the optical fiber 19 to the EDF 32. In this specification, the wavelength width of the “wavelength region” is extremely narrow, and light in each wavelength region is regarded as almost monochromatic light.

Here, the arrangement and function of each component (11 to 23) of the inverse dispersion double spectroscope 10 shown in FIG. 1 will be described. Incidentally, the inverse dispersion double spectroscope 10 is configured to function as an inverse dispersion double spectroscope by circulating the optical path twice in one spectroscope as hardware.
The optical fiber 11 at the input port (corresponding to the “input means” in claim 1) is a single line, and is a member (for example, a single) for taking the wavelength multiplexed light from the EDF 31 into the inverse dispersion type double spectrometer 10. Mode fiber). The inside of the inverse dispersion double spectroscope 10 is free space, and the wavelength multiplexed light from the EDF 31 is emitted to the free space by the optical fiber 11. The diameter of the core on the exit end face of the optical fiber 11 is, for example, 10 μm.

The collimator 12 (corresponding to “collimating means” in claim 1) has a positive focal length optimized with respect to the NA (numerical aperture) of the optical fiber 11. The collimator 12 is an optical element (input interface unit) for collimating the wavelength multiplexed light from the exit end face of the optical fiber 11 and guiding it to the grating 13.
The optical fiber 11 and the collimator 12 (corresponding to “input means” in claim 3 as a whole) are arranged so that the emission end face of the optical fiber 11 coincides with the focal position of the collimator 12. For this reason, the wavelength division multiplexed light L1 (corresponding to “input light” in the claims) taken in via the optical fiber 11 and the collimator 12 becomes parallel light. The chief ray of the wavelength multiplexed light L1 coincides with the optical axis 12a of the collimator 12 (FIG. 3). In the following description, a plurality of wavelength ranges included in the wavelength multiplexed light L1 are assumed to be λ1, λ2,.

The grating 13 is a reflective planar diffraction grating in which a number of linear grooves are arranged one-dimensionally at equal intervals. The arrangement direction of the linear grooves corresponds to the wavelength dispersion direction of the grating 13. Further, the grating constant of the grating 13 is as large as several times the wavelength range used, has relatively small polarization characteristics, and is blazed by high-order diffracted light (so-called echelle grating).
The grating 13 gives a first wavelength dispersion action to the wavelength multiplexed light L1 taken in via the optical fiber 11 and the collimator 12. As a result, diffracted light is generated from the grating 13 in various directions. All the diffracted light generated from the grating 13 is parallel to a plane perpendicular to the linear groove of the grating 13 (hereinafter referred to as “reference plane”).

  Of the diffracted light generated from the grating 13, the diffracted light L2 shown in FIG. ) (Diffracted light of the diffraction order with the strongest blaze) (for example, first-order diffracted light), which corresponds to the “first diffracted light” in the claims. As shown in FIG. 3, the chief ray of the diffracted light L2 is slightly different in diffraction angle for each wavelength region λ1, λ2,. A branch point of the chief ray in each wavelength region λ1, λ2,.

  The grating 13 also receives light L5 (FIG. 1) after an attenuation operation by an attenuator (14 to 17) described later. For this light L5, the grating 13 gives a second chromatic dispersion action that is opposite to the first chromatic dispersion action (the action given to the wavelength multiplexed light L1). Also in this case, diffracted light is generated from the grating 13 in various directions parallel to the reference plane.

  Of the diffracted light generated from the grating 13 by the second wavelength dispersion action, the diffracted light L7 shown in FIG. 1 is a part of the diffracted light generated in the direction of the condensing optical system 18 (to be described later). Diffracted light of different diffraction orders) (diffracted light of diffraction order with the strongest blaze) (for example, first-order diffracted light). The diffracted light L8 is a part of diffracted light (diffracted light having a different diffraction order from the diffracted light L7) (for example, 0th order diffracted light) generated in the direction of a spectrum monitor (20, 21) described later.

The light relating to the second wavelength dispersion action (the light L5 after the attenuation operation and the diffracted lights L7 and L8) will be described in detail later. The diffracted lights L7 and L8 respectively correspond to “second diffracted light” and “fourth diffracted light” in the claims. In the first embodiment, the grating 13 corresponds to both “first wavelength dispersion means” and “second wavelength dispersion means” in the claims.
Next, the attenuator (14-17) will be described. The attenuators (14 to 17) are optical attenuators for performing an attenuation operation on the diffracted light L2 from the grating 13, and are composed of a relay optical system 14, a micromirror array 15, a trap mirror 16, and a trap 17. .

  The relay optical system 14 has a positive focal length, and condenses the diffracted light L <b> 2 on the micromirror array 15. Further, as shown in FIG. 3, the principal rays of the diffracted light L3 after passing through the relay optical system 14 are arranged so as to be arranged in parallel for each of the wavelength ranges λ1, λ2,... Λn (telecentric system). Further, aberration correction is performed so that a flat image can be obtained in a necessary image range, and a sufficiently small spot-like monochromatic image can be obtained. A monochromatic image is an image formed by light in an arbitrary single wavelength region.

  As shown in FIG. 4, the relay optical system 14 causes a large number of spectral images A1, A2,..., An having different wavelength regions λ1, λ2,. Are formed in a state of being discretely arranged in a row. Each spectral image A 1, A 2,..., An is a monochromatic image and has a spot shape substantially similar to the exit end face of the optical fiber 11. The wavelength regions λ1, λ2,..., Λn are obtained by separating a plurality of wavelength regions (single wavelengths) included in the wavelength multiplexed light L1.

  When the optical path of the diffracted light L2 incident on the relay optical system 14 is viewed from the side (direction parallel to the reference plane), it is parallel to the optical axis 14a of the relay optical system 14 as shown in FIG. It can also be seen that it is eccentric from the optical axis 14a. For this reason, the optical path of the diffracted light L3 after passing through the relay optical system 14 is inclined with respect to the optical axis 14a. This is to prevent the lights L4 and L5 after being reflected by the micromirror array 15 described below from overlapping the diffracted lights L2 and L3.

As shown in FIG. 4, the micromirror array 15 is an array portion in which a plurality of micromirrors 15a are arranged in a one-dimensional manner (for example, a MEMS (Mycro Electro Mechanical Systems) system). The plurality of micromirrors 15a are all plane mirrors having the same size. The size of the micromirror 15a is approximately several tens of μm square to several hundreds of μm square.
This micromirror array 15 aligns the arrangement direction of the micromirrors 15a with the wavelength dispersion direction of the spectral images A1, A2,..., An, and forms the focal position of the relay optical system 14 (formation of spectral images A1, A2,. Position). The micromirror array 15 has a size of the micromirror 15a larger than the spot diameter of the spectral images A1, A2,..., An, and the interval between the micromirrors 15a is between the spectral images A1, A2,. It is configured to be equal to the interval (interval of principal rays for each of the wavelength ranges λ1, λ2,..., Λn of the diffracted light L3 shown in FIG. 3).

Therefore, one spectral image A1, A2,..., An is formed on each micromirror 15a of the micromirror array 15. That is, each micromirror 15a and each spectrum image (monochromatic image) have a one-to-one correspondence.
Furthermore, the individual micromirrors 15a can be tilted independently about a rotation axis parallel to the arrangement direction. The inclination angle of the micromirror 15a is continuously variable within a certain range, and is adjusted according to the drive signal from the driver 23. Note that the rotation axes of the individual micromirrors 15a are parallel to the reflecting surface and parallel to each other.

In the following description, a state where the reflecting surface of the micromirror 15a is perpendicular to the optical axis 14a of the relay optical system 14 is referred to as an “initial state”, and a state inclined with respect to the optical axis 14a is referred to as an “inclined state”.
When all the micromirrors 15a are in the initial state (this is referred to as the initial state of the micromirror array 15), as shown in FIG. 6A, the reflecting surfaces of all the micromirrors 15a are arranged on the same plane. This same plane is also perpendicular to the optical axis 14 a of the relay optical system 14. When one or more micromirrors 15a are tilted in accordance with a drive signal from the driver 23, each reflecting surface is in an uneven state as shown in FIG.

  Here, when the micromirror array 15 is in the initial state (see FIG. 6A), the light L4 reflected by the micromirror array 15 (hereinafter referred to as “reflected light L4”) will be described. As described above, the diffracted light L3 incident on the micromirror array 15 has principal rays parallel to each of the wavelength regions λ1, λ2,..., Λn, and when viewed from above (see FIG. 3), Incident from the vertical direction. When viewed from the side (see FIG. 5A), the light enters the micromirror 15a from an oblique direction.

Therefore, the reflected light L4 from the micromirror array 15 in the initial state has principal rays parallel to each of the wavelength regions λ1, λ2,..., Λn, and is perpendicular to the micromirror 15a when viewed from above (see FIG. 7). Inject in the direction. When viewed from the side (see FIG. 5A), the light is emitted from the micromirror 15a in an oblique direction.
Here, as shown in FIG. 5B, the angle when the chief ray of the diffracted light L3 is incident on the micromirror 15a is θ ₀ . The reference for the angle θ ₀ is the optical axis 14 a of the relay optical system 14. In addition, an angle when the principal ray of the reflected light L4 is emitted from the micromirror 15a is θ ₁ . The reference for the angle θ ₁ is also the optical axis 14a. When the micromirror 15a is in the initial state, the incident angle θ ₀ of the principal ray of the diffracted light L3 and the emission angle θ ₁ of the principal ray of the reflected light L4 coincide.

  Then, the reflected light L4 returns to the relay optical system 14 without being vignetted by the trap mirror 16 (described later) (the state of FIG. 5A), passes through the relay optical system 14 again (light L5), and then the grating 13 Focused on top. At this time, as shown in FIG. 7, the incident light with respect to the grating 13 of the chief ray of the light L5 is slightly different for each of the wavelength regions λ1, λ2,.

  However, the principal ray in an arbitrary wavelength region λk (k = 1 to n) out of the wavelength regions λ1, λ2,..., Λn of the light L5 and the wavelength regions λ1, λ2,. , λn and the principal ray in an arbitrary wavelength region λk, that is, when the principal rays are compared in the same wavelength region λk, the incident angle of the light L5 to the grating 13 is the diffracted light L2 from the grating 13. Equal to diffraction angle. In addition, the chief rays of the wavelength regions λ1, λ2,..., Λn of the light L5 are collected at a common point D. This collection point D is conjugate with the principal ray branch point C of each wavelength region λ1, λ2,..., Λn of the diffracted light L2.

Next, when one or more micromirrors 15a of the micromirror array 15 are tilted according to the drive signal from the driver 23 (see FIG. 6B), the micromirrors 15a are emitted from the tilted micromirrors 15a. The reflected light L4 will be described. Even when the micromirror 15a is tilted, the state seen from above (see FIG. 7) is the same as the initial state.
However, the state seen from the side (see FIG. 8A) changes from the initial state (see FIG. 5A). That is, when the micromirror 15a is in an inclined state (see FIG. 8A), the reflected light L4 is emitted further downward than in the initial state (see FIG. 5A). Then, the exit angle θ ₁ of the principal ray of the reflected light L4 (FIG. 8B) is larger than the incident angle θ ₀ of the principal ray of the diffracted light L3. For this reason, a part of the reflected light L4 reaching the trap mirror 16 (see the hatched portion in FIG. 8C) is vignetted by the trap mirror 16.

The trap mirror 16 is disposed between the micro mirror array 15 and the relay optical system 14, and is a flat mirror by polishing the surface of a substance (for example, ND filter) that can absorb light in the used wavelength range. . The reflection surface of the trap mirror 16 is provided with an antireflection coating.
For this reason, most of the energy of some of the light emitted from the tilted micromirror 15a and incident on the trap mirror 16 (hatched portion in FIG. 8C) is absorbed and lost here. Only a small amount of light L6 (FIG. 8A) reaches the trap 17 via the trap mirror 16.

The trap 17 includes two flat mirrors having the same material and the same finish as the trap mirror 16 arranged in a wedge shape. The reflective surface of the trap 17 may or may not be provided with an antireflection coating. In any case, the amount of the light L6 that reaches the trap 17 is very small, and the light L6 can be almost completely absorbed and lost without letting out the light L6.
Thus, in a state where the tilt angle of the micro mirror 15a is changed from the initial state, vignetting by the trap mirror 16 is intentionally generated with respect to a part of the reflected light L4 (hatched portion in FIG. 8C), Since the trap mirror 16 and the trap 17 absorb and disappear, the energy of the light L5 that returns to the grating 13 via the relay optical system 14 can be attenuated by the amount of disappearance of absorption.

Further, since the amount of vignetting by the trap mirror 16 can be freely changed in accordance with the inclination angle of the micro mirror 15a, the amount of absorption loss by the trap mirror 16 and the trap 17 also returns to the grating 13 through the relay optical system 14. The energy of the light L5 can also be changed continuously.
Further, each of the plurality of micromirrors 15a and each of the plurality of spectral images A1, A2,..., An (monochromatic image) have a one-to-one correspondence (see FIG. 4). By independently changing the angle, the energy of the light L5 returning to the grating 13 can be changed independently for each of the wavelength regions λ1, λ2,.

  That is, the attenuators (14 to 17) incorporated in the inverse dispersion double spectroscope 10 of the first embodiment are each (spectrum image) for each wavelength region λ1, λ2,. (For each of A1, A2,..., An), an attenuation operation is performed. Such attenuators (14 to 17) are generally called a channel type. One channel corresponds to one wavelength range (λ1, λ2,..., Λn). The attenuators (14 to 17) and the driver 23 generally correspond to “light operation means” in the claims.

Now, the light L5 after the attenuation operation by the attenuators (14 to 17) and the diffracted lights L7 and L8 generated from the grating 13 by the second wavelength dispersion action will be described.
As described above, the chief ray of the light L5 after the attenuation operation (see FIG. 7) has an incident angle with respect to the grating 13 slightly different for each of the wavelength regions λ1, λ2,. . This set point D is conjugate with the principal ray branch point C of each wavelength region λ1, λ2,..., Λn of the diffracted light L2 (FIG. 3) generated from the grating 13 by the first wavelength dispersion action.

In the first embodiment, the same grating 13 is arranged so that the branch point C and the set point D have an equivalent positional relationship. For this reason, the second wavelength dispersion action that the light L5 receives from the grating 13 is opposite to the wavelength dispersion action that the diffracted light L2 receives from the grating 13 (the wavelength dispersion action that the grating 13 gives to the wavelength multiplexed light L1). Become.
Here, as shown in FIG. 3, the angle at which the chief ray in the arbitrary wavelength region λk (k = 1 to n) of the diffracted light L2 is emitted from the grating 13 is φk. The reference for the angle φk is the optical axis 12 a of the collimator 12. The angle φk corresponds to the angle formed between the principal ray of the wavelength multiplexed light L1 incident on the grating 13 from the collimator 12 and the principal ray of the wavelength range λk of the diffracted light L2.

  Then, as shown in FIG. 7, the angle formed by the principal ray of the light L5 (wavelength region λk) after the attenuation operation among the diffracted light generated from the grating 13 by the second wavelength dispersion action is described with reference to FIG. The principal ray of the diffracted light L7 (wavelength region λk) equal to the angle φk is superimposed (combined) in almost one linear direction in all the wavelength regions λ1, λ2,. The diffracted light L7 is light that can combine all the wavelength elements (λ1, λ2,..., Λn) included in a plurality of wavelength regions to form the same image.

  That is, the diffracted light L7 in all wavelength regions λ1, λ2,..., Λn is multiplexed. The multiplexed diffracted light L7 (hereinafter referred to as “wavelength multiplexed light L7”) is parallel light having the same thickness as the wavelength multiplexed light L1 shown in FIG. The principal ray of the wavelength multiplexed light L7 coincides with the optical axis 18a of the condensing optical system 18. The wavelength multiplexed light L7 and the wavelength multiplexed light L1 are parallel to each other.

The condensing optical system 18 (FIG. 1) has a positive focal length optimized for the NA of the optical fiber 19 at the output port. The condensing optical system 18 is an optical element (output interface unit) for condensing the wavelength multiplexed light L 7 from the grating 13 and guiding it to the input end face of the optical fiber 19.
The optical fiber 19 at the output port is a single wire, and is a single mode fiber having the same specifications as the optical fiber 11 at the input port. The optical fiber 19 is a member for guiding the wavelength multiplexed light from the condensing optical system 18 to the EDF 32 shown in FIG.

  The condensing optical system 18 and the optical fiber 19 (generally corresponding to “output means” in the claims) are arranged so that the incident end face of the optical fiber 19 coincides with the focal position of the condensing optical system 18. Therefore, the wavelength multiplexed light after the attenuation operation by the attenuators (14 to 17) is output to the EDF 32 with high coupling efficiency through the condensing optical system 18 and the optical fiber 19.

  On the other hand, as shown in FIG. 7, among the diffracted light generated from the grating 13 by the second wavelength dispersion action, the diffracted light L8 having the diffraction order of 0th order has a diffraction angle of the principal ray in the wavelength region λ1, λ2, ..., slightly different for each λn. However, since the 0th-order diffracted light L8 is specularly reflected light, when the normal line 13a of the grating 13 is used as a reference, the angle of the principal ray of the diffracted light L8 (wavelength range λk) is the light L5 (wavelength range λk). Is equal to the angle of the chief ray.

Then, the diffracted light L8 in the wavelength ranges λ1, λ2,..., Λn travels to the spectrum monitor (20, 21) described below. The spectrum monitor (20, 21) is a mechanism for monitoring the spectrum information (spectral characteristic information) of the diffracted light L8 generated from the grating 13, and includes a monitor optical system 20 and a one-dimensional array sensor 21. Corresponding to “Monitoring means”
The monitor optical system 20 has a positive focal length and collects the diffracted light L8 on the one-dimensional array sensor 21. Further, the principal rays of the diffracted light L9 after passing through the monitor optical system 20 are arranged so as to be arranged in parallel in each of the wavelength regions λ1, λ2,... Λn (telecentric system). Further, aberration correction is performed so that a flat image can be obtained in a necessary image range, and a sufficiently small spot-like monochromatic image can be obtained.

  As shown in FIG. 9, the monitor optical system 20 causes a large number of spectral images B1, B2,..., Bn having different wavelength regions λ1, λ2,. It is formed in a state of being lined up discretely along the line. Each of the spectral images B1, B2,..., Bn is a monochromatic image and has a spot shape substantially similar to the exit end face of the optical fiber 11. Further, the spectral images B1, B2,..., Bn correspond to conjugate images of the spectral images A1, A2,..., An (FIG. 4) on the micromirror array 15.

  As shown in FIG. 9, the one-dimensional array sensor 21 has a light receiving surface on which a large number of light receiving portions 21a are arranged one-dimensionally. The plurality of light receiving portions 21a are all the same size. The one-dimensional array sensor 21 aligns the arrangement direction (array direction) of the light receiving portions 21a with the wavelength dispersion directions of the spectral images B1, B2,..., Bn, and the light receiving surface is the focal position (spectral image B1) , B2,..., Bn).

In the one-dimensional array sensor 21, the size of the light receiving portion 21a is larger than the spot diameter of the spectral images B1, B2,..., Bn, and the interval between the light receiving portions 21a is between the spectral images B1, B2,. (The principal ray spacing for each of the wavelength regions λ1, λ2,..., Λn of the diffracted light L9 shown in FIG. 7).
Therefore, one spectral image B1, B2,..., Bn is formed on each light receiving portion 21a of the one-dimensional array sensor 21. That is, each light-receiving part 21a and each spectrum image (monochromatic image) have a one-to-one correspondence. Therefore, the energy of the diffracted light L9 can be detected independently for each wavelength region λ1, λ2,.

The detection result by each light receiving unit 21a of the one-dimensional array sensor 21 represents the spectrum information of the diffracted light L9. It also corresponds to spectral information of the diffracted light L8. This spectrum information is output to the processor 22 as a monitoring result by the spectrum monitor (20, 21).
Then, the processor 22 calculates the spectral information to obtain the current tilt angle of each micromirror 15a of the micromirror array 15, and calculates the difference from the target tilt angle stored in advance in the wavelength regions λ1, λ2. ,..., Λn, the rotation amount of the micromirror 15a necessary for correcting this difference is obtained, and the information is output to the driver 23.

The driver 23 outputs a drive signal to the micromirror array 15 of the attenuators (14-17) based on an instruction from the processor 22 (instruction value of the rotation amount of each micromirror 15a), and each micromirror 15a is turned on. Rotate to change its tilt angle. The processor 22 corresponds to “control means” in the claims.
In this way, the monitoring results of the spectrum monitors (20, 21) are fed back to the attenuators (14-17) via the processor 22 and the driver 23, so that the individual micromirrors 15a of the micromirror array 15 are tilted to the target inclination. Can be set to angle.

The target tilt angle of the micromirror 15a corresponds to the target attenuation amount of the light L5 after the attenuation operation by the attenuators (14 to 17), and is output to the EDF 32 from the inverse dispersion double spectroscope 10 of the first embodiment. Corresponding to the target spectrum of the wavelength multiplexed light (after attenuation operation).
Therefore, instead of the target tilt angle of the micromirror 15a, the target spectrum of the wavelength multiplexed light output to the EDF 32 in FIG. 2 may be stored in the processor 22 in advance. The target spectrum is an optimum spectrum corresponding to the gain characteristic of the EDFA in FIG.

  In this case, when acquiring the spectrum information from the spectrum monitor (20, 21), the processor 22 compares this spectrum information with the target spectrum, and is necessary as the attenuation factor of the light L5 for each of the wavelength ranges λ1, λ2,. Calculate the correct value. Further, based on a known correlation between the attenuation factor of the light L5 and the rotation amount of the micromirror 15a, the rotation amount of the micromirror 15a is obtained for each wavelength region λ1, λ2,. Output.

Note that when the processor 22 calculates the rotation amount of the micromirror 15a based on the monitor result of the spectrum monitor (20, 21), the tilt angle of the micromirror 15a and the coupling efficiency (coupling efficiency) of the optical fiber 19 are known. Correlation is also taken into account. The processor 22 also considers commands from the external CPU as necessary.
Therefore, the spectrum of the wavelength multiplexed light (after the attenuation operation) output from the inverse dispersion type double spectrometer 10 to the EDF 32 is fed back by feeding back the monitor results of the spectrum monitors (20, 21) to the attenuators (14-17). It can be optimized according to the gain characteristics of the EDFA of FIG. That is, it is possible to perform an attenuation operation with an appropriate spectral characteristic. As a result, stable WDM optical communication is possible.

  By constantly monitoring the spectrum information by the spectrum monitor (20, 21), even if the spectrum of the wavelength multiplexed light input from the EDF 31 in FIG. 2 varies, the tilt angle of the macro mirror 15a is adjusted according to the variation. In addition, the spectrum of the wavelength multiplexed light output to the EDF 32 can be maintained in an optimum state by appropriately maintaining the attenuation operation by the attenuators (14 to 17).

  As described above, since the inverse dispersion double spectrometer 10 according to the first embodiment operates as a dynamic gain equalizer (DGE), the spectral characteristics in the EDFA of FIG. 2 can be changed in real time according to the situation. In an ultra-long distance transmission system at a bit rate of 40 Gbps or higher, it is possible to avoid a situation in which spectral fluctuations caused by various factors such as temperature fluctuations exceed the allowable range of the optical amplifier.

Furthermore, since each micromirror 15a of the micromirror array 15 performs an attenuation operation independently for each wavelength region λ1, λ2,..., Λn (for each spectral image A1, A2,..., An) ( Channel type), strict equalizing becomes possible.
Note that the inverse dispersion double spectrometer 10 according to the first embodiment is not limited to the EDFA of FIG. 2, and is for flattening the gain of an optical amplifier (optical amplifier) to which another rare earth element (Nd or the like) is added. It can also be used.

  Further, if the inverse dispersion type double spectroscope 10 of the first embodiment is realized by a conventional free space optical element, the temperature characteristics are remarkably stabilized as compared with the case where a waveguide type spectroscope is used. This simplifies handling. Optical communication equipment is generally preferred because it is required to operate under severe environmental temperature conditions. Stable optical communication is possible even when the environmental temperature changes.

Furthermore, since the inverse dispersion type double spectrometer 10 according to the first embodiment has a built-in spectrum monitor (20, 21), not only can an appropriate attenuation operation be performed, but also space saving and cost reduction can be achieved. Realize.
In addition, among the diffracted lights generated from the grating 13, in order to monitor the spectrum information by taking in unnecessary diffracted light L8 (, L9) generated in a direction deviating from the main optical path (wavelength multiplexed light L7), the inverse dispersion type is used. The amount of wavelength multiplexed light output from the dual spectrometer 10 is not lost. In other words, it can be monitored efficiently.

Further, since the attenuation operation is performed using the micromirror array 15, it is possible to suppress a light amount loss (insertion loss) in the inverse dispersion double spectroscope 10. For this reason, attenuation operation and spectrum information can be monitored efficiently.
Further, in the inverse dispersion double spectroscope 10, since the diffracted light L8 (, L9) generated from the grating 13 by the second wavelength dispersion action is taken into the spectrum monitor (20, 21), the following effects << 1 >>, Play << 2 >>.

<< 1 >> The spectrum information on the output side that is relatively similar to the spectrum of the wavelength multiplexed light output from the inverse dispersion double spectrometer 10 can be monitored. For this reason, the calculation at the time of calculating | requiring the rotation amount of the micromirror 15a from the spectrum information of a monitor result becomes easy.
<< 2 >> Since the dispersion of the diffracted light L8 (, L9) can be largely secured, each light receiving unit 21a of the one-dimensional line sensor 21 can reliably detect individual energy for each of the wavelength regions λ1, λ2,. it can.

Further, since the one-dimensional array sensor 21 is used as an element for detecting the monitor spectral images B1, B2,..., Bn, the spectral images B1, B2,. Can be detected simultaneously. That is, it is possible to easily measure (monitor) the intensity of each wavelength band λ1, λ2,.
Further, the arrangement of the relay optical system 14 in the attenuators (14 to 17) is a telecentric system, and the chief rays of the diffracted light L3 after passing through the relay optical system 14 are arranged in parallel in the wavelength ranges λ1, λ2,. As a result, the micromirror array 15 having a simple configuration in which the rotation axes of the micromirrors 15a are parallel to each other can be used (controllable with one axis).

In addition, since one relay optical system 14 serves as both the “optical path from the grating 13 to the micromirror array 15” and the “optical path from the micromirror array 15 to the grating 13”, it is generated from the grating 13 by the second wavelength dispersion action. The diffracted light L7 of the main optical path can be multiplexed with high accuracy.
Further, the trap 17 is provided in the attenuators (14 to 17), and the slight light L6 reflected by the trap mirror 16 is completely absorbed and disappeared here, so that stray light in the inverse dispersion double spectroscope 10 is surely prevented. it can. For this reason, accurate monitoring is possible.

Furthermore, since the monitoring is performed by the unnecessary diffracted light L8 generated from the grating 13, the spectrum information can be reliably monitored regardless of the configuration of the attenuators (14-17).
That is, even when a liquid crystal element is used in place of the micromirror array 15, the spectrum information can be reliably monitored by unnecessary diffracted light L8 generated from the grating 13. Incidentally, the attenuation operation in this case is performed by associating a monochromatic image with each cell of the liquid crystal element and rotating the polarization plane for each cell.

  Even when the attenuators (14 to 17) have a subband configuration instead of the channel configuration, the spectrum information can be reliably monitored by the unnecessary diffracted light L8 generated from the grating 13. The subband configuration is a configuration in which a micromirror array 15 or a liquid crystal element is arranged at a position deviated from the spectral images A1, A2,..., An, and an attenuation operation is performed for each subband consisting of a plurality of wavelength channels. It is.

Further, even when the arrangement of the relay optical system 14 constituting the attenuators (14 to 17) is a non-telecentric optical system or when the trap 17 is omitted, the unnecessary diffracted light L8 generated from the grating 13 ensures the reliable operation. Spectral information can be monitored.
Also, in place of the attenuators (14 to 17) for performing the attenuation operation, when a mechanism for performing other operations (for example, <1>, <2>, <3>, etc. described below) is provided, Spectral information can be reliably monitored by the unnecessary diffracted light L8 generated from the grating 13.

  For operations other than the attenuation operation, for example, <1> one slit is installed to cut out only one wavelength range included in the wavelength multiplexed light, or <2> multiple slits are installed to make the wavelength multiplexed light. An operation to cut out and combine a plurality of included wavelength ranges, a <3> beam steering operation, and the like are conceivable. A configuration example for performing the beam steering operation will be specifically described in a second embodiment described later.

As described above, the spectrum monitor (20, 21) built in the inverse dispersion type double spectrometer 10 of the first embodiment is independent of the mode of operation between the two wavelength dispersion actions (in opposite directions). Since spectrum information can be reliably monitored, versatility is improved.
Here, a conventional inverse dispersion double spectroscope (for example, Japanese Patent Application Laid-Open No. 2002-196173) configured to perform an attenuation operation on the light to be operated and in which the attenuation operation is performed by a micromirror array. The difference from FIG.

  It has been proposed that a conventional apparatus incorporates a spectrum information monitoring mechanism in order to perform an appropriate attenuation operation and realize space saving and cost reduction. Further, in the conventional apparatus, the spot diameter of light (operation target light) incident on the micromirror array is larger than that of each micromirror, and the spot diameter is set so as to include a number of micromirrors two-dimensionally. Yes. For this reason, a part of the micromirror in the spot diameter is tilted and a part of the light is guided out of the optical path (that is, discarded), the attenuation operation is performed, and then the spectrum is obtained by capturing the discarded light. Information can be monitored (monitor mechanism). The number of micromirrors to be tilted is controlled based on the spectrum information, thereby realizing an attenuation operation.

  However, since the conventional monitoring mechanism described above is a technique for monitoring the spectrum using a part of the discarded input light, (1) the attenuation operation is performed by the micromirror array. (2) the micromirror array. This is a technique unique to an inverse dispersion double spectroscope that satisfies the requirements (1) and (2) that a large number of micromirrors are included within the beam diameter of the incident light on the beam. Accordingly, the requirements (1) and (2) are satisfied, such as a mode in which an attenuation operation is performed by means other than various other forms of inverse dispersion double spectroscopes, for example, a micromirror array, and a mode in which an operation other than the attenuation operation is performed. It is difficult to apply the above monitoring mechanism to an unsatisfactory inverse dispersion type double spectrometer. That is, the monitor mechanism has a problem that it lacks versatility.

On the other hand, in the inverse dispersion type dual spectrometer 10 of the first embodiment, as already described, the built-in monitor mechanism (that is, the spectrum monitor (20, 21)) performs two wavelength dispersion actions (in opposite directions to each other). ), The spectral information can be reliably monitored regardless of the mode of operation during (), thus improving versatility.
(Modification of the first embodiment)
In the first embodiment described above, unnecessary diffracted light L8 generated from the grating 13 by the second wavelength dispersion action is taken into the spectrum monitor (20, 21) and the spectrum information of the diffracted light L8 is monitored. It is not limited to this.

  For example, as in the case of the inverse dispersion type double spectrometer 50 of FIG. 10, unnecessary diffracted light L10 generated from the grating 13 by the first wavelength dispersion action [1] (in “at least one of the diffracted lights” in claim 2). May be taken into another spectrum monitor 51 and the spectrum information of the diffracted light L10 may be monitored. The optical operation unit 52 of the inverse dispersion double spectroscope 50 is a mechanism that performs a predetermined operation (for example, an attenuation operation).

  The diffracted light L10 by the first wavelength dispersion action [1] is diffracted light having a diffraction order different from that of the 0th-order diffracted light and the diffracted light L2 to the optical operation unit 52. Similarly to the chief ray of the diffracted light L2, the chief ray of the diffracted light L10 has a slightly different diffraction angle for each wavelength region λ1,..., Λn, as shown in FIG. Similar to the spectrum monitor (20, 21), the spectrum monitor 51 includes a monitor optical system and a one-dimensional array sensor.

In this case, the processor 22 outputs a monitoring result (output-side spectrum information) by the spectrum monitor (20, 21) and a monitoring result (input-side spectrum information) by the spectrum monitor 51. For this reason, the processor 22 obtains the rotation amount of the micromirror 15 a based on the two types of spectrum information and outputs the information to the driver 23.
According to the modified examples of FIGS. 10 and 11, unnecessary diffracted lights L8 and L10 generated from the grating 13 are monitored by each of the two wavelength dispersion actions [1] and [2], and two types of obtained diffracted lights L8 and L10 are obtained. Since the optical operation unit 52 is controlled based on the spectrum information, an operation with higher accuracy (for example, an attenuation operation) can be performed.

Further, in the inverse dispersion double spectrometer 50 of FIG. 10, the output side spectrum monitor (20, 21) may be omitted. In this case, only the monitoring result by the spectrum monitor 51 is output to the processor 22, and the processor 22 obtains the rotation amount of the micromirror 15 a based on the spectrum information on the input side and outputs the information to the driver 23.
Further, like the inverse dispersion type double spectroscope 55 of FIG. 12, the optical operation unit 56 includes a function of decomposing the light flux group, and a plurality of light L5 returning from the optical operation unit 56 to the grating 13 (that is, the light L5−). 1, L5-2,..., L5-n), the present invention can also be applied. The optical operation unit 56 is a mechanism that performs a predetermined operation (for example, an attenuation operation).

  The light beams L5-1, L5-2,..., L5-n after the operation have slightly different incident angles with respect to the grating 13 for each wavelength region λ1,. The grating 13 is reached. In FIG. 13, for easy understanding, light rays gathering at points D-1, D-2,..., Dn on the surface of the grating 13 are selected and illustrated. Light beams in an arbitrary wavelength range λk (k = 1 to n) of the lights L5-1, L5-2,..., L5-n are parallel to each other.

Further, the wavelength multiplexed lights L7-1, L7-2,..., L7-n from the respective collection points D-1, D-2,. These are parallel and output from the output ports (OUT1, OUT2,..., OUTn) to the outside via the condensing optical system 18 of FIG.
On the other hand, among the diffracted lights generated from the grating 13 by the second wavelength dispersion action [2], the diffracted lights L8-1, L8-2,..., L8-n of the zeroth order are as shown in FIG. In addition, the diffraction angle of the principal ray is slightly different for each wavelength region λ1,. However, chief rays in an arbitrary wavelength region λk (k = 1 to n) of the diffracted beams L8-1, L8-2,..., L8-n are parallel to each other.

Further, since the 0th-order diffracted lights L8-1, L8-2,..., L8-n are specularly reflected lights, when the normal line 13a of the grating 13 is used as a reference, the diffracted lights L8-1, L8-2,. ..., the angle of the chief ray of L8-n (wavelength range λk) is equal to the angle of the chief ray of light L5-1, L5-2, ..., L5-n (wavelength range λk).
These diffracted lights L8-1, L8-2,..., L8-n go to the spectrum monitor (57, 58). The spectrum monitor (57, 58) is composed of a monitor optical system 57 and a one-dimensional array sensor 58, like the spectrum monitor (20, 21). However, the arrangement of the monitor optical system 57 is a non-telecentric system.

In the spectrum monitor (57, 58), the monitor optical system 57 condenses each of the diffracted lights L8-1, L8-2,..., L8-n on the one-dimensional array sensor 58. At this time, arbitrary wavelength regions λk (k = 1 to n) of the diffracted lights L8-1, L8-2,..., L8-n are condensed at the same position on the one-dimensional array sensor 58.
That is, even if the collection points D-1, D-2,..., D-n of the grating 13 are different or the passing positions of the monitor optical system 57 are different, the one-dimensional array sensor is used as long as it is in the same wavelength range λk. Condensed at the same position on 58.

As a result, on the one-dimensional array sensor 58, a large number of spectral images having different wavelength ranges λ1,..., Λn (see B1,..., Bn in FIG. 9) are discretely arranged in a line along the wavelength dispersion direction. Formed in a state.
Therefore, the sum of the energy in the wavelength region λk (k = 1 to n) included in each of the diffracted lights L8-1, L8-2,..., L8-n is detected by the one-dimensional array sensor 58, and the second time It is possible to monitor the spectrum information of the unnecessary diffracted lights L8-1, L8-2,..., L8-n generated from the grating 13 by the wavelength dispersion action [2].

  According to the modification of FIG. 12, unnecessary diffracted lights L8-1, L8-2,..., L8-n, L10 generated from the grating 13 by each of the two wavelength dispersion actions [1], [2] are generated. Since the optical operation unit 56 is controlled based on the two types of spectral information obtained by monitoring, an operation with higher accuracy (for example, an attenuation operation) can be performed. In the inverse dispersion type double spectroscope 55 of FIG. 12, the spectrum monitor 51 on the input side may be omitted.

Furthermore, in the above-described embodiment, the configuration example in which the hardware functions as an inverse dispersion type double spectroscope by wrapping the optical path twice in one spectroscope has been described. It is not limited.
As in the case of the inverse dispersion double spectrometer 60 shown in FIG. 14, two spectrometers may be connected as hardware. In this inverse dispersion type double spectrometer 40, a grating 61 different from the grating 13 is provided in the inverse dispersion type double spectrometer 55 shown in FIG. 12, and this grating 61 gives the second wavelength dispersion action [2]. Is. The grating 61 is preferably the same design as the grating 13.

In this case, the spectrum monitor (57, 58) takes in unnecessary diffracted light L8-1, L8-2,..., L8-n generated from the grating 61 by the second wavelength dispersion action [2], and diffracted light L8. -1, L8-2,..., L8-n spectral information is monitored.
According to the modification of FIG. 14, unnecessary diffracted lights L8-1, L8-2,..., L8-n, generated from the gratings 13, 61 by the two wavelength dispersion actions [1], [2], respectively. Since L10 is monitored and the optical operation unit 56 is controlled based on the obtained two types of spectrum information, an operation with higher accuracy (for example, an attenuation operation) can be performed. The spectrum monitor 51 on the input side of the inverse dispersion double spectroscope 60 may be omitted. Instead of the light operation unit 56, the light operation unit 52 of FIG. 10 may be provided.

  In the above-described embodiment, the input port is configured with a single-line optical fiber, but may be replaced with a multi-line optical fiber bundle. In this case, a plurality of independent wavelength-division multiplexed lights can be taken in parallel. The optical operation units 52 and 56, the spectrum monitors (20, 21), 51, (57, 58), the processor 22 and the driver 23 need to have a parallel processing type configuration capable of supporting a plurality of wavelength-multiplexed lights. . The output ports (OUT1, OUT2,..., OUTn) also have a configuration corresponding to the signal system included in each wavelength multiplexed light.

  Furthermore, in the above-described embodiment, of the diffracted light generated from the grating 13 (or 61) by the second wavelength dispersion action [2], the 0th-order diffracted light L8 (or diffracted light L8-1, L8-2, .., L8-n) are incorporated in the spectrum monitor (20, 21), (57, 58) on the output side, but the present invention is not limited to this. If the diffracted light has a diffraction order different from that of the wavelength multiplexed light L7, it can be used for monitoring spectrum information even if it is other than the 0th order diffracted light.

Further, in the above-described embodiment, spectrum images (FIG. 5) having different wavelength regions λ1,..., Λn are received by the respective light receiving portions of the one-dimensional array sensor constituting the spectrum monitors (20, 21), 51, (57, 58). 9 (see B1,..., Bn) are detected independently, but the present invention is not limited to this. One spectral image may be detected by a plurality of light receiving units.
In the above-described embodiment, a one-dimensional line sensor is used as an element for detecting a spectral image, but an exit slit and a detector can be used instead. The exit slit has one elongated opening, and is arranged so that the opening coincides with the formation position of the spectral image. And the partial image which passed the opening part among the spectrum images is received by the detector. In this configuration, spectral images in different wavelength ranges can be detected by moving the exit slit and the detector along the wavelength dispersion direction.

Furthermore, in the above-described embodiment, the attenuators (14-17) and the optical operation units 52 and 56 are feedback controlled based on the monitoring results of the spectrum monitors (20, 21), 51, (57, 58). You may control by.
In the above-described embodiment, an example of an inverse dispersion double spectroscope using a reflection type grating has been described. However, the present invention can also be applied to a configuration using a transmission type grating. A concave diffraction grating may be used instead of the planar diffraction grating. Furthermore, although a grating (diffraction grating) is used as a wavelength dispersion element, a prism or a grism (a combination of a grating and a prism) can also be used. The collimator 12 and the condensing optical system 18 may be reflective optical systems.

Further, in the above-described embodiment, the single-line optical fiber (11, 19) or the multi-line optical fiber bundle is used as the input / output port of the inverse dispersion type double spectrometer, but it is used in the optical communication field. If not presupposed, it can be replaced with a slit member. The slit member has one or more elongated openings.
Moreover, you may package the above-mentioned reverse dispersion type | mold double spectrometer in one housing | casing. For example, the reverse dispersion double spectrometer 10 shown in FIG. 1 will be described as an example. As shown in FIG. 15, the vicinity of the end face of the optical fiber 11, the collimator 12, the grating 13, the attenuators (14 to 17), the condensing optical system 18. The vicinity of the end face of the optical fiber 19, the spectrum monitor (20, 21), the processor 22, and the driver 23 may be packaged in one housing 24. In this case, since all the components of the inverse dispersion type double spectroscope 10 are integrated, the handling becomes simple. The vicinity of the end face of the optical fiber 11 and the collimator 12 generally correspond to the “end of the input means” in the claims. The vicinity of the end face of the optical fiber 19 and the condensing optical system 18 generally correspond to “end portion of output means” in the claims.
(Second Embodiment)
Here, an inverse dispersion double spectroscope will be described as an example.

  The inverse dispersion type dual spectrometer 70 (FIG. 16) of the second embodiment operates as an optical cross connect (OXC), and includes an optical fiber 9 for an input port and optical fibers 1 to 1 for an output port. 8 includes an optical fiber bundle including 8, an expansion optical system 71, a transmission type grating 72, a beam steering mechanism (73 to 75), a spectrum monitor (76, 77), and a control unit 78.

  The magnifying optical system 71 includes a microlens 11a provided in the vicinity of each end face of the optical fibers 1 to 9, and two lenses 11b and 11c having a positive focal length. The magnifying optical system 71 has a focal position that matches the position of each end face of the optical fibers 1 to 9. The light (wavelength multiplexed light) from the optical fiber 9 at the input port becomes parallel light whose beam diameter is enlarged via the magnifying optical system 71. The optical fiber 9 and the magnifying optical system 71 of the input port generally correspond to “input means” in the claims. The optical fibers 1 to 8 of the output port and the magnifying optical system 71 generally correspond to “output means” in the claims.

  The transmissive grating 72 is a one-dimensional array of a large number of linear grooves at equal intervals. By passing light from one direction through this, a predetermined wavelength dispersion action (first time) is given to the light. By passing light from the opposite direction, the wavelength dispersion action (second time) opposite to the predetermined wavelength dispersion action is given to the light. In the transmissive grating 12, in the present embodiment, the diffracted light having the strongest blaze diffraction order is the first-order diffracted light, and the 0th-order diffracted light described later is an extremely weak blaze with respect to the first-order diffracted light. The transmissive grating 12 corresponds to “wavelength dispersion means” in the claims.

  The beam steering mechanism (73 to 75) includes an imaging optical system 73 that forms an image of diffracted light (for example, first-order diffracted light) from the transmissive grating 72, a micromirror array 74, and a mirror driver 75. The micromirror array 74 is called a MEMS (Mycro Electro Mechanical System), and is a one-dimensional array of a plurality of micromirrors 74a, 74b, 74c,. The reflecting surfaces of the micromirrors 74a, 74b, 74c,... Coincide with the focal position of the imaging optical system 73. The size of the micromirrors 74a, 74b, 74c,... Is approximately several tens of μm to several hundreds of μm square. The direction in which the micromirrors 74a, 74b, 74c,... Are arranged one-dimensionally is the same as the wavelength dispersion direction of the transmissive grating 72. The mirror driver 75 individually drives each of the micromirrors 74a, 74b, 74c,... Constituting the micromirror array 74.

The light reflected by the micromirror array 74 again passes through the imaging optical system 73 and reaches the transmissive grating 72. The light reaching the transmission type grating 72 is subjected to a reverse wavelength dispersion action (combining action), and the first-order diffracted light of the light subjected to the reverse wavelength dispersion action is transmitted through the magnifying optical system 71. , And enters one of the optical fibers 1 to 8 of the output port.
The spectrum monitor (76, 77) is a mechanism for monitoring the spectral information of the 0th-order diffracted light out of the light reflected by the micromirror array 74 and subjected to the chromatic dispersion action by the transmissive grating 72. An imaging optical system 76 that forms an image and a light receiving sensor 77 that receives light from the imaging optical system 76 are configured.

  The light receiving sensor 77 includes a plurality of light receiving elements arranged one-dimensionally, and among the plurality of light receiving elements, the light receiving element that has received light outputs an electrical signal corresponding to the amount of received light to the control unit 78. That is, the light receiving sensor 77 outputs to the control unit 78 a signal indicating how much light is received at which position. The light receiving sensor 77 is disposed at a position where the light receiving surface is conjugate with the reflecting surface of the micromirror array 74, that is, at the focal position of the imaging optical system 76.

Next, the operation and operation of the inverse dispersion double spectroscope 70 of the second embodiment will be described with reference to FIGS.
As shown in FIG. 17, it is assumed that white light L (solid line in the figure) is output from the optical fiber 9 of the input port. The light L has its beam diameter enlarged by the magnifying optical system 71, then passes through the transmission type grating 72, and the first-order diffracted light among the light that has passed through the transmissive grating 72 is directed to the imaging optical system 73 and the micromirror array 74. . The light L from the optical fiber 9 at the input port is dispersed into light of each wavelength λ1, λ2, λ3,... By the chromatic dispersion action (first time) in the transmission grating 72. Thereafter, the light of each wavelength λ1, λ2, λ3,... Travels to the micromirror array 74 through the imaging optical system 73 as described above.

As shown in FIG. 18, the light of each wavelength λ1, λ2, λ3,... Is individually micromirrors 74a, 74b, 74c,. Reflected in the direction.
Thereafter, as shown in FIG. 17, the light of each wavelength λ1, λ2, λ3,... Again passes through the imaging optical system 73 and is combined by the transmission grating 72 (second wavelength dispersion action). receive. The light of wavelength λ1 and the light of wavelength λ2 are combined if they pass through the same position in the transmissive grating 72. However, here, since the light of each wavelength λ1, λ2, λ3,... Passes through different positions in the transmission grating 72, it receives an action opposite to the chromatic dispersion action when it passes the first time. Passes parallel to each other without being waved.

  The first-order diffracted light λ11, λ12, λ13,... Out of the light that has passed through the transmission grating 72 is incident on the optical fibers 1, 2,. To do. At this time, according to the inclination angle of each of the micromirrors 74a, 74b, 74c,... Constituting the micromirror array 74, light in each wavelength region (first-order diffracted light λ11, λ12, λ13,...) It is led to the target optical fiber (any one of 1, 2,..., 8).

On the other hand, the 0th-order diffracted light λ 0 1, λ 0 2, λ 0 3,... Out of the light that has passed through the transmissive grating 72 is directed to the imaging optical system 76 of the spectrum monitor (76, 77). The 0th-order diffracted light λ01, λ02, λ03,... That has passed through the imaging optical system 76 is received by the light receiving sensor 77. In the above, the small subscript after “λ” indicates the diffraction order.
When the light receiving sensor 77 arranged at a position optically conjugate with the macro mirror array 74 receives light at which position on the light receiving surface, what wavelength λ01, λ02, λ03,... Are associated.

  Specifically, as shown in FIG. 19, in the light receiving sensor 77, the light receiving surface is divided into a plurality of regions, and region numbers are assigned to the regions. With respect to the light receiving sensor 77, it is related which region number 1, 2,... Receives light and what the wavelength of the light is. For example, the light received at region number 8 has a wavelength λ01, the light received at region number 19 has a wavelength λ02, and the light received at region number 30 has a wavelength λ03. ing. Such a relationship between the position of the light receiving surface and the wavelength is examined in advance, and this is stored as a table in the control unit 78 (FIG. 16).

For example, when the control unit 78 receives a signal indicating that light is received at the area number 19 from the light receiving sensor 77, the control unit 78 recognizes that light having the wavelength λ02 has been received with reference to the above-described table. Further, it recognizes how much the intensity of the light of wavelength λ02 is from the received light intensity.
Thus, according to the inverse dispersion double spectrometer 70 of the second embodiment, each of the micromirrors 74a, 74b, 74c,... For each spectral image) a beam steering operation can be performed. Further, the spectrum information of the 0th-order diffracted light λ01, λ02, λ03,... That has passed through the transmission type grating 72 can be monitored by the spectrum monitor (76, 77).

In addition, since the inverse dispersion type double spectrometer 70 according to the second embodiment has a built-in spectrum monitor (76, 77), it is possible not only to perform an appropriate beam steering operation but also to save space and cost. Also realized.
Further, out of the diffracted light generated from the transmissive grating 72, the direction deviates from the main optical path (the output optical path until the light taken from the optical fiber 9 of the input port is guided to the optical fibers 1 to 8 of the output port). Since unnecessary zero-order diffracted light λ01, λ02, λ03,... Generated is taken in and spectrum information is monitored, the amount of light output from the inverse dispersion double spectroscope 70 is not lost. In other words, light can be used effectively and can be monitored efficiently.

Further, since the beam steering operation is performed using the micromirror array 74, it is possible to suppress a light amount loss (insertion loss) in the inverse dispersion double spectroscope 70. For this reason, beam steering operation and spectrum information monitoring can be performed efficiently.
(Modification of the second embodiment)
In the inverse dispersion type dual spectrometer 70 of the second embodiment described above, the 0th-order diffracted light λ01, λ02, λ03,... From the transmission type grating 72 is used as the monitoring light, but the present invention is not limited to this. . As long as the light of the diffraction order other than the light of the diffraction order used as the output light (first-order diffracted light in the second embodiment), basically any order of light may be used as the monitoring light.

  In the second embodiment described above, unnecessary diffracted light (for example, 0th-order diffracted light λ01, λ02, λ03,...) Generated by the second wavelength dispersion action (that is, the above-described combining action) by the transmission grating 72 is added. Although spectrum information was monitored based on this, the present invention is not limited to this. In addition, spectrum information may be monitored based on unnecessary diffracted light (light other than the light of the wavelengths λ1, λ2, λ3,... In FIG. 17) generated by the first wavelength dispersion action by the transmission type grating 72. , Spectrum information may be monitored based on both.

In the second embodiment described above, an example in which a transmissive grating is used as the wavelength dispersion means has been described. However, the present invention can also be applied to a configuration using a reflective grating.
(Modification common to the first embodiment and the second embodiment)
In the above-described embodiment, an example of an inverse dispersion double spectroscope configured to perform each of an attenuation operation and a beam steering operation has been described. However, the present invention can also be applied to performing both of them.

  In this case, using the inverse dispersion type double spectroscope 70, out of the optical fibers 1 to 8 at the output port, for example, every other optical fiber 2, 4, 6, 8 is disposed for light and the rest. Optical fibers 1, 3, 5, and 7 are used for output light, and the intensity (spectrum) of output light is adjusted by adjusting the ratio of light incident on two adjacent optical fibers (for discarded light and for output light). It is possible to easily adjust both the attenuation operation and the beam steering operation.

  In this case, the spectrum of the output light is controlled by feedback-controlling the micromirrors 74a, 74b, 74c,... Of the beam steering mechanism (73-75) based on the monitoring result by the spectrum monitor (76, 77). (Light intensity for each wavelength region) can be optimized. That is, it is possible to realize both appropriate attenuation operation and beam steering operation.

  Furthermore, in the above-described embodiment, the inverse dispersion type double spectrometer has been described as an example, but the present invention is not limited to this. For example, the present invention can also be applied to a case where a wavelength dispersion action is given only once to input light as in the optical device 80 shown in FIG. Further, the present invention can also be applied to an optical apparatus (not shown) that sequentially gives three or more wavelength dispersion actions to input light. As described above, in a configuration in which chromatic dispersion action is performed twice or more, each chromatic dispersion action may be given by the same grading or different grading.

  The optical device 80 receives input light K1 having a plurality of wavelength ranges, collimates the input light K1, and emits parallel light K2 (including an optical fiber of a not-shown input port and a collimator lens 81). , A wavelength dispersion means (for example, a reflective grating 82) that generates first diffracted light K3, K4, K5,... For output by giving a single wavelength dispersion action to the parallel light K2, and parallel light. Output means for outputting the first diffracted light K3, K4, K5,... (Collimator lens 81) arranged on the extension of the output optical path from the generation of the first diffracted light K3, K4, K5,. And second diffracted light K6 generated in a direction deviating from the output optical path among the diffracted light generated by the wavelength dispersion action in the reflection type grating 82. The monitor means (including the condensing lens 83 and the light receiving sensor 84) for monitoring the spectrum information of K7, K8,...

The diffraction order “m” of the output light (first diffracted lights K3, K4, K5,...) And the diffraction order “n” of the monitor light (second diffracted lights K6, K7, K8,. Different.
Also in the optical device 80, for example, out of the diffracted light generated from the reflection type grating 82, the direction deviates from the output optical path (the main optical path until the light taken from the optical fiber of the input port is guided to the optical fiber of the output port). Since the unnecessary diffracted light K6, K7, K8,... Generated is taken in and the spectrum information is monitored, the amount of light output from the optical device 80 is not lost. In other words, light can be used effectively and can be monitored efficiently. Similar effects can be obtained when a transmissive grating is used instead of the reflective grating 82 of the optical device 80.

  Such an optical device 80 may be provided with a mechanism for performing an optical operation (for example, at least one of an attenuation operation and a beam steering operation) on the diffracted light generated along the output optical path. Further, when the attenuation operation is performed, it is preferable to feedback-control the attenuator based on the monitoring result by the monitoring means (including the condensing lens 83 and the light receiving sensor 84). Further, the optical device 80 is preferably packaged by a housing similar to the housing 24 of FIG.

  Further, the optical device 80 calculates at least one of the spectrum information of the input light and the spectrum information of the output light based on the spectrum information monitored by the monitor means (including the condensing lens 83 and the light receiving sensor 84). It is preferable to further provide calculation means. Incidentally, an optical fiber (not shown) of the input port emits the input light K1 to free space. The collimator lens 81 collimates the input light K1 propagating in the free space.

  Further, in an optical apparatus that sequentially applies the wavelength dispersion action three times or more to the input light, when a mechanism for performing an optical operation (for example, at least one of an attenuation operation and a beam steering operation) is provided, along the output optical path. A predetermined operation may be performed on at least one of the diffracted light generated.

1 is a perspective view showing an overall configuration of an inverse dispersion double spectroscope 10. FIG. It is a block diagram which shows schematic structure of an erbium addition fiber amplifier (EDFA). FIG. 6 is a diagram for explaining a first wavelength dispersion action by the grating 13 and “an optical path from the grating 13 to the micromirror array 15”. It is a figure explaining the structure and spectrum image A1, A2, ..., An of the micromirror array 15. FIG. It is the figure which looked at the optical path between the grating 13 and the micromirror array 15 (micromirror 15a of an initial state) from the side. It is a figure explaining the initial state (a) and inclination state (b) of the micromirror 15a. FIG. 5 is a diagram for explaining a second wavelength dispersion action by the grating 13, “an optical path from the micromirror array 15 to the grating 13”, and “an optical path from the grating 13 to the one-dimensional array sensor 21”. It is the figure which looked at the optical path between the grating 13 and the micromirror array 15 (micromirror 15a of the inclined state) from the side. It is a figure explaining the structure and spectrum image B1, B2, ..., Bn of the one-dimensional array sensor 21. FIG. 2 is a block diagram showing an overall configuration of an inverse dispersion double spectroscope 50. FIG. It is a figure explaining the unnecessary diffracted light L10 which generate | occur | produces from the grating 13 by the wavelength dispersion effect | action of the 1st time. 3 is a block diagram showing an overall configuration of an inverse dispersion double spectroscope 55. FIG. .., L5-n after being decomposed into a plurality of wavelengths and wavelength multiplexed light L7-1, L7-2,..., L7 generated from the grating 13 by the second wavelength dispersion action. It is a figure explaining -n and 0th-order diffracted light L8-1, L8-2, ..., L8-n. 2 is a block diagram showing an overall configuration of an inverse dispersion double spectroscope 60. FIG. It is a block diagram explaining the structure of the packaged reverse dispersion type | mold double spectrometer. It is a figure which shows the whole structure of the reverse dispersion type | mold double spectrometer 70 of 2nd Embodiment. It is a figure explaining the optical path in the reverse dispersion type | mold double spectrometer 70. FIG. It is a figure explaining the optical path change by the micromirror array 74 of the reverse dispersion type | mold double spectrometer 70. FIG. It is a figure explaining the mode of the light which injects into the light reception sensor 77 of the reverse dispersion type | mold double spectrometer 70. FIG. FIG. 3 is a diagram showing an overall configuration of an optical device 80.

Explanation of symbols

10, 50, 55, 60, 70 Inverse dispersion double spectrometer 1-9, 11, 19 Optical fiber 12 Collimator 13, 61 Grating 14 Relay optical system 15, 74 Micro mirror array 16 Trap mirror 17 Trap 18 Condensing optics System 20, 57 Monitor optical system 21, 58 One-dimensional array sensor 22 Processor 23 Driver 24 Case 31, 32 Erbium-doped fiber (EDF)
33 Optical multiplexer 34 Optical demultiplexer 35, 36 Optical isolator 37, 38 Excitation light source 51 Spectrum monitor 52, 56 Optical operation unit 71 Magnifying optical system 72 Transmission type grating 73, 76 Imaging optical system 75 Mirror driver 77 Light receiving sensor 78 Control unit 80 Optical device

Claims (18)

Input means for emitting input light composed of a plurality of wavelength regions to free space;
Collimating means for collimating the input light and emitting parallel light;
Wavelength dispersion means for generating first diffracted light for output by giving at least one wavelength dispersion action to the parallel light;
An output means arranged on an extension of an output optical path from the parallel light until the first diffracted light is generated, and outputs the first diffracted light;
An optical device comprising: monitor means for monitoring spectrum information of second diffracted light generated in a direction deviating from the output optical path among diffracted light generated for each wavelength dispersion action. The optical device according to claim 1.
Light operating means for performing a predetermined operation on at least one of the diffracted lights generated along the output optical path among the diffracted lights generated for each of the wavelength dispersion actions;
An optical apparatus comprising: control means for controlling the light operating means based on spectrum information monitored by the monitoring means. Input means for emitting input light composed of a plurality of wavelength regions to free space;
First chromatic dispersion means for giving a first chromatic dispersion action to the input light;
Light operating means for performing a predetermined operation on the first diffracted light having a diffraction order different from the 0th order diffracted light among the diffracted light generated from the first wavelength dispersion means;
A second chromatic dispersion means for giving a second chromatic dispersion action opposite to the first chromatic dispersion action for the light after the operation by the light manipulation means;
Output means for outputting second diffracted light that can form the same image by combining all the wavelength elements included in the plurality of wavelength regions among the diffracted light generated from the second wavelength dispersion means;
Of the diffracted light generated from the first wavelength dispersion means, spectral information of the 0th-order diffracted light and third diffracted light having a different diffraction order from the first diffracted light, and from the second wavelength dispersion means And a monitor means for monitoring at least one of spectral information of fourth diffracted light having a diffraction order different from that of the second diffracted light among the generated diffracted light. Spectroscope. The inverse dispersion double spectroscope according to claim 3,
The inverse dispersion type double spectroscope further comprising control means for controlling the optical operation means based on a monitoring result by the monitoring means. The inverse dispersion double spectroscope according to claim 3 or 4,
The input means includes an input port composed of a single-wire optical fiber or a multi-wire optical fiber bundle,
The output means includes an output port formed of a single-line optical fiber or a multi-line optical fiber bundle. The inverse dispersion double spectroscope according to any one of claims 3 to 5,
The optical dispersion means is an attenuator that performs an attenuation operation on the first diffracted light. The inverse dispersion double spectroscope according to claim 6,
The light operating means forms a plurality of spectral images having different wavelength ranges by condensing the first diffracted light, and performs the attenuation operation for each of the plurality of spectral images. Double spectrometer. The inverse dispersion double spectroscope according to claim 7,
The optical operation means includes an array unit in which a plurality of micromirrors are arranged one-dimensionally, and the attenuation operation is performed on each of the plurality of spectral images by each of the plurality of micromirrors. Dispersive double spectrometer. The inverse dispersion double spectroscope according to claim 3 or 5,
The light dispersion means performs a beam steering operation on the first diffracted light. The inverse dispersion double spectroscope according to claim 9,
The light operating means forms a plurality of spectral images having different wavelength ranges by condensing the first diffracted light, and performs the beam steering operation for each of the plurality of spectral images. Type double spectrometer. The inverse dispersion double spectroscope according to claim 10,
The optical operation means includes an array unit in which a plurality of micromirrors are arranged one-dimensionally, and the beam steering operation is performed on each of the plurality of spectral images by each of the plurality of micromirrors. Inverse dispersion type double spectrometer. The inverse dispersion double spectroscope according to any one of claims 3 to 5,
The light operating means performs an attenuation operation and a beam steering operation on the first diffracted light. The inverse dispersion double spectroscope according to claim 12,
The light operating means forms a plurality of spectral images having different wavelength ranges by condensing the first diffracted light, and performs the attenuation operation and the beam steering operation for each of the plurality of spectral images. Inverse dispersion type dual spectrometer. The inverse dispersion double spectroscope according to claim 13,
The optical operation means includes an array unit in which a plurality of micromirrors are arranged one-dimensionally, and performs the attenuation operation and the beam steering operation on each of the plurality of spectral images by each of the plurality of micromirrors. An inverse dispersion type double spectrometer characterized by that. In the inverse dispersion double spectroscope according to any one of claims 10, 11, 13, and 14,
The output means includes an output port composed of a plurality of optical fibers,
The optical operation unit causes light having a different wavelength range to be incident on any one of the output ports. In the inverse dispersion double spectroscope according to any one of claims 10, 11, 13, and 14,
The output means includes an output port made of at least one optical fiber,
The light operating means causes the light having a different wavelength range to enter or not enter any optical fiber of the output ports. The inverse dispersion double spectroscope according to any one of claims 3 to 16,
The end of the input means, the first wavelength dispersion means, the optical manipulation means, the second wavelength dispersion means, the monitor means, and the end of the output means are one case. An inverse dispersion type dual spectrometer characterized by being packaged in The optical device according to claim 2.
An end of the input unit, the wavelength dispersion unit, the optical operation unit, the monitor unit, and the end of the output unit are packaged in one housing. .

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