JP2003021724A - Optical circuit element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical circuit element with which an excellent attenuated light is available, the wavelength characteristic can be arbitrarily set further, a nonreciprocity characteristic can be given. SOLUTION: A diffraction member (20) having a diffraction grating is arranged between the input/output faces of a pair of optical waveguide members (11 and 12) arranged with a space, light emitted from the optical waveguide member (11) is diffracted with the diffraction grating (20), non-diffracted light (0-order diffracted light) only or a combination of non-diffracted light and prescribed diffracted light only is coupling made incident in the other optical waveguide member (12) as a waveguide mode and the light form the optical waveguide member is attenuated and outputted to the other optical waveguide member.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical circuit element,
In particular, it relates to an optical circuit element that attenuates light from one optical waveguide member and outputs it to another optical waveguide member.

[0002]

2. Description of the Related Art In an optical communication system, the intensity of transmitted light transmitted through an optical waveguide member such as an optical cable is preferably within a predetermined intensity range. Therefore, an optical circuit element that appropriately attenuates the intensity of the transmitted light is arranged in the optical transmission line to attenuate the strong transmitted light from the incident side optical transmission line and to transmit the transmitted light of an appropriate intensity to the emission side optical transmission line. I am sending it to.

A conventional optical circuit device of this kind is shown in FIG.
There is an optical fiber connector type optical circuit element 70 shown in FIG.
In this optical circuit element 70, two optical fibers 71 and 72 are covered with ferrules 73 and 74, and a core 75 of each optical fiber,
The ferrules 73 and 74 are fixed by a sleeve 78 so that the space 76 can be arranged with an interval 77 or can be inclined. According to such an optical circuit element, the light emitted from the core 75 of the one optical fiber 71 is diffused and emitted from the end surface of the core 75, and a part of the light is emitted to the end surface of the core 76 of the other optical fiber 72. The incident light is attenuated and then emitted. Other light is absorbed by the end faces of the ferrules 73 and 74 and the inner peripheral surface of the sleeve 78.

[0004]

However, in the above-mentioned optical circuit element, only a part of the transmission wave having a continuous field distribution (for example, Gaussian distribution) of the optical fiber transmission mode is extracted and the core on the emission side is taken out as the transmission wave. Therefore, the removed field is likely to become a cladding mode, and an attenuation ripple may occur due to the recombination of the cladding mode.

Further, in such an optical circuit element,
It has been difficult to use a non-reciprocal attenuator that changes the attenuation amount depending on the transmission direction and to set the attenuation to a desired value depending on the wavelength of the transmitted light.

An object of the present invention is to provide an optical circuit element capable of obtaining good attenuated light, arbitrarily setting wavelength characteristics, and imparting non-reciprocity.

[0007]

Means for Solving the Problems The means of the present invention for solving the above-mentioned problems is to dispose a diffractive member having a diffraction grating between the input and output end faces of a pair of optical waveguide members which are arranged at a distance. The light emitted from the optical waveguide member is diffracted by the diffraction grating, and only the non-diffracted light (0th-order diffracted light) or only the non-diffracted light and the predetermined diffracted light is incident on the other optical waveguide member as a guided mode. An optical circuit element that attenuates light from one optical waveguide member and outputs the attenuated light to another optical waveguide member.

Further, in the optical circuit element according to the present invention, the diffractive member is arranged at a position close to one of the optical input / output end faces of the pair of optical waveguide members, and the attenuation amount due to one-way transmission of light is provided. , The amount of attenuation due to transmission in the other direction is different.

Further, in the optical circuit element according to the present invention, the grating shape is rectangular, and the grating height is set so as to have a predetermined wavelength characteristic that gives desired attenuation to incident lights of different wavelengths. It has a grid.

Further, in the optical circuit element according to the present invention, the diffractive member is provided with diffraction gratings on both the input and output surfaces, and the diffraction gratings on both surfaces are formed so as to be orthogonal to each other.

Furthermore, the optical circuit element according to the present invention is
An optical fiber is used as the pair of optical waveguide members.

According to the present invention, the necessary non-diffracted light, or only the non-diffracted light and the predetermined diffracted light are taken out to spatially separate them from the unnecessary diffracted light, and the generation and attenuation of the cladding mode. It is possible to prevent the occurrence of ripples, whereby the optical attenuation factor can be set to a desired value.

Further, in the present invention in which the diffractive member is arranged at a position close to one of the optical input / output end faces of the pair of optical waveguide members, the light is directed in one direction (upward) with the diffractive member interposed therebetween.
When transmitting light in both the reverse direction (downward) and the reverse direction (downward), the attenuation amount of the light can be set to be different in each direction,
A non-reciprocal attenuator can be constructed.

In the access system of optical communication, the optical signal intensity is different between the upstream and the downstream for each subscriber, so that it is necessary to make the levels of both signal lights uniform. In such cases,
The optical circuit element according to the present invention is effective for optimizing the optical signal with the base station for each subscriber.

Further, according to the present invention, which has a diffraction grating having a rectangular grating shape and a grating height set so as to have a predetermined wavelength characteristic which gives desired attenuation to incident lights of different wavelengths, When the characteristic according to the wavelength of light is set to a desired characteristic, in this example, the only element that can be set is the grating height, and therefore the wavelength characteristic is set only by the grating height, which is easy.

Particularly, in a WDM (optical multiplex communication) system, optical equalization for correcting the wavelength-dependent characteristics of a light emitting / receiving element and an optical amplifier to make the signal light level in a wide wavelength band uniform to almost the same energy level. Many optical circuit elements as a container will be used.

Further, in the case where the diffractive member is provided with diffraction gratings on both the input and output sides and the directions of the diffraction gratings on both sides are orthogonal to each other, the result is that regardless of the state of the polarization direction of the incident light. Stable attenuation characteristics can be obtained by giving the same diffraction result.

Furthermore, an optical circuit element having various wavelength characteristics can be obtained by changing the grating width and grating height of the diffraction grating on both sides.

Furthermore, the present invention in which the pair of optical waveguide members are optical fibers is highly versatile for optical fibers used in general optical communication systems.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 schematically shows an example of the form of an optical circuit element 10 according to the present invention. In this example, the optical circuit element 10 includes two optical fibers 11 and 12 coaxially arranged at a distance. A core (not shown) is formed at the center of each of the optical fibers 11 and 12, and a clad (not shown) is formed around the core.

Further, the optical circuit element 10 is provided with a lattice member 20 on the shaft portions of the both optical fibers 11 and 12. The grating member 20 is formed by connecting a condenser lens 21 and a diffraction grating member 22.

The condenser lens 21 transmits the transmitted light diverged from the core of one optical fiber (for example, the optical fiber 11).
A convex lens for focusing on the core of the optical fiber of the other party (for example, the optical fiber 12) is formed. In this example, the condenser lens 21
And the diffraction grating member 22 are integrally formed.

The diffraction grating member 22, as shown in FIG.
A rectangular lattice surface 31 is formed on one surface of the substrate 30. In this example, the diffraction grating member 22 is provided with a slight inclination with respect to the optical axis so that the reflected light from the diffraction grating member 22 does not return to the optical fiber 11.
The grating surface 31 converts incident light into transmitted light (non-diffracted light: 0th-order light),
Diffracted light (± 1st order, ± 2nd order, ... ± nth order (n is a positive integer))
Diffract to. In this example, the diffraction grating member 22
The diffractive characteristic of changes with the grating height H of the grating surface as shown in FIG. In this example, the horizontal axis is H
/ Λ (wavelength of λ incident light), and the vertical axis represents diffraction efficiency.

According to FIG. 3, the 0th order light (transmitted light) is continuously from 0.95 or more when the height of the rectangular lattice is 0 (no lattice) to 0.0 when the height is 1.0. You can see that it is changing.

Further, the diffraction grating member 22 can be constructed by forming a sawtooth grating surface 41 on one surface of the substrate 40, as shown in FIG. In this case, the grating surface 41 separates the incident light into transmitted light (non-diffracted light: 0th-order light) and diffracted light, but the diffracted light has a + 1st-order most component as shown in FIG. There are few primary components. And in this example,
The diffraction characteristic of the diffraction grating member 22 changes as shown in FIG. 5 by changing the grating height H of the grating surface. In this example, as in FIG. 3, the horizontal axis represents H / λ (wavelength of λ incident light) and the vertical axis represents diffraction efficiency.

According to FIG. 5, the 0th-order light (transmitted light) continues from 0.95 or more when the height of the rectangular lattice is 0 (no lattice) to 0.0 when the height is 2.0. You can see that it is changing.

Therefore, if the transmission light from the optical fiber 11 is made incident on the diffraction grating member 22 and only the transmitted light is emitted to the optical fiber 12, the attenuation rate of the emitted light with respect to the incident light can be freely controlled. It will be possible.

According to the optical circuit element of this example, the necessary non-diffracted light, or the non-diffracted light and the predetermined diffracted light are extracted to spatially separate the unnecessary diffracted light and generate the cladding mode. It is possible to prevent the occurrence of a ripple and an attenuation amount ripple, and thereby to set the light attenuation rate to a desired value.

Further, in the optical circuit element according to the present example, since the transmission wave having the continuous field distribution (for example, Gaussian distribution) of the optical fiber transmission mode is uniformly taken out as the attenuation wave, the clad mode does not occur. In addition, the attenuation ripple does not occur.

In each of the above examples, the case where the diffraction member is provided with the diffraction grating only on the exit surface side has been described. However, the diffraction grating is provided on both the input and output surfaces, and the directions of the diffraction gratings on both surfaces are orthogonal to each other. (The lattice plane of the incident surface is shown by reference numeral 42 in FIG. 4). In this case, regardless of the state of the polarization direction of the incident light, the same diffraction result is eventually given and a stable attenuation characteristic can be obtained. Further, by changing the grating width and grating height of the diffraction grating on both sides, it is possible to obtain an optical circuit element having various wavelength characteristics.
Further, the saw-toothed grating on the incident surface can reduce the reflected return light to the optical fiber 11, so that the diffraction grating member can be arranged orthogonal to the optical axis.

(Second Embodiment) Next, an embodiment of an optical circuit element according to the second embodiment of the present invention will be described. FIG. 6 schematically shows an example of the form of the optical circuit element 50 according to the present invention. In this example, the optical circuit element 50 is
Two optical fibers 51 arranged coaxially at a distance,
52 is provided. Each optical fiber 51, 52 is formed of a core and a clad.

The optical circuit element 50 is provided with a condenser lens 60 at the center of the entrance / exit surfaces of both the optical fibers 51 and 52, and is also provided with a grating member 65 close to the optical fiber 52. The distance between the optical fiber 52 and the grating member 65 depends on the conditions described later.

The condenser lens 60 has one optical fiber 51.
It forms a convex lens that focuses the transmission light diverged from the core of (52) on the core of the other optical fiber 52 (51).

The structure of the grid member 65 is the same as that of the grid member of the first embodiment described above. That is, as shown in FIG. 2, a rectangular lattice surface 31 is formed on one surface of the substrate 30, or as shown in FIG. 4, a sawtooth lattice surface 41 is formed on one surface of the substrate 40. .

According to the optical circuit element of this example, the light incident from the optical fiber 51 is diffracted by the grating member 65 and split into transmitted light (0th order light) and diffracted light (± 1st order light). Since it is arranged close to the optical fiber 52, both the transmitted light and the diffracted light are applied to the core of the optical fiber 52, and the amount of light attenuation is small.

On the other hand, the light incident from the optical fiber 52 is diffracted by the grating member 65 and transmitted light (0th order light) and diffracted light (±
(1st order light) and a sufficient distance is provided with respect to the optical fiber 51, the transmitted light is applied to the core of the optical fiber 51, but the diffracted light is not applied to the core of the optical fiber 51. After all, the light incident on the optical fiber 51 becomes only the transmitted light, and the light attenuation amount becomes large.

Therefore, according to this example, the attenuation amount of light can be set differently in each direction, and a non-reciprocal attenuator can be constructed.

(Third Embodiment) In the third embodiment of the optical circuit element according to the present invention, the lattice shape is rectangular,
The optical circuit element includes a diffraction grating whose grating height is set so as to have a predetermined wavelength characteristic that gives desired attenuation to incident lights of different wavelengths.

That is, the optical circuit element according to this example has the same optical element arrangement as that of the example shown in FIG. 1, and the grating height of the grating member 20 is set to, for example, light of two wavelengths. It is set so as to give different diffraction efficiencies.

Here, transmitted light (0th order light) and diffracted light (± 1) of light having a wavelength of 1.3 μm with respect to the grating height H of the grating member.
FIG. 7 shows the diffraction efficiencies of (next and ± 3rd) orders. FIG. 8 shows diffraction efficiencies of transmitted light (0th order light) and diffracted light (± 1st order, ± 3rd order) of light having a wavelength of 1.55 μm under the same conditions. In addition, wavelengths of 1.2 μm to 1.7 μm for three types of grating heights H (0.5 μm, 2.5 μm and 3.0 μm) of the grating member.
Transmitted light (0th order light) and diffracted light (± 1st order, ± 3rd order)
The diffraction efficiency of is shown in FIGS. 9 to 11.

According to each drawing, for example, when the light having the wavelength of 1.3 μm and the light having the wavelength of 1.55 μm are used as the transmission light, and the grating height H is 0.5 μm, the present embodiment is concerned. The transmittance of each light of the optical circuit element can be about 0.65 for a wavelength of 1.3 μm and about 0.73 for a wavelength of 1.55 μm. Similarly, if the grating height H is 2.5 μm, the transmittance of each light of the optical circuit element according to the present example is 1.
About 0.84 for 3 μm and about 0.55 for wavelength 1.55 μm. Further, if the grating height H is 3.0 μm, about 0.67 for wavelength 1.3 μm, wavelength 1 .5
It can be about 0.82 for 5 μm.

Therefore, by selecting the grating height of the grating member, a desired amount of attenuation can be given to lights of different wavelengths, and the attenuation rate of the emitted light with respect to the incident lights of a plurality of wavelengths can be freely controlled. It will be possible.

[0043]

As described above, according to the present invention,
By extracting the required non-diffracted light, or the non-diffracted light and the predetermined diffracted light, it is possible to spatially separate the unnecessary diffracted light and prevent the generation of the cladding mode and the amount of attenuation ripple. Thereby, the light attenuation rate can be set to a desired value.

Further, in the present invention in which the diffractive member is arranged at a position close to one of the optical input / output end faces of the pair of optical waveguide members, the light is directed in one direction (upward) with the diffractive member interposed therebetween.
When passing light in both the reverse direction (downward) and the reverse direction (downward), the light attenuation amount can be set to be different in each direction.
A non-reciprocal attenuator can be constructed.

In the access system of optical communication, the optical signal intensity is different between the upstream and the downstream for each subscriber, so it is necessary to make the levels of the signal light of both subscribers uniform. In such cases,
The optical circuit element according to the present invention is effective for optimizing the optical signal with the base station for each subscriber.

Further, the present invention is provided with a diffraction grating in which the grating shape is rectangular and the grating height is set so as to have a predetermined wavelength characteristic which gives desired attenuation to incident lights of different wavelengths. When the characteristic according to the wavelength of light is set to a desired characteristic, in this example, the only element that can be set is the grating height, and therefore the wavelength characteristic is set only by the grating height, which is easy.

Particularly, in the WDM (optical multiplex communication) system, optical equalization for correcting the wavelength-dependent characteristics of the light emitting / receiving element and the optical amplifier to make the signal light level in a wide wavelength band uniform to almost the same energy level. Many optical circuit elements as a container will be used.

Further, in the case where the diffractive member is provided with the diffraction gratings on both the input and output sides and the directions of the diffraction gratings on both sides are orthogonal to each other, the result is regardless of the state of the polarization direction of the incident light. Stable attenuation characteristics can be obtained by giving the same diffraction result.

Further, by changing the grating width or grating height of the diffraction grating on both sides, it is possible to obtain an optical circuit element having various wavelength characteristics.

Furthermore, the present invention in which the pair of optical waveguide members are optical fibers is highly versatile for optical fibers used in general optical communication systems.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of an optical circuit element according to the present invention.

FIG. 2 is a diagram showing a configuration of a lattice member of the optical circuit element shown in FIG.

FIG. 3 is a graph showing diffraction efficiency with respect to the grating height of the grating member shown in FIG.

FIG. 4 is a diagram showing another configuration of the lattice member of the optical circuit element shown in FIG.

5 is a graph showing diffraction efficiency with respect to the grating height of the grating member shown in FIG.

FIG. 6 is a diagram showing a second embodiment of an optical circuit element according to the present invention.

FIG. 7 shows a wavelength of 1.3 μm with respect to a grating height H of a grating member.
5 is a graph showing the diffraction efficiency of transmitted light (0th order light) and diffracted light (1st order and 3rd order) of light of FIG.

FIG. 8 shows a wavelength of 1.55 μ with respect to a grating height H of a grating member.
It is a graph which shows the diffraction efficiency of the transmitted light (0th-order light) and the diffracted light (1st-order and 3rd-order) of the light of m.

FIG. 9 is a graph showing the diffraction efficiency of transmitted light (0th order light) and diffracted light (1st order and 3rd order) of light having a wavelength of 1.2 μm to 1.7 μm with respect to the grating height H of the grating member: 0.5 μm. Is.

FIG. 10: Transmitted light (0th order light) of light having a wavelength of 1.2 μm to 1.7 μm with respect to the grating height H of the grating member: 2.5 μm
3 is a graph showing diffraction efficiency of diffracted light (first-order and third-order).

FIG. 11: Transmitted light (0th-order light) of light having a wavelength of 1.2 μm to 1.7 μm with respect to the grating height H of the grating member: 3.0 μm
3 is a graph showing diffraction efficiency of diffracted light (first-order and third-order).

FIG. 12 is a diagram showing a conventional optical element.

[Explanation of symbols]

10 Optical circuit element 11 optical fiber 12 optical fiber 20 Lattice member 21 Condensing lens 22 Diffraction grating member 30 substrates 31 lattice plane 32 optical fiber 40 substrates 41 lattice plane 42 lattice plane 50 Optical circuit element 51 optical fiber 52 optical fiber 60 condenser lens 65 Lattice member 70 Optical circuit element 71 optical fiber 72 optical fiber 73 Ferrule 74 The ferrule 75 core 76 core 77 intervals 78 Sleeve

Claims (5)

[Claims] 1. A diffractive member having a diffractive grating is arranged between the input and output end faces of a pair of optical waveguide members arranged at intervals.
The light emitted from one optical waveguide member is diffracted by the diffraction grating, and only the non-diffracted light (0th order diffracted light) or the non-diffracted light and a predetermined diffracted light are combined and incident on the other optical waveguide member as a guided mode. , An optical circuit element that attenuates light from one optical waveguide member and outputs the attenuated light to another optical waveguide member. 2. A diffractive member is arranged at a position on one of the input / output end faces of a pair of optical waveguide members in the vicinity of one optical waveguide member, and an attenuation amount due to transmission of light in one direction and an attenuation amount due to transmission of light in the other direction are provided. The optical circuit element according to claim 1, wherein the optical circuit element is different. 3. A diffraction grating having a rectangular grating shape and having a grating height set so as to have a predetermined wavelength characteristic that gives desired attenuation to incident lights having a plurality of different wavelengths. Item 2. The optical circuit element according to Item 2. 4. The diffractive member according to claim 1, 2 or 3, wherein the diffractive member has diffractive gratings on both the input and output sides, and the diffractive gratings on both sides are formed so as to be orthogonal to each other. Optical circuit element. 5. The optical circuit element according to claim 1, claim 2, claim 3 or claim 4, wherein the pair of optical waveguide members are optical fibers.