JP3875524B2 - Optical branching device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical branching device, and particularly includes a diffraction function unit that receives incident light and emits at least transmitted light and first-order diffracted light, and a condensing function unit that converges the emitted light. The present invention relates to an optical branching apparatus that emits at least two optical fibers as at least two emitted lights.
[0002]
[Prior art]
In an optical fiber communication system, an optical branching device that emits incident light having a specific wavelength as two or more light beams is used. Such an apparatus is used in a communication system, for example, when it is desired to extract a part of an optical signal in order to monitor a transmitted signal.
[0003]
Conventionally, there is such an optical branching device as shown in FIG. This branching device 30 uses a diffraction grating 31.
[0004]
The optical branching device 30 includes a collimator lens 34 that collimates incident light diffused from a light source 32 such as an optical fiber or a laser diode, and diffraction that emits transmitted light (0th-order light) and first-order diffracted light. A grating 31 and a condensing lens 33 for converging the emitted light to the respective converging positions are provided. Optical fibers 35 and 36 are arranged at the converging positions of the respective lights. It is configured so that folding light is incident.
[0005]
[Problems to be solved by the invention]
However, in the conventional optical branching device 30 as described above, incident light is incident on the light receiving surface at an angle to the optical fiber 36 that receives the first-order diffraction. There is a problem that efficiency decreases. Such a decrease in incidence efficiency is about -0.5 dB when the inclination from the vertical plane is 1 °, and about 2 dB when 2 °.
[0006]
In order to avoid a decrease in incidence efficiency as described above, it is conceivable to tilt the optical fiber 37 so that its incident surface is perpendicular to the diffracted light, as indicated by phantom lines in FIG. However, if the optical fiber 37 is tilted in this way, it takes time to set the tilt angle accurately, and the size of the optical branching device increases as the optical fiber 37 is tilted. .
[0007]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical branching device that can efficiently enter a branched incident light beam into an optical fiber.
[0008]
[Means for Solving the Problems]
In the present invention, in order to solve the above problems, the optical branching device is configured as follows.
In the present invention, the optical branching device receives the incident light emitted from the first optical fiber , and at least the diffractive function unit that emits the transmitted light and the first-order diffracted light, and the condensing function unit that converges the emitted light. An optical branching device for emitting the converged light to at least two second optical fibers as at least two exit lights, and for condensing a radiation member that emits light toward the diffraction function section A rear side position that is arranged at a front side position that is twice as long as the focal length of the unit, and that is twice the focal length of the condensing function unit of the second optical fiber on which the branched light is incident The light receiving surface is arranged so as to be parallel to the first optical fiber and perpendicular to the emitted light .
[0009]
In the optical branching device according to the present invention, the diffraction function unit is a diffraction grating, and the light collection function unit is a condensing lens. In the present invention, the diffraction grating may have any shape as long as it has a diffraction function, and a rectangular diffraction grating, a stepped diffraction grating, a sawtooth diffraction grating, or the like is used. Can do.
[0012]
According to each of the above means, the following effects can be obtained. In the case where the diffraction function unit is disposed at the front focal position of the light collection function unit and the incident surface of the optical fiber is disposed on the imaging surface of the emitted light by the light collection function unit, the diffraction function unit and the diffraction function unit are diffracted. In addition to being able to form the functional part integrally, the branched light can be made to enter the incident surface of the optical fiber perpendicularly, so that the incident loss of the branched light is not reduced, and the optical signal as a whole The branching efficiency can be made high.
[0013]
In addition, in the case where the diffraction function unit is a diffraction grating and the light collection function unit is a condensing lens, a combination of a diffraction grating and a condensing lens that exhibits the best performance as an optical branching element is selected and combined. be able to.
[0015]
Furthermore, a radiation member that radiates light toward the diffraction function unit is disposed at the front side position that is twice the focal length of the light collection function unit, and the optical fiber on which the branched light is incident is the light collection function. In the case of the one arranged at the rear position that is twice the focal length of the unit, it is not necessary to use a collimator lens that collimates the incident light, so the number of parts of the optical branching device is reduced. it can.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an optical branching device according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a first example of an embodiment of the present invention.
[0017]
In this example, the optical branching device 10 receives incident light, transmits transmitted light (0th-order light), a diffraction grating 11 that forms a diffraction function unit that emits first-order diffracted light, and emitted light from the diffraction grating 11. And a condensing lens 13 composed of a convex lens having a focal length f forming a condensing function unit that converges. In this example, light incident on the diffraction grating 11 enters the diffraction grating 11 from the incident optical fiber 12 through the collimator lens 14 as parallel light. The diffraction grating 11 has a rectangular diffractive surface formed in a cross section, and emits transmitted light (0th order light) of incident light having a predetermined wavelength and ± 1st order diffracted light.
[0018]
The diffraction grating 11 is arranged such that its diffractive surface is disposed at the front focal position of the condenser lens 13, that is, at a position separated from the front principal point p of the condenser lens 13 by a distance f. Two optical fibers 15 and 16 for receiving two light beams composed of folded light are provided at the rear focal position of the condenser lens 13, that is, at a position f away from the rear principal point p ′ of the condenser lens 13. ing. In this example, the light receiving surfaces of the two optical fibers 15 and 16 are arranged so that the light receiving surfaces are perpendicular to each incident light.
[0019]
Therefore, in this example, the transmitted light (0th-order light) branched from the optical fiber 12 through the collimator lens 14 by the diffraction grating 11 is incident perpendicularly to the incident surface of the optical fiber 15. In addition, since the branched first-order diffracted light can also be incident perpendicularly to the light receiving surface of the optical fiber 16, the incident loss to the optical fibers 15 and 16 can be minimized, The branching efficiency of the optical signal can be increased.
[0020]
In this example, since the incident light to the diffraction grating 11 is perpendicular to the diffraction grating 11, the diffraction efficiency in the diffraction grating 11 can be made constant.
[0021]
Further, in the optical branching device 10 according to the present invention, the diffraction function unit is configured as a diffraction grating, and the condensing function unit is individually configured as a condensing lens. A diffraction grating and a condenser lens can be combined.
[0022]
The diffraction grating and the condensing lens can be manufactured as a single optical element. In this case, adjustment of the distance between the diffraction grating and the condensing lens can be omitted. The score can be reduced.
[0023]
FIG. 2 shows a second example of the optical branching device 20 according to the present invention. In this example, the light exit surface of the optical fiber 22 that is a radiation member that emits light toward the diffraction grating 21 constituting the diffraction function unit is twice the focal length f of the focusing lens 23 that is the light collection function unit. The rear side which is disposed at the front side position of the distance 2 f and the optical fibers 25 and 26 into which the transmitted light and the first-order diffracted light branched by the diffraction grating 21 are incident becomes a distance 2 f which is twice the focal length f of the focusing lens 23. It is arranged at the imaging position.
[0024]
According to this example, the light emitted from the optical fiber 22 enters the diffraction grating 21 while being diffused, and is diffracted into transmitted light (0th order light) and diffracted light (± first order,...). Each light is converged by the converging lens 23, and the transmitted light and the first-order diffracted light form a real image at the focal point on the incident surfaces of the optical fibers 25 and 26 and enter perpendicularly to the incident surface.
[0025]
Therefore, according to this example, the branched light can be perpendicularly incident on the incident surface of the optical fiber, the incident loss of the branched light is not reduced, and the optical signal branching efficiency is improved as a whole. In addition, since it is not necessary to use a collimator lens that collimates incident light, the number of parts of the optical branching device can be reduced.
[0026]
In addition, the optical branching device of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.
[0027]
【The invention's effect】
As described above, according to the optical branching device according to the present invention, the following excellent effects can be obtained.
[0028]
That is, the optical branching device of the present invention is such that the diffraction function unit is arranged at the front focal position of the light collection function unit, and the incident surface of the optical fiber is arranged on the imaging surface of the emitted light by the light collection function unit. In addition, the condensing function unit and the diffraction function unit can be integrally formed, and the branched light can be incident on the incident surface of the optical fiber perpendicularly, and the incident loss of the branched light is reduced. As a whole, the branching efficiency of the optical signal can be increased.
[0029]
Further, the optical branching device of the present invention has the best performance as a light branching element as a diffraction grating and a condensing lens when the diffraction function unit is a diffraction grating and the condensing function unit is a condensing lens. You can select and combine what you want to demonstrate.
[0030]
In addition, a collimator lens that collimates the light incident on the diffraction function unit and has an optical fiber disposed at the rear focal position of the light collection function unit diffracts the incident light on the diffraction grating. It can enter perpendicularly to the grating, and the diffraction efficiency in the diffraction grating can always be constant.
[0031]
Furthermore, a radiation member that radiates light toward the diffraction function unit is disposed at the front side position that is twice the focal length of the light collection function unit, and the optical fiber on which the branched light is incident is the light collection function. In the case of the one arranged at the rear position that is twice the focal length of the unit, it is not necessary to use a collimator lens that collimates the incident light, so the number of parts of the optical branching device is reduced. it can.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an optical branching apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration of an optical branching device according to a second embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of a configuration of a conventional optical branching device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Optical branching device 11 Diffraction grating 12 Optical fiber 13 Condensing lens 14 Collimator lens 15 Optical fiber 16 Optical fiber 20 Optical branching device 21 Diffraction grating 22 Optical fiber 23 Focusing lens 25 Optical fiber 26 Optical fiber

Claims (2)

A diffractive function unit that receives incident light emitted from the first optical fiber, emits at least transmitted light, and emits first-order diffracted light, and a condensing function unit that converges the emitted light. An optical branching device that emits at least two second optical fibers as at least two emission lights,
The diffraction function unit is disposed at a front focal position of the light collection function unit, and a radiation member that emits light toward the diffraction function unit is disposed at a front position that is twice the focal length of the light collection function unit. Arrange the second optical fiber into which the branched light is incident so that the second optical fiber is parallel to the first optical fiber at a rear position that is twice the focal length of the condensing function unit. And an optical branching device arranged such that the light receiving surface is perpendicular to the emitted light .   The optical branching device according to claim 1, wherein the diffraction function unit is a diffraction grating, and the light collection function unit is a condensing lens.

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