JPH0432809A - Multiplexing/demultiplexing device - Google Patents

Abstract

PURPOSE:To obtain a stable multiplexing/demultiplexing device reducing its optical loss by setting up the focal distance of coupling lenses arranged on the projecting optical path for projecting optical fibers to a value longer than that of coupling lenses arranged on incident optical path for incident optical fibers. CONSTITUTION:The coupling lenses 2 to 5 are arranged on the optical paths of light beams transmitted or reflected through/by an interference filter 1 for transmitting/reflecting light with a specific wavelength, the projecting optical fibers 6, 7 and the incident optical fibers are respectively arranged on the projecting optical path and incident optical path of these lenses 2 to 5 and the focal distance of the lenses 2, 3 arranged on the projecting optical path of the fibers 6, 7 is set up to a value longer than that of the lenses 4, 5 arranged on the incident optical path of the fibers 8, 9. Consequently the position adjustment of the fibers 8, 9 can easily by executed and the stable multiplexing/ demultiplexing device reducing its optical loss can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multiplexer/demultiplexer used in a wavelength multiplex transmission device using optical fibers.

2. Description of the Related Art Conventionally, there are various types of multiplexers and demultiplexers (multiplexers, demultiplexers) that perform wavelength multiplex transmission of light using optical fibers. For example, as the first conventional example, JP-A No. 62-2570
There is one disclosed in Publication No. 9. In this, a diffraction grating used for wavelength dispersion is created by a hologram obtained by interference between an aspherical wave and a spherical wave for aberration correction. A diffraction grating made of such a hologram is a planar diffraction grating, and by using it as a diffraction grating for wavelength dispersion, lenses etc. are not required, the overall configuration of the optical system is simplified, and it is possible to A highly efficient multiplexer/demultiplexer can be obtained.

A second conventional example is disclosed in Japanese Patent Application Laid-Open No. 64-37508. In this case, the multiplexer/demultiplexer includes a substrate, a slab-type leading waveguide provided on the substrate,
The end face of this slab-type leading waveguide is processed into a convex shape to provide a lens effect, and a flexible replica diffraction grating is attached to the surface. This makes it possible to easily create a concave diffraction grating by simply pasting together a flexible replica diffraction grating along the edge of a convex substrate.Moreover, the diffraction grating is a replica. Therefore, it can be mass-produced and high-precision elements can be manufactured at low cost.

A third conventional example is disclosed in Japanese Patent Laid-Open No. 64-57214. In this case, the multiplexer/demultiplexer is a parallelogram prism with an optical wavelength filter that transmits or reflects light in a specific wavelength range tightly fixed on one surface of the prism. As a result, even if the parallelogram prism on which the optical wavelength filter is fixed is slightly moved in parallel, the optical axis hardly changes, and it is possible to create a multiplexer/demultiplexer that always obtains constant loss.

Problems to be Solved by the Invention In the various multiplexers and demultiplexers as described above, the multiplexer and the demultiplexer are common, and the magnification of the imaging system is 1:1. For this reason, the output end face (end face of the optical fiber) is coupled to the input end face of the input side optical fiber at the same size or larger, so it is very difficult to adjust the position of the input side optical fiber end face. This causes optical loss upon incidence.

In addition, in order to deal with such problems, methods have been considered such as polarizing the magnification of the imaging system or increasing the core diameter of the input optical fiber. It is impossible to use a multiplexer and a demultiplexer in common and with low loss.

Means for Solving the Problem Therefore, in order to solve such problems, claim 1
In the described invention, an interference filter that transmits or reflects light of a specific wavelength is provided, a coupling lens is provided on the optical path of the light transmitted or reflected by the interference filter, and an output light is provided on the output optical path of these coupling lenses. an optical fiber is disposed, an input optical fiber is disposed on the input optical path of the coupling lens, and the focal length of the coupling lens disposed on the output optical path of the output optical fiber is set to the input optical fiber. The focal length was set to be longer than the focal length of the coupling lens disposed on the incident optical path of the optical fiber.

In the invention according to claim 2, a plurality of output optical fibers;
A lens is provided to collimate the light beams of different wavelengths emitted from these output optical fibers, and a reflection type diffraction grating is provided to reflect and diffract the light beams collimated by the lens in different directions depending on the difference in wavelength. A plurality of input optical fibers are provided, into which the light beam reflected and diffracted by the grating is incident, and the distance from the output end of the output optical fiber to the lens is set to be longer than the distance from the input end of the input optical fiber to the lens. It was set to be longer.

According to the invention described in claims 1 and 2, the image of the light beam emitted from the output end face of the output optical fiber is reduced and combined at the input end face of the input optical fiber, both during multiplexing and demultiplexing. Therefore, it becomes easier to adjust the position of the input optical fiber, and it becomes possible to obtain a stable multiplexer/demultiplexer with less optical loss.

Embodiment An embodiment of the invention set forth in claim 1 will be described based on FIG. An interference filter 1 that transmits or reflects light of a specific wavelength is provided at the center. Coupling lenses 2, 3, and 4.degree. 5 are disposed on each optical path of the light transmitted and reflected by this interference filter 1. Output optical path a of these four coupling lenses 2, 3, 4.5,
Output optical fibers 6 and 7 are disposed on the coupling lenses 2, 3 and 4.
9 are arranged.

In this case, the focal length Mf of the coupling lenses 2 and 3 disposed on the output optical paths a and b of the output optical fiber 6.7 is the input optical path c of the input optical fiber 8°9, d
The focal length f of the coupling lenses 4 and 5 disposed above
The length <(f, >f,) is set to be longer than 8.

In such a configuration, first, at the time of multiplexing, two output optical fibers 6.7 are used for output, and one input optical fiber 9 is used for input. Now, the output wavelengths of the output optical fibers 6.7 are set to λ1. λ, these emitted light beams pass through coupling lenses 2 and 3, respectively, and enter an interference filter l.

This interference filter l has a characteristic of transmitting a light beam of λ and reflecting a light beam of λ. Therefore, the incident λ
The light beams □, λ, are guided in the direction of the coupling lens 5 and transmitted through the input optical fiber 9 with wavelengths λ, 10λ,
It is detected as follows.

At this time, the focal length f1 of the coupling lenses 2 and 3 on the output side is the focal length f3 of the coupling lens 5 on the input side.
Since it is set longer than the output optical fiber 2.
Since the image height of the light beam emitted from the input optical fiber 9 is reduced at the position of the input optical fiber 9, the position of the input optical fiber 9 can be easily adjusted. It becomes possible to obtain a stable multiplexer/demultiplexer with low loss.

Further, during demultiplexing, one output optical fiber 7 is used for output, and two input optical fibers 8.9 are used for input. Assuming that the wavelength of the light beam emitted from the output optical fiber 7 is λ1+λ2, the emitted light beam passes through the coupling lens 3 and is divided into two by the interference filter 1 (λ, .

λ,) and enters the input optical fibers 8 and 9 via the coupling lens 4.5. In this case as well, the focal length f1 of the coupling lens 3 on the output side is set longer than the focal length f2 of the coupling lens 4.5 on the input side. This makes it easier to adjust the positions of the optical fibers 8 and 9.

The reason why the position of the input end surfaces of the input optical fibers 8 and 9 can be easily adjusted will be described based on FIGS. 3 and 4. FIG. 3 shows the magnification relationship when one lens 10 is present. In this case, the following relationship exists: m=-...(2) H,= mH,...(3).

Then, assuming that H8 is the image height at the exit end face and H2 is the image height at the entrance end face, each focal length a, b is a )
In the case of b, H,>H.

In addition, in the case of a lens system as shown in FIG. 4, an object of image height H1 has focal lengths of lenses 11 and 12 f,
f, then fl H,=-・H3...(4) f.

The image is formed at an image height H3. As a result, the image height H,,
H, is regarded as the core diameter of the optical fiber, and the image height on the output side is H.
l, when the image height on the incident side is H3, the lens 11 on the exit side
By setting the focal length f of
H, which makes it easier to adjust the position of the input end face of the optical fiber on the input side. For this reason, the core diameter of a normal optical fiber is approximately 10 to 200 μm, and when imaging such a minute end face, aberrations occur due to the lens system, and in a 1-magnification imaging system, the imaging plane However, by using the configuration of the embodiment as described above, it was possible to deal with this problem.

An embodiment of the invention set forth in claim 2 will be described based on FIG. 2. Three emitting optical fibers 13°, 14, and 15 are provided that emit light beams having mutually different wavelengths (λ8, λ2, and λ3). These output optical fibers 13, 14.1
A lens 16 is provided to collimate the light beams having different wavelengths emitted from the light source 5 . A reflection type diffraction grating 17 is provided which reflects and diffracts the light beam collimated by the lens 16 in different directions depending on the difference in wavelength. A diffraction grating 18 formed on one surface of this reflection type diffraction grating 17
The light beam reflected and diffracted by the lens 16 enters the three input optical fibers 19, 20, and 21 again.
is provided.

In this case, the output optical fibers 13, 14, 15
The distance from the output end of the lens 16 to the lens 16 is set longer than the distance from the input end of the input optical fiber 19, 20, 21 to the lens 16.

In such a configuration, at the time of multiplexing, the light beams (λ1, λ,
.
, 10λ□10λ. At this time, lens 16
The light beam passes through twice, but due to the same principle as in Figure 3,
It can be considered as one lens.

Therefore, by setting the distance from the output end of the output optical fiber 13, 14.15 to the lens 16 longer than the distance from the input end of the input optical fiber 19 to the lens 16, the output optical fiber 13, 14. Since the image height of the light beam emitted from .15 is reduced at the position of the input optical fiber 19, it becomes easier to adjust the position of the input optical fiber 19. It becomes possible to obtain a stable multiplexer/demultiplexer with low optical loss.

In addition, at the time of demultiplexing, the light beam (λ1+λo+λ) emitted from one output optical fiber 13 is reflected by the diffraction grating 18 of the reflection type diffraction grating 17 via the lens 16, and then passes through the lens 16 again. Input optical fibers 19, 2
0.21 states (λ1.λ2.λ,
) is detected. Also in this case, since the distance from the output ends of the output optical fibers 13, 14, 15 to the lens 16 is set longer than the distance from the input end of the input optical fiber 19 to the lens 16, the input It becomes possible to obtain a stable multiplexer/demultiplexer with little optical loss during operation.

Effects of the Invention The invention described in claim 1 provides an interference filter that transmits or reflects light of a specific wavelength, and a coupling lens is provided on the optical path of the light that is transmitted or reflected by the interference filter. An output optical fiber is arranged on the output optical path, an input optical fiber is arranged on the input optical path of the coupling lens, and the coupling lens is arranged on the output optical path of the output optical fiber. Since the focal length is set longer than the focal length of the coupling lens disposed on the input optical path of the input optical fiber, the light from the output end face of the output optical fiber is Since the image of the emitted light beam is reduced and combined at the input end face of the input optical fiber, it becomes easier to adjust the position of the input optical fiber, resulting in a stable multiplexer/demultiplexer with low optical loss. It is something that can be done.

The invention according to claim 2 provides a plurality of output optical fibers and a lens that collimates the light beams having different wavelengths emitted from these output optical fibers, and the light beams collimated by the lens are different in accordance with the difference in wavelength. A reflection type diffraction grating that reflects and diffracts in the direction is provided, a plurality of input optical fibers are provided into which the light beam reflected and diffracted by the reflection type diffraction grating is incident, and a distance from the output end of the output optical fiber to the lens is provided. Since the distance is set to be longer than the distance from the input end of the input optical fiber to the lens, the image of the light beam emitted from the output end face of the output optical fiber during both combining and demultiplexing. is reduced and coupled at the input end face of the input optical fiber, so
The position of the input optical fiber can be easily adjusted, and a stable multiplexer/demultiplexer with little optical loss can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the invention as claimed in claim 1,
FIG. 2 is a configuration diagram showing an embodiment of the invention as claimed in claim 2,
FIGS. 3 and 4 are principle diagrams showing the basic relationship between lens magnifications.

Claims (1)

[Claims] 1. An interference filter that transmits or reflects light of a specific wavelength, a coupling lens provided on the optical path of the light transmitted or reflected by this interference filter, and light emitted from these coupling lenses. An output optical fiber placed on the road,
An input optical fiber is arranged on the input optical path of the coupling lens, and the focal length of the coupling lens is set on the output optical path of the output optical fiber. A multiplexer/demultiplexer characterized in that the focal length is set longer than the focal length of the coupling lens disposed on the optical path. 2. A reflective type that includes a plurality of output optical fibers, a lens that collimates the beams of different wavelengths emitted from these output optical fibers, and a reflection type that reflects and diffracts the collimated beams in different directions depending on the difference in wavelength. It consists of a diffraction grating and a plurality of input optical fibers into which the light beam reflected and diffracted by the reflective diffraction grating is incident, and the distance from the output end of the output optical fiber to the lens is determined by the input optical fiber. A multiplexer/demultiplexer characterized in that the distance is longer than the distance from the end to the lens.