JP3193927B2 - Light tuner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength division multiplexing optical communication system, and more particularly to an optical tuner used at the subscriber end of an optical CATV using this system.

[0002]

2. Description of the Related Art In recent years, various forms of optical tuners have been proposed and studied as devices for selecting desired light from light multiplexed in a wavelength division multiplexing optical communication system.
In particular, the wavelength selection method using a diffraction grating is capable of tuning light with high accuracy over a wide band.

An example of the above-described conventional optical tuner will be described below with reference to the drawings.

FIG. 4 shows a configuration of a conventional optical tuner. 4A and 4B are a top view and a side view of the configuration of a conventional optical tuner. In FIG. 4, 41 is an input fiber, 42 is a light receiving fiber, 43 is a lens, 44
Is a diffraction grating, 45 is a rotation mechanism, and 46 is a fiber end face.

The operation of the optical tuner configured as described above will be described below. The wavelengths are λ _a , λ _b , and λ _c from the long wavelength side.

The wavelength λ _a emitted from the input fiber 41 is
The wavelength multiplexed light of λ _c is incident on the diffraction grating 44 via the lens 43. The incident light undergoes wavelength dispersion by the diffraction grating 44, and light in a desired wavelength range is coupled to the light receiving fiber 42 via the lens 43, so that wavelength selection can be performed. For example, FIG.
The diffraction grating 44 by the rotation of the rotary mechanism 45 in the state, it is possible to light of the wavelength lambda _a to [lambda] _c is taken into the light receiving fiber 42, respectively. (For example, Japanese Application Akira 60-
256,901 No. see)

[0007]

However, in the above configuration, the input fiber 41 and the light receiving fiber 4 are not provided.
2 is polished perpendicularly to the longitudinal direction of the fiber, and the return light reflected by the optical system is
In addition, the optical fiber reciprocates between the end faces of the light receiving fiber 42, and this becomes a Fabry-Perot resonator. In particular, in the case of analog transmission, there is a problem that the quality of a transmission signal is impaired.

The present invention has been made in view of the above problems, and provides an optical tuner that does not generate reflected return light.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, an optical tuner according to the present invention has an input fiber and a light receiving fiber whose end faces are obliquely polished and whose polishing directions are the same. It is.

Preferably, the input fiber and the light receiving fiber are sandwiched by a block, and the end face of the input fiber and the light receiving fiber is obliquely polished together with the fiber end face of the block. .

The relative position between the input fiber and the light receiving fiber is set to a direction different from the dispersion direction of the diffraction grating.

[0012]

According to the present invention, the return light reflected between the input fiber and the light receiving fiber is reflected by the obliquely polished end face at an angle which does not return to the original optical system. Further, by shifting the relative position of the input fiber and the light receiving fiber from the chromatic dispersion direction, other chromatic dispersion light can be prevented from returning to the input fiber.

[0013]

An optical tuner according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an optical tuner according to a first embodiment of the present invention. FIG. 1 (a) is a top view and FIG. 1 (b) is a side view.

In FIG. 1, 11 is an input fiber, and 12 is
Light receiving fiber, 13 is a lens, 14 is a diffraction grating, 15 is
The rotation mechanism 16 is a surface on the fiber end surface side. Also, figure
Reference numeral 2 denotes the input fiber 11 and the receiving
FIG. 2 is a perspective view of an optical fiber 12, and reference numeral 18 denotes a block fiber.
This is the face on the side of the end face of the rib. The wavelength relationship starts from the long wavelength side
λ _a, Λ_b, Λ_cAnd

The operation of the optical tuner configured as described above will be described below with reference to FIGS.

Light multiplexed at wavelengths λ _a to λ _c from the input fiber 11 enters the diffraction grating 14 via the lens 13. Light of each wavelength light of wavelength lambda _a to [lambda] _c is subjected to wavelength dispersion by the diffraction grating 14 is diffracted into different angles. The diffraction grating 14 rotating mechanism 15 to rotate the grating groove direction as the rotation axis, the light receiving fiber 12 via the lens 13, to set the angle as a wavelength lambda _a is attached. Assuming that the setting angle viewed from the normal direction of the diffraction grating is θ _i and the grating groove interval of the diffraction grating is d, the setting angle is

[0018]

(Equation 1)

In this configuration, θ _a > θ _b > θ _c is satisfied. End face 1 of input fiber 11 and light receiving fiber 12
6 is polished obliquely in the same direction, and the input fiber 11
In addition, the long direction of the light receiving fiber 12 is arranged to be inclined with respect to the optical axis in accordance with the angle of oblique polishing. If the angle of inclination of the fiber from the optical axis is δ, the refractive index of the fiber is _ng , and the angle of oblique polishing is φ,

[0020]

(Equation 2)

Can be expressed as follows. In order to make the obliquely polished surfaces 16 of the input fiber 11 and the light receiving fiber 12 in the same direction, the surface 18 of the block is obliquely polished with the input fiber 11 and the light receiving fiber 12 sandwiched by the block 17 as shown in FIG. Good.

As described above, according to the present embodiment, the light returning from the optical system to the end faces of the input fiber and the light receiving fiber reflects the angle of reflection に 対 し て with respect to the optical axis, that is,

[0023]

(Equation 3)

Since the light is reflected at a satisfying angle, it is possible to prevent the light from returning to the optical system again. The of the present invention in FIG. 3
FIG. 8 is a configuration diagram of an optical tuner according to a second embodiment. The relative positions of the input fiber 11 and the light receiving fiber 12 are in the same direction as the grating groove direction of the diffraction grating 14 as shown in FIGS.

With this configuration, the wavelength multiplexed light from the input fiber 11 is wavelength-dispersed linearly including the light receiving fiber 12 in a direction perpendicular to the grating groove direction. An optical system in which the wavelength-dispersed light does not return can be provided. This is the input fiber 11 obliquely polished between the blocks 17 shown in FIG.
And the light receiving fiber 12 can be easily realized by rotating the light receiving fiber 12 by 90 degrees.

The input fiber 11 and the output fiber 1
In this example, the relative position of No. 2 is the same as the direction of the grating groove. However, the relative position is not limited as long as the wavelength-dispersed light does not return to the input fiber 11.

In the embodiment, the diffraction grating is simply used. However, if a Fourier diffraction grating having high efficiency and little polarization dependence is used as the diffraction grating, the ratio of the wavelength-dispersed light,
That is, since the diffraction efficiency is 90% or more, the intensity of light coupled to the light receiving fiber can be increased.

Further, since the obliquely polished surfaces in the state where the input fiber 11 and the light receiving fiber 12 are sandwiched by the block 17 have the same angle, both the input fiber and the light receiving fiber can be held in the same direction. Is easy and the reproducibility is good.

[0029]

As described above, according to the present invention, the end faces of the input fiber and the light receiving fiber are obliquely polished in the same direction, so that the reflected return light does not return to the optical system again, and the positioning can be easily performed. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical tuner according to a first embodiment of the present invention.

FIG. 2 is a perspective view of an input / output fiber sandwiched between blocks used in the optical tuner according to the embodiment of the present invention.

FIG. 3 is a configuration diagram of an optical tuner according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical tuner according to a conventional embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Input fiber 12 Light receiving fiber 13 Lens 14 Diffraction grating 15 Rotation mechanism 16 Fiber end face 17 Block 18 Fiber end face side of block

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsuji Miwa 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-62-1115403 (JP, A) JP-A-3-3 239207 (JP, A) JP-A-62-286004 (JP, A) JP-A-1-186904 (JP, A) JP-A-1-172910 (JP, A) Shokai Sho 63-138505 (JP, U)

Claims (1)

(57) [Claims] 1. A system comprising: a diffraction grating, a lens, one input fiber, one light receiving fiber, and a mechanism for rotating the diffraction grating about a grating groove direction as a rotation axis; The diffraction grating is arranged such that the wavelength-multiplexed light undergoes chromatic dispersion at the diffraction grating through the lens, and light in a desired wavelength range is again coupled to the one light receiving fiber via the lens. in rotating system, the relative position of the receiving fiber and the input fiber, wavelength dispersion light arising by the diffraction is staggered to the wavelength dispersion direction of the diffraction grating so as not returning to the input fiber again, the input The end faces of the fiber and the receiving fiber are obliquely polished so as to be in the same direction, and the longitudinal direction of the input fiber and the receiving fiber is the angle of oblique polishing with respect to the optical axis. Light tuner, characterized in that it is arranged to be inclined in accordance.