JPH0453906A - Optical delaying circuit - Google Patents

Abstract

PURPOSE:To vary a delay time by providing an incident part on which signal light can be made incident at an incident angle of 45 deg. from an arbitrary position of one side of a rectangle, on a plane optical waveguide. CONSTITUTION:A principal component of the circuit is a plane optical waveguide 1 having a rectangular cross section of a refractive index(n) > sq. rt. 2, on which signal light is made incident at an incident angle of 45 deg.. The incident signal light is reflected repeatedly by each side of this plane optical waveguide 1, emitted after going round, and delayed by going round in the plane optical waveguide 1. Also, the plane optical waveguide 1 whose cross section is a rectangle is provided with an incident part 2 on which the signal light is made incident at an incident angle of 45 deg.. This incident part 2 is moved. In such a way, an optical path in which the signal light goes round in the plane optical waveguide 1 is changed, and the delay time can be changed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to optical delay circuits. More specifically, the present invention relates to an optical delay circuit that performs delay control of optical signals in an optical communication system.

BACKGROUND OF THE INVENTION With the development of optical communication networks, it has become necessary to repeat branching and multiplexing of optical signals many times. When multiplexing the same optical signals propagating through a plurality of optical fibers, distortion will occur in the optical signals unless the optical path lengths are completely matched. In order to completely match the optical path lengths of a plurality of optical fibers, an optical delay circuit is required to finely adjust the optical path lengths.

Conventional optical delay circuits use optical delay lines constructed from optical fibers of appropriate lengths.

Problems to be Solved by the Invention Since conventionally used optical delay lines use optical fibers of a fixed length, they have only been able to always provide a fixed delay time. Therefore, each time the configuration of the optical communication network changes or a new element or the like is inserted into the optical fiber, the optical delay line must also be replaced.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical delay circuit with variable delay time that solves the problems of the prior art described above.

Means for Solving the Problems According to the present invention, in an optical delay circuit that delays and outputs an incident signal light, the optical delay circuit is made of a material that is substantially transparent to the signal light and has a refractive index n>JT. A light source comprising: a planar optical waveguide with a rectangular cross section; and an input section that allows the signal light to enter the planar optical waveguide at an incident angle of 45° from any position on one side of the rectangle. A delay circuit is provided.

1. The main component of the optical delay circuit of the present invention is a planar optical waveguide with a rectangular cross section and a refractive index n>J";' on which the signal light is incident at an incident angle of 45°.The input signal light is , the signal light is repeatedly reflected on each side of the planar optical waveguide and output after being circulated sequentially.The signal light is delayed by circulating sequentially within the planar optical waveguide.

The optical delay circuit of the present invention includes an input section that allows signal light to enter the planar optical waveguide having a rectangular cross section at an incident angle of 45 degrees. By moving this entrance part, the optical path along which the signal light travels within the planar optical waveguide changes, making it possible to change the delay time.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention in any way.

Example FIG. 1 shows a plan view of an example of the optical delay circuit of the present invention.

The optical delay circuit shown in FIG. 1 includes a planar optical waveguide 1 having a rectangular cross section with an aspect ratio of 5:4, and a long side 11 of the planar optical waveguide l and an oblique side 2.
1 is configured to be movable while being in contact with each other and has an isosceles right triangular cross section.

The signal light enters the long side 11 of the planar optical waveguide 1 from the optical fiber 3 fixed to the equal side 22 of the input section 2 at an angle of 45°.

When the position where the signal light is incident coincides with the fifth equidistant point ASBSC,D of the long side 11 of the planar optical waveguide 1, the signal light is emitted from the vertex 12 or 13 of the planar optical waveguide 1. For example, if the length of the long side 11 of the planar optical waveguide 1 is 5J, the signal light incident from point A will travel within the planar optical waveguide 1 by 4J.
It advances by JYl and emits from vertex 13. Furthermore, the light incident from point B travels through the planar optical waveguide 1 by 817! The signal light that has proceeded and exited from the vertex 12 and entered from point C is 12J"l
l! The light that has advanced from vertex 13 and entered from point D is 161
They travel Tβ and are emitted from the apex 12, respectively.

On the other hand, if the position where the signal light is incident does not coincide with any of the above points A-D, as shown in Fig. 2(a), after repeated total reflection within the planar optical waveguide l, The light is emitted from the equal sides 23 of the part 20, or the light is emitted from the equal sides 23 of the incident part 20 as shown in FIGS.

As described above, in the optical delay circuit of the present invention, the signal light is
-D If the signal light is incident from any point, the delayed signal light will exit from the apex 12 or 13 of the planar optical waveguide 1, but if it is incident from any other point, it will be emitted from the apex 12 or 13. do not. Therefore, when the exit ports are provided at the vertices 12 and 13 of the planar optical waveguide 1, as described above, the optical path length of the light incident from the point A propagating in the planar optical waveguide l is compared to the point B. The optical path length is 2L when it enters from point C, the optical path length is 3L when it enters from point C, and the optical path length is 4L when it enters from point D, so the optical path length, that is, the delay time, can be changed discretely. .

In the optical delay circuit of the present invention, the range in which the optical path length can be changed is
It is determined by the size of the planar optical waveguide 1 and the aspect ratio of the cross section. Therefore, by appropriately selecting the dimensions of the planar optical waveguide structure, a necessary range of delay can be imparted to the signal light.

FIG. 3 shows a more specific example of the configuration of the optical delay circuit of the present invention. The delay circuit in FIG.
It comprises a planar optical waveguide l with a rectangular cross section formed by i-diffusion, and an input section 2 with a right-angled isosceles triangular cross-section also formed on a LiNbO5 substrate 10 by TI diffusion.

The refractive index of LiNb0a is approximately 2.2. The incident portion 2 has an oblique side portion 21 in close contact with the long side 11 of the planar optical waveguide 1, and is slidable. Further, the optical fiber 3 into which the signal light enters is fixed to the equilateral portion 22 of the input section 2, and the signal light enters the long side 11 of the planar optical waveguide 1 at an angle of 45°.

The vertices 12 and 13 of the planar optical waveguide 1 are chamfered and have optical fibers 7I and 72 of equal length attached thereto. Optical fibers 71 and 72 are connected by coupler 8 to optical fiber 7 which outputs signal light.

In the optical delay circuit of this embodiment, the two vertices 12 and 13, which are the output ends of the planar optical waveguide 1, are chamfered.
Even if the stomach is slightly shifted at the entrance point 20, the signal light will be at the apex 12.
Or emit from 13. Therefore, positioning of the incidence section 2 is easy.

As described in detail, the optical delay circuit of the present invention can change the optical path length, and is therefore effective for optical communication systems in which the optical path length must be adjusted frequently.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an example of the optical delay circuit of the present invention, FIG. 2 is a plan view for explaining the operation of the optical delay circuit of FIG. 1, and FIG. 3 is a plan view of an example of the optical delay circuit of the present invention. FIG. 3 is a perspective view showing a more specific configuration of the optical delay circuit of FIG. [Main reference numbers] 1...Planar optical waveguide, 2...Incidence part, 3.7...Optical fiber, 8...Coupler, 9.10...Substrate

Claims (1)

[Claims] An optical delay circuit that delays input signal light and outputs the delayed signal light is substantially transparent to the signal light and has a refractive index n>√
a planar optical waveguide with a rectangular cross section formed of the material No. 2; and an input section that allows the signal light to enter the planar optical waveguide at an incident angle of 45 degrees from any position on one side of the rectangle. An optical delay circuit characterized by: