CN113031258A

CN113031258A - Optical system and light processing method thereof

Info

Publication number: CN113031258A
Application number: CN201911357951.3A
Authority: CN
Inventors: 陈汝霞; 宋云峰; 丁明昊; 刘红魏; 刘爽
Original assignee: Yuyao Sunny Optical Intelligence Technology Co Ltd
Current assignee: Zhejiang Shunchuang Intelligent Optical Technology Co ltd
Priority date: 2019-12-25
Filing date: 2019-12-25
Publication date: 2021-06-25

Abstract

The invention provides an optical system and a light processing method thereof, wherein the optical system comprises: the optical coupler comprises a micro-lens array, a plurality of first optical couplers, an optical waveguide, a second optical coupler, a third optical coupler and an output end, wherein the micro-lens array is used for gathering light to be processed; a plurality of the first optical couplers for coupling the collected light to the optical waveguides, respectively; the optical waveguide is used for respectively and directionally transmitting the multiple beams of light; the second optical coupler is used for combining the light after directional transmission into a beam of light; and the third optical coupler for coupling the light synthesized by the second optical coupler to an output terminal; the output end is used for transmitting the light through an optical fiber.

Description

Optical system and light processing method thereof

Technical Field

The present invention relates to the field of optics, and in particular, to an optical system and a light processing method thereof.

Background

Optical systems, such as optical receiving systems or optical transmitting systems, are generally suitable for the field of laser intelligent detection, or Charge Coupled Device (CCD) image sensors, or complementary metal semiconductor (CMOS) image sensors, etc. The optical receiving system is used for receiving and converging received light, for example, a laser beam is emitted into a space by a laser emitter, reflected by an object, and reflected light in the space is received by the optical receiving system. The optical emission system is used for processing light emitted by a laser emitter (such as a laser emission array), for example, the light emitted by the laser emitter is emitted or modulated by the optical emission system and then emitted to be projected towards the space with a certain field angle, so that the measurement requirement of a laser area array is met.

In an existing optical system, a spherical lens, an aspherical lens or a combination lens of a spherical surface and an aspherical surface is generally adopted to achieve collimation, divergence or convergence of a light beam, however, the lens occupies a large space and has a large thickness along the optical axis, which results in a large overall thickness of the optical system and fails to meet the requirement of miniaturization. Moreover, the lens has low design precision, large processing error of the light beam and difficult achievement of ideal processing effect.

In addition, the existing optical system generally has the disadvantages of poor detection sensitivity, weak output optical signal, poor stability, difficulty in integrating with an active electronic device (or an active circuit) and the like, and the development of laser intelligent detection is limited. Therefore, there is an urgent need for an optical system and a light processing method thereof having a smaller size and higher detection sensitivity.

Disclosure of Invention

One of the main advantages of the present invention is to provide an optical system and a light processing method thereof, which, compared to the existing optical system, uses a microlens array, has a smaller dimension along the optical axis direction, has higher detection sensitivity, and is easier to meet the miniaturization requirement.

Another advantage of the present invention is to provide an optical system and a light processing method thereof, in which the design accuracy of the microlens array is high to reduce the processing error of the light beam, so as to achieve a desired processing effect.

Another advantage of the present invention is to provide an optical system and a light processing method thereof that can output light through an optical fiber to be suitable for integration with active electronic devices (or active circuits).

Another advantage of the present invention is to provide an optical system and a light processing method thereof, which can combine a plurality of light beams to enhance output light intensity to improve stability.

Additional advantages and features of the invention will be set forth in the detailed description which follows and in part will be apparent from the description, or may be learned by practice of the invention as set forth hereinafter.

According to an aspect of the present invention, there is provided an optical system including: a microlens array, a plurality of first optical couplers, an optical waveguide, a second optical coupler, a waveguide-fiber coupler, and an output end, wherein,

the micro lens array is used for gathering light to be processed;

a plurality of the first optical couplers for coupling the collected light to the optical waveguides, respectively;

the optical waveguide is used for respectively and directionally transmitting the multiple beams of light;

the second optical coupler is used for combining the light after directional transmission into a beam of light; and

the third optical coupler is used for coupling the light synthesized by the second optical coupler to an output end;

the output end is used for transmitting the light through an optical fiber.

In an embodiment of the present application, the third optical coupler is a waveguide-fiber coupler.

In one embodiment of the present application, the waveguide end of the waveguide-fiber coupler has a size corresponding to the size of the optical waveguide, and the fiber end has a size corresponding to the size of the optical fiber.

In an embodiment of the present application, the waveguide end of the waveguide-fiber coupler is configured to focus the light, and the fiber end is configured to transmit the focused light to the optical fiber.

In one embodiment of the present application, the waveguide-fiber coupler is a tapered or tapered structure.

In an embodiment of the present application, a gap between each microlens in the microlens array is not less than 0.3 um.

In an embodiment of the present application, there is a gap between the microlens array and the first optical coupler and the optical waveguide.

In an embodiment of the present application, the optical system further includes:

a collimating microlens array, wherein the collimating microlens array is disposed between the microlens array and the first optical coupler, wherein the collimating microlens array is configured to collimate the collected light.

In an embodiment of the present application, the collimating micro-lens array corresponds to each of the first optical couplers, and makes an angle between the collimated light incident on the first optical coupler and an axis of the first optical coupler be less than or equal to 45 degrees.

In an embodiment of the present application, the first optical coupler is a prism coupler.

According to another aspect of the present application, there is also provided a light processing method, including:

condensing light to be processed by a microlens array;

respectively coupling the collected light to optical waveguides through a plurality of first optical couplers, wherein the optical waveguides are used for respectively transmitting a plurality of beams of the light in a directional mode;

combining the light after directional transmission into a beam of light through a second optical coupler; and

and coupling the light synthesized by the second optical coupler to an output end through a waveguide-fiber coupler, wherein the output end is used for transmitting the light through an optical fiber.

Further objects and advantages of the invention will be fully apparent from the ensuing description and drawings.

These and other objects, features and advantages of the present invention will become more fully apparent from the following detailed description, the accompanying drawings and the claims.

Drawings

FIG. 1 illustrates a perspective view of an optical system according to a preferred embodiment of the present application.

Fig. 2 illustrates a cross-sectional view of a microlens array, a collimating microlens array, a first optical coupler, and an optical waveguide according to a specific example of the optical system in accordance with a preferred embodiment of the present application.

FIG. 3 illustrates an alternative cross-sectional view of a microlens array, collimating microlens array, first optical coupler, and optical waveguide of a specific example of the optical system according to the preferred embodiment of the present application.

FIG. 4 illustrates a cross-sectional view of an optical waveguide of a specific example of the optical system according to the preferred embodiment of the present application.

FIG. 5A is a perspective view of a waveguide-fiber coupler with a waveguide end dimension larger than a fiber end dimension for a specific example of the optical system according to the preferred embodiment of the present application.

FIG. 5B is a perspective view of a waveguide-fiber coupler having a waveguide end dimension equal to a fiber end dimension for a specific example of the optical system according to the preferred embodiment of the present application.

FIG. 5C is a perspective view of a waveguide-fiber coupler with a smaller waveguide end dimension than a fiber end dimension for a specific example of the optical system according to the preferred embodiment of the present application.

FIG. 6 illustrates a method flow diagram of a method of light processing according to a preferred embodiment of the present application.

Detailed Description

The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The basic principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.

It will be understood by those skilled in the art that in the present disclosure, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for ease of description and simplicity of description, and do not indicate or imply that the referenced devices or components must be in a particular orientation, constructed and operated in a particular orientation, and thus the above terms are not to be construed as limiting the present invention.

It is understood that the terms "a" and "an" should be interpreted as meaning that a number of one element or element is one in one embodiment, while a number of other elements is one in another embodiment, and the terms "a" and "an" should not be interpreted as limiting the number.

Exemplary optical System

Fig. 1 is a block diagram schematically illustrating an optical system according to a preferred embodiment of the present application, as shown in fig. 1 to 6, the optical system according to the preferred embodiment of the present application including: a microlens array 10, a collimating microlens array 20, a plurality of first optical couplers 30, an optical waveguide 40, a second optical coupler 50, a third optical coupler 60, and an output end 70 for implementing optical processing in the field of laser measurement or laser detection.

As shown in fig. 1, the microlens array 10 is used for collecting light to be processed, wherein the microlens array 10 includes a set of microlenses 101, and the light to be processed is collected by each microlens 101 of the microlens array 10 to form a plurality of collected lights. The light to be processed is typically a laser beam, which may be return light or reflected light from within space, or the light to be processed may be laser light from a laser emitter or laser emitting array, without limitation herein.

It should be noted that the gap between the microlenses 101 in the microlens array 10 should not be too large, nor too small. If the gap between the microlenses 101 is too large, it is easy to cause a part of the light to pass through the microlens array 10 without being condensed. If the gap is too small, a bridging phenomenon is easily caused in the manufacturing process of the microlenses 101 of the microlens array 10, so that some of the microlenses are bridged together, thereby being unfavorable for light collection. Preferably, the gap between each of the microlenses 101 in the microlens array 10 is not less than 0.3 um.

In this embodiment, the size of the microlens array 10 is preset according to parameters such as laser intensity and detection distance, and the design accuracy of the microlens array is high, so as to reduce the processing error of the light beam and achieve an ideal processing effect. It can be understood that the size of the microlens array 10 along the optical axis direction is significantly smaller than the size of a spherical lens, an aspherical lens, or a combination of a spherical lens and an aspherical lens along the optical axis direction, so that the size of the optical system along the optical axis direction in the present application can be smaller, the overall thickness is smaller, and it is easier to meet the miniaturization requirement, compared with the conventional optical system. It is understood that the microlenses of the microlens array 10 can be micro convex mirrors, micro spherical mirrors, micro aspherical mirrors or micro combined lenses, etc. to achieve the function of collecting light.

As shown in fig. 2, the collimating microlens array 20 corresponds to the microlens array 10, wherein the collimating microlens array 20 is used for collimating the collected light. Further, the collimating microlens array 20 includes a set of collimating microlenses 201, wherein each collimating microlens 201 corresponds to each microlens 101.

Further, the microlens array 10 and the collimating microlens array 20 are respectively formed on two side surfaces of a transparent substrate, that is, the microlens array 10 is located on one side surface of the transparent substrate, and the collimating microlens array 20 is located on the other side surface of the transparent substrate. The transparent substrate may be made of a transparent material such as a glass material, plastic, resin, or the like. Alternatively, the microlens array 10 and the collimating lens array 20 may be formed on the surfaces of two independent transparent substrates, respectively, without limitation.

As shown in fig. 3, a plurality of the first optical couplers 30 respectively correspond to the collimating micro-lens arrays 20, wherein the first optical couplers 30 are used for respectively coupling the collimated light to the optical waveguides 40. I.e. the collimated light enters the optical waveguide 40 via the first optical coupler 30. Preferably, the first optical coupler 30 is a prism coupler, and more preferably, the prism coupler is a triangular prism coupler having a triangular cross section. Alternatively, the first optical coupler 30 may also be another coupler such as a grating coupler or a wedge coupler, and the corresponding technical effects may also be implemented, which is not limited herein.

Further, a gap 301 is formed between the collimating micro-lens array 20 and the first optical coupler 30 and the optical waveguide 40, so that the collimated light enters the first optical coupler 30 after passing through the gap 301. That is, the void 301 is used to form an evanescent field. The size of the gap 301 may be preset according to actual requirements.

Further, each of the collimating microlenses 201 of the collimating microlens array 20 corresponds to each of the first optical couplers 30, and makes an angle between the collimated light incident to the first optical coupler 30 and the axis 31 of the first optical coupler 30 be 45 degrees or less, so as to improve the coupling efficiency of the first optical coupler 30 (preferably, the prism coupler). In the present embodiment, the axis 31 of the first optical coupler 30 is defined as a perpendicular bisector of the first optical coupler, or the axis 31 of the first optical coupler 30 is parallel to the optical axis of the collimating microlens array 20, or the axis 31 is perpendicular to the optical waveguide 40.

The optical waveguide 40 corresponds to each of the first optical couplers 30, wherein the optical waveguide 40 is used for respectively transmitting a plurality of beams of the light in a directional manner. That is, a plurality of beams of the light directionally propagate within the optical waveguide 40. The optical waveguide 40 may be made of an optically transparent medium such as quartz glass.

Further, a plurality of the first optical couplers 30 are positioned on one side surface of the optical waveguide 40, wherein the optical waveguide 40 may be formed as an integral optical structure, wherein each of the first optical couplers 30 is positioned on the surface of the optical waveguide 40 in parallel. Alternatively, the optical waveguide 40 may be implemented as a plurality of optical structures respectively corresponding to the first optical couplers 30, that is, a split structure.

As shown in fig. 4, the second optical coupler 50 corresponds to the optical waveguide 40, wherein the second optical coupler 50 is configured to combine the light directionally transmitted through the optical waveguide 40 into a beam of light, so as to increase the output light intensity and improve the stability. Preferably, the second optical coupler 50 is a branched waveguide coupler, wherein the second optical coupler 50 couples the light transmitted through the plurality of optical waveguides 40 to a single optical waveguide 40, so that the plurality of beams of the light are combined into one beam of light in the single optical waveguide 40 and directionally propagate, thereby realizing the combination of the plurality of beams of the light into one beam of light. That is, the second optical coupler 50 is provided between the plurality of optical waveguides 40 and the single optical waveguide 40 to realize the combination of the plurality of beams of light into one beam of light.

As shown in fig. 5A, the third optical coupler 60 is preferably a waveguide-fiber coupler 60, and the waveguide-fiber coupler 60 corresponds to the optical waveguide 40 (i.e. the single optical waveguide 40 mentioned above) for directionally transmitting the combined light, wherein the waveguide-fiber coupler 60 is used for coupling the combined light to the output end 70. The output end 70 is used to transmit the light through an optical fiber. That is, the waveguide fiber coupler 60 is capable of coupling the light transmitted within the optical waveguide 40 to the optical fiber to enable the optical fiber to transmit the light. The output end 70 comprises a fiber optic material through which light is output to be suitable for integration with active electronic devices (or active circuitry). That is, the optical system of the present invention outputs the light through an optical fiber, which can be connected to an electronic device, suitable for integration. Optionally, the third optical coupler 60 may also be an optical coupler of another type or structure, so as to couple the light transmitted in the optical waveguide 40 to the optical fiber. It will be appreciated by those skilled in the art that the output end 70 may output the light through a single optical fiber or multiple optical fibers, or the output end 70 may output the light through other optical output media.

It will be appreciated that the optical waveguide 40 typically has a size range of 8um x 8um to 50um x 50um or 70um x 70um, etc., the optical fiber may have a size range of 8um x 8um to 50um x 50um or 70um x 70um, etc., and the single-mode optical fiber typically has a core size of 10um and below, such that direct coupling between the optical waveguide 40 and the optical fiber is typically not possible. To solve this problem, the optical system of the present application employs the waveguide-fiber coupler 60 as an optical coupler between the optical waveguide 40 and the optical fiber, so that the light transmitted in the optical waveguide 40 can be coupled to the optical fiber to be output by the optical fiber.

Further, the waveguide end 601 (one end) of the waveguide-fiber coupler 60 has a size corresponding to the size of the optical waveguide 40, and the fiber end 602 (the other end) has a size corresponding to the size of the optical fiber, i.e. the waveguide end 601 of the waveguide-fiber coupler 60 corresponds to the optical waveguide 40 and the fiber end 602 corresponds to the output end 70. The waveguide end 301 is configured to focus the light and the fiber end 602 is configured to transmit the focused light to the optical fiber. Optionally, the waveguide end 601 of the waveguide-fiber coupler 60 has a size ranging from 8um × 8um to 50um × 50um or 70um × 70um corresponding to the size of the optical waveguide 40. The size of the fiber end 602 of the waveguide-fiber coupler 60 may range from 8um x 8um to 50um x 50um or 70um x 70um, corresponding to the size of the fiber.

Preferably, as shown in fig. 5A, the waveguide-fiber coupler 60 is a tapered or cone-like structure with a cross-section of a cone or a cone-like shape, etc., wherein the size of the optical waveguide is larger than the size of the optical fiber. The size of the waveguide end 601 is larger than that of the optical fiber end 602, the cross-sectional shape of the waveguide end 601 may be square, rectangular, or circular, and the cross-sectional shape of the optical fiber end 602 may be square, rectangular, or circular. Further, the waveguide end 601 has a size of 8um × 10um, 8um × 50um, 50um × 50um, or 70um × 70um, etc., and the fiber end 602 has a size of 8um × 8um, 8um × 10um, or 8um × 50um, etc.

Optionally, as shown in fig. 5B, the size of the optical waveguide is equal to the size of the optical fiber, the size of the waveguide end 601 of the waveguide-fiber coupler 60 is equal to the size of the optical fiber end 602, and further, the sizes of the waveguide end 601 and the optical fiber end 602 are 8um × 8um, 8um × 10um, 8um × 50um, 50um × 50um, or 70um × 70um, etc.

Optionally, as shown in fig. 5C, the size of the optical waveguide is smaller than the size of the optical fiber, the size of the waveguide end 601 of the waveguide-fiber coupler 60 is smaller than the size of the optical fiber end 602, further, the size of the waveguide end 601 is 8um × 8um, 8um × 10um, 8um × 50um, 50um × 50um, etc., and the size of the optical fiber end 602 can be 8um × 10um, 8um × 50um, 50um × 50um, or 70um × 70um, etc.

Further, the optical system further includes a substrate 80, wherein the waveguide-fiber coupler 60 is disposed on a surface of the substrate 80. The substrate 80 may be made of a glass material, a resin material, a plastic material, or the like. The surface of the substrate 80 may be planar, wherein the waveguide-fiber coupler 60 is located on the planar surface of the substrate 80. It is understood that the base 80 may be a separate structure from the transparent substrate or an integrated structure, and is not limited herein.

Optionally, the microlens array 10, the collimating microlens array 20, the plurality of first optical couplers 30, the optical waveguide 40, the second optical couplers 50, the waveguide-fiber couplers 60, and the output end 70 are disposed on the substrate 80, which has integrity, is beneficial to integration, reduces the occupied space, and meets the miniaturization requirement.

It should be noted that, in the present invention, the collimating microlens array 20 may not be needed for the optical system, that is, the optical system includes a microlens array 10, a plurality of first optical couplers 30, an optical waveguide 40, a second optical coupler 50, a waveguide-fiber coupler 60 and an output end 70, wherein the microlens array 10 corresponds to the first optical coupler 30, wherein the first optical coupler 30 couples the collected light to the optical waveguide 40, the optical waveguide 40 respectively transmits a plurality of beams of the light in a directional manner, wherein the second optical coupler 50 combines the light transmitted in the directional manner into one light, wherein the waveguide-fiber coupler 60 couples the combined light to the output end 70, and wherein the output end 70 transmits the light through a fiber. Further, the gap 301 is provided between the microlens array 10 and the first optical coupler 30 and the optical waveguide 40 to form an evanescent field.

Exemplary light processing method

Fig. 6 is a flow chart of a method of processing light according to a preferred embodiment of the present application. As shown in fig. 6, the light processing method according to the preferred embodiment of the present application includes:

the light to be processed is collected by the microlens array 10;

respectively coupling the collected light to the optical waveguides 40 through a plurality of first optical couplers 30, wherein the optical waveguides 40 are used for respectively transmitting a plurality of beams of the light in a directional manner;

the light after the directional transmission is combined into a beam of light by a second optical coupler 50; and

the light combined by the second optical coupler 50 is coupled to an output terminal 70 for transmitting the light through an optical fiber by a third optical coupler 60.

In an embodiment of the present application, in the optical processing method, the third optical coupler 60 is a waveguide-fiber coupler.

In an embodiment of the present application, in the optical processing method, a size of the waveguide end 601 of the waveguide-fiber coupler 60 corresponds to a size of the optical waveguide, and a size of the optical fiber end 602 corresponds to a size of the optical fiber.

In an embodiment of the present application, in the optical processing method, the waveguide end 601 of the waveguide-fiber coupler is configured to focus the light, and the fiber end 602 is configured to transmit the focused light to the optical fiber.

In an embodiment of the present application, in the optical processing method, the waveguide-fiber coupler 60 is a tapered structure.

In an embodiment of the present application, in the light processing method, a gap between each microlens 101 in the microlens array 10 is not less than 0.3 um.

In an embodiment of the present application, in the light processing method, a gap is formed between the microlens array 10 and the first optical coupler 30 and the optical waveguide 40.

In an embodiment of the present application, in the light processing method, after the light is collected by the microlens array 10, before the collected light is respectively coupled to the light waveguides 40 by the plurality of first light couplers 30, the method further includes:

the collected light is collimated by a collimating micro-lens array 20.

In an embodiment of the present application, in the light processing method, an incident angle of the collimated light to the first optical coupler 30 is in a range of 45 degrees or less.

In an embodiment of the present application, in the light processing method, the first light coupler 30 is a prism coupler.

The foregoing describes the general principles of the present application in conjunction with specific embodiments, however, it is noted that the advantages, effects, etc. mentioned in the present application are merely examples and are not limiting, and they should not be considered essential to the various embodiments of the present application. Furthermore, the foregoing disclosure of specific details is for the purpose of illustration and description and is not intended to be limiting, since the foregoing disclosure is not intended to be exhaustive or to limit the disclosure to the precise details disclosed.

The block diagrams of devices, apparatuses, systems referred to in this application are only given as illustrative examples and are not intended to require or imply that the connections, arrangements, configurations, etc. must be made in the manner shown in the block diagrams. These devices, apparatuses, devices, systems may be connected, arranged, configured in any manner, as will be appreciated by those skilled in the art. Words such as "including," "comprising," "having," and the like are open-ended words that mean "including, but not limited to," and are used interchangeably therewith. The words "or" and "as used herein mean, and are used interchangeably with, the word" and/or, "unless the context clearly dictates otherwise. The word "such as" is used herein to mean, and is used interchangeably with, the phrase "such as but not limited to".

It should also be noted that in the devices, apparatuses, and methods of the present application, the components or steps may be decomposed and/or recombined. These decompositions and/or recombinations are to be considered as equivalents of the present application.

The previous description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the application. Thus, the present application is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

It will be appreciated by persons skilled in the art that the embodiments of the invention described above and shown in the drawings are given by way of example only and are not limiting of the invention. The objects of the invention have been fully and effectively accomplished. The functional and structural principles of the present invention have been shown and described in the examples, and any variations or modifications of the embodiments of the present invention may be made without departing from the principles.

Claims

1. An optical system, comprising: a microlens array, a plurality of first optical couplers, an optical waveguide, a second optical coupler, a third optical coupler, and an output end, wherein,

the micro lens array is used for gathering light to be processed;

the output end is used for transmitting the light through an optical fiber.

2. The optical system of claim 1, wherein the third optical coupler is a waveguide-fiber coupler.

3. The optical system of claim 2, wherein a dimension of a waveguide end of the waveguide-fiber coupler corresponds to a dimension of the optical waveguide, and a dimension of a fiber end corresponds to a dimension of the optical fiber.

4. The optical system of claim 3, wherein the waveguide end of the waveguide-fiber coupler is configured to focus the light, and the fiber end is configured to transmit the focused light to the optical fiber.

5. The optical system according to any one of claims 1 to 4, wherein a gap between each microlens in the microlens array is not less than 0.3 um.

6. The optical system according to any one of claims 1 to 4, wherein a gap is provided between the microlens array and the first optical coupler and the optical waveguide.

7. The optical system according to any one of claims 1 to 4, further comprising:

8. The optical system according to claim 7, wherein the collimating micro-lens array corresponds to each of the first optical couplers, and makes an angle between the collimated light incident to the first optical coupler and an axis of the first optical coupler equal to or less than 45 degrees.

9. The optical system of claim 8, wherein the first optical coupler is a prism coupler.

10. A light processing method implemented by an optical system as claimed in any one of claims 1 to 9, characterized in that the light processing method comprises:

condensing light to be processed by a microlens array;

and coupling the light synthesized by the second optical coupler to an output end through a third coupler, wherein the output end is used for transmitting the light through an optical fiber.