KR100405969B1 - Surface emitting optical fibers and their illuminating systems - Google Patents

Abstract

Disclosed are a side emitting optical fiber using an optical fiber grating and an optical fiber lighting system using the same. The side-emitting optical fiber and the optical fiber illumination system using the same, the optical fiber for transmitting an external beam from any light source; At least one optical fiber lattice having different mode coupling characteristics of coupling the optical beams from the optical waveguide mode to the radiation mode so as to emit light of a corresponding wavelength band according to a parameter value to the periphery of the optical fiber; It comprises a discharge portion formed in the optical fiber. According to the present invention, by forming a grating in the optical fiber to implement side light emission can reduce the damage of the optical fiber, by adjusting the parameter value of the grating can emit light of the desired wavelength range, not only is easy to manufacture but also cost It has the advantage of being small and small. It may also be used in the field of lighting systems, optical displays, optical sensors and optical communications.

Description

Surface emitting optical fibers and their illuminating systems

The present invention relates to a side-emitting optical fiber using an optical fiber grating and an optical fiber lighting system using the same. In particular, an optical fiber that emits light around the optical fiber by forming gratings having different mode coupling characteristics in the optical fiber waveguide mode to the radiation mode. The present invention relates to a side emitting optical fiber using a grating and an optical fiber lighting system using the same.

The optical fiber consists of a core and a cladding, and the optical waveguide becomes a core when there is a cladding, and when there is no cladding, the optical fiber itself becomes a waveguide. The optical fiber mode is composed of a core mode and a cladding mode. The waveguide mode mainly refers to an optical fiber core mode, and the radiation mode refers to a mode in which light is emitted. The optical fiber grating is an optical device having a shape in which the refractive index of the optical fiber core changes periodically, and is manufactured in the optical fiber core, and thus has an advantage of reducing the manufacturing cost due to less insertion loss and easier manufacturing than other bulk devices. In addition, by changing parameter values such as induced index change, grating length, grating period, orientation of grating plane, tilt angle of grating, etc., it is possible to easily have desired spectral characteristics. There is also flexibility.

Such an optical fiber grating can be made by exposing a light-sensitive optical fiber to an interference pattern of a UV beam for a predetermined time. The manufacturing method includes a method using a mask or a method using a laser interferometer.

On the other hand, the illumination system using the optical fiber by applying the above-described radiation mode is currently used in a lot of real life. The optical fiber emitting from the end and the optical fiber emitting from the side are used a lot. The existing method of making the optical fiber emitting from the side is to bend below the bending radius of the allowed optical fiber so that the light leaks out through the cladding layer. It is a method to remove the light by the physical or chemical method so that the light leaks from the side, the method of emitting the light to the outside using a holder or reflector attached adjacent to the cladding.

As such, the conventional lighting system using optical fiber has problems such as damage by applying stress of the optical fiber itself when using the method of bending the optical fiber, and damage to the optical fiber itself when peeling off the cladding layer and adding another material therein. There was also a disadvantage to this.

Accordingly, an object of the present invention is to use a grating having a different mode coupling property for coupling the optical fiber itself from the optical waveguide mode to the radiation mode while preventing stress or breakage applied to the optical fiber itself, and to transmit light of an arbitrary wavelength band to the periphery of the optical fiber. The present invention provides a side emitting optical fiber using an optical fiber grating to emit and an optical fiber lighting system using the same.

Side-emitting optical fiber using the optical fiber grating of the present invention for achieving the above-described invention, the optical fiber for transmitting an external beam from any light source; At least one optical fiber lattice having a different mode coupling characteristic for coupling the optical waveguide mode in the radiation mode to the optical fiber condensing the external beam to emit light of a corresponding wavelength band according to a parameter value to the periphery of the optical fiber; It characterized in that it comprises a discharge formed on the optical fiber. At this time, the optical fiber grating formed in the emission unit may be made of a combination of at least two or more optical fiber gratings having different lattice parameter values so that the wavelength of light may be differently emitted according to the position of the optical fiber, and having the same spectral distribution. The same fiber grating may be made in combination of two or more so that light is emitted regardless of the position of the fiber. In this case, the combination of the optical fiber gratings may form an optical fiber grating group having the same parameters continuously formed in series, or form an optical fiber grating group having different parameters in series. At this time, the optical fiber grid group may be formed at a predetermined interval, or may be formed adjacent to each other continuously.

The combination of the optical fiber gratings may overlap at least a portion of the optical fiber gratings having different parameters, and an angle between the optical fiber gratings intersecting when the optical fiber gratings overlap may have a value within a range of 0 ° to 180 °.

In addition, the combination of the optical fiber grating may make the optical fiber grating different directions of the grating plane.

Finally, the optical fiber grating may be formed into a spiral grating in which the grating plane of the optical fiber is different depending on the grating position so that the outgoing direction of light may be helically emitted according to the position of the optical fiber.

Here, it is most preferable that the optical fiber grating includes at least one optical fiber grating in which at least one parameter value of the optical fiber grating period, the optical fiber grating inclination angle, the optical fiber grating plane direction, and the optical fiber grating length is changed. .

On the other hand, the present invention is a fiber optic lighting system using an optical fiber grating, the optical fiber for transmitting the external beam from any light source, and the mode coupling coupled in the radiation mode in the optical waveguide mode to the optical fiber for condensing the external beam One or more optical fiber gratings having different characteristics are formed on the optical fiber to perform a lighting function by combining a plurality of side emitting optical fibers including an emission part for emitting light of a predetermined wavelength band to the periphery of the optical fiber.

In addition, the optical fiber that transmits the external beam from any light source, and one or more optical fiber gratings having different mode coupling characteristics of coupling the optical beam for condensing the external beam from the optical waveguide mode to the radiation mode The spectral characteristics are formed differently according to position and direction by using the side-emitting optical fiber formed by including the emission unit for emitting light of a predetermined wavelength band to the periphery of the optical fiber.

1A and 1B are diagrams schematically illustrating a side emitting optical fiber emitting light in the vicinity of the optical fiber due to the conversion from the optical fiber waveguide mode to the radiation mode in a grating formed in the optical fiber, and a waveform diagram schematically showing a wavelength band of the emitted light;

2 is a view showing the characteristics of a general optical fiber grating emitting light to the side of the optical fiber,

3a to 3e are views showing various forms of the optical fiber grating constituting the emission portion in the optical fiber as the first to fifth embodiments of the present invention;

4A is a spectral waveform diagram of a side emitting optical fiber grating showing that wavelengths of light emitted from sides of gratings having different characteristics do not overlap each other;

4B is a spectral waveform diagram of a side emitting optical fiber grating in which at least a portion of wavelength bands of light emitted from sides of gratings having different characteristics overlap;

FIG. 5A is a view showing that wavelengths of light are differently emitted according to positions of optical fibers shown in the first embodiment of FIG. 3A;

FIG. 5B is a view showing that light is emitted in a spiral direction according to the position of the optical fiber in the spiral optical fiber grating shown in the fifth embodiment of FIG. 3E.

Explanation of symbols on the main parts of the drawings

2: optical waveguide 4: optical fiber grating

30: first optical fiber lattice 32: second optical fiber lattice

34: Nth optical fiber grating

S1: incident beam

S2: reflected beam

S3: output beam

W: Spectrum of light emitted laterally

Λ: period of optical fiber grating

θ: tilt angle of optical fiber grating

L: length of optical fiber grating

The present invention is characterized by emitting light from the side to the outside due to the grating by using a core of an optical fiber for transmitting light incident from a light source, a cladding surrounding the core, and a grating made in the core.

By changing many parameter values corresponding to the grating, the grating can change the wavelength band of the light emitted outward from the side of the optical fiber and the size of the emission beam. The basic operation principle is that the light can be emitted to the outside through the cladding from the core due to the mode coupling characteristic of coupling from the waveguide mode to the radiation mode of the optical fiber, where the wavelength of the emitted light is the index of change of the refractive index of the grating. , The lattice length (L), the lattice period (Λ), the grating plane orientation (ψ), the lattice angle (θ) and the like. Among the parameters of the optical fiber lattice, the refractive index change value of the optical fiber lattice fabricated by exposing the optical fiber lattice, especially the ultraviolet laser beam pattern, to the optical fiber with light sensitivity for a predetermined time ( ) Can be defined as the difference between the refractive indices of the optical fiber core when the optical fiber is exposed to light and the refractive index of the core when the optical fiber is not exposed. lattice [ref: Kyung S. Lee and T. Erdogan, "Fiber mode coupling ing transmissive and reflected tilted fiber gratings", Applied optics, Vol. 39, No. 9] From the direction of the optical fiber lattice plane inclined clockwise from, the direction is taken in the direction of the lattice plane rotated clockwise by ψ about the optical fiber axis of the lattice plane.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

1A and 1B are diagrams schematically showing a side emitting optical fiber emitting light in the vicinity of the optical fiber due to the conversion from the optical fiber waveguide mode to the radiation mode in a grating formed in the optical fiber and a waveform diagram schematically showing the wavelength band of the emitted light. Referring to FIG. 1, in the side-emitting optical fiber of the present invention, an optical fiber grid 4 is formed on the optical fiber waveguide 2. The principle of light emission from the side-emitting optical fiber is that when the incident beam S1 is incident from the outside, Transmitted along the optical fiber waveguide (2) to reach the optical fiber grid (4) mode coupling from the waveguide mode to the radiation mode to emit light from the core to the outside through the cladding. The spectral characteristics W of the emitted light, ie, λ ₁ , λ ₂ , and the magnitude of the spectrum vary depending on the parameter values of the grating, that is, length, period, tilt angle, direction of the grating plane, and the like. For reference, in the drawings, S2 represents a reflected beam and S3 represents an output beam.

2 is a view showing the characteristics of a general optical fiber grating emitting light to the side of the optical fiber. Referring to FIG. 2, the period Λ of the lattice may be changed from Λ ₁ , Λ ₂ , Λ ₃ to Λ _n or have an arbitrary same period according to the lattice position, and the grids having the same period may be grouped. Can be used to increase or decrease the period of each group. In addition, the inclination angle (θ) of the lattice can be changed from θ ₁ , θ ₂ , θ ₃ , to θ _n or have any same inclination angle including 0, and the angle of inclination can also be grouped to form periods as a group. Can change In addition, the length L of the lattice may be the same value, or may be different from each other, or may be grouped to have the same length for each group.

3A to 3E show various forms of the optical fiber lattice forming the emission section in the optical fiber.

3A is a diagram illustrating a state in which a group of gratings having the same slope is implemented in series on an optical waveguide as a first embodiment of the present invention. Referring to FIG. 3A, the lattice planes have the same direction and have lengths of L ₁ , L ₂ , and L ₃ , respectively, inclination angles of θ ₁ , θ ₂ , and θ ₃ , and periods of Λ ₁ , Λ ₂ , and Λ, respectively. _{It can be seen} that the optical fiber lattice group consisting of the first optical fiber lattice 30 of ₃ , the optical fiber lattice group consisting of the second optical fiber lattice 32, and the optical fiber lattice group consisting of the N-th optical fiber lattice 34 are formed in series.

FIG. 3B illustrates a second embodiment of the present invention, in which gratings having different inclinations are superimposed on the optical waveguide. Referring to FIG. 3B,

The periods Λ of the first optical fiber grating 30, the second optical fiber grating 32, and the N-th optical fiber grating 34 are equal, and the inclination angle θ of the grating is different, or the inclination angle θ of each grating is You can make it the same and make the period (Λ) different. In addition, both the period Λ and the inclination angle θ may be equal to or different from each other, or a group may be formed as described in FIG. The grid length L can also be the same, all different, or grouped so that each group has the same length.

3A and 3B are examples of side-emitting optical fibers composed of X-tilted gratings having the same lattice plane direction, and FIGS. 3A and 3B may be formed of gratings having arbitrary angles ψ having different lattice plane directions. have.

FIG. 3C illustrates a third embodiment of the present invention, in which gratings having different lattice planes are superimposed on the optical waveguide. As shown in FIG. 3C, an example in which the lattice planes are alternate with each other and the lattice directions of the first optical fiber grating 30 and the second optical fiber grating 32 have a difference of 180 ° is shown. This means that the gratings with arbitrary arbitrary angles can be staggered. In this case, the period (Λ) of the first optical fiber grid 30 and the second optical fiber grid 32 is the same, and the inclination angle (θ) of the grating is made the same, and the inclination angle (θ) of the grating is the same, and the period (Λ) May be different. In addition, both the period Λ and the inclination angle θ may be equal to each other, may be different from each other, or may be grouped to increase or decrease as a whole with the same value for each group.

FIG. 3D illustrates a fourth embodiment of the present invention in which the lattice plane has an X-tilted grating and a Y-tilted grating implemented in series on an optical waveguide. As shown in FIG. 3D,

The first optical fiber grating 30, which is an X-tilted grating having a lattice plane of 0 degrees, and the second optical fiber grating 32, which is a Y-tilted grating having a grating plane of 90 degrees, are arranged in series. In this case, the period (Λ) of the first optical fiber grating 30, the second optical fiber grating 32, and the N-th optical fiber grating 34 is the same, and the inclination angle θ of the grating is different, or the inclination angle of each grating is different. (θ) may be the same and the period Λ may be different. In addition, both the period Λ and the inclination angle θ may be equal to or different from each other, or a group may be formed as described in FIG. The grid length L can also be the same, all different, or grouped so that each group has the same length.

FIG. 3E is a view showing a state in which a grating is spirally formed on an optical waveguide by twisting an optical fiber with a grating as a fifth embodiment of the present invention. As shown in FIG. 3E, a spiral grating created by twisting the X-tilted grating is shown. [References: Kyung S. Lee, T. Erdogan "Mode coupling in spiralfibre gratings", Electronics Letters, Vol. 37, No. 3, 2001.] The optical fiber gratings of this spiral grating form the direction of the grating plane. Since the direction of the grating plane varies depending on the location, the direction of emitted light may vary depending on the location, and the spectral characteristics of the light may also vary depending on the location.

FIG. 4A is a spectral waveform diagram of a side emitting optical fiber grating showing that wavelength bands of light emitted from different gratings having different characteristics do not overlap each other, and FIG. 4B is wavelength band of light emitted from side gratings having different characteristics. Is a spectral waveform diagram of the side emitting optical fiber grating at least partially overlapping. As shown in Figure 4a and 4b, showing the wavelength band of the beam emitted to the outside through the cladding in the core by the optical fiber grating, the wavelength band of the beam from each grating may come out side by side without overlapping, The wavelength bands of the beams coming out of the grating overlap and appear to result in large bandwidths of light.

FIG. 5A is a view showing that wavelengths of light are differently emitted according to the positions of the optical fibers shown in the first embodiment of FIG. 3A. As shown in Fig. 5A, the wavelength of the emitted light varies as lambda ₁ , lambda ₂ , lambda ₃ ,... can be changed to λ _N. Thus, when the spectral characteristics of the gratings increase adjacent gratings, the total spectral width emitted can be increased.

FIG. 5B is a view showing that light is emitted in a spiral direction according to the position of the optical fiber in the spiral optical fiber grating shown in the fifth embodiment of FIG. 3E. As shown in FIG. 5B, the direction in which light is emitted is spirally emitted according to the position of the optical fiber by the optical fiber grating in which the spiral grating is formed. The wavelength of light at this time is also λ ₁ , λ ₂ , λ ₃ ,. can be changed to λ _N.

On the other hand, the optical fiber used herein may be made of only the core, or the core is coated with a transparent plastic material, or may be formed of a cladding layer surrounding the core and the core. In addition, the core, the cladding layer surrounding the core, and the cladding layer may be coated with a transparent plastic material. At this time, the core uses a material having a photosensitivity including Ge.

As described above, the side-emitting optical fiber and the optical fiber lighting system using the optical fiber grating according to the present invention, unlike the conventional optical fiber can reduce the damage of the optical fiber by making a grating in the optical fiber, and adjust the parameter value of the grating It can emit light in the desired wavelength range, and it is easy to manufacture, and has the advantages of low manufacturing cost and small size. It may also be used in the field of lighting systems, optical displays, optical sensors and optical communications.

The present invention is not limited to the above-described embodiment, and it will be apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Claims (18)

Optical fiber for transmitting the external beam from any light source; And At least one optical fiber lattice having different mode coupling characteristics of combining the optical waveguide mode from the optical waveguide mode to the radiation mode so as to emit light of a corresponding wavelength band according to a parameter value around the optical fiber. An emission part formed on the optical fiber Side emitting optical fiber using an optical fiber grating, characterized in that consisting of. The optical fiber of claim 1, wherein the optical fiber grating formed in the emitter is formed of a combination of at least two optical fiber gratings having different lattice parameter values so that light wavelengths can be differently emitted according to the position of the optical fiber. Side Emitting Fiber Using Gratings. The side-emitting optical fiber using an optical fiber grating according to claim 2, wherein the combination of the optical fiber gratings is formed by forming a series of optical fiber gratings having the same parameters formed in series. The side-emitting optical fiber using an optical fiber grating according to claim 2, wherein the combination of the optical fiber gratings is formed by forming a group of optical fiber gratings having different parameters successively formed in series. The side-emitting optical fiber using an optical fiber grating according to claim 3 or 4, wherein the optical fiber grating group is formed at a predetermined interval. The side-emitting optical fiber of claim 3 or 4, wherein the optical fiber lattice group is formed adjacent to each other continuously. The side emitting optical fiber of claim 2, wherein the combination of the optical fiber gratings is formed by overlapping at least a portion of the optical fiber gratings having different parameters. 8. The side-emitting optical fiber using an optical fiber grating according to claim 7, wherein an angle between the optical fiber gratings intersecting when the optical fiber gratings overlap is in a range of 0 ° to 180 °. The side-emitting optical fiber using an optical fiber grating according to claim 2, wherein the combination of the optical fiber gratings causes the optical fiber gratings to have different lattice directions. The optical fiber grating according to claim 1 or 2, wherein the optical fiber grating includes a spiral grating in which the grating plane of the optical fiber differs according to the grating position so that the direction of light is helically emitted according to the position of the optical fiber. Side emitting optical fiber using an optical fiber grating. 10. The optical fiber grating according to any one of claims 2 to 4, 7, or 9, wherein at least one of the optical fiber grating period, the optical fiber grating tilt angle, the optical fiber grating plane direction, and the optical fiber grating length which are parameters of each optical fiber grating. A side emitting optical fiber using an optical fiber grating, characterized in that at least one or more optical fiber gratings having one parameter value changed. The side-emitting optical fiber of claim 1, wherein the optical fiber is a core. The side-emitting optical fiber of claim 1, wherein the optical fiber is coated with a transparent plastic material. The side-emitting optical fiber of claim 1, wherein the optical fiber comprises a core and a cladding layer surrounding the core. The optical fiber of claim 1, wherein the optical fiber is coated with a core, a cladding layer surrounding the core, and the cladding layer with a transparent plastic material. The side-emitting optical fiber using an optical fiber grating according to any one of claims 12 to 15, wherein the core is made of a material having a light sensitivity including Ge. At least one optical fiber lattice having a different mode coupling characteristic for coupling an optical beam for transmitting an external beam from an arbitrary light source and an optical fiber for condensing the external beam in a fiber waveguide mode to a radiation mode And an optical fiber grating in which a plurality of side emitting optical fibers are formed, including an emission unit for emitting light of a predetermined wavelength band to the periphery of the optical fiber. At least one optical fiber lattice having a different mode coupling characteristic for coupling an optical beam for transmitting an external beam from an arbitrary light source and an optical fiber for condensing the external beam in a fiber waveguide mode to a radiation mode Optical fiber lighting system using the optical fiber grating to display the spectral characteristics differently according to the position and direction by using a side-emitting optical fiber formed by including a light emitting portion for emitting a predetermined wavelength band around the optical fiber.