JPS63501903A - optical fiber equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] fiber optic device FIELD OF THE INVENTION The present invention relates to fiber optic devices. Biconical taper in single mode optical fiber It is possible to manufacture optical fiber couplers by adding It's been found. By tapering in this way, the core HE mode is HEl, mode can be combined. Note that the above waveguide can be used in an efficient manner. Formed by crutding.

The object of the present invention is to detect using an optical fiber having such a biconical taper. and a tunable attenuator, wherein the attenuator is It is a device that incorporates simple and inexpensive electronic equipment.

Accordingly, one aspect of the invention provides an optical coupler formed in the form of a double conical taper. a single mode optical fiber with a specific wave traveling along said fiber For longer lengths, the transmitted power changes according to the change in the refractive index of the material below. means for changing the refractive index of a medium surrounding the fiber portion; and means for detecting light transmitted by a fiber optic device.

Next, two components of an apparatus manufactured according to the invention will be explained so that the invention can be easily understood. An example will be described as an example according to the accompanying drawings. In these drawings: Figure 1 is Variations along the diameter of optical fibers that can be advantageously used in sensors according to the invention It shows the shape of the refractive index. Figure 2 shows the elongation of an optical fiber during the process of forming a double conical taper on the fiber. A graph plotting the transmitted power against the expansion. Figure 3 is a graph similar to Figure 2, where the stretching is stopped at a predetermined position. Figure 4 is a graph showing the refractive index response state of the taper. The above refractive index changes according to temperature changes, and Figure 5 shows the refractive index related to temperature. How a refractive index change is applied to a tapered fiber to form a fusible attenuator. Reeds in the diagram showing the Figure 6 plots the refractive index response of the tapered fiber at the second wavelength. Figure 7 is a schematic diagram of the detector. Figures 8 to 10 show the results when the degree of taper and the surrounding refractive index are changed. The shape of the refractive index in the various diagrams illustrating the response states in FIG. shows several types of single mode optical fibers that can be utilized. Ru. Each shape a, b, c, d, e and f is Matc hed) optical fiber, Depressed optical fiber, Quadruple clad (Quadruple C1ad) optical 7 fiber, Segmented Core (8egmented Core) Hikari 7 fiber and and raised cladding (Ra1sed cladding) optical fiber - represents.

All these types of 7-eyepers are simultaneously Formed into a coaxial kagura by the method described in Continuing British Application No. 8519086 can do. In this method, one end of the optical fiber is irradiated with a laser beam. However, the transmitted power is detected at the other end of the optical fiber. While transmitting light, the optical fiber A portion of the fiber is simultaneously heated and drawn to form a biconical taper in the fiber.

Light guided into the core of a single mode optical fiber is directed into a tapered section. Tae The tapered part where the pad has been applied is a multimode area, local HE11 and For special taper shapes, the power appears at the tapered end within the fiber core. If the tapered length is such that light is transmitted. However, the light is If it appears during the process, it will disappear and become a concern. This means that the tapered shape From the diagram shown in Figure 2, which is based on the power oscillations caused by the construction process, I can understand. Figure 2 shows the results when the taper is stretched until it breaks. are doing. However, the taper forming process can be stopped at will.

Figure 3 shows the 7-eye bar for forming a double conical taper immediately after measuring the power oscillation at t5. It shows the power transmission response state when stretching of a part is stopped.

The tapered optical cup formed by this method utilizes the refractive index response of the taper. can be included within the range of the detector. Silica has a high refractive index. The tapered part is immersed in a liquid such as recon oil, and the refractive index changes. Heating the liquid changes the response of the taper to light with a specific wavelength. Ru. This change is shown in the diagram of FIG.

From this diagram it can be seen that at point A the power transfer is maximum. This point is 29 The temperature is in °C. At higher temperatures, the amount of power used decreases as the temperature increases. It decreases almost linearly. Note that point B indicates the amount of power transmitted at 55°C. this The area A-B of the diagram has relatively low sensitivity and good dynamic range. can be used to provide senna. The above dynamic range within which a change in refractive index of about 10-2 corresponds to a temperature change of about 30°C, and ~2 odB detection sensitivity range is required. These numbers are the intensity settings that measure temperature. sensors, refractive index sensors, acoustic sensors, biological sensors and other sensors. Provide the basic information. Note that each sensor above has this refractive index and intensity relationship. It is used directly or indirectly.

However, the use of devices such as intensity sensors is associated with a number of problems. For example, a song External changes such as ridges and small ridges do not affect the transmission strength. these shortcomings In order to solve this problem, a compensation method is necessary. This can be achieved by dual wavelength transmission. can be achieved. Figure 6 shows a graph of the refractive index response of the same Taber at a second wavelength. The graph in Figure 6 has the same refractive index as when drawing the graph in Figure 4. This is the case when processed under changes. As understood here, the direct A linear slope is replaced by a nearly constant plateau. Two separate conclusions like this It is the ability of a single fiber to give the effect, and the inverse compensation factor depends on the above two results. can be incorporated into the sensor.

Such a compensation sensor is shown in FIG. Two different wavelengths λ4. of λ2 A single mode optical fiber 10 is irradiated with a laser beam. Above optical fiber 1 0 has a right circular conical taper formed at the position of reference number 11, and the optical fiber -10 is surrounded by a sensor area designated by the reference numeral 12. with The sensor area may be covered with silicone oil, for example as in the embodiment shown in FIG. It is a capillary tube filled with water. In any case, the sensor area is the Taber portion 11 in response to changes in the refractive index of the surrounding sensor area, and for each wavelength λ1 and λ2 light. The power transfer graphs shown in Figures 4 and 6 are created in response to It is designed to be drawn. The above two wavelengths are transferred into the fiber by a coupler. can be introduced. As will be understood, for a device with the characteristics just mentioned, Measurements are made only at wavelength λ. At the output end of the fiber 10, two For example, the wavelengths λ1 and λ2 are separated by another Kagura, and each wavelength is The transmitted power is thus detected by detectors D1 and D2. detector output The power is connected to a logarithmic amplifier 1<S, 17, and the output of the logarithmic amplifier is connected to a diode. It is divided by a binder 18. The result is that the material surrounding the right circular taper Linear output as a function of temperature 'i or refractive index. Therefore, temperature, refractive index and and acoustic sensors can be manufactured with this arrangement.

Such sensors can be easily manufactured using inexpensive electronic materials.

Other applications involving this relationship, and in particular the A-B portion of the refractive index response, include tunable reduction. It is that of a G-type device. treatment by changing the refractive index surrounding Taber. The quantity attenuation varies linearly in dB. Figure 5 therefore shows a tunable attenuator. Ru. The single mode optical fiber 1 has a conical shape in the area indicated by reference numeral 2. It has a tapered shape. This area is filled with a liquid such as silicone oil ( The refractive index of the silicone oil is within a desired range. It changes with temperature across the range. The end of capillary tube 3 is UV-cured epoxy sealed with resin. This capillary is coated with a resistive material and the electrodes 4 and 5 are It is provided. By applying a voltage between the electrodes, the released heat is transferred to the liquid. is heated and its refractive index is lowered, resulting in a transmission pattern in the fiber 1. change the situation. In this way, an attenuation of )'5 odB can be achieved.

Also, according to the graph in Figure 4, it can be seen that the power transfer is maximum at point A. . Therefore, optical modulators can be manufactured using this fact. Manufacturing optical modulators In order to Surround the bar. When the refractive index of the surrounding material is moved to a higher direction (to the left in Figure 4), The transmitted power decreases rapidly to a minimum value, ie a loss of about 30 dB.

It is possible to modify this basic concept. Figure 4 shows a tapered right circular cone. It shows a graph created using bars. In addition, the drawing of the above-mentioned right circular conical fiber It is stopped at the time when the power oscillation at t5 occurs. Instead, as shown in Figure 8. Stretch the taber with two complete power oscillations, as shown, and this tapered circle If you use a conical fiber to sweep a straight line that responds to changes in refractive index, you will get something like Figure 9. A straight line is obtained. Similarly, if we expand the number of vibrations to 12, we can see in Figures 7 and 8. An equivalent graph is obtained.

due to the increased Taber effect as shown in Figures 8 and 9. One advantage is that the range of refractive index movement required to cause modulation is narrow. That's what it means. This can be seen by examining the graphs in Figures 10 and 11. It's even more obvious. In Figures 10 and 11, the center peak The effective bandwidth of the refractive index along the Sai. Again, the index of refraction can be changed in one direction to cause modulation. can. This latter arrangement is disadvantageous in that the temperature must be precisely controlled. Accompanied by points.

The various types of materials to which tabers are applied have variable refraction no matter what their properties are. Can be used for rate enveloping materials. One possible way is to align with S102 fibers. The first step is to use an electro-optic material with a sufficiently low refractive index to match. another state As a single mode fiber, it is difficult to match it with an electro-optic crystal such as KDP. can be manufactured from a material with a suitable refractive index. In this case the electro-optical effect is A section of tapered fiber and a crystal can be used together to act as a regulator. can be done. Electro-optic crystal is used as a cladding material surrounding the taber If so, this crystal needs to be carefully grown around the Theba. Te A single KDP crystal long enough to cover the m-electrode and surround the m-electrode. It is also possible to grow it.

Another option is to use a liquid crystal with a low refractive index as a SiO2 guide or a taberite with a high refractive index. It is to be used with fiberglass.

For the modulator just described, the required change in the refractive index of the surrounding medium is (1o-3).

Such modulators are easily applied in digital transmission systems. The above principle The actual structure of the modulator employing is similar to that shown in Figure 5 of the drawings. ing.

Taber formation time refractive index international search report 1ms small. 48. A. , 6°, 1°. ,,pcTlas a67oons 2

Claims (7)

[Claims] 1. A single mode optical fiber having an optical cutter with a double conical taper portion, and this fiber. Transmitted by the medium surrounding the double conical taper of the eyebar and the core of the fiber. the refractive index of the medium is variable; For a particular wavelength traveling along a fiber, the power transmitted is due to the refraction of the medium. An optical fiber device characterized in that it changes in response to changes in rate. 2. means for irradiating said fiber with two different wavelengths and an output of said fiber; A means for separating the two wavelengths at the power end and a means for detecting the power of each transmitted wavelength. and means for generating a compensation factor for one wavelength from the two detected outputs. 2. A device according to claim 1, characterized in that: 3. Claims 1 or 2, characterized in that they include means for changing the refractive index of the medium. or the device described in paragraph 2. 4. Under certain conditions, the fiber transmits maximum power at a given wavelength. Select a medium that surrounds the fiber so that the transmission power is said medium in such a way that the device is qualitatively reduced, thereby allowing the device to act as an attenuator. Claim 3, characterized in that the means for changing the refractive index of is actuated. Device. 5. Claims characterized in that the medium is a liquid surrounding the tapered portion. A device described in any of the following. 6. Claim 5, wherein the liquid is silicone oil. Device. 7. The means for changing the refractive index of the silicone oil comprises a heating means. The apparatus according to claim 6.