JPH02211404A - Polarized light eliminator - Google Patents

Abstract

PURPOSE:To realize the polarized light eliminator which is high in the random extent of the polarized state of projection light by using a compound prism formed by cementing a crystal body which has its optical axis slanting to a plane of polarization at an angle of 0 deg.<theta<90 deg. and a crystal body which has its optical axis perpendicularly to the plane of polarization. CONSTITUTION:Light from an optical fiber 1 is made incident on a polarizing prism 5 through a lens 3 and only light having a vertical polarized light component is transmitted and made incident on the compound prism 10. The compound prism 10 is formed by cementing the crystal body which has its optical axis at 45 deg. to the plane of polarization of the incident light and the crystal body which has its optical axis perpendicular to the plane of polarization, the incident light is separated into three components of light beams 11, 12, and 13 and made incident on a lens body 4, and the respective pieces of luminous flux overlap with one another, so that light having a random polarization direction is obtained. Thus, the inexpensive polarized light eliminator which is high in the random extent of the polarization direction is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a depolarization device, and more particularly to a depolarization device for correcting polarization characteristics used in optical communications and the like.

(Conventional technology) Original fiber has low loss and broadband characteristics.

In addition to being used as a means of long-distance, high-capacity communication, it is also widely used in the measurement field as a sensor for temperature, pressure, etc.

The polarization state of the optical fiber changes depending on the temperature or the state of curvature. For example, if a polarizing beam splitter (hereinafter referred to as PB8) is used in the optical system, the splitting ratio of light at the PBS changes depending on the state of the fiber to obtain the correct output. In order to solve this problem, it is necessary to make the source of light transmitted through the optical fiber non-polarized. A depolarization device as shown in FIG. 4 has been proposed in the past.

In the figure, 1 and 2 are original fiber cables.

3.4 is a lens, 5 is a polarizing prism, and 6 is a depolarizing element. The depolarization cable 6 is made of a birefringent material such as calcite, has an uneven surface, and a protective glass 7 is adhered to the uneven surface with a gold optical adhesive 8.

In the depolarization device configured in this way, the light emitted from the optical fiber cable 1 enters the polarizing prism 5 via the lens 3, and only the light having a polarization component in a certain direction is sent to the next stage depolarization element 6. incident on . The light that enters the depolarization element 6 is transmitted through the uneven surface, causing a phase difference, and is emitted to the optical fiber cable 2 via the lens 4, resulting in light having a random polarization direction. .

However, the material used for the depolarization element may be a birefringent material, but if a material with a low refractive index difference between ordinary and extraordinary rays is used, such as relatively inexpensive quartz, it is necessary to make the unevenness large. It is difficult to manufacture because it must not be
- If calcite, which has a high refractive index difference, is used, the unevenness can be reduced, but it has the disadvantage of being expensive.

(Object of the invention) The present invention was made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a depolarization device that has a high degree of randomness in the polarization state of emitted light despite being inexpensive and simple in configuration. shall be.

(Summary of the Invention) In order to achieve this object, the depolarization device of the present invention includes a crystal body having an optical axis tilted by 0 degrees and θ<90 degrees with respect to the polarization plane of the incident light; Depolarization is performed to obtain non-polarized light from partially polarized light or completely polarized light by overlapping the three components of light emitted from the complex prism using a composite prism joined to a crystal body with an optical axis perpendicular to the wavefront. Configure the device Ft.

(Example) The present invention will be described in detail below based on an example shown in two drawings.

FIG. 1 is a diagram showing an embodiment of the present invention.

The same parts as those in the previous figure are given the same reference numerals, and the explanation thereof will be omitted.

In the same figure, 10 is approximately 45 with respect to the polarization plane of the incident light.
A composite prism, that is, a modified Wollaston prism, is obtained by joining a crystal body having an optical axis tilted by a degree and a crystal body having an optical axis perpendicular to the plane of polarization of the incident light.

In the depolarization device configured in this way, the light emitted from the single fiber enters the polarizing prism via the next stage lens 3, and only the light having a vertically polarized component is transmitted and enters the compound prism 10. incident. As shown in FIG. 2, the light incident on the composite prism 10 is a ray 11 which is a combination of an ordinary ray and an extraordinary ray, and an ordinary ray 12 which has a predetermined angle with the incident light. The extraordinary light ItM13 is separated into three components.

Therefore, by inputting the light separated into the three components into the next stage lens 4, the respective light beams overlap as shown in FIG. 3, and light having random polarization directions can be obtained.

Furthermore, since the smaller the separation angle of the emitted light from the composite prism 10 is, the more overlap occurs, it is preferable to use a crystal or the like having a small difference in refractive index.

Therefore, it is possible to construct a depolarization device that is inexpensive and has a high degree of randomness in the polarization direction.

1 In the embodiment of the present invention, the optical system of the I″lt compound prism was explained using an optical system tilted at 45 degrees, but the optical system is not limited to this, and optical systems tilted in the range of 0 degrees, <θ, and 90 degrees were used. It is clear that an axial crystal may also be used.

(Effects of the Invention) Since the present invention is configured and functions as described above, it is possible to obtain non-polarized light with an inexpensive and simple configuration, and exhibits a remarkable effect in reducing manufacturing costs.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, Fig. 2 shows a composite prism of the invention, Fig. 3 shows the state of emitted light, and Fig. 4 shows a conventional depolarization device. It is a diagram. 1.2...9 fibers, 3
．． 4-1. −・・・Lens 5・・・・・・・・・
・Polarizing prism. 6... Depolarization element, 7...
...protective glass. 8...Optical adhesive. 10...Composite prism, 11...
...... Synthesis of ordinary and extraordinary rays 4. 1
2...... Ordinary ray, 13...
...Anomalous rays. Patent applicant: Toyo Tsushinki Co., Ltd.

Claims (1)

[Claims] A composite prism in which a crystal body having an optical axis tilted by 0 degrees < θ < 90 degrees with respect to the polarization plane of the incident light and a crystal body having an optical axis perpendicular to the polarization plane of the incident light are joined. use,
A depolarization device characterized in that unpolarized light is obtained from partially polarized light or completely polarized light by overlapping three components of light emitted from the composite prism.