JPH0267989A - Gravity-wave measuring apparatus - Google Patents

Abstract

PURPOSE:To simplify an apparatus by inputting coherent light beams from the ends of two optical fiber coils which are arranged so as to receive gravity waves in the different directions into the other ends, and measuring inference fringes of the coherent light beams. CONSTITUTION:Laser light rays are used as coherent light rays 1. Two optical fiber coils A and B are formed by winding optical fibers around cylinders each having a diameter of, e.g. about 1m, by one million times. It is not necessary that the two coils A and B have the equal length and equal diameter. The coils A and B are fixed to the surfaces having an angle which is not zero, e.g. at a right angle. The light emitted from one hyperstable light source 1 is split into two beams. The light beams are inputted into the ends of the respective coils A and B. The light beams which are emitted from the other ends of the coils A and B are combined again. The light beams are made to interfere and inputted into an interferometer 2. By this constitution, an optical element and an optical apparatus can be formed with the coherent light source such as the laser light source, the optical fiber coils and the optical interferometer. Thus the apparatus can be made simple.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a gravitational wave measuring device using an optical fiber.

BACKGROUND OF THE INVENTION It has become clear that unlike electromagnetic waves, gravitational waves are extremely difficult to generate and detect.

In recent years, research has been conducted in various fields to detect gravitational waves arriving from celestial bodies, but it is still not possible to detect them efficiently.

In order to solve this problem, for example,
Publication No. 7788 proposes a method that utilizes the fact that the transmittance of electromagnetic waves to a gravitational wave receiver made of a conductive material or crystal varies depending on the presence or absence of distortion in the gravitational wave receiver.

Problems to be Solved by the Invention The present invention aims to provide a simple gravitational wave measurement device that uses optical fibers as the gravitational wave receiving body and is mainly composed of optical elements. purpose.

Means for Solving the Problems The gravitational wave measuring device of the present invention includes two optical fiber coils arranged to receive gravitational waves in different directions, a light source that enters coherent light from one end of each optical fiber coil, By the above-mentioned configuration, an interferometer is provided to receive coherent light from the other end of each optical fiber coil, and to measure interference fringes due to the coherent light that has passed through both optical fibers. Light from two ultra-stable laser sources is split into two non-parallel optical fiber coils. At the other ends of the optical fibers, the light is recombined and interfered. If the length of each optical fiber is about 100 km, this interferometer will be an ML channel with one arm of 100 km.
This is a gravitational wave measuring instrument with sensitivity comparable to that of the Elson interferometer.

In the above configuration, as shown in FIG. 1, light from a coherent light source 1 is incident on both optical fiber coils A and B, and further incident on an interferometer 2 through optical fiber coils A and B, respectively. When gravitational waves act on two optical fiber coils, each optical fiber coil deforms in different directions.

The wavelength of light within both optical fiber coils also changes.

The light passing through both optical fiber coils is combined into one and input into an interferometer. The number of interference fringes that cross the interferometer changes depending on the gravitational waves.

The present invention will be further explained in detail below.

Assume that two optical fiber coils A and B are perpendicular to each other as shown in FIG. 1, and that a gravitational wave comes perpendicular to plane A. For simplicity, assuming that the frequency of gravitational waves is less than IHz (we are aiming for gravitational waves from binary stars, but the period of binary stars is usually longer than one day), for light inside an optical fiber, Gravitational waves are considered non-oscillating. When this happens, the gravitational wave, which is a quadrupole, distorts the optical fiber A in the direction of the dotted line in FIG. Since the strength of the gravitational wave is given by h(・Δ1/l), A extends by h1 in one direction and contracts by h1 in the direction perpendicular to that direction. Therefore, the circular coil becomes an ellipse with a/b=1+2h or eccentricity e=25. On the other hand, coil B is deformed in the direction of the dotted line in Figure 1 by the same gravitational wave, and since it is deformed only in one direction, it changes from a circle to an ellipse with e=i. Both A and B are deformed into ellipses, but the degree of deformation is different. It is known that the amplitude and polarization plane of light passing through an optical fiber change depending on the deformation of the optical fiber. If the deformation changes the length or refractive index of the optical fiber, the phase of the light in the optical fiber also changes. The degree of deformation depends on the material of the optical fiber, but the degree of deformation, in this case Δe・o, r5 or Δe2・
It is proportional to h. In the case of gravitational waves, the deviation is predicted to be on the order of 10E-16, so the deviation between the two lights due to such deformation is small. However, if each optical fiber is made into a coil with n turns, the deviation will also be amplified by n times. If the properties of light change by nΔe, then if n is 1068, the change due to gravitational waves can be observed.

If the frequency of the gravitational waves is much lower than the solid frequency of the optical fiber, it is best to consider that the optical fiber is a rigid body and the wavelength of the light passing through it changes by λh in the polarization direction of the gravitational waves. At this time, in coil A, the wavelength is extended at the right and left ends, but the wavelength is shortened at the front and rear ends, and there is no change as a whole.In contrast, in coil B, the wavelength is only extended at the top and bottom, so if dx is the contraction of space due to gravitational waves, it is one revolution. Therefore, the wavelength will be extended by (π/4)dx (see Figure 2). The coil has a circumference of n
If it circulates, the wavelength becomes shorter by n(π/4)dx.

In other words, if the total length of the optical fiber is X and the diameter of the cylinder is X, the number of interference fringes that cross the interferometer due to this effect is (L/4λXd
x/x)(L/4λ)h.

Example As the coherent light source 1, a laser light source is used.

For the optical fiber coils A and B, two coils are made by winding an optical fiber around a cylinder with a diameter of 1 m in 100 directions. The two coils do not need to have the same length and diameter. The two coils are fixed at a non-zero angle, for example in planes perpendicular to each other. The light emitted from one ultra-stable laser light source 1 is divided into two parts and input to one end of each optical fiber coil A and B. One light emitted from the other ends of the optical fiber coils A and B is recombined to interfere with each other and enter the interferometer 2.

Now, if the strength h of the gravitational wave is l0E-16, and the wavelength of the laser beam is λ, which is 1 μm, then if the total length of one optical fiber is l0EIIm, and n is about l0EII, then the gravitational wave can be measured. become. This is the distance between the earth and the sun.

The interferometer using a geostationary satellite is i0E5km, but it would be relatively easy to make an optical fiber of this length. Even with this, it is predicted that gravitational waves from a binary star consisting of two black holes can be measured. In any case, the interferometer proposed here is significantly easier to make smaller than conventional long and large interferometers. If the cross-sectional area of the optical fiber is 10 μm2, then if n is 10EII, the cross-sectional area of the coil will be 1 m''.

Of course, if it is difficult to create this length with one optical fiber, it is sufficient to place many amplifiers that do not disturb the phase in the middle.

This interferometer is extremely temperature sensitive and requires very precise temperature control. This may be accomplished by placing the entire coil in an oil bath. It will also help prevent distortion of the optical fiber due to its own weight. Alternatively, it is also possible to place the entire system in a sanitary or space station.

Effects of the Invention As described above, according to this invention, it is possible to create a gravitational wave measuring device using only optical elements and equipment such as a coherent light source such as a laser light source, an optical fiber coil, and an optical interferometer, and it is possible to compare the devices. It can be made very simple.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the device of the present invention, and FIG.
FIG. 3 is a diagram showing the direction of operation of gravitational waves in the device shown in the figure. lx...Laser light source, 2...Interferometer, A, B...
fiber optic coil. Patent applicant: A.T.R. Optical Radio Communication Research Institute, patent attorney; Patent attorney, Aobai Bo, and one other person

Claims (1)

[Claims] (1) Two optical fiber coils arranged to receive gravitational waves in different directions, a light source that inputs coherent light from one end of each optical fiber coil, and coherent light from the other end of each optical fiber coil. 1. A gravitational wave measurement device comprising: an interferometer that is arranged to receive a gravitational wave and measures interference fringes caused by coherent light that has passed through both optical fibers.