JPS60117219A - Device for controlling polarization of optical fiber - Google Patents

Abstract

PURPOSE:To enable desired control of polarization at a high speed with low electric power consumption, small size and light weight by providing two plain-sliding and oscillating members to an optical fiber fixed to a fixing member so as to intersect orthogonally said members and impressing prescribed frequencies and prescribed voltages thereto at a prescribed phase difference. CONSTITUTION:When input light Oi of orthogonal components are inputted to an optical fiber 1 from one end thereof, the pulse voltages V1, V2 generated from power sources 10, 11 are attenuated by attenuators 12, 13 to voltages V1', V2' which are impressed to oscillating members 3, 7. The members, 3, 7 impressed with the voltages V1', V2' of the same frequency as the own resonance frequency generate stress strains. The strains are applied to the fiber 1 thereby pressing the core part. A difference in refractive index is generated in the pressed part and non-pressed part of the core part by which the light is polarized. The rate of polarization, i.e., the change in the refractive index is changed by the magnitude of the voltages V1' and V2'. The output light O0 of a fixing member 6 yields therefore the output light subjected to desired polarization when the polarization is controlled. The effect similar to the effect obtainable when a high voltage DC voltage is impressed is equivalently obtd. and since the voltage level to be impressed may be a TTL level signal, electric power consumption as well as the size and weight are reduced.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an apparatus for controlling the polarization direction of light waves propagating within an optical fiber cable.

Background of the Technology For example, in a light wave propagating in a single mode fiber, if the values of two orthogonal components are the same, they are combined and become circularly polarized light, and if their values are different, the light waves become elliptically polarized light depending on the ratio. Generally, elliptically polarized light is used, but it is desired to be able to realize desired polarized light at high speed and with low power consumption.

Prior Art and Problems Conventionally, the above-mentioned polarization control is performed by installing two electromagnets adjacent to each other orthogonally in a part of the path of an optical fiber, and the electromagnetic force of these electromagnets causes a deviation in the optical fiber. In particular, devices are known that control polarization by changing the refractive index of engineered optical fibers (for example, Appli
ed・physicsletter VOl 35. &
11 (November 1, 1979 issue No. 84 (J~842 pages)
). However, in this method, since one electric power is driven, the power consumption is limited, and the t7v response is limited and becomes larger by one dimension. There are problems such as the generation of heat generation noise from the ton magnet.

In addition, instead of electromagnets, piezoelectric elements such as PZT are provided adjacent to each other at right angles, a DC high voltage is applied to the piezoelectric elements, the optical fiber is deflected by the vibration of the piezoelectric element, and the refractive index of the optical fiber is changed. Polarization control devices are also known (for example, Electronics
September 29, 1983 Vol 9. High school 20th class 816-818
page). However, this method also has a problem in that it requires a high DC voltage, for example, several kilovolts, to perform preload control.

Purpose of invention The purpose of the present invention is to reduce power consumption by 1U, and to make it small and lightweight.

Another object of the present invention is to provide an optical fiber polarization control device that can respond quickly and perform desired polarization control.

Structure of the Invention The above-mentioned object of the present invention is as follows: Firstly, without using the standard vibration method, two plane-slip vibrating members are provided adjacently to the optical fiber fixed to the fixed member so as to intersect with each other for 1 h, and these vibrations are This is achieved by applying to the member all the signals having the resonant frequency of the vibrating member and having a predetermined phase difference in pulses having a magnitude responsive to polarization control.

In the present invention, along the long axis of the optical fiber.

A concave surface that matches the external shape of the optical fiber and allows the optical fiber to be buried a predetermined amount in the radial direction? at least one first sliding vibration member provided opposite to the fixing part with the optical fiber metal sandwiched therebetween, and having the same shape as the first fixing member.

a second fixing member that is orthogonal to each other and fixes the optical fiber; and a second fixing member that is provided to face the second fixing member across the optical fiber tray and that is orthogonal to the first plane-sliding vibration part. and a second plane-sliding vibrating member, and a predetermined frequency and a predetermined voltage are applied to the first and second plane-sliding vibrating members with a predetermined phase difference. . An optical fiber polarization control device is provided.

Examples of the invention Examples of the present invention will be described below.

FIG. 1 shows a first embodiment of the present invention. In FIG. 1, a part of the optical fiber 1 is fixed with a first fixing member 21 such as alumina (Al2O2), and a plane sliding vibration member 31 such as PZT is attached on the opposite side. Furthermore, the first fixing part It2 and the facing peri-vibrating member 3 are made of the same material, but they and the Ekll of the optical fiber 1 are made of the same material.
The second fixing member 6 is disposed orthogonally in the l11 direction.
and a second plane-sliding vibration section 8 are provided adjacently. Hereinafter, the direction in which the first plane-slip vibrating part @3 is oriented will be referred to as the X direction, and the direction perpendicular to this (referred to as the iY direction). A source 10, 1 that emits a pulse voltage v1 + V2 f having an oscillation frequency and an opposite phase difference (frequency fol/)
1 (7) Magnetic pressure vt + V2 is R reducer 12, 13tl
− is applied through.

The attenuation factors of the attenuators 12 and 13 are changed by a circuit not shown.

Optical fiber 1 in Figure 1, fixed foot part 2. A cross-sectional view of the vibrating member 3 is shown in FIG. The optical fiber 1 has a core portion 1° at the center through which light propagates. The diameter of the core part is, for example, 10 μm.
For example, the outer diameter of the optical fiber 1 is 120 μm.
That's about it. The fixing member 2 has a concave shape 9 that matches the outer diameter shape of the optical fiber 1, and has a depth that allows the optical fiber 1 to be buried approximately halfway in the diameter direction. The plane sliding vibration member 3 is attached to the fixed member 2 so as to be able to suppress the twisted optical fiber 1.

The length L in the longitudinal direction of the fixing member 2.6 can be any length, for example, about 20 lengths.

1st. Even if the second fixing member is included, the total length is about several tens of thousands of feet. Further, the width W of the fixing member 2.6 can be set to any length, for example, around 10 mm. These dimensions are determined mainly by considering workability and retainability. However, the concave shape 9 needs to be precisely rotated around the outer diameter of the optical fiber 1 and processed in a preferred manner. When compressive force is applied to the optical fiber by the flat surface 9 vibrating member described later, a constant displacement occurs so that a constant refractive index change occurs, and when used for a long period of time, unnecessary stress due to uneven displacement is applied to the optical fiber. This is to prevent damage to the core portion due to the applied voltage being applied to the core portion.

Optical fiber 1. Fixed member 6. The positional relationship and conditions of the vibrating members 7 are as shown in FIG. 2 and above, except that they are orthogonally provided.

The operation of the above embodiment will be described below. optical fiber 1
When the input light Oi of orthogonal components is input from one end, the pulse voltage v1 generated by the power supply 10 is applied to the attenuator 12.
A voltage 1' attenuated to a predetermined value is applied to the vibrating member 3. The vibrating member 3 generates a predetermined stress strain by applying a voltage 1' having the same frequency as its own resonant frequency fO, and this strain is applied to the optical fiber 1, causing the core portion 1
Press 1. The core portion 11 produces a difference in refractive index between the pressed portion and the unpressed portion, thereby polarizing the X-component light. The amount of polarization, ie, the change in refractive index, depends on the magnitude of voltage vl'. That is, it changes depending on the attenuation rate of the attenuator 12.

The main purpose of the polarization is to change the plane of polarization, and the polarization is performed within a range that causes as little loss as possible.

Regarding the Y direction, the polarization plane of the Y direction component light is changed by a desired amount in the same manner as described above.

The output light 00 of the fixing member 6 is a combination of the polarized X component light and the polarized X component light, so by controlling the X component and the polarization of the X component, a desired ellipse can be created. Polarized or circularly polarized output light 00 can be obtained.

Note that the pulse voltage V,, V2 is, or v,', 2/ is usually a signal in which a pulse component is superimposed on a DC component so that a predetermined preload can be applied from the vibrating member 3.7 to the optical core inode 1. There is.

In this way, by using the plane sliding vibrating member 3.4 and applying complementary signals to these vibrating members, that is, pulse voltages V 1/ and V 2/ with a phase difference of 180°, the conventional It is possible to obtain the same effect as applying a high voltage DC voltage -q to the PZT to excite the PZT. Since the pressure level applied in the present invention can be a TTL level signal, power consumption can be reduced, and the power supply system can be made smaller and lighter.

Also, compared to the conventional method of polarizing light using electromagnets.

Since there is no mechanical operating part, the device can be made highly reliable.1 Changes in the attenuation factors of the attenuators 12 and 13 in the present invention can be responded to faster by the circuit.1 For example, several tens of Ml-12
．． It is possible to speed up the process to a certain extent.

In addition, since the power consumption due to the use of electromagnets is relatively large, the power supply system i, L+t+] can be simplified, and the device as a whole can be made smaller.

FIG. 3 shows a fourth embodiment of the present invention. This example is 1
If the excitation signal to be applied to the plane-slip vibration member 3.7 is applied by another method, the optical fiber 1.
The positional relationship between the fixed member 2 and the 61-plane sliding vibration member 3.7 is the same as in the 10th embodiment.

This embodiment uses only one power supply 20 that emits a predetermined frequency, on which a modulated pulse signal SM is superimposed via a transistor 21, and a complementary signal
l'+ ■2' *In other words, a pulse voltage of opposite phase is applied to the vibrating part @3.7. The effects of this embodiment are also similar to those of the first embodiment ψ1j.

FIG. 4 shows a third embodiment of the present invention.
Compared to the plane-slip vibrating member 3.7 in the X direction and the Y direction in FIG. Two plane-slip vibrating members in series in the direction7. τ is provided.

The positional relationship between the plane sliding vibration member, the optical fiber, and the fixing member is as shown in FIG. By providing two vibrating members in series as in this embodiment, the plane of polarization can be controlled more efficiently.

Effects of the Invention As stated above, according to the present invention, an optical fiber polarization control device can be obtained which can perform desired polarization control with low power consumption, small size, light weight, and high speed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an optical fiber polarization control device as an embodiment of the present invention. FIG. 2 is a sectional view of a part of FIG. 1. FIG. 3 is a diagram showing another embodiment of the present invention. FIG. 4 is a diagram showing still another embodiment of the present invention. It is. (Explanation of symbols) 1...Optical fiber, 2...Fixed part. 3... Facing bevel vibration part 4J. 6. Kidnapping of fixed department. 7... Plane sliding vibration part 41°IQ, 11... Power supply. 12.13...Attenuator. Patent applicant Fujitsu Limited Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate 1) Yukio Patent attorney Akiyuki Yama D. Figure 2

Claims (1)

[Claims] 1. A first fixing member that has a concave surface along the long sleeve of the optical fiber that matches the outer surface shape of the optical fiber and in which the optical fiber is buried a predetermined amount in the radial direction; At least one first surface-to-plane υ vibration provided opposite to the fixing member across the front, has the same shape as the first fixing member, and is provided perpendicularly to the optical fiber. A second fixing member for fixing. and at least one second plane-slip vibrating member that is provided opposite to the second rigid crab member of [IJ] with the optical fiber in between and is orthogonal to the first plane-slip vibrating member. . A predetermined frequency is applied to the first and second sliding vibration members,
It is characterized in that a predetermined voltage is applied with a predetermined phase difference. Optical fiber 11i:l optical control device.