JPS627021A - Polarizing compensation element - Google Patents

Abstract

PURPOSE:To obtain the titl element having a small size and capable of operating at a low voltage and also producing with ease by utilizing a multiple reflection and using a translucent ceramics composed of (Pb,La)(Zr,Ti)O3 as a main component. CONSTITUTION:The cable terminals 4, 4' and 5, 5' are connected to a pair of the first electrodes 2, 2' and a pair of the second electrodes 3, 3' in a longitudinal direction respectively, in a such a way that a direction of impressing a voltage has the slope of 45 deg. towards a side surface parallel to a direction of propagating a light of the element 1 having a lozenge in a cross-section, and composedof (Pb,La)(Zr,Ti)O3. The reflective layer 6, 6' are provided on one or other and surface of both end surfaces perpendicular to the direction of propagating a light of the element 1. The focusing rod lens 7, 7' for an incident light and an outgoing light are placed on the both side parts which are not provided the reflective layer 6' respetively. The sides of the element 1 not facing to the lens 7, 7' are connected to a single mode fiber 8, 8' for the incident and the out-going lights respectively. The incident light is effected the multiple reflection at the reflection layers 6, 6', 6 in order, and is led to the fiber 8'.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polarization compensation element that converts incident light of arbitrary polarization into a desired polarization state.

(Prior Art and its Problems) In recent years, in optical communication systems, particularly in long-distance, high-capacity optical communication, research and development of optical heterogeneous a-dyne communication using a single mode fiber as an optical fiber transmission system has become active.

In this optical heterodyne communication, it is necessary that the polarization states of the local light and the light emitted after long-distance transmission from a single mode fiber match. However, in a single mode 7-eyeper, the birefringence inside the fiber changes due to temperature, pressure, etc., so the polarization state at the fiber output end changes in a complicated manner, and does not always match the polarization state of the local light, causing the reception This results in a significant decrease in sensitivity.

Therefore, in optical heterodyne communication, it is necessary to insert a polarization compensator to always obtain a desired polarization state at the output end of a single mode fiber or at the local oscillation light source side. Also, miniaturization and integration.

Even in waveguide optical devices such as optical switches and optical modulators, which have recently been actively researched and developed to improve performance and reliability, their functional effects differ depending on the polarization state of the guided light. Polarization compensation when using a single mode fiber connected between waveguide optical elements! ! location is required.

Conventionally, polarization compensation elements constituting such a polarization compensation device have been described, for example, by Shokudo et al., Journal of Quantum.

z ref) a=ri x (IEEE Journal of
Quantum Electronics) J 1
Volume 7, 1981.

Reported on pages 991-994.

This is a configuration in which two phase modulators using two bulk sheets of lithium niobate (LiNb03) are combined at an angle of 45 degrees to each other, and by utilizing the electro-optical effect of LiNbO3, A voltage is applied to change the phase difference of the propagating light, thereby changing the polarization pattern IIl of the emitted light. However, this polarization compensation element has a thickness of 9.5 m.
The shortcomings were that the length was 40 wpm, the driving voltage was high at a half-wavelength voltage of 66 [V], and the dimensions were large. Also,
This polarization compensation element also has the disadvantage that it is difficult to manufacture because it is necessary to arrange the phase modulators at an angle of 45 degrees with respect to each other.

(Object of the Invention) An object of the present invention is to eliminate these drawbacks and provide a polarization compensation element that is small, can be driven at low voltage, and is easy to manufacture.

(S appendix of the invention) The polarization compensation element of the present invention is made of (Pb, La) (Zr.

A translucent ceramic member consisting of a columnar body mainly composed of Ti)03 and having all inclined surfaces inclined at 45 degrees to each other; It is configured to include a first and second electrode pair provided in series so as to be inclined at 45 degrees, and a reflective layer provided on both end surfaces of the member perpendicular to the propagation direction of the light.

(Operation, principle of the invention) Generally, (Pb, La) (Zr, Ti)
The primary and secondary electro-optic effects of the translucent ceramic made of 03 are very large, and for example, the refractive index change of the material with respect to the applied voltage is greater than that of the conventional L i N b O 3 material. big. Therefore, this ()'b
, La) (Zr, Ti)03 By injecting propagating light into the material and applying a driving voltage, large birefringence is produced, thereby changing the phase difference of the propagating light and changing the polarization state of the emitted light. can be changed more easily than before, making it possible to lower the driving voltage. Also, (Pb, La)
Since the (Zr, Ti)03 material is polycrystalline, unlike the conventional L i N b 03 material, the magnitude of the electro-optic effect does not change depending on the direction of the applied voltage. [Two phase modulators are connected to each other by 4
There is no need to place it at an angle of 5 degrees, and (1) (Pb, L)
a) With the (Zr, Ti)03 member, it is sufficient to provide pairs of electrodes in series so that the directions of voltage application are inclined at 45 degrees with respect to each other, which greatly facilitates manufacturing. In addition, since the electrode pairs are provided in series, the propagating light is controlled by (Pb, La) (Zr
, Ti) by multiple reflections within the 03 material.
, (Pb, La) (Zr, Ti)03 The length of the material can be shortened, and the polarization compensation element can be made smaller. In this way, the polarization state can be changed with a low driving voltage, the size is small,
Furthermore, a polarization compensation element that is easy to manufacture can be obtained.

(Example) The present invention will be explained in detail below with reference to the drawings.

FIGS. 1A and 1B are a perspective view and a side view of an embodiment of the present invention.

In this example, (Pb, La) (
Zr.

Ti) 03 part member, the first electrodes are connected in series on the side surface parallel to the light propagation direction so that the directions in which voltages are applied are inclined by 45 degrees to each other.
an electrode pair 2.2' and a second electrode pair 3.3' are provided;
These first and second electrode pairs 2, 2' and 3.3'
Lead terminals 4, 4' and 5.5' are connected to the terminals 4, 4' and 5.5', respectively. This (Pb, La) (Zr.

Reflective layers 6 and 6' are provided on both end faces perpendicular to the light propagation direction of the Ti)03 member, and reflective layers 6 and 6' are provided on both end faces perpendicular to the light propagation direction. is a focusing rod lens for input and output 7.7
' are arranged respectively. (Pb, La) (Zr, Ti) 03 member 1 of these focusing rod lenses 7, 7'
Single mode fiber for input/output is provided on the side not facing 8.
8' is connected.

With such a configuration, (Pb, La) (Zr, Ti
)03 member 1 has a rhombic cross-sectional shape with a side length of approximately 2.4 cm and an angle between the two sides of 45°, and its length is 10 cm.
It is a thing. In addition, its composition is PbZrO3/PbTi03=65/3, which has a relatively large electro-optic effect of -order
5, La = g atom% O to h:b
o The first and second electrode pairs 2.2' and 3.3' are
The reflective layer 6.6' is made of aluminum and the reflective layer 6.6' is made of chromium.
made of gold.

The single mode fibers 8, 8' are arranged so that the propagating light '1 (Pb.

La)(Zr,Ti)03 In order to cause multiple reflections by the reflective layer 6.6' of the part member and focus it by the focusing rod lens 7' for output, a focusing rod lens (7,
The optical axes of the single mode fibers 8.8' are arranged symmetrically shifted outward with respect to the optical axis of the single mode fibers 7'. In addition, in this embodiment, since Km is formed so that multiple reflections occur three times, the specific focusing rod lens 7.
' is placed.

The single mode fibers 8, 8' have an outer diameter of 125 μm and a core diameter of 9 μm.

In this configuration, light in an arbitrary polarization state propagates from the single mode fiber 8 to the focusing a-rad lens 7 for incidence, and enters the (Pb, La) (Zr, Tj)03 member. The incident light is reflected in the order of the reflective layer 6, the reflective layer 6'9, and the converging lens 7' for output.
The single mode fiber 8' is coupled to the single mode fiber 8'. At that time, between the lead terminals 4 and 4', that is, the first electrode pair 2, 2
When a voltage is applied between '(Pb, La) (Zr,
The Ti ) 03 member 1 produces birefringence due to the first-order electro-optic effect, and changes the phase difference between two mutually orthogonal polarization modes of the propagating light. This changes the polarization state of the propagating light, and it becomes either linearly polarized light, elliptically polarized light, or 9-circularly polarized light.

Since the direction of voltage application to the second pair of electrodes 3, 3' is tilted by 45 degrees with respect to the polarization direction of the previously obtained polarization state, this propagating light requires a voltage between the lead terminals 5, 5'. By applying , the polarization state of the propagating light can always be made into a desired polarization state in a constant direction, for example, linearly polarized light, elliptically polarized light, or circularly polarized light.

Then, the propagating light in the obtained polarized state is coupled to a single mode fiber 8' via an output focusing rod lens 7'. Changing the polarization state by multiple reflection of the propagating light in this way is the same as providing the first and second electrode pairs 2.2' and 3,3't-(repeatedly in multiple stages).

With this configuration, when changing the polarization state of propagating light from, for example, M-line scratched light to the next linearly polarized light whose polarization plane is orthogonal to this linearly polarized light, the phase difference between the two orthogonal polarization modes is π
(rad), but it is necessary to change π(rad
) As a result of measuring the half-wave voltage to be changed, approximately 1O [■
] and the voltage was low. At this time (7) (Pb, La) (Z
r, Ti )03 The maximum beam diameter in member 1 is 178
The diffraction loss was negligible as it was approximately μm, which was sufficiently small compared to the thickness, and an insertion loss of approximately α5 (dB) was obtained.

Additionally, in this configuration, the polarization state of the propagating light obtained by the polarization compensation element is detected, and the necessary driving voltage is applied between the first and second electrode pairs 2.2' and 3.3' using the detected signal. By providing a feedback control system for applying voltage, it becomes possible to automatically control the polarization state of propagating light.

In this example, the cross-sectional shape of the (Pb, Lr) (Zr, Ti) 03 member is rhombic; 2 and 2' and 3 and 3' may be arranged, for example, in a hexagonal shape, a hexagonal shape, etc.

Further, in this example, a -order electro-optic effect is used, but a second-order electro-optic effect may be used, and the composition at that time is not limited. For example, PbZrO3/PbTi03 = 65/35, which has a relatively large second-order electro-optic effect.
, La=9 atom%, etc. may be used.

In addition, this Example 0 (Pb, La) (Zr, Ti) 03
Composition of parts PbZrO3/PbTiO3=65/35
゜La = 8 atom% is not limited to this, for example, PbZrO3/PbTi03=62/3B, La
=7atom chi, PbZrO3/PbTi03=4
0/60, La = 12 atom% Furthermore, by metamorphosis with other elements (P b (L a # L t )
) (Zr * T t ) 03 * P L Z
T-(pb, La) (Zn, Nb)
03 etc. is also fine.

In addition, the propagating light di(Pb, La)(Zr, Ti)03
Although the focusing rod lens 7.7' was arranged so that the beam diameter would be the minimum at about half the propagation distance of the member, the propagating light 2>E (pb, La) (Zr, Ti
) A converging rod lens 7,7' may be arranged to form a parallel beam within the 03 member l.

Further, in this embodiment, the propagating light is (Pb, La) (Zr.

Although the light enters and exits the T.sub.03 member from the same side, the light is not limited to this, and the light entering and exiting surfaces may be opposed to each other, and the number of times of multiple reflections is not limited.

Further, in this embodiment, the optical axis of the single mode fiber 8.8' is shifted from the optical axis of the focusing rod lens 7.7', but the single mode fiber 8.8' and the focusing rod lens 7.7' The optical axes of the lenses 7 and 7' may be made to coincide with each other, and the output end surface of the focusing rod lens may be arranged at an angle with respect to the optical axis.

In this example, aluminum was used for the electrode pairs 2, 2' and 3, 3', but for example, transparent electrodes I To.

Chromium, nickel, etc. may be used, and the reflective layer 6.6
Although chromium-gold was used for ', aluminum, nickel, copper, etc. may also be used.

(Effect of the invention) As described above, according to the present invention, (pb.

Since it uses translucent ceramics whose main components are La)(Zr, Ti)03 and utilizes multiple reflections, it is small and can be driven at low voltage, and it also has one (pb.

Since it can be constructed from La)(Zr,Ti)03 members, a polarization compensating element that is easy to manufacture can be obtained.

[Brief explanation of drawings]

FIGS. 1x) and 1b) are a perspective view of an embodiment of the present invention and a side map thereof viewed from the light propagation direction. In the figure, 1”-(Pb, La) (Zr, Ti)03 member, 2,
2' and 3.3'...first and second electrode pair, 4°4' and 5.5'...lead terminal,
6'6'...Reflection layer, 7,7'...Focusing rod lens for input and output, 8.8'...
...It is a single mode fiber.

Claims (1)

[Claims] (Pb, La) (Zr, Ti) A translucent ceramic member consisting of a columnar body whose main component is O_3 and whose side surfaces are inclined at 45 degrees to each other, and
A pair of first and second electrodes are provided in series on a side surface inclined at 5 degrees so that the direction of voltage application is inclined at 45 degrees to each other, and a pair of electrodes are provided on both end surfaces of the member perpendicular to the propagation direction of the light. What is claimed is: 1. A polarization compensation element comprising: a reflective layer;