JPH02260722A - Phase modulator and light modulator - Google Patents

Abstract

PURPOSE:To surely invert the phase of light by providing an optical switch comprised in such a way that the phase of the light when the light passes a first light waveguide is set differently by 180 deg. from that when it passes a second light waveguide on the first and second light waveguides. CONSTITUTION:The length of the light waveguide 11 and the light waveguide 12 are set so that the phases of the light are deviated by 180 deg. between the branching point of an optical demultiplexer 3 and the coupling point of a photocoupler 4. And a state where the optical switch 1 is turned on and the optical switch 2 is turned off is changed to the state where the optical switch 1 is turned off and the optical switch 2 is turned on, or the state where the optical switch 1 is turned off and the optical switch 2 is turned on is changed to the state where the optical switch 1 is turned on and the optical switch 2 is turned off. In such a way, the phase of emitting light 22 can be inverted by 180 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to coherent optical communications, where binary phase shift keying (PSK modulation) signals, or differentially synchronized PS
The present invention relates to a phase modulator and an optical modulator for obtaining a K modulation (hereinafter referred to as DPSK modulation) signal.

BACKGROUND OF THE INVENTION Conventional phase modulators use crystals such as LiNb0a. The refractive index of this crystal changes depending on the voltage applied to the crystal. Therefore, the speed of the light propagating through the optical waveguide in the phase modulator changes depending on the voltage applied to the crystal, and the phase of the light shifts when it exits from the optical waveguide. In the conventional phase modulator, the applied voltage (2) is appropriately controlled to invert the phase of the emitted light by 180@, thereby performing PSK modulation of the light.

Problems to be Solved by the Invention When performing PSK modulation with a conventional phase modulator, it is necessary to accurately control the voltage applied to the phase modulator so that the phase of light passing through the phase modulator is inverted by 180°. must,
If the shifted phase deviates from 180', there is a drawback that the transmission characteristics deteriorate.

Further, conventional phase modulators cannot be monolithically integrated with NV group materials such as semiconductor lasers made of crystals such as LiNbO3.

In view of the above points, it is an object of the present invention to provide a phase modulator that can reliably invert the phase of light and obtain a good PSK signal or DPSK signal.

In addition, the present invention provides optical modulation that can be monolithically integrated with a semiconductor laser, improves optical coupling between the semiconductor laser and the phase modulator, and reduces the overall size of the optical modulator. The purpose is to provide equipment.

Means for Solving the Problems In the phase modulator of the present invention, the input ends of the first and second optical waveguides are respectively connected to two output ends of a 1-input, 2-output optical splitter, and the two optical waveguides The output ends of are respectively connected to the two input ends of a 2-input 1-output optical coupler, and the light that enters the input end of the optical splitter and exits from the output end of the optical coupler is connected to the first light guide. The phase of the light is 180" when passing through the waveguide and when passing through the second optical waveguide.
Optical switches having different configurations and having the function of passing or blocking light are provided on the first and second optical waveguides, respectively.

Further, in the phase liquid 5 adjuster of the present invention, the input ends of the first and second optical waveguides are respectively connected to the two output ends of the first 2×2 directional coupler, and the output ends of the two optical waveguides are connected to the output ends of the first 2×2 directional coupler. are respectively connected to the two input ends of the second 2×2 directional coupler, and are input from the first input end of the first directional coupler to the first input end of the second directional coupler. The light emitted from the output end is configured such that the phase of the light differs by 180° between when it passes through the first optical waveguide and when it passes through the second optical waveguide, so that the light is passed or blocked. Functional lights and switches are provided on the first and second optical waveguides, respectively.

Further, a phase modulator is constructed of at least a semiconductor laser and the same semiconductor material as the semiconductor laser.

Function As described above, the incident light is split into two and guided into the optical waveguides, and the lengths of the two optical waveguides are determined in advance so that the phases of the lights are shifted by 180 degrees from each other. If the lights are combined by an optical coupler and emitted from one optical waveguide, and one of the two split waveguide lights is passed through and the other is blocked, and vice versa, The phase of the light emitted from the optical coupler can be reversed by 180°.

Further, in the 2×2 directional coupler, the phases of the two output lights are shifted by 90' from each other. Therefore, if the lengths of the two optical waveguides between the two directional couplers are the same, the light propagating through one of the two optical waveguides will be at 9o° at the directional coupler on the input side. The directional coupler on the output side is shifted by 90", and the light propagating through the other waveguide is shifted by 180".
"The phase shifts. Therefore, if one of the two optical waveguides between the two directional couplers is passed through and the other is blocked, and vice versa, the phase of the output light can be reversed by 180 can be done.

In addition, optical splitters, optical couplers, which are components of phase modulators,
Since directional couplers, optical waveguides, optical switches, and the like can be made of semiconductor materials of the ■■ group, the phase modulator of the present invention can be monolithically integrated with a semiconductor laser.

Embodiment FIG. 1 shows a first embodiment of the present invention. In the figure, 1.2 is an optical switch, 3 is an optical splitter with 1 input and 2 outputs, 4 is an optical coupler with 2 inputs and 1 output, 11.12 is an optical waveguide, 21 is incident light, and 22 is output light. . The operation will be explained below.

The incident light 21 is split into two by the optical splitter 3, and the - side is guided to the optical waveguide 11 and the other is guided to the optical waveguide 12. Now, assuming that the optical switch 1 is on and allows light to pass through, and the optical switch 2 is off and blocking light, the optical waveguide 1
The light propagating through the optical waveguide 1 passes through the optical switch 1 and exits as output light 22 via the optical coupler 4, and the light propagating through the optical waveguide 12 is blocked by the optical switch 2. Next, optical switch 1
is off and the optical switch 2 is on, the optical waveguide 12
The light propagating through the optical waveguide 11 is emitted as an output light 22.
The light propagating through is blocked by the optical switch 1. An optical waveguide 11 is connected between the branching point of the optical splitter 3 and the coupling point of the optical coupler 4.
Since the lengths of the optical waveguides 12 and 12 are set so that the phase of the light is shifted by 180 degrees, the state where optical switch 1 is on and optical switch 2 is off changes from the state where optical switch 1 is on and optical switch 2 is off to when optical switch 1 is off and optical switch 2 is on. The phase of the emitted light 22 can be inverted by 1800 degrees by changing the state or from the state where the optical switch 1 is off and the optical switch 2 is on to the state 2 where the optical switch 1 is on and the optical switch 2 is off.

FIG. 2 shows the second embodiment of the present invention.

In the figure, 1.2 is an optical switch, 5.6 is a 2×2 directional coupler, 13.14 is an optical waveguide, 23 is incident light, and 24.2
5 indicates the emitted light. The operation will be explained below.

The incident light 23 is split into two by the directional coupler 5, one of which is guided to the optical waveguide 13 and the other to the optical waveguide 14. Now, assuming that the optical switch 1 is on and passes light, and the optical switch 2 is off and blocking the light, the light propagating through the optical waveguide 13 passes through the optical switch 1 and passes through the directional coupler. The light that is outputted as output light 24 and 25 through the optical waveguide 6 and propagated through the optical waveguide 14 is blocked by the optical switch 2 . Next, when the optical switch 1 is off and the optical switch 2 is on, the light propagating through the optical waveguide 14 is emitted as output light 24.25, and the light propagating through the optical waveguide 13 is blocked by the optical switch 1. Ru. By the way, in the directional coupler 5, the phase of the light guided to the optical waveguide 14 is delayed by 90'' with respect to the light guided to the optical waveguide 13.Furthermore, in the directional coupler 6,
The phase of the emitted light 24 is delayed by 90° in the case of the light coming from the optical waveguide 14 than in the case of the light coming from the optical waveguide 13.

From this, the state where optical switch 1 is on and optical switch 2 is off changes to the state where optical switch 1 is off and optical switch 2 is on, or optical switch 1 is off and optical switch 2 is on.
The phase of the emitted light 24 is changed from the on state to 18 by turning the optical switch 1 on and the optical switch 2 off.
0″′ can be inverted.

FIG. 3 shows a third embodiment of the invention. In the figure, 100 is a substrate, 101 is a semiconductor laser, 102 is a phase modulator which is the first embodiment described above, and 26 is an emitted light. The operation will be explained below.

The light emitted from the semiconductor laser 101 is transmitted to the phase modulator 10.
2 and exits from the optical modulator as output light 26.

The operation of the phase modulator 102 is as described above, and the output light 2 is changed by turning on and off the optical switch 1 and the optical switch 2.
6 can be inverted by 180 degrees to perform PSK modulation of light.

By the way, since the phase modulator 102 is formed from the same group semiconductor material as the semiconductor laser 101, the substrate 1
The semiconductor laser 101 and the semiconductor laser 101 can be monolithically integrated on the semiconductor laser 00. Therefore, the light from the semiconductor laser 101 can be efficiently taken into the phase modulator 102, and the entire optical modulator can be made smaller.

FIG. 4 shows a fourth embodiment of the present invention. In the figure, 100 is a substrate, 101 is a semiconductor device, 103 is a phase modulator according to the second embodiment described above, and 27 and 28 are output lights. The operation will be explained below.

The light emitted from the semiconductor laser 101 is transmitted to the phase modulator 10.
3 and exit from the optical modulator as output light 27 and output light 28. The operation of the phase modulator 103 is as described above, and by turning on and off the optical switches 1 and 2, the phase of the emitted light 27 can be inverted by 180'', thereby performing PSK modulation of the light.

By the way, since the phase modulator 103 is formed from the same group semiconductor material as the semiconductor laser 101, the substrate 1
The semiconductor laser 101 and the semiconductor laser 101 can be monolithically integrated on the semiconductor laser 00. Therefore, the light from the semiconductor laser 101 can be efficiently taken into the phase modulator 103, and the entire optical modulator can be made smaller.

Effects of the Invention By configuring as described above, the phase of light can be reliably inverted simply by passing through one of the two optical waveguides and blocking the other, resulting in a good PSK signal or DP signal.
SK signal can be obtained.

In addition, the components of the above two types of phase modulators, such as optical splitters, optical couplers, directional couplers, optical waveguides, and optical switches, can be made from group V semiconductor materials.
By making the phase modulator with a semiconductor material of the ■■ group, it can be monolithically integrated with the semiconductor laser, and the optical coupling between the semiconductor laser and the phase modulator can be improved.
The overall size of the optical modulator can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a phase modulator according to a first embodiment of the present invention, FIG. 2 is a block diagram showing a phase modulator according to a second embodiment of the present invention, and FIG. 3 is a block diagram showing a phase modulator according to a second embodiment of the present invention. FIG. 4 is a block diagram showing an optical modulator as a third embodiment of the present invention. FIG. 4 is a block diagram showing an optical modulator as a fourth embodiment of the present invention. 1.2... Optical switch, "3... Optical splitter, 4...
・Optical coupler, 5.6...Directional coupler, 11-14・
・・Optical waveguide, 21.23 ・・Incoming light, 22.24～
28... Emitted light, 100... Substrate, 101... Semiconductor laser, 102... Phase modulator, 103... Phase modulator. Name of agent: Patent attorney Shigetaka Awano and 1 other person @1 Figure 2 Figure

Claims (4)

[Claims] (1) The input ends of the first and second optical waveguides are respectively connected to two output ends of a 1-input 2-output optical splitter, and the output ends of the two optical waveguides are connected to a 2-input 1-output optical coupler. where the light entering from the input end of the optical splitter and exiting from the output end of the optical coupler passes through the first optical waveguide and the second optical waveguide. A phase modulator comprising an optical switch on each of the first and second optical waveguides, which is configured so that the phase of light differs by 180 degrees when passing through the optical waveguide, and has the function of passing or blocking light. (2) The input ends of the first and second optical waveguides are the first 2×2
The output ends of the two optical waveguides are respectively connected to the two input ends of a second 2×2 directional coupler, and the output ends of the two optical waveguides are connected to the two input ends of a second 2×2 directional coupler, and A case where the light entering from the first input end of the directional coupler and exiting from the first output end of the second directional coupler passes through the first optical waveguide, and a case where the light passes through the second optical waveguide. A phase modulator comprising optical switches on the first and second optical waveguides, each of which is configured such that the phase of the light differs by 180° depending on when the light passes through and has a function of passing or blocking the light. (3) The phase modulator according to claim 1, comprising at least a semiconductor laser and the same semiconductor material as the semiconductor laser, wherein light from the semiconductor laser enters the phase modulator from an input end of the phase modulator. An optical modulator configured as follows. (4) The phase modulator according to claim 2, comprising at least a semiconductor laser and the same semiconductor material as the semiconductor laser, wherein light from the semiconductor laser enters the phase modulator from an input end of the phase modulator. An optical modulator configured as follows.